Question

Why is DNA replication said to be semi-conservative?

Answer 1

Hint: DNA replication depends on the complementary base pairing. The Meselson- Stahl experiment confirmed the theory that DNA replication is semi- conservative.

Complete step by step answer:
DNA replication is semi-conservative because in the replication process the resulting DNA helix is composed of both a new strand and an old strand. This occurs because of the complementary base pairing, I.e. each nitrogenous base only pairs with its complementary pair. These two strands are identical to the initial double helix. Each strand becomes a template for the synthesis of a new strand.
- DNA replication is the process of duplication of DNA.
- DNA replication to be semi- conservative is confirmed by the Meselson- Stahl experiment in 1958.
- In the semiconservative model of DNA, each strand of DNA serves as a template for the making of a new complementary strand, resulting in two DNA molecules with one old and one new strand.
- Even though three different models of DNA replication were proposed, the semi- conservative one was most popular among scientists of that time. The other two models were named as conservative and dispersive.

- Meselson and Stahl carried out their experiment of DNA replication in E. coli bacteria for many generations.
- Analyzation of DNA from the first four- generation of E. coli confirmed that DNA replication is closest to the semi- conservative model, rather than the other two.
- Though the experiment was conducted on E. coli, the theory of DNA replication being semi- conservative is true universally.

Note: In the semi-conservative process of DNA replication, the resultant DNA helix is composed of both a new and an old strand, and both are identical to the initial helix. The reason for the semiconductive nature of DNA replication is that the nitrogenous bases can only pair with its complementary partner I.e. adenine pair with thymine and cytosine pairs with guanine.