Question

During the course of evolution why DNA was chosen over RNA as genetic material? Give reasons by first discussing the desired criteria in a molecule that can act as genetic material and in the light of biochemical differences between DNA and RNA.

Answer 1

A molecule that can act as a genetic material must fulfill the following

1. It should be able to generate its replica (replication).
2. It should chemically and structurally be stable.
3. It should provide the scope for slow changes (mutation) that are required for evolution.
4. It should be able to express itself in the from of Mendelian.

Biochemical differences between DNA and RNA

1. Both nucleic acid (DNA and RNA) are able to direct their duplication proteins fails for the first criteria.
2. RNA is reactive, it also acts are catalyst, hence DNA is less reactive and structurally more stable then RNA.
3. Presence of thymine at the place of uracil also confers additional stability to DNA.