Biology Question Bank – 137 MCQs on “Applied Biology” – Answered!

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137 Questions with Answers and Explanations on “Applied Biology” for Students.

1. In crop movement programme, haploids are important because they

(a) require one half of nutrients

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(b) are helpful in study of meiosis

(d) form perfect homozygous.

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Answer and Explanation:

1. (d): in crop movement programme, haploids are important because they form perfect homozygous lines. Homozygous are the pure line selection plants resulting from self pollination. In this way, considerable homozygosity is obtained. Haploids are those plants which possess a gametophytic number of chromosomes. Haploids are used in plant breeding, especially for the production of homozygous plants and in their studies in the detection of mutation.

2. Which ones produce androgenic haploids in anther cultures?

(a) anther wall

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(b) tapetal layer of anther wall

(d) young pollen grains.

Answer and Explanation:

2. (d): Haploid production through a culture has been referred to as androgenesis. The androgenic method of haploid production is from the male gametophyte of an angiosperm plant i.e., microspore (immature pollen). Young pollen grains produced androgenic haploids in anther cultures while anther wall, tapetal layer of anther wall and connective tissue are the parts of anther. Tapetal layer is the nutritive tissue.

3. Cellular totipotency was demonstrated by

(a) Theodore Schwann

(b) A.V. Leeuwenhoek

(d) Robert Hooke

Answer and Explanation:

3. (c): Cellular totipotency is the technique of regeneration or development of complete plant from explants or cell or tissue of the plant. This technique was established by F. C. Steward and developed the new carrot plant from carrot root culture.

4. Haploid plants are preferred over diploids for mutation study because in haploids

(a) recessive mutation express immediately

(b) induction of mutations is easier

(d) dominant mutation express immediately.

Answer and Explanation:

4. (a): Haploids are preferred over diploids for mutation study because in haploids recessive mutation is easier. Most of the induced mutations are recessive and these have to be in double to be expressed phenotypically. Mutations are not seen in heterozygous conditions. So, in haploid plants, recessive mutation express immediately.

5. Which crop variety is not due to induced mutations?

(a) reimei of rice

(b) prabhat of arhar

(d) aruna of castor.

Answer and Explanation:

5. (d): Aruna of castor is a crop variety which is not due to induced mutations. Aruna variety has been developed by mutation, where maturity period has been reduced from normal 270 days to 102 days.

6. Haploid plants can be obtained by culturing

(a) pollen grains

(b) root tips

(d) endosperm.

Answer and Explanation:

6. (a): Haploid plants are those plants which have single set of chromosomes. Pollen grains are haploid as they are produced after meiosis so they are used for haploid production. It was first made in Datura innoxia by Guha and Maheshwari in 1964.

Haploids are important in plant breeding as mutation can be easily detected in them and they are also used to produce homozygous diploids.

7. Silk is produced by

(a) adult moth

(b) cocoon

(d) both (a) and (c).

Answer and Explanation:

7. (c): The silkworm, Bombyx mori is reared on mulberry leaves on a mass scale to get raw silk from the cocoons of the caterpillars (larvae) of the moth. The eggs of the silkworm moth hatch out within a few days into creamy white rapidly moving caterpillars. The latter feed voraciously on the fresh mulberry leaves and soon undergo a fast growth and are popularly referred to as silkworms.

The silk glands of caterpillar secrete a sticky secretion which is spun around the worms to form a hard covering of silk fibres, known as the cocoon. The silk worm with cocoon is known as pupa. After one or two days of cocoon formation, the pupae are killed either by drying them in the sun or by boiling them. The raw silk fibres forming the cocoon are then reeled out into silk threads.

8. Which among the following is the real product of the honey bee?

(a) honey

(b) propolis

(d) bee wax.

Answer and Explanation:

8. (d): Beeswax is a very useful by-product of bee keeping industry. It is yellowish to greyish brown in colour and insoluble in water but completely soluble in ether. Beeswax is a natural secretion of the worker bees and is poured out in thin delicate scales or flakes. It is secreted by pair of wax glands placed ventrally on the abdomen. Beeswax is used in the manufacture of cosmetics, for Catholic churches, face cream, paints, ointments, insulators, plastic works, polishes, carbon paper, lubricant etc. Honey is not the real product of honey bees. It is a mixture of nectar, pollen, cane-sugar and saliva of honeybees.

9. Biological control of agricultural pests, unlike chemical control, is ;

(a) self perpetuating

(b) polluting

(d) toxic.

Answer and Explanation:

9. (a): The control of insect pests by the introduction, encouragement and artificial increase of biological agencies like predaceous and parasitic insects, other animals and diseases is termed as biological control. It is basically a natural control in which man plays significant role of making the biological agencies more effective.

Of these agencies, insect enemies play important role in nature for managing the phytophagous insect pests and keep a balance e.g., lady bugs or praying mantis, frog, toads, lizard and birds are employed by man to eat up the insect pests like aphids. It is a self perpetuating method.

10. In cheese manufacture, the microorganisms are important for

(a) the ripening only

(b) the souring of milk only

(d) both the souring and the ripening processes.

Answer and Explanation:

10. (d): Cheese is a protein rich nutritive preparation obtained after fermentation and curding of milk. Cheese contains proteins (20-35%), fats (20-30%), minerals, vitamins and water. Milk is first curdled (soured) with the help of a lactic acid bacterium. Curd is gently heated
to separate cheese from liquid called whey. Curd is placed in cloth-lined porous containers for draining out whey. The left out solidified material is called cottage cheese. For preservation and ripening, blocks of cottage cheese are salted and placed in brine solution. Salt solution is drained out. Cheese blocks are wiped and placed in sterilised rooms for ripening with the help of microorganisms.

11. Which of the following organelles is related with genetic engineering?

(a) mitochondria

(b) plasmids

(d) lysosomes.

Answer and Explanation:

11. (b): Plasmids are extra chromosomal genetic element found in many bacteria and in a few eukaryotic cells. Plasmids are closed circles of double-stranded DNA, ranging in size from one to 200 kilobases.

They frequently carry genes conferring antibiotic resistance. Plasmids are becoming important tools for genetic engineering since they have the ability to replicate and migrate to daughter cells. Plasmids are widely used as carriers of cloned genes, as for example the E. coli plasmid pBR322. When plasmids are used as cloning vectors and carry a novel DNA sequence they are referred to as chimeric plasmids.

12. Which of the following species does not have the ability to fix atmospheric nitrogen?

(a) Azotobactor

(b) Anabaena

(d) Spirogyra.

Answer and Explanation:

12. (d): Members of kingdom monera – bacteria and cyanobacteria (blue green algae) have the ability to fix nitrogen. Azotobacter is a N₂-fixing bacteria. Anabaena and Nostoc are heterocystous blue-green algae. The heterocysts are the sites of N₂-fixation. Spirogyra is one of the commonest green algae. It has no function in nitrogen fixation.

13. Which one of the following statements is correct?

(a) legumes fix nitrogen only through the specialized bacteria that live in their roots

(b) legumes fix nitrogen independently of the specialized bacteria that live in their roots

(d) legumes are incapable of fixing nitrogen.

Answer and Explanation:

13. (a): The nitrogen-fixing ability of leguminous plants is not a property of the plants as such but results from infection of their roots by bacteria in the soil, infection leading to the formation of nodules. These organisms are Gram-negative motile rods that are classified in the genus Rhizobium.

14. The citric acid is produced by

(a) Candida utilis

(b) Azotobacter suboxydans

(d) Streptococcus lactis.

Answer and Explanation:

14. (c): Citric acid is produced by aerobic fermentation of sucrose in beet molasses by Aspergillus Niger. The fermentation process is completed in about 5-14 days at 27 – 33°C. Citric acid is made available in the market in the form of anhydrous crystalline chemical as powder. Citric acid is used in food industry (e.g. fruit drinks, confectionery, jams, jellies, preserved fruits), pharmacy (e.g. blood transfusion), consmetics (e.g. astringent lotions, shampoos and hair setting fluids), and industries (e.g. electroplating leather tanning).

15. Which of the following is the New World spice, that has become an essential part of Indian cuisine?

(a) red pepper

(b) black pepper

(d) cardamom.

Answer and Explanation:

15. (a): New world crops are those which have their centre of origin in America. Red peppers are the dried ripe fruits of Capsicum sp, indigenous to the American tropics and subtropics and the West Indies. It is a new world crop.

16. The rotenone is

(a) a natural herbicide

(b) a natural insecticide

(d) a bioherbicide.

Answer and Explanation:

16. (b): Natural insecticides are those which are obtained from microorganisms and plants. The first natural insecticide used by man is azadirachtin obtained from Azadirachta indica.

Rotenone is another natural insecticide which is obtained from the roots of Derris and Lonchocarpers. It is harmless to warm blooded animals.

17. The organism, used for alcohol fermentation, is

(a) Aspergillus

(b) Saccharomyces

(d) Penicillium.

Answer and Explanation:

17. (b): Fermentation is the enzymatic destruction of a substrate by microorganisms. Basically it is a respiratory process, usually anaerobic. It involves the conversion of private to ethanol and CO₂ or lactic acid and other organic acids depending on the organism involved. Yeast especially strain of Saccharomyces cerevissae are the main producers of ethanol.

18. Agar is commercially obtained from

(a) red algae

(b) blue-green algae

(d) green algae.

Answer and Explanation:

18. (a): Algae are useful source of many commercial products, e.g. agar which is a jelly-like substance and a complex polysaccharide (phycocolloid), and is extracted in water from certain sps. of red algae belonging to Gelidium, produced and stored in their cell walls along with cellulose. It is gel containing galactose and sulphate. It is used as base in culture media for algae, fungi, bacteria and tissues. It is also used as stablizer or emulsifier in food, cosmetics, leather and pharmaceutical industries.

