Chapter 13, Problem 7STP

Summary Introduction

Introduction :

The sequence of three nucleotides on DNA or on mRNA is called codon. Each codon matches with a specific amino acid during protein synthesis. Among 64 codes, three codons do not code for any amino acid. Thus these three codons are stop codons or nonsense codons.

Answer to Problem 7STP

Correct answer :

The correct answer is option (D) UAA.

Explanation of Solution

Explanation/justification for the correct answer :

Option (D) UAA codon on the mRNA is a stop or nonsense codon. It does not code for any amino acid. UAG and UGA are two other stop or nonsense codons. Thus, this is the correct answer.

The explanation for the incorrect answer :

Option (A) AUG. AUG codon on the mRNA is the initiation codon which codes for the amino acid methionine.Thus, this is an incorrect option.

Option (B) AUU. AUU is a codon that codes for amino acid isoleucine. Thus, this is an incorrect answer.

Option (C) CAU. CAU codes for the amino acid histidine. Thus, this is an incorrect answer.