Semi-Conservative DNA Replication

Semi-Conservative Replication

This was proposed by Watson and Crick in 1953 on the basis of their model of DNA molecule. This is the mostly widely and accepted method of DNA-replication. It occurs in the nucleus of the cell. It requires a supply of free nucleotides which exist singly in nucleoplasm of the cell.It occurs in the following steps:

1)    The DNA molecule unwinds and the two strands are seprated by the breakage of the hydrogen bonds between the bases.

2)    Each strand acts as a template for the synthesis of the new strand.

3)    Nucleotides with the appropriate complementary bases then slot into place opposite the exposed bases on each strand by base pairing, that is A with T and C with G.

4)    Hydrogen bonds between the complementary bases hold them in place. The sugar of one nucleotide is then joined to the phosphate of the next nucleotide to form a new polynucleotide chain.

5)    The result is that two new DNA molecules are formed from a DNA molecule. These processes are dependent on a number of enzymes, including DNA polymerase.

6)    Each new DNA molecule contains one polynucleotide strand and one new strand. In other words, during replication, half of the original DNA molecules is conserved and the complementary half is newly synthesised by base pairing. SO, this method of replication is known as semi-conservative replication.