19. One of the major difficulties in the biological control of insect pest is that

(a) the method is less effective as compared with the use of insecticides

(b) the practical difficulty of introducing the predator to specific areas

(d) the predator does not always survive when transferred to a new environment.

Answer and Explanation:

19. (d): The control of insect pests by the introduction, encouragement and artificial increase of biological agencies like predaceous and parasitic insects, other animals and diseases is termed as bilological control. It is basically a natural control in which man plays significant role of making the biological agencies more effective. Of these agencies, insect enemies play important role in nature for managing the phytophagous insect pests and keep a balance.

It is just possible that predators of a particular plant pest are unable to get established and multiply in a particular environment. In such cases, the predators are reared in the laboratory and let off at a particular time when the pests are about to threaten the crops. And then this practice becomes expensive.

20. The silkworm silk is the product of

(a) salivary gland of the larva

(b) salivary gland of the adult

(d) cuticle of the adult.

Answer and Explanation:

20. (a): The eggs laid by the female moth are rounded and white in colour. The eggs, after ten days of incubation hatch into a larva called as caterpillar. After hatching, caterpillars need continuous supply of food because they are voracious feeders. As they are voracious feeders, they grow rapidly which is marked by four moultings.

The full grown caterpillar is 7.5 cm in length. It develops salivary glands, stops feeding and moves towards corner among the leaves and secretes a sticky fluid through silk gland. The secreted fluid comes out through spinneret (a narrow pore situated on the hypopharynx) and takes the form of long fine thread of silk which hardens on exposure to the air and wrapped around the body of the caterpillar in the form of a covering called as cocoon.

21. The transgenic animals are those which have

(a) foreign RNA in all its cells

(b) foreign DNA in some of its cells

(d) both ‘a’ and ‘b’.

Answer and Explanation:

21. (c): Transgenic organism is one that has become transformed following the introduction of novel genes into its genome. It is most frequently achieved by integration of cloned DNA sequences following their injection into the fertilized egg.

This fertilized egg divides mitotically to form the whole organism so that all the cells of the organism will carry the transferred gene. The transferred genes are known as transgenes. Tran genesis can be done by pronuclear microinjection and somatic cell nuclear transfer or cloning. Transgenic animals produced by this technology include mice, Drosophila, menopause and some of the fish species.

22. The restriction enzymes are used in genetic ‘engineering, because

(a) they can cut DNA at specific base sequence

(b) they are nucleases that cut DNA at variable sites

(d) they can join different DNA fragments.

Answer and Explanation:

22. (a): DNA restriction endonuciease are a class of restriction end nucleases, which cut double-stranded DNA molecules only at sites characterized by a specific nucleotide sequence. Restriction enzymes are isolated from bacterial cells, and are tools for molecular biologists. Several hundred restriction enzymes are now known, each with a specific sequence requirement dictating where it will cut DNA. Some, such as Hind 111, make staggered cuts leaving ‘sticky ends’ three nucleotides long protruding on one strand from each severed terminus; other make clear cuts in both strands at the same place and thus generate blunt ends’.

23. Which of the following radioactive isotopes is used of in the detection of thyroid cancer?

(a) uranium-238

(b) phosphorus- 131

(d) carbon-14.

Answer and Explanation:

23. (c): Iodine is an element used by thyroid for the synthesis of thyroid hormones. Thus radioactive isotope iodine – 131 is used as radioactive material for detection of thyroid cancer.

24. 2, 4-D is an effective

(a) rodenticide

(b) wormicide

(d) weedicide

Answer and Explanation:

24. (d): It has been established that 2, 4, D. (2, 4, dichlorophenoxyacetic acid), NAA (a-naphthalene acetic acid) and some other compounds kill weeds or herbs. The weedicides are effective against broad leaved herbs or weeds but they are little effective against narrow leaved weeds. Modern view is that the herbicides inhibit DNA transcription and RNA translation. As a result of this enzymes required, for overall growth are not synthesised and thus the plants will die.

25. Coir is the commercial product of coconuts

(a) endocarp

(b) endosperm

(d) mesocarp.

Answer and Explanation:

25. (d): Coir is the term applied to short course and rough fibres which are obtained from the fibrous mesocarp of coconut. The fibres of this plant are highly resistant to water. They are very light and elastic. To obtain the fibres, the husks of coconut are soaked in salt water for several months to loosen the fibres. It is then dried in sun and spun into coir by hand or by machine.

26. Which one of the following constitutes natural silk?

(a) nitrogen

(b) magnesium

(d) phosphorus.

Answer and Explanation:

26. (a): Silk is a pasty secretion of the silkworm produced by the silk gland. As this pasty secretion comes in contact with air, it becomes hard and forms strong and pliable silk strands. This secretion forms two cores of fibroin: (i) a tough elastic insoluble protein consisting of 75% of the fibre’s weight and cemented together with sericin from the middle region of the silk gland at the time of secretion, and (ii) a gelatious protein which is easily soluble in warm water. As proteins consist of nitrogen component it is a main constituent of natural silk.

27. Pasteurization is a process, which means heating of drinks. It is carried out at what temperature and for how much duration?

(a) 70°C and 60 minutes

(b) 80°C and 30 minutes

(d) 60-70°C and 30 minutes.

Answer and Explanation:

27. (d): Pasteurization is a method of partial sterilization named after famous pioneer microbiologist. Lewis Pasteur, who found that heating at temperature well below boiling point destroyed bacteria causing wine spoilage without affecting its flavour. Best known example is pasteurization of milk (heating for 30 minutes at 62°C) which kills tubercles and other harmful bacteria.

28. Which one of the following fish is introduced into India by foreigners?

(a) Mystus singhala

(b) Clarius batrachus

(d) Pomphret.

Answer and Explanation:

28. (d): Pomphret fish is the one which was introduced in India by foreigners. It is consumed as an edible fish.

29. Nowadays cornea transplantation is very popular. The reason is that, it

(a) can be easily obtained

(b) does not link blood supply and immune system

(d) is transplants very easily.

Answer and Explanation:

29. (b): Cornea is a transparent portion that forms the anterior one-sixth of the eyeball. The cornea admits and helps to focus light waves as they enter the eye. The cornea is avascular (i.e., gets no blood supply). This part of eye absorbs oxygen from the air. As it has no blood supply, so it is also lacking in lymphocytes (component of immune system), thus, it can be easily transplanted (as there will be no rejection of transplant from immune system).

30. Cochineal insects have proved very useful for

(a) Cactus prevention

(b) Eicchornia prevention

(d) Parthenium contol.

Answer and Explanation:

30. (a): Extensive growth of Opuntia (Cactus) in Australia was checked through introduction of its natural herbivore, cochineal insect (Cactoblastis cactorum).

31. When a natural predator (living being) is applied on the other pathogen organism to control them, this process is called

(a) artificial control

(b) confusion technique

(d) genetic engineering.

Answer and Explanation:

31. (c): Refer answer 9.

32. When scientists make an animal superior by view of genotype, introducing some foreign genes in it, is called

(a) immunization

(b) genetic engineering

(d) biotechnology.

Answer and Explanation:

32. (b): Genetic engineering is experimental manipulation of genetic material, especially for industrial or medical uses. It encompasses the techniques of gene cloning, the modification DNA by changes in sequence arrangement or deletion, and the introduction of novel genes into cells and organisms.

It may prove possible to advantageously modify the genes of fanned animals, to correct genetic deficiencies of the human by inserting novel genes.

This can be done by breakage of a DNA molecule at two desired places into another DNA molecule of the desired animal.

33. The first hormone artificially produced by culturing bacteria is

(a) testosterone

(b) adrenalin

(d) thyroxin.

Answer and Explanation:

33. (c): Insulin is a polypeptide hormone that reduces the blood glucose concentrations. It is synthesized exclusively by the (3 cells the islets of Langerhans. During synthesis it has a molecular precursor, proinsulin. Gilbert and Villakomaroff (1980) isolated mRNA for insulin from (3 cells of rat’s pancreas and inserted into pBR322 piasmid in the middle of a gene normally coding the penicillinase, and incorporated it into E. coli cells. E. coli cells produced a hybrid protein (penicillinase + proinsulin) from which the proinsulin was separated by using typsin. It is estimated that clones of E. coli are capable of producing about one million molecules of insulin per bacterial cells.

34. Improvement of human race by controlled selective breeding between individual with desirable characteristics is called

(a) inbreeding

(b) euthenics

(d) none of these.

Answer and Explanation:

34. (c): Eugenics is study of human heredity as applied to the improvement of the human race. Practical eugenics involves promoting interbreeding between individuals having favourable genetic endowment and discouraging or preventing interbreeding of those with relatively unfavourable genetic endowment.

Euthenics is the suitable environment for human well being, health and intellect.

Inbreeding involves production of progenies by mating between relatives.

35. The biofertilizers are

(a) Anabaena and Azolla

(b) cow dung, manure and faryard waste

(d) none of these.

Answer and Explanation:

35. (a): Biofertilizers are organisms which bring about nutrient enrichment of the soil. Biofertilizers are of three types – nitrogen fixing bacteria, nitrogen fixing cyanobacteria and mycorrhiza. Among symbiotic nitrogen fixing cyanobacteria Anabaena azollae and Noslocpunctaeformae are present symbiotically in leaves of Azolla and Anthoceros. Azolla-Anabaena symbiotic system is the main biofertilizer which is inoculated in rice fields in South-Eastern Asia, which is found to increase yield upto 50%.

