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During 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.

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The desired criteria in a molecule that can act as genetic material are as follows:

  • It should have the capability of replication.
  • It should be chemically and structurally stable.
  • It should be able to incorporate slow changes (mutation) which are required for evolution.
  • It should be able to express itself in the form of Mendelian characters.

Biochemistry of DNA and RNA:

  • Both DNA and RNA show complementarity of base pairs and hence are capable of replication.
  • As shown by Griffith's experiment, DNA is more stable than RNA because it can survive even heat-killing during the experiment.
  • 2'-011 group is present in RNA. This makes RNA labile and degradable, which is not the case with DNA.
  • Both RNA and DNA can carry on mutations. But DNA being more stable is better suited for the long-term storage of mutations.

Hence, DNA was preferred as the genetic material during evolution.

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