Which end of a new mRNA transcript gets a cap during processing in the nucleus?

a. the top

b. the bottom

c. the 3' end

d. the 5' end

d. the 5' end

Explanation:

Capping is a co-transcriptional modification made to RNA in the nucleus after the first 25-30 nts are incorporated into the nascent transcript, which is synthetized in the 5' - --> 3' direction.

The cap consists of a methylated guanosine nucleotide added to the 5' end of the new mRNA transcript, and is important for several processes, which include:

Protection of the mRNA from the attack of phosphatases and nucleases. Splicing of mRNA in the nucleus. Nuclear export of the mRNA to the cytoplasm. Cap-dependent protein synthesis.