If there are 999 bases in an RNA that codes for a protein with 333 amino acids, and the base at position 901 is deleted such that the length of the RNA becomes 998 bases, how many codons will be altered ?
- 1
- 11
- 333
- 33
Answer
(4) 33
Solution
Each codon is a triplet, so 999 bases make 333 codons.
Base 901 lies in codon number 901 + 23 = 301 (codon 301 = bases 901–903).
A deletion shifts the reading frame (frameshift) from that point onwards, so codons 1 to 300 remain unchanged while codons 301 to 333 are altered.
∴ Number of altered codons = 333 - 300 = 33
Answer: (4)