Three different types of replication have been proposed at the molecular level for DNA; these are – Semi conservative, Conservative and Dispersive.
1. Semi conservative:
In this model of replication the DNA helix unwinds but there is no rupture of a separated polynucleotide strands.
ADVERTISEMENTS:
Thus the primary helices of DNA are not completely changed. According to this mechanism the unwinding of the original strand would be followed by the synthesis of complementary strands for each of the two separated original polynucleotide strands.
This mechanism was proposed by Crick and Watson the discoverers of the molecular structure of DNA. In this method of replication, after replication of the original molecule, two molecules of DNA are formed.
Image Source: eskipaper.com
Each one will have one parental strand and °ne newly synthesized strand. Thus in the semi conservative process, after replication the molecules of the next generation can be regarded as hybrids.
The mechanism is called semi conservative because of the two strands of the parental molecule only one strand remains in the molecule whereas the other goes to another molecule.
2. Conservative:
ADVERTISEMENTS:
In this mechanism the original molecule is completely conserved and thus form a part of the second generation molecule.
Both the strands of the parental helix will synthesis an entirely new molecule the new molecule synthesized would have both of its strands produced newly.
After one generation of application 50% of the molecules will be parental and 50% newly produced molecules.
This is called conservative because the original combination of both the parental strands will remain together and will not be separated.
3. Dispersive:
ADVERTISEMENTS:
In this method of replication the parental DNA helix breaks up at several points forming many fragments. Each fragment of the helix would replicate and recombine at random to produce two daughter molecules of DNA.
This is called dispersive because the original combination of the strands is completely disturbed as they get fragmented into bits.