36. High milk yielding varieties of cows are obtained by

(a) use of surrogate mothers

(b) super ovulation

(d) all of these.

Answer and Explanation:

36. (d): High milk yielding varieties of cows® obtained by use of surrogate mothers, super ovulate artificial insemination. To get an increased yield of mil surrogate mothers are used in dairy. Super ovulation the hormonal stimulation of multiple ovarian follicles resulting in release from the ovary of larger number of oocytes (ova) than normal.

So, implantations into surrogate mothers increase the number of off spring usually from highly selected cows. Artificial insemination is a reasonably straight forward process to remove semen from a chosen male animal, and transfer it into a female at the appropriate stage of the oestrous cycle. This process is well developed in case of dairy cattle breeding for more milk production.

37. Amniocentesis is a process to

(a) know about the disease of brain

(b) determine any disease in heart

(d) all of the above.

Answer and Explanation:

37. (c): Amniocentesis is a withdrawal of a sample of the fluid (amniotic fluid) surrounding an embryo in the uterus by piercing the amniotic sac through the abdominal wall. As the amniotic fluid contains cells from the embryo (mostly shed from the skin), cell cultures enable chromosome patterns to be studied so that prenatal diagnosis of chromosomal abnormalities (such as Down’s syndrome) can be made. Metabolic errors and other diseases, such as spina bifida, can also be diagnosed prenatally from the biochemistry of the cells or that of the fluid.

38. Honey is

(a) alkaline

(b) basic after some days

(d) neutral.

Answer and Explanation:

38. (c): Honey is very acidic. Its pH is between 3 and 4 about the same as orange juice or a can of coke.

39. Gobar gas contains mainly

(a) CO₂ + H₂

(b) CO₂ + H₂O

(d) CH₄ + CO₂.

Answer and Explanation:

39. (d): Gobar gas is 55 – 65% CH₂, 30 – 35% CO; with some H₂, N₂ and other traces. About one cubic foot of gas may be generated from one pound of cow manure at 75°F. This is enough gas to cook a day’s meals for4- 6 people.

40. Pebrine is a disease of

(a) silk worm

(b) lac insect

(d) fish.

Answer and Explanation:

40. (a): Pebrine is a disease of silkworm caused by a small parasite Nosema which has a devastating effect on silk industry.

41. Recombinant DNA is achieved by cleaving the pro- DNAs by

(a) ligase

(b) restriction endonulcease

(d) exonucleases.

Answer and Explanation:

41. (b): Recombinant DNA is the product obtained after isolating a specific DNA segment and then inserting it into another DNA molecule at a desired position Restriction end nucleases are the enzymes that digest DNA at specific sites to isolate a specific DNA segment Thus they are required for producing recombinant DNA.

42. The reason for vegetatively reproducing crop plants to suit for maintaining hybrid vigour is that

(a) they are more resistant to diseases

(b) once a desired hybrid produced, no chances of losing it

(d) they have a longer life span.

Answer and Explanation:

42. (b): Hybrid vigour or heterosis is defined as the superiority of the hybrid over its parents. It is lost on inbreeding. It is lost in the F₂ generation in self pollinated plants and declines slowly in cross pollinated plants. So it is more profitable in vegetatively propagated plants as they do not involve sexual reproduction and so hybrid vigour is not lost in subsequent crops, e.g. sweet potato, sugarcane, strawberry and grapes etc.

43. Two bacteria found to be very useful in genetic engineering experiments are

(a) Nitrobacter and Azotobacter

(b) Rhizobium and Diplococcus

(d) Escherichia and Agrobacterium.

Answer and Explanation:

43. (d): E. coli contains many important standard cloning vectors widely used in gene cloning experiments’ like PBR322 contains origin of replication (ori). Other cloning vectors like PACYC177, PBR324, and PRK 64.6; contain ampicillin resistance gene they are also found in E.coli. Among higher plants, Ti plasmid of Agrobacterium tumefaciens and RI plasmid of Arhizogenes is the best known vector. T-DNA from Ti or Ri plasmid of Agcobacterium is considered to be a very potential vector for cloning experiments with higher plants.

44. Restriction endonucleases are

(a) used for in vitro DNA synthesis

(b) used in genetic engineering

(d) present in mammalian cells for degradation of DNA.

Answer and Explanation:

44. (b): Restriction endonucleases (restriction enzymes) are enzymes that digest doublest randed DNA following recognition of specific nucleotide sequences. This is achieved by cleaving the two phosphodiester bonds, one within each strand of the DNA duplex.

45. Genetic engineering is possible, because

(a) we can cut DNA at specific sites by endonucleases like DNAase

(b) restriction endonucleases purified from bacteria can be used in vitro

(d) we can see DNA by electron microscope.

Answer and Explanation:

45. (b): DNA restriction endonuciease are most important class of restriction endonucleases, which cut double-stranded DNA molecules only at sites characterized by a specific nucleotide sequence. Restriction enzymes are isolated from bacterial cells, and are tools for molecular biologists.

Several hundred restriction enzymes are now known, each with a specific sequence requirement dictating where it will cut DNA. Some, such as Hind III, make staggered cuts leaving ‘sticky ends’ three nucleotides long potruding on one strand from each severed terminus; other make clear cuts in both strands at the same place and thus generate blunt ends’. Digesting DNA with a restriction enzyme therefore which can be isolated by electrophoresis and subsequently analysed.

46. Which of the following is non-symbiotic biofertilizer?

(a) Anabaena

(b) Rhizobium

(d) Azotobacter.

Answer and Explanation:

46. (d): Biofertilizers are organisms which bring about nutrient enrichment of the soil. Azotobacter is a free living, aerobic, nitrogen fixing bacteria. Anabena is a nitrogen fixing cyanobacteria that occurs in both free living and symbiotc associations with Azolla, Cycas roots etc. Rhizobium lives symbiotically in root nodules of legumes and non-legumes. Vesicular-arbuscular mycorrhiza (VAM) is an example of endomycorrhiza in which fungal hyphae penetrate the cortical cells of grasses to form vesicles.

47. Yeast (Saccharomyces cerevisiae) is used in the industrial production of

(a) tetracyline

(b) ethanol

(d) citric acid.

Answer and Explanation:

47. (b): Fermentation is the enzymatic destruction of substrate by microorganisms. Basically it is a respiratory process, usually anaerobic. More specifically it refers to the production of ethanol by yeast from monosaccharide sugars. Yeast (Saccharomyus cerevisiae) converts sugars through EMP pathway into pyruvic acid. It is then converted to acetaldehyde and finally to ethanol.

48. What is Agent Orange?

(a) colour used influorescent lamp

(b) a hazardous chemical used in luminous paints

(d) a weedicide containing dioxin.

Answer and Explanation:

48. (d): Agent orange is a herbicide containing dioxin. It is called Agent orange because it was transported in orange containers during its use in Vietnam War from 1961 to 1971 by USA. Agent Orange is roughly 1: 1 mixture of two phenoxy herbicides in ester form 2, 4-D and 2, 4, 5-T. When sprayed on broad-leaf plants they induce rapid uncontrolled growth and eventually kill the plants. When sprayed on fields they selectively kill seeds. Significant impact of these dioxins would induce mutations and genetic defects as these chemicals are known to bind to DNA.

49. Which of the following pesticides is an acetyl cholinesterase inhibitor?

(a) endosulfan

(b) malathion

(d) Y-BHC.

Answer and Explanation:

49. (b): Pesticides are chemicals that are used to destroy pests and thus increase crop productivity. They are often persistent, induce resistance and ecological imbalance. Malathion is an organophosphate pesticide which affects the nervous system. It inhibits the action of acetyl cholinesterase enzyme.

50. Farmers have reported over 50% higher yields of rice by using, which of the following biofertilizer?

(a) Cyan bacteria

(b) legume- Ryzobium symbiosis

(d) Azolla pinnata.

Answer and Explanation:

50. (d): The symbiotic nitrogen fixing blue green algae include Anabaena azollae which forms symbiotic associations with Azolla. It resides in leaf cavities of the free Azolla. A part of the fixed nitrogen is excreted in the cavities and becomes available to the fern. The fern can coexist with rice plants because it does not interfere with their growth. The decaying fern plants release the nitrogen for utilization of the rice plants. When field is dried at the time of harvesting, the fern functions as the green manure, decomposing and enriching the field for the next crop. It is mostly inoculated in rice fields in south-east Asia and is found to increase yield upto 50%.

51. Which of the following micro-organisms is used for production of citric acid in industries?

(a) Aspergillus niger

(b) Rhizopits nigricans

(d) Penicillium citrinum.

Answer and Explanation:

51. (a): Citric acid is obtained through the fermentation carried out by Aspergillus niger on sugary syrups. Citric acid is employed in dyeing, engraving, medicines, inks, flavouring and preservation of food and candies.

52. Biological control component is central to advanced agricultural production. Which of the following is used a^c ° third generation pesticide?

(a) insect repellants

(b) organophosphate and carbamates

(d) pheromones.

Answer and Explanation:

52. (d): Pheroniones are volatile chemicals produced by a given species to communicate with other individuals of the same species to change their behaviour. The synthetic versions of lepidopteran pheromones can be used as pesticides.

Sometimes the relative amount of several pheromone chemicals in a pesticide product determine which specific pests are controlled when the pesticide product releases pheromone into the air where males are looking for females, the males become confused and cannot easily locate the females.

As a result, many of the females do not mate and lay eggs, and there are many fewer offspring than usual. These insect pheromones are third generation pesticides. Other third generation pesticides are insect growth regulators, chitin synthesis inhibitors, and juvenile hormones.

