Question

Assertion : A change in nitrogen base at the third position of a codon causes change in the expression of the codon.
Reason : A codon is mostly read by all the three nitrogen bases.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (D)

According to the Wobble hypothesis, only the first two position of a triplet codon on $mRNA$ have a precise pairing with the bases of the $tRNA$ anticodon. The pairing of the third position bases of the codon may be ambiguous and varies according to the nucleotide present in this position. Thus, a single $tRNA$ type is able to recognise two or more codons differing only in the third base. The same is called wobble position.