If 4 types of nitrogen bases are present in nucleic acid,genetic code ...
Possible Number of Base Substitutions in Total Codon
Explanation:
The genetic code is made up of pentaplets or codons, each of which contains three nitrogenous bases. There are four types of nitrogen bases present in nucleic acid: adenine, guanine, cytosine, and thymine. Therefore, the total number of possible codons is 4^3 or 64.
However, some of these codons code for the same amino acid. For example, both UCU and AGU code for serine. Therefore, the number of different codons is actually only 61.
If a single base substitution occurs in a codon, it can lead to a different amino acid being coded for. There are three possible base substitutions that can occur in a codon: a transition (a purine base is replaced by another purine, or a pyrimidine base is replaced by another pyrimidine), a transversion (a purine base is replaced by a pyrimidine, or vice versa), or a silent mutation (a base substitution that does not change the amino acid that is coded for).
Therefore, the total number of possible base substitutions in a codon is:
3 x (3 + 12 + 36) = 3 x 51 = 153
Since there are 61 different codons, the total number of possible base substitutions in a codon is:
61 x 153 = 9312
Therefore, the possible number of base substitutions in a total codon is 9312.
Answer: (b) 960
If 4 types of nitrogen bases are present in nucleic acid,genetic code ...
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