53. The new varieties of plants are produced by

(a) introduction and mutation

(b) selection and introduction

(d) mutation and selection.

Answer and Explanation:

53. (c): The new plant varieties are produced by selection and hybridization. Selection is a non-random process which leads to individuals of different genotypes being represented unequally in their progeny in later generations of a population of self propagating units. Selection can be natural or artificial. Hybridization is the crossing of two varieties, species or genera having desired genes by bringing together the useful characters of these into one progeny. Both these processes produce new plant varieties.

54. Which of the following fern is an excellent biofertilizer?

(a) Marsilia

(b) Pteridium

(d) Salvinia.

Answer and Explanation:

54. (c): Azolla is a fern in the leaf cavities of which the blue green algae Anabaena is found. This Azolla- Anabena symbiotic system is the main biofertilizer which increases yield upto 50% Anabaena fixes nitrogen which is excreted in the leaf cavities and is made available to the fern. When the fern plants die and decay they release nitrogen for utilization of the rice plants.

55. Due to which of the following organism, yield of rice is increased?

(a) Sesbania

(b) Bacillus popilliae

(d) Bacillus subtilis.

Answer and Explanation:

55. (c): Anabaena is a nitrogen fixing cyanobacteria that forms symbiotic associations with Azolla. Azolla- Anahaena symbiotic system is the main biofertilizer which is inoculated in rice fields in South-Eastern Asia, is found to increase yield upto 50%.

56. The term aquaculture means

(a) inland fisheries

(b) aspergillosis

(d) both (a) and (c).

Answer and Explanation:

56. (d): Aquaculture involves production of useful aquatic plants and animals such as fishes, prawns, shrimps, lobsters, crabs, molluscs by proper utilization of small and large bodies of water. The production of fishes is called pisciculture. Inland fishery deals with the fishery aspects of waters other than marine water. Marine fishery deals with the fishery aspects of the sea water or ocean.

57. Fish, which eradicate the mosquito larva, is

(a) Gambusia

(b) cutter fish

(d) rohu.

Answer and Explanation:

57. (a): Gambusia fish is employed for malaria control. It eats mosquito larvae. Such fishes are propagated and introduced into ponds and lakes for the control of malaria.

58. Life span of a worker bee is

(a) 6 weeks

(b) 10 weeks

(d) 15 days.

Answer and Explanation:

58. (a): A good and well developed colony of bees has 40 to 50 thousand individuals consisting of 3 castes viz., queen, drone and worker. Although the workers are the smallest of the three castes but they function as the main spring of the complicated machinery like honey bee colony. It takes 21 days in the development from the egg to the adult and the total life span of a worker is about 6 weeks. The workers are atrophid female which sacrifice themselves for the well-being of the colony. The total indoor and outdoor duties of the colony are performed by the workers only.

59. The term ‘humulin’ is used for

(a) hydrolytic enzyme

(b) powerful antibiotic

(d) isoenzyme.

Answer and Explanation:

59. (c): Human insulin (humulin) is the first therapeutic product produced by means of recombinant technology by Elililly and Co. on July 5, 1983.

60. Hybridoma cells are

(a) only cells having oncogenes

(b) product of spore formation in bacteria

(d) hybrid cells resulting from myeloma cells.

Answer and Explanation:

60. (d): Hybridoma is hybrid cell resulting from the artificial fusion of an antibody-producing lymphocyte and a myeloma cell from a lymphoid tumour. Such cells can produce a clone that may be maintained in tissue culture and used for the continuing production of monoclonal antibody.

61. The process of replication in plasmid DNA, other than initiation, is controlled by

(a) mitochondrial gene

(b) piasmid gene

(d) none of these.

Answer and Explanation:

61. (c): Piasmid are extra chromosomal genetic element found in many bacteria and in a few eukaryotic cells. Plasmids are closed circles of doule-stranded DNA. They frequently carry genes conferring antibiotic resistance or coding for molecules such as colicin; infective drug resistance, originally discovered in Shigella, is due to plasmids. The DNA piasmid replicates in a semi-conservative manner. The initiation of replication is controlled by piasmid gene and elongation and termination are controlled by bacterial genes.

62. The first transgenic crop was

(a) tobacco

(b) cotton

(d) flax.

Answer and Explanation:

62. (a): Transgenic plants are those plants in which a foreign gene has been introduced and stably integrated into host DNA. The first transgenic plants were produced in tobacco (Nicoliana labacum). A gene resistant to PPT (L-phosphinothricin), an active ingredient of herbicide ‘Basta’, was isolated from Medicago saliva. It inhibits the enzyme GS (glutamine synthase) which is involved in ammonia assimilation. This gene resistant to PPT was incorporated into tobacco, as a result of which transgenic tobacco was produced which was resistant to PPT.

63. Which of the following is related to genetic engineering?

(a) heterosis

(b) mutation

(d) plasmid.

Answer and Explanation:

63. (d): Plasmids are extra chromosomal genetic element found in many bacteria and in a few eukaryotic cells. Plasmids are closed circles of double-stranded DNA. They frequently carry genes conferring antibiotic resistance or coding for molecules such as colic in infective drug resistance.

They are becoming important tools for genetic engineering since they have the ability to replicate and migrate to all the daughter cells. Plasmids am widely used as carriers of cloned genes, as for example the E. coli plasmid pBR322. When plasmids are used as cloning vectors and carry a novel DNA sequence they are referred to as chimaeric plasmids.

64. Coconut milk is used in tissue culture in which is present

(a) cytokinin

(b) auxin

(d) ethylene.

Answer and Explanation:

64. (a): Coconut milk or liquid endosperm of coconut I could initiate as well as sustain the proliferation of tissues in aculture. Eventually coconut milk was shown to contain the cytokimn zeatin, but this finding was not obtained until several years after the discovery of cytokinins. The first cytokinin to be discovered was the synthetic analog kinetin.

65. Which aquatic fern is used to increase the yield in paddy crop?

(a) Azolla

(b) Salvinia

(d) Isoetes.

Answer and Explanation:

65. (a): Refer answer 54.

66. Which of the following is used to manufacture ethanol from starch?

(a) Penicillin

(b) Saccharomyces

(d) Lactobacillus.

Answer and Explanation:

66. (b): Saccharomyces convert starch or sugars to pyruvic acid through EMP pathway. Then this pyruvic acid is converted to acetaldehyde and finally to ethyl alcohol in the absence of oxygen. This entire process is called fermentation.

67. Which statement is correct?

(a) A. indica is largest wild honey bee

(b) wax is waste material of honey bee

(d) Drone of honey bee is diploid.

Answer and Explanation:

67. (c): A highly organised division of labour is found in the colony of honey bees. A good and well developed colony of bees had 40 to 50 thousand individuals consisting of 3 castes viz., queen, drone and worker. Although the workers are the smallest of the three castes but they function as the main spring of the complicated machinery like honey bee colony.

It takes 21 days in the development from the egg to the adult and the total life span of a worker is about 6 weeks. The workers are atrophid female which sacrifice themselves for the well- being of the colony. The total indoor and outdoor duties of the colony are performed by the workers only. Apis dorsata is the largest honey bee and A. indica is slightly smaller than it. Bees wax is a byproduct of honey bee and drone of honey bee is haploid in nature.

68. The bacteria generally used for genetic engineering

(a) Agrobacterium

(b) Bacillus

(d) Clostridium.

Answer and Explanation:

68. (a): Agro bacterium tumefaciens is the causative agent of crown gall, an important disease of many commercial crops, such as raspberries. This disease has come to be recognized in recent years as being caused by a DNA plasmid (Ti plasmid) carried by bacterium and transferred to the plant cells.

Following the discovery of the relationship between crown gall and the Ti plasmid, this plasmid has come to be widely used in plant genetic engineering as a vector, novel plant genes being spliced into the plasmid sequence by gene manipulation and thus carried into the host plant cells.

This offers the possibility of recombination between the novel sequence in the plasmid and the plant genomic DNA. Successful recombination would result in integration of the novel sequence into the plant cell genome and expression of the sequence in the life of the cell. This provides the opportunity to develop new and better plant species.

69. A giant rat is formed in the laboratory, what is the reason

(a) gene mutation

(b) gene synthesis

(d) gene replication.

Answer and Explanation:

69. (c): A giant rat is formed in the laboratory, due to gene manipulation. Genetic manipulation refers to the creation of new life forms through deliberate modification of DNA, the material responsible for inherited characteristics. Genetic manipulation of animals has become a lucrative enterprise for the pharmaceutical, biotechnology etc. fields.

70. Plasmid has been used as vector because

(a) it is circular DNA which have capacity to join to eukaryotic DNA

(b) it can move between prokaryotic and eukaryotic cells

(d) it has antibiotic resistance gene.

Answer and Explanation:

70. (a): Plasmids are the extra chromosomal self- replicating, and double stranded closed and circular DNA molecules present in the bacterial cell. Plasmids contain sufficient genetic information’s for their own replication. Plasmids are used as vectors because they can carry a foreign DNA fragment when inserted into it.

71. First cloned animal

(a) dolly sheep

(b) Polly sheep

(d) dog.

Answer and Explanation:

71. (a): “Dolly”, the world’s first mammalian clone has been created from a fully differentiated non- reproductive cell of an adult sheep. It 1995, Ian Wilmot and his team of researchers at Roslin Institute, Edinburgh. Scotland, took udder (a fully differentiated tissue) from six year old sheep, and placed it in special solution that controlled cell cycle of cell division.

The cell was deprived off certain nutria. At the same time an unfertilized egg was obtained from another adult sheep. Its nucleus was carefully removed leaving the intact cytoplasm in egg. The nucleus of udder cell was taken out and transferred into nucleus-free egg.

