Question

How many initiations codons termination codons are present in a lac mRNA

• A. $3$ and $2$
• B. $3$ and $3$
• C. $2$ and $3$
• D. $2$ and $4$

Answer 1

Answer: (A)

$3$ and $2$

• Triplet codons, meant for the starting of formation of polypeptide chains are called initiation codons and triplet codons meant for stopping of polypeptide chain formation are called termination codons.
• In the lac operon, 3 structural genes Z, Y and A are present. They produce 3 types of polypeptide chains. For the formation of one polypeptide chain one initiation codon and one initiation codon is required. So in the lac operon, 3 initiation codons and 3 termination codons are required.

So, the correct option is ‘3 and 3’.