Question

The cap structure of mRNA is of methyl GTP and the tail is of

• A. Methionine
• B. Formylmethionine
• C. Poly A
• D. UAG codon

Answer 1

Answer: (C)

Poly A

mRNA capping refers to addition of 7-methylguanylate at the 5' end of the nascent RNA shortly after RNA polymerase II initiates transcription at the first nucleotide of the first exon of a gene. RNA polymerase II terminates transcription at any one of multiple termination sites downstream from the poly(A) site. The poly(A) site is located at the 3' end of the final exon. After cleavage of the primary transcript at the poly(A) site, a string of adenosine (A) residues is added. Methionine is among standard amino acids and serves as first amino acid of a protein in eukaryotes while formylmethionine serves as first amino acid of a protein in prokaryotes. UAG is a stop codon that specifies termination of translation. Correct option is C.