The newly transplanted nucleus soon became functional according to the new cytoplasm in which it had been artificially transferred. This viable combination underwent cleavage like normal zygote. This so called embryo was then transplanted into the uterus of a third adult sheep (surrogate mother/foster mother) for its further development.

Finally, a normal healthy little lamb, Dolly was born in February, 1996 which was genetically similar to the clone mother from whom nuclear DNA was taken out.

72. Before the European invader which vegetable was absent in India

(a) potato and tomato

(b) shimla mirch and brinjal

(d) bitter gourd.

Answer and Explanation:

72. (a): Potato and tomato are new world crops. Their center of origin is Peru, so they are new world crops. They were brought to India by the European invaders.

73. Which of the following is the pair of biofertilizers?

(a) Azolla and BGA

(b) Nostoc and legume

(d) Salmonella and E. coli.

Answer and Explanation:

73. (a): Refer answer 54

74. Triticale is obtained by crossing wheat with

(a) oat

(b) barley

(d) rye.

Answer and Explanation:

74. (d): Triticale is the first man made crop. It is an artificial allopolyploid derived by crossing wheat (Triticum) with rye (Secale). Triticale is of two types – hexaploid and octaploid triticales. The hexaploid triticale is obtained by crossing tetraploid durum wheat and diploid rye followed by chromosome doubling, and octaploid triticale is obtained by crossing hexaploid bread wheat and diploid rye. Triticale is being used as a forage crop because its grains are wrinkled.

75. Which fish selectively feed on larva of mosquito?

(a) Gambusia

(b) Rohu

(d) Exocoetus.

Answer and Explanation:

75. (a): Gambusia affinis is regarded as a larvicidal fish as it selectively feeds on mosquito larvae. It forms an effective tool for biological control of mosquitoes.

76. Spoilage of oil can be detected by which fatty acid

(a) oleic acid

(b) linolenic acid

(d) erucic acid.

Answer and Explanation:

76. (d): Erucic acid is an unsaturated fatty acid belonging to the oleic acid series, occurring as glycerides in rape seed oil and other vegetable oils. It is the cis- isomer, the trans-isomer being brassidic acid. Erucic acid is used as a binder for oil paints. Its high tolerance to temperature makes it suitable for Tran’s mission oil. It is useful in manufacture of emulsions to coat photographic films and papers. Oleic acid is found in various animal and vegetable sources. It is widely used in industries including textile, chemical, medicine, leather, stationary, paper making etc.

Linolenic acid is used in making soaps, emulsifiers and quick-drying oils, in beauty products. It helps in acne reduction, moisture retention etc. Linoleic acid is an important fatty acid especially for growth and development of infants. Commercially it is used in margarine, animal feeds, soaps and drugs.

77. What is true for monoclonal antibodies?

(a) these antibodies obtained from one parent and for one antigen

(b) these obtained from different parents and for one antigen

(d) these obtained from many parents and for many antigens.

Answer and Explanation:

77. (b): Monoclonal antibody is synthesized and secreted by individual clonal populations of hybrid cells – hybridomas – produced by the fusion of individual lymphocytes from an immunized animal with individual cells from a lymphocytic tumour. Hybridomas comprising each selected clone can thus be propagated and grown in bulk to obtain, from each one, copious amounts of specific and homogeneous antibody.

78. Which of the following cut the DNA from specific places?

(a) E.Coli restriction endonuclease

(b) ligase

(d) alkaline phosphate.

Answer and Explanation:

78. (a): Restriction end nucleases (restriction enzymes) are enzymes that digest double stranded DNA following recognition of specific nucleotide sequence. This is achieved by cleaving the two phosphodiester bonds, one within each strand of the DNA duplex.

79. Maximum number of bases in plasmids discovered so far

(a) 50 kilo base

(b) 500 kilo base

(d) 5 kilo base.

Answer and Explanation:

79. (b): A plasmid is a DNA molecule separate from the chromosomal DNA and capable of autonomous replication. In many cases, it is typically circular and double-stranded. It usually occurs in bacteria, and is sometimes found in eukaryotic organisms. The size of plasmids varies from I to over 400 kilobase pairs (kbp). There may be one copy, for large plasmids, to hundreds of copies of the same plasmid in a single cell. The term plasmid was first introduced by the American molecular biologist Joshua Lederberg in 1952.

80. E. Coli about to replicate was placed in a medium containing radioactive thymidine for five minutes. Then it was made to replicate in a normal medium. This of the following observation shall be correct

(a) both the strands of DNA will be radioactive

(b) one strand radioactive

(d) none is radioactive.

Answer and Explanation:

80. (b): Since the DNA replication is semiconserative so each of the two double helice conserves only one parent strand. So only one strands gets labelled with thymidine it was again shifted to normal medium so only that one strand remained radioactive.

81. At the time of organogenesis genes regulate the process at different levels and at different time due to

(a) promoter

(b) regulator

(d) exon.

Answer and Explanation:

81. (d): At the time of organogenesis genes regulate the process at different levels and at different time due to exon. An exon is any region of DNA within gene that is transcribed to the final messenger RNA (mRNAI molecule, rather than being spliced out from the transcribed RNA molecule. Exons of many eukaryotic genes interleave with segments of non-coding DNA (introns). The term exon was coined by American biochemist Walter Gilbert in 1978.

82. A mutant strain of T4 – Bacteriophage, R-II, fails to lyse the E-Coli but when two strains R-IIX and R-IIY are mixed then they lyse the E. coli. What may be the possible reason?

(a) bacteriophage transforms in wild

(b) it is not mutated

(d) both strains have different cistrons.

Answer and Explanation:

82. (d): A mutant strain of T₄-bacteriophage, RII fails to lyse the E. Coli but when two strains R-ll (X) and R- I1Y are mixed then they lyse the E. Coli because both strains have different cistrons.

83. In Lederberg’s replica plating experiment what shall be used to obtain streptomycin resistant strain

(a) minimal medium and streptomycin

(b) complete medium and streptomycin

(d) only complete medium.

Answer and Explanation:

83. (b): If streptomycin resistant mutant are to be obtained, material should be allowed to grow on medium lacking streptomycin so that both mutant and wild types may grow. These colonies are imprinted on petriplatesto form the master pattern and other plates having streptomycin can then be pressed on velveteen to get an impression. The plate now containing only mutants for streptomycin resistance will grow.

84. Reason of fast speciation in present day crop plants is due to

(a) mutation

(b) isolation

(d) sexual reproduction.

Answer and Explanation:

84. (c): Polyploidy leads to instant speciation by hybridization and doubling of chromosomes. It involves acquiring 3 or more times the haploid number of chromosomes. After hybridisation the plant gets the desired genome and then chromosome doubling gives it viability. It plays a very important role in plant evolution.

85. Which bacteria is utilized in gober gas plant?

(a) methanogens

(b) nitrifying bacteria

(d) denitrifying bacteria.

Answer and Explanation:

85. (a): Methanogens are a type of archaebacteria that occurs in marshes, swamps and rumen of catties. They are obligate anaerobes that can catabolize acetate and H- to gaseous products and are used in the final stage called hanogenesis of biogas production in gobar gas plant, ttrifying bacteria oxidise NH, into N0₂ and later to N0₃ Ammonifying bacteria convert proteins into NH₃ nitrifying bacteria reduce N0₃ into NH₃.

86. During the formation of bread it becomes porous due to release of C0₂ by the action of

(a) yeast

(b) bacteria

(d) protozoans.

Answer and Explanation:

86. (a): Sacharomyces converts starch or sugars to pyruvic acid through EMP pathway. Then this pyruvic acid is converted to acetaldehyde and finally to ethyl alcohol in the absence of oxygen. This entire process is called fermentation.

87. If a diploid cell is treated with colchicine then it becomes

(a) triploid

(b) tetraploid

(d) monoploid.

Answer and Explanation:

87. (b): Colchicine is an alkaloid extracted from seed and corm of Colchicum autumnale. It has the property of esting and breaking the spindle so that a cell division without cell wall formation may be affected leading to doubling of chromosome number. So a diploid cell wills some tetraploid by chromosome doubling.

88. In tissue culture medium, the embryoids formed from pollen grains is due to

(a) cellular totipotency

(b) organogenesis

(d) test tube culture.

Answer:

(a) cellular totipotency

89. Which of the following crops have been brought to India from New world?

(a) cashewnut, potato, rubber

(b) mango, tea

(d) coffee.

Answer and Explanation:

89. (a): New world crops are those which have their center of origin as America. Cashewnut and rubber have their center of origin in Brazil and potato has Peru as its center of origin. All of them have been brought to India from New world.

90. Manipulation of DNA in genetic engineering became possible due to the discovery of

(a) restriction endonuclease

(b) DNA ligase

(d) primase.

Answer and Explanation:

90. (a): DNA restriction endonuciease are important class of restriction exonucleases, class II, which cut double-stranded DNA molecules only at sites characterized by a specific nucleotide sequence. Restriction enzymes are isolated from bacterial cells, and are tools for molecular biologists. Several hundred restriction enzymes are now known, each with a specific sequence requirement dictating where it will cut DNA.

Some, such as Hind III, make staggered cuts leaving ‘sticky ends’ three nucleotides long protruding on one strand from each severed terminus; others make clean cuts in both strands at the same place and thus generate ‘blunt ends’. Digesting DNA with a restriction enzyme therefore creates a characteristic set of fragments, which can be isolated by electrophoresis and subsequently analysed.

