In eukaryotes, the process of processing of primary transcript involves

Options

A. removal of introns
B. capping at 5' end
C. tailing (polyadenylation) at 3' end
D. all of these.

Answer

D

Explanation

(d) : The primary mRNA transcript is longer and localised into the nucleus , where it is also called heterogenous nuclear RNA (hnRNA) or pre-mRNA. At the 5' end of hnRNA, a cap (consisting of 7-emthyl guanosine triphosphate or 7 mG) and a tail of poly A (Adenylate residues) at the 3' end are added. These processes are respectively called as capping and tailing. The cap is a chemically modified molecule of guanosine triphosphate (GTP) . The primary mRNA are made up of two types of segments, non-coding nitrons and the coding exons. The introns are removed by a proces called RNA splicing and the exons are joined in a defined order .