Question

Capping of RNA is necessary as_______

(a) It helps us distinguish 5’ from 3’ end

(b) It has a rolling action and condenses the transcript as it is produced

(c) To protect the transcript from exonuclease

(d) To prevent the transcript from sticking to DNA

This question was addressed to me in homework.

This intriguing question comes from Transcription in Prokaryotes : Elongation in section Gene Expression : Transcription Prokaryotes of Cytogenetics

Answer 1

The correct answer is (c) To protect the transcript from exonuclease

Explanation: There are several free exonuclease in the nucleus and the 5’ cap protects the mRNA from them. In its absence, valuable information will be lost from the transcript and abnormal proteins would result after translation. RNA normally font stick to DNA and absence of ATPase activity rules out 2^nd option.