91. Which one of the following plants are used as green manure in crop fields and in sandy soils?

(a) Crotalaria juncea and Alhagi camelorum

(b) Calotropis procera and Phyllanlhus niruri

(d) Dichanthium annulatum and Azolla nilotica

Answer and Explanation:

91. (a): Green manures are fast growing herbaceous crops which are ploughed down and mixed with the soil while still green for enrichment of soil. These provide both organic matter and nitrogen to the soil, in which Indian soils are generally poor. The green manure checks soil erosion by forming protective soil cover and also prevents leaching. Increase in yield by 30-50% has been observed by use of green manures. Some important green manure crops, which are mostly members of family Leguminosae, are Alhagi Crotolaria juncea.

92. During anaerobic digestion of organic waste, such as in producing biogas, which one of the following is left undegraded?

(a) lipids

(b) lignin

(d) cellulose

Answer and Explanation:

92. (b): Lignin is a complex polymer of phenylpropane units, which are cross-linked to each other with a variety of different chemical bonds. This complexity has thus far proven as resistant to microbial degradation. Cellulose is a long chain of glucose molecules, linked to one another primarily with glycosidic bonds.

The simplicity of the cellulosic structure, using repeated identical bonds, means that only a small number of enzymes are required to degrade this material. Hemicelluloses are branched polymers of xylose, arabinose, galactose, mannose, and glucose. Hemicelluloses bind bundles of cellulose fibrils to form microfibrils, which enhance the stability of the cell wall but these can be degraded by increasing the number of enzymes.

93. Which one of the following bacteria has found extensive use in genetic engineering work in plants?

(a) Clostridium septicum

(b) Xanthomonas citri

(d) Agrobacterium tumefaciens

Answer and Explanation:

93. (d): Agrobacterium tumefaciens is the causative agent of crown gall, an important disease of many commercial crops, such as raspberries. This disease has come to be recognized in recent years as being caused by a DNA plasmid (Ti plasmid) carried by bacterium and transferred to the plant cells. Following the discovery of the relationship between crown gall and the Ti piasmid, this piasmid has come to be widely used in plant genetic engineering as a vector, novel plant genes being spliced into the host plant cells.

94. Maximum application of animal cell culture technology today is in the production of

(a) insulin

(b) interferons

(d) edible proteins

Answer and Explanation:

94. (c): Maximum application of animal cell culture technology is in the production of vaccines. Vaccines are chemical substances prepared from the proteins of other animals which confer immunity to a particular virus. Some of the vaccines synthesized biologically through genetic engineerring are vaccines for hepatitis B virus, vaccines for rabies .virus, vaccines for polivirus and vaccines for small pox virus etc.

95. In recent years, DNA sequences (nucleotide sequence) of m/DNA and Y chromosomes were considered for the study of human evolution, because

(a) they are small and therefore, easy to study

(b) they are uniparental in origin and do not take part in recombination

(d) they can be studied from the samples of fossil remains

Answer and Explanation:

95. (b): Sequence of both wi/DNA and Y chromosomes are considered for the study of human evolution because they are uniparental in origin. N/fDNA is inherited along with the maternal cytoplasm and Y chromosome is inherited from father. So they do not take part in recombination. In addition, m/DNA has a higher mutation rate then nuclear DNA so that it is more useful for short term evolutionary studies.

96. ELISA is used to detect viruses where the key reagent is

(a) alkaline phosphatase

(b) catalase

(d) RNase

Answer and Explanation:

96. (a): ELISA (enzyme linked immunosorbent assay) screening test is the initial test to diagnose AIDS. The test works by detecting anitibodies/substances or protein which are produced in the blood when virus is present. Alkaline phosphatase and peroxidases are commonly used enzymes as key reagent to perform the ELISA test. These enzymes are used to provide antibody-antigen complex in a specialised ELISA plate or tray.

In ELISA test for detecting a particular antigen, its antibody is buffered and a drop of serum Supernatant of centrifuged blood) poured over it. If the latter contains antigen, it will produce antigen-antifc.xiy complex. A second enzyme labelled antibody is added. It forms enzyme-antigen-antibody complex, if the antigen is present. Substrate is now added. It produces a stain if the antigen is present.

97. The technique of obtaining large number of plantlets by tissue culture method is called

(a) plantlet culture

(b) organ culture

(d) macropropagation.

Answer and Explanation:

97. (c): Micropropagation is the latest method of obtaining a large number of plantlets from plant tissues culture. It i; called micropropagation because of the minute size of the propagules. It involves repeated subcultuie of the explant by changing the medium so as to form a large number of plantlets from that single explant.

98. Dough kept overnight in warm weather becomes soft and spongy because of

(a) absorption of carbon dioxide from atmosphere

(b) fermentation

(d) osmosis.

Answer and Explanation:

98. (b): Refer answer 86.

99. India’s wheat yield revolution in the 1960s was possible primarily due to

(a) hybrid seeds

(b) increased chlorophyll content

(d) quantitative trait mutations.

Answer and Explanation:

99. (d): Sharbati Sonara and Pusa Lerma are the two important varieties of wheat that are responsible for green revolution in India. These are produced by gamma rays treatment of Sonora-24 and Lerma Rojo – 64 which are the Mexican dwarf varieties.

100. The most likely reason for the development of resistance against pesticides in insects damaging a crop is

(a) random mutations

(b) genetic recombination

(d) acquired heritable changes.

Answer and Explanation:

100. (a): Mutations can be beneficial, neutral or harmful for the organism. There are many factors for developing resistance. In a population of insects there may be a few individuals that carry genes for resistance. These genes arise from mutations which are rare. Mostly random mutations are responsible for developing resistance.

101. Which one of the following pairs is not correctly matched?

(a) Streptomyces – Antibiotic

(b) Serratia – Drug addiction

(d) Rhizobium – Biofertilizer.

Answer and Explanation:

101. (b): Serratia marcescnx is considered a harmful human pathogen which has been known to cause urinary tract infections, wound infections, and pneumonia. Serratia bacteria also have many antibiotic resistance properties which may become important if the incidence of Serratia infections dramatically increases.

102. A major component of gobar gas is

(a) ammonia

(b) methane

(d) butane.

Answer and Explanation:

102. (b): Refer answer 39.

103. DNA fingerprinting refer to

(a) molecular analysis of profiles of DNA samples

(b) analysis of DNA samples using imprinting devices

(d) techniques used for identification of fingerprints of individuals.

Answer and Explanation:

103. (a): DNA fingerprinting technique in which the banding pattern of DNA fragments is compared and can be used in many species, including the human, to indicate relatedness. DNA is digested with restriction enzymes, run on an electrophoretic gel, and blots made from the gel. Such blots are then hybridized with radiolabeled probe DNA consisting of cloned sequences of the short interspersed repeat sequences which are common in vertebrate genomes. Autoradiography the provides a distinct banding pattern of DNA fragments containing such DNA sequences.

104. Restriction end nucleases

(a) are present in mammalian cells for degradation of DNA when the cell dies

(b) are used in genetic engineering for ligating two DNA molecules

(d) are synthesized by bacteria as part of their defense mechanism. (2004)

Answer and Explanation:

104. (d): Restriction endonucleasses are enzymes that digest double stranded DNA following recognition of specific nucleotide sequences. This is achieved by cleaving the two phosphodiester bonds, one within each strand of the DNA duplex.

They are found in bacteria and their function in bacteria is to cut up any invading virus as a part of it defense mechanism, thus restirictingthe multiplication of viruses in the bacterial cell. Different species of bacteria produce different restriction endonucleases.

105. The 77 plasmid, is often used for making transgenic plants. The plasmid is found in

(a) Azotobacter

(b) Rhizobium of the roots of leguminous plants

(d) Yeast as a 2 m plasmid.

Answer and Explanation:

105. (c): Refer answer 93.

106. In transgenics, expression of transgene in target tissue is determined by

(a) enhancer

(b) transgene

(d) reporter.

Answer and Explanation:

106. (d): The plants, in which a functional foreign gene has been incorporated by any biotechnological methods that generally is not present in plant, are called transgenic plants. When plant cell are transformed by any of the tranformation methods it is necessary to isolate the transformed cells/tissue.

There are certain selectable markers genes present in vectors that facilitate the selection process. In transformed cells the selectable marker genes or are introduced through vector. There are a number of marker genes which are commonly described as reporter genes screenable genes. Some of the reporter genes which are most commonly used in plant transformation are: cat, Gus, lux, nptll, etc.

107. The most thoroughly studied of the known bacteria- plant interactions is the

(a) cyanobacterial symbiosis with some aquatic ferns

(b) gall formation on certain angiosperms by Agrobacterium

(d) plant growth stimulation by phosphate- solubilising bacteria.

Answer and Explanation:

107. (b): Agrobacterium tumefaciens is the causative agent of crown gall, an important disease of many commercial crops. This disease has come to be recognized in recent years as being caused by a DNA plasmid (Ti plasmid) carried by bacterium and transferred to the plant cells.

Following the discovery of the relationship between crown gall and the Ti plasmid, this plasmid has come to be widely used in plant genetic engineering as a vector, novel plant genes being spliced into the plasmid sequence by gene manupulation and thus carried into the host plant cells.

This offers the possibility of recombination between the novel sequence in the plasmid and the plant geniomic DNA. Successful recombination would result in integration of the novel sequence into the plant cell genome and expression of the sequence in the life of the cell. Since many plants can be grown from single somatic cells into complete plants, this system provides the opportunity to develop new and better plant species. Some such success has already been achieved.

108. Cancer cells are more easily damaged by radiation than normal cells because they are

(a) starved of mutation

(b) undergoing rapid division

(d) non-dividing.

