Eukaryotic Pre-MRNAs Undergo a Number of Modifications Such as Capping

Question

Eukaryotic pre-mRNAs undergo a number of modifications such as capping at the 5' end. A 5' cap...
A) consists of a modified terminal adenine nucleotide.
B) has a 3'-to-5' linkage between the terminal nucleotide and the 5' end of the pre-mRNA.
C) contains a triphosphate bridge between the terminal base and the 5' end of the pre-mRNA.
D) carries a negative charge in the terminal base due to methylation.
E) is identical for all mRNAs that are transcribed by RNA polymerase II.

Accepted Answer

The cap is a 7-methyl G residue linked to the 5' end of the transcript via a 5'-to-5' triphosphate bridge. Methyl transferase enzymes methylate the terminal guanine base (giving it