Question

Question 3: Answer the following questions related to the genetic code.

3.1)If there were 6 different bases, and a codon consisted of 4 bases, how many different codons could be coded for?

3.2)The DNA of an alien species only contains adenine and thymine. However, the genetic code of this species codes for 70 amino acids and 4 stop codons. What is the minimum expected size for a codon of this species? And how many codons would then be possible?

Answer 1

ANSWER 3.1 :-

1. First of all, it should be taken into consideration that there are 6 different bases and the codon is made up of 4 codons.
2. This indicates that there will be total of (6)⁴ = 1296 combinations of codons.

ANSWER 3.2 :-

First of all, it should be taken into consideration that there are only two nucleotides namely Adenine and Thymine and hence in order for them to result in the production of 70 amino acids, there should be more than 70 possible codons and this in turn depends upon the number of nucleotides in the codon.

So, 2⁷= 128 is the only possible result after 2⁶ = 64 which will not be able to encode for 70 amino acids. So, it is already mentioned that 4 codons will not encode for any amino acids and will be considered as stop codons.

So, the minimum expected size of the codon should be 7.

The total number of codons that will be possible are 128 out of which 4 will be considered as stop codon and remaining 124 will be considered as functional codons involved in synthesis of amino acids.