Answer and Explanation:

108. (b): Cancer is large and complex family of malignancies which is the result of a continuous, abnormal and relatively autonomous cell proliferation. It is a disease caused by the loss of control over a cells reproduction capacity. Therefore they are more easily damaged by radiation than normal cells.

109. A major component of gober gas is

(a) ammonia

(b) methane

(d) butane.

Answer and Explanation:

109. (b): A major component of gobar gas is methane. Gobar gas (methane) is generated by the decomposition of organic cow-dung. Gobar gas is 55-65% methane, 30- 35% carbon dioxide, with some hydrogen, nitrogen and other traces. They are so environmentally friendly that they are often subsidized by government grants.

110. Golden rice is a transgenic crop of the future with the following improved trait

(a) insect resistance

(b) high lysine (essential amino acid) content

(d) high vitamin-A content.

Answer and Explanation:

110. (d): Golden rice is a transgenic crop rice with high vitamin A content. It has been developed by transferring beta carotene synthesizing gene into the transgenic rice. Beta carotene is the precursor of vitamin A. This transgenic rice has been crossed with the already adapted varieties of rice to make them grow well in a particular area. It is very useful for the people suffering from vision impairment due to vitamin A deficiency.

111. Three crops that contribute maximum to global food grain production are

(a) wheat, rice and maize

(b) wheat, rice and barley

(d) rice, maize and sorghum.

Answer and Explanation:

111. (a): Most important source of food in the world are cereals. They are a rich source of carbohydrates, present in endosperm which is the edible portion in cereals. Wheat, corn and rice contribute to about two thirds of the total world’s food. Rice alone is the staple food of 60% of world population and more than 50% Indians. Wheat is world’s most widely cultivated crop. Maize is an important kharif crop of India and also contributes to food production.

112. An important step in the manufacture of pulp for paper industry from the woody tissues of plants is the

(a) preparation of pure cellulose by removing lignin

(b) treatment of wood with chemicals that break down cellulose

(d) removal of water from the wood by prolonged heating at approximately 50°C.

Answer and Explanation:

112. (a): Lignin is a complex organic material that together with cellulose forms the woody cell walls of plants. It is chemically stable in wood, but becomes unstable when wood is broken down to make paper. Lignin is susceptible to photochemical deterioration and it breaks down producing acids that are harmful to paper. Therefore the preparation of pure cellulose by removing lignin is an important step in the manufacture of paper pulp in industries.

113. Which of the following is generally used for induced mutagenesis in crop plants?

(a) X-rays

(b) UV (260 nm)

(d) alpha particles.

Answer and Explanation:

113. (c): Gamma rays are produced when an unstable atomic nucleus like cobalt-60 releases energy to gain stability. Sharbati Sonora and Pusa Lerma are the two important varieties of wheat that are produced by gamma rays treatment of Sonora-64 and Lerma Rojo-64 which are Mexican dwarf wheat vareicties.

114. Bacillus thuringiensis (Bt) strains have been used for designing novel

(a) biofertilizers

(b) bio-metallurgical techniques

(d) bioinsecticidal plants.

Answer and Explanation:

114. (d): Bacillus thuringiensis strains have been used for designing bioinsecticidal plants. A gene from this bacteria have insecticidal property which is transferred to cotton plants to produce Bt cotton which is resistant to bollworm insect which is a major pest of cotton. Similarly insects affecting maize; cabbage, Sunflower etc are also controlled by mutant strains of Bacillus thuringiensis bacteria.

These transgenic plants which have resistance to insects are called bionsecticidal plants.

115. The name of Norman Borlaug is associated with

(a) white revolution

(b) green revolution

(d) blue revolution.

Answer and Explanation:

115. (b): Green revolution refers to the increased yield obtained by developing new crop varieties under intensive programme of fertilizers, water and pesticides management. The uses of high yielding varieties of wheat have been responsible for green revolution. Norman E. Borlaug developed Sonara – 64 and Lerma Rojo-64 which were later introduced to India. These were treated with gamma rays to produce Sharbati Sonora and Pusa Lerma that are responsible for Indian green revolution.

116. The world’s highly prized wool yielding ‘Pashmina’ breed is

(a) goat

(b) sheep

(d) Kashmir sheep – Afghan sheep cross.

Answer and Explanation:

116. (a): Pashmina refers to a type of cashmere wool and textiles made from it. This wool comes from a special breed of goat indigenous to high altitudes of the Himalayan mountains. The Himalayan mountain goat, Capra hircus, sheds its winter coat every spring and the fleece is caught on thorn bushes. One goat sheds approximately 3-8 ounces of the fibre.

117. Production of a human protein in bacteria by genetic engineering is possible because

(a) the human chromosome can replicate in bacterial cell

(b) the mechanism of gene regulation is identical in humans and bacteria

(d) the genetic code is universal.

Answer and Explanation:

117. (d): Genetic code may be defined as the sequence of nucleotides in polynucleotide chain which determines the sequence of amino acids in a polypeptide chain. Thus the genetic code is universal. These are no ambiguity regarding genetic code. It means that each codon codes for the same amino acid in all organisms including bacteria, plants and animals.

118. Golden rice is a promising transgenic crop. When released for cultivation, it will help in

(a) producing a petrol-like fuel from rice

(b) alleviation of vitamin A deficiency

(d) herbicide tolerance

Answer and Explanation:

118. (b): Golden rice or miracle rice is rich in Vitamin A or B-carotene and iron. It could only be achieved using genetic engineering because although there is provitamin A in the leaves of rice plants but it is absent in the endosperm which is the edible part of rice.

So the poor people dependent mainly on rice as their daily energy source suffered from vitamin A deficiency. Golden rice proved to be a rich source of vitamin A for the consumers of rice.

119. Crop plants grown in monoculture are

(a) highly prone to pests

(b) low in yield

(d) characterised by poor root system

Answer and Explanation:

119. (a): Monoculture describes systems that have very low diversity. Monoculture is the destruction of a diverse ecosystem and replacement with a single species or crop. It depletes the soil and fruits and vegetables become more susceptible to pests and diseases than those grown in a diverse crop environment, thus requiring larger amount of chemical spray.

120. In maize, hybrid vigour is exploited by

(a) inducing mutations

(b) bombarding the protoplast with DNA

(d) harvesting seeds from the most productive plants

Answer and Explanation:

120. (c): Hybridization or crossing leads to hybrid vigour heterosis. It refers to the superiority of the hybrid over its parents. The changes in the progeny or hybrid can be seen with naked eyes.

Hybrid vigour has been commercially exploited in different commercial crops like maize, sorghum, bajra, tomato, sugar beet. The hybrid vigour is lost after few generations.

121. In order to obtain virus-free plants through tissue culture the best method is

(a) meristem culture

(b) protoplast culture

(d) anther culture

Answer and Explanation:

121. (a): Virus free plants can be developed by using meristem as explant in tissue culture. In systematically infected plants virus concentration decreases as they approached the apical meristem.

It is so because the cells of apical meristem undergo rapid mitotic divisions and virus cannot divide so fast and thus it cannot keep pace with the fast dividing meristmatic cells. So apical meristems are virus free. Morel and Maetin (1952) successfully obtained virus free Dahlia plants through meristem culture of infected plants.

122. Triticale, the first man-made cereal crop, has been obtained by crossing wheat with

(a) barley

(b) rye

(d) sugarcane

Answer and Explanation:

122. (b): Triticale is the first man made cereal or crop, which has been produced by intergeneric hybridization between common wheat (Triticum aestivum) and European rye (Secale cereale) with a view to combine characters of these two parent plants. Triticale is hexaploid, i.e., 2n = 6x = 62 (when tetraploid wheat is used) or octaploid, i.e., 2n = 8x = 56 (when hexaploid wheat is used). Triticale or Triticosecale is not suitable for purpose of bread making due to low glutein content, but it is a good forage crop.

123. Restriction end nuclease

(a) synthesizes DNA

(b) cuts the DNA molecule randomly

(d) restricts the synthesis of DNA inside the nucleus

Answer and Explanation:

123. (c): Restriction endonucleases are protein enzymes that recognize specific nucleotide sequences and cleave both strands of the DNA containing those sequences. Restriction endonucleases provide an anti-viral protection for bacteria by cleaving the DNA of invading bacteriophages.

Restriction endonucleases were discovered during experiments to determine the ability of a bacteriophage (the name given to viruses that infect bacteria) to infect two different laboratory strains of Escherichia coli called strain B and strain K. The enzyme makes two incisions, one through each of the phosphate backbones of the double helix without damaging the bases.

124. A person showing unpredictable moods, outbursts of emotion, quarrelsome behaviour and conflicts with others is suffering from

(a) addictive disorders

(b) schizophrenia

(d) mood disorders

Answer and Explanation:

124. (c): Borderline personality disorder (BPD) is a serious mental illness characterized by pervasive instability in moods, interpersonal relationships, self- image, and behaviour. This instability often disrupts family and work life, long-term planning, and the individual’s sense of self-identity.

Originally thought to be at the “borderline” of psychosis, people with BPD suffer from a disorder of emotion regulation. Schizophrenia is a group of severe mental disorders characterized by disturbances of language and communication; thought disturbances that may involve distortion of reality, misperceptions, delusions and hallucinations; mood changes and withdrawn, regressive, or bizarre behaviour, lasting longer than six months.

A mood disorder is a condition where the prevailing emotional mood is distorted or inappropriate to the circumstances. Addiction is a state of dependence produced by the habitual taking of drugs, alcohol etc.

125. Two microbes found to be very useful in genetic engineering are

(a) crown gall bacterium and Caenorhabditis elegans

(b) Escherichia coli and Agro bacterium tumefaciens

(d) Diplococcus sp. and Pseudomonas sp.

