CBSE - XII Science - Biology - Molecular Basis of Inheritance
List the crieteria a molecule that can act as a genetic material must fulfill. Which one of the crieteria are best fulfilled by DNA or by RNA thus making one of them a better genetic material than the other ? explain.
Criteria for a molecule to act as the genetic material:
- Replication: The molecule should be able to duplicate its genetic material by faithful replication. This property is shown by both DNA and RNA. Proteins and other molecules present in living being do not exhibit this property.
- Stability: Stability of genetic material should exist. It should not change its structure easily with changed stages of life, age of physiology of living beings. RNA is liable and easily degradable due to presence of 2’—OH group present in each nucleotide. As RNA is catalytic, it has become reactive. Because DNA is more stable than RNA, it is said to be better genetic material. Presence of thymine instead of uracil is another reason which leads to stability of DNA.
- Mutation: Genetic material should be able to undergo mutation and such a change should be stably inherited. Both nucleic acids DNA and RNA have the capacity to mutate. RNA mutates at a faster rate as compared with DNA. Virus with RNA genome show mutation and evolution at a faster rate and thus has shorter life span.
- Genetic expression: RNA expresses easily the characters in the form of proteins. DNA requires RNA for formation of proteins. DNA being more stable is considered better than RNA for storage of genetic information. However, for transmission of genetic characters, RNA gives better results.
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