Question

If the number of amino acid in a polypeptide chain is $100$, what will be the number of nucleotides in its cistron?

• A. $100$
• B. $300$
• C. $400$
• D. $200$

Answer 1

The correct option is B $300$

Cistron defined as the functional unit of the DNA or RNA molecule or alternatively called a gene. To code 100 amino acids 100 codons are required along with one starting codon and a stop codon. The code is triplet i.e. consisting of three nucleotides. Thus, the number of nucleotides for 100 codons will be (100X3 =300). If the number of amino acids in a polypeptide chain is 100, then the number of nucleotides in its cistron will be 300 (along with starting codon and stop codon).

So, the correct answer is option B.