Answer and Explanation:

125. (b): Refer answer 43.

126. Which one of the following is the most suitable medium for culture of Drosophila Melanogasterl?

(a) cow dung

(b) moist bread

(d) ripe banana

Answer and Explanation:

126. (d): Drosophila melanogaster, is also called fruit fly because it is easily available hovering over ripe, mango and banana fruits where it feeds over yeast cells present over the feuit surface. The flies can be reared inside bottles having yeast culture over medium containing cream of wheat molasses and agar. Thus breeding Drosophila is quite cheap. A very suitable culture medium therefore is curshed banana which provides all the necessary nutrients for both the larval as well as adult stages.

127. If you suspect major deficiency of antibodies in a person, to which of the following would you look for confirmatory evidence?

(a) serum globulins

(b) fibrinogen in the plasma

(d) serum albumins.

Answer and Explanation:

127. (a): Serum globulin are globulins occurring in blood serum and containing most of the antibodies of the blood. Serum globulin electrophoresis is a laboratory test that examines specific proteins in the blood called globulins. Globulins are roughly divided into alpha, beta, and gamma globulins.

These can be separated and quantitated in the laboratory by electrophoresis and densitometry. Fibrinogen (also called serum fibrinogen, plasma fibrinogen and factor 1) is a protein produced by the liver. Fibrinogen helps to stop bleeding by helping in the formation of blood clots. Fibrinogen has been shown to be strongly predictive of both mortality and the onset of cardiovascular disease. Haemocytes is any blood or formed element especially in invertebrates.

These are free floating cells within the haemolymph. It plays a role in insect immune responses, e.g. to parasitoid eggs. Serum albumin is the most abundant plasma protein in humans and other mammals.

Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues. Albumin is negatively charged. Low levels of serum albumin occur in people with malnutrition, inflammation, and serious liver and kidney disease.

128. Probiotics are

(a) cancer inducing microbes

(b) new kind of food allergens

Answer and Explanation:

128. (c): Probiotics are dietary supplements containing potentially beneficial bacteria or yeast, with lactic acid bacteria (LAB) as the most common microbes used. LAB have been used in the food industry for many years, because they are able to convert sugars (including lactose) and other carbohydrates into lactic acid.

This not only provides the characteristic sour taste of fermented dairy foods such as yogurt, but acts as a preservative, by lowering the pH and creating fewer opportunities for spoilage organisms to grow. Probiotic bacterial cultures are intended to assist the body’s naturally occurring gut flora to re-establish them. Experiments into the benefits of probiotic therapies suggest a range of potentially beneficial medicinal uses for probiotics, like –

– Managing lactose intolerance

– Prevention of colon cancer

– Cholesterol lowering

– Lowering blood pressure

– Improving immune function and preventing infections

– Reducing inflammation

– Improving mineral absorption

– Prevents harmful bacterial growth under stress

– Irritable bowel syndrome and colitis

129. In cloning of cattle a fertilized egg is taken out of the mother’s womb and

(a) in the eight cell stage, cells are separated and cultured until small embryos are formed

(b) in the eight cell stage the individual cells are separated under electrical field for further development in culture media

(d) the egg is divided into 4 pairs of cells which are implanted into the womb of other cows.

Answer and Explanation:

129. (a): Cloning in animals is more complex, but has been accomplished successfully in sheep and cattle. The first mammal to be cloned experimentally from the body cell of an adult was a sheep (‘Dolly’) born in 1997 after over 200 previous failed attempts.

The nucleus containing DNA was extracted from an udder cell (which had been deprived of nutrients) and inserted into an ’empty’ egg cell (from which the nucleus had been removed) using the technique of nuclear transfer. This reconstituted egg cell was then stimulated to divide by an electric shock and implanted into the uterus of a surrogate mother ewe, who subsequently gave birth to a clone of the original sheep.

130. Ultrasound of how much frequency is beamed into human body for sonography?

(a) 15 – 30 MHz

(b) 1 – 15 MHz

(d) 30 – 45 MHz.

130. (b): Ultrasound uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Medical ultrasonography (sonography) is an ultrasound-based diagnostic imaging technique used to visualize muscles and internal organs, their size, structures and possible pathologies or lesions.

In physics the term “ultrasound” applies to all acoustic energy with a frequency above human hearing (20,000 hertz or 20 kilohertz). Typical diagnostic sonography scanners operate in the frequency range of 2 to 15 megahertz, hundreds of times greater than this limit. The choice of frequency is a trade-off between spatial resolution of the image and imaging depth: lower frequencies produce less resolution but image deeper into the body.

Sonography is effective for imaging soft tissues of the body. Superficial structures such as muscles, tendons, testes, breast and the neonatal brain are imaged at a higher frequency (7-15 MHz), which provides better axial and lateral resolution.

Deeper structures such as liver and kidney are imaged at a lower frequency 1-6 MHz with lower axial and lateral resolution but greater penetration. Medical sonography is used in, for example: cardiology; endocrinology; gastroenterology; gynaecology; obstetrics; ophthalmology; urology; musculoskeletal tendons, muscles nerves; vascular, arteries and veins etc.

131. Compared to a bull a bullock is docile because of

(a) higher levels of cortisone

(b) lower levels of blood testosterone

(d) higher levels of thyroxine.

Answer and Explanation:

131. (b): Compared to a bull a bullock is docile because of lower levels of blood testosterone.

A bullock is a castrated bull. Bulls have castrated to make them more meek and docile. Castration is any action, surgical, chemical, or otherwise, by which a male loses the functions of the testes or a female loses the functions of the ovaries.

Castration is the removal or destruction of one or both testicles and results in sterility, decreased sexual desire, and inhibition of secondary sex characteristics. It is performed for the purpose of improving the quality of meat and decreasing the aggressiveness of farm animals; in pet animals it prevents unwanted mating behaviour, reproduction, and wandering.

132. Which one of the following is a viral disease of poultry?

(a) coryza

(b) new castle disease

(d) salmonellosis.

Answer and Explanation:

132. (b): New castle disease is a highly contagious zoonoic bird disease affecting many domestic and wild avian species. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epidemic on the poultry industries. It is endemic to many countries.

The causal agent, New castle disease virus (NDV), is a negative- sense single-stranded RNA virus. Transmission occurs by exposure to faecal and other excretions from infected brids, and through contact with contaminated feed, water, equipment and clothing. Signs of infection with NDV vary greatly depending on factors such as the strain of virus and the health, age and species of the host. They can include respiratory signs (gasping, coughing), nervous signs (depression, inappetence, drooping wings, paralysis), swelling of the eyes and neck, diarrhoea, rough or thin-shelled aggs and reduced egg production.

133. A genetically engineered micro-organism used successfully in bioremediation of oil spills is a species of

(a) Trichoderma

(b) Xanthomonas

(d) Pseudomonas.

Answer and Explanation:

133. (d): Bioremediation is the process of using living micro-organisms to clean up a contaminated site. Microorganisms do this by removing toxins from materials. They decompose these compounds by using enzymes, specific proteins that control reactions in living cells.

Organisms that produce enzymes capable of degrading petroleum are useful in cleaning up oil spills. Some common ones that break down oil are genetically engineered species of Pseudomonas, and Azotobacter.

Bioremediation accounts for 5 to 10 percent of all pollution treatment and has been used successfully in cleaning up leaking underground gasoline storage tanks. Bioremediation has many applications, from the ordinary garden compost to the removal of selenium and other toxic metals from waste. The best agents for bioremediation are the ones that can break down contaminants without becoming contaminated or harmful themselves.

134. Molecular basis of organ differentiation depends on the modulation in transcription by

(a) ribosome

(b) transcription factor

(d) RNA polymerase.

Answer and Explanation:

134. (d): Molecular basis of organ differentiation depends on the modulation in transcription by RNA polymerase. RNA polymerase catalyse the synthesis of RNA using as template either on existing DNA strand or an RNA strand.

135. Which one of the following is being utilized as a source of biodiesel in the Indian countryside?

(a) beetroot

(b) sugarcane

(d) Euphorbia.

Answer and Explanation:

135. (c): Pongamia, Jatropha, neem simarouba, rapeseed and Mahua are species that yield seeds rich in oil for bio-diesel. Most of these species produce seeds having 32-35% oil content. Of these, Pongamia and Jatropha are emerging as favourites. These species yield about 1800-1900. It’s of oil per hectare. Both the species are drought resistant hardy shrubs. They can easily grow on area of low rainfall and waterlands and do not require tillage.

These plants help in upgrading the quality of the soil besides controlling erosion and desertification. Some of the plants even have medicinal uses. The plants are also not browsed by cattle. They are fast growing and start giving economic yields at the end of fourth year. Also since the fuel blends easily with diesel, there is no need for engine modifications.

136. Which one of the following pairs is wrongly matched?

(a) Yeast – Ethanol

(b) Streptomycetes – Antibiotic

(d) Methanogens – Gobar gas.

Answer and Explanation:

136. (c): Coliform bacteria are a commonly used bacterial indicator of sanitary quality of foods and water. It is not involved in the production of vinegar.

137. In maize, hybrid vigour is exploited by

(a) crossing of two inbred parental lines

(b) harvesting seeds from the most productive plants

(d) bombarding the seeds with DNA

Answer and Explanation:

137. (a): Hybridisation or heterosis is defined as superiority of hybrid over parents. It has been commercially exploited in different commercial crops like maize, sorghum, bajra etc. The main steps include: selection of parents, selfing of parents, emasculation, bagging, crossing of desired and selected parents and finally seed setting and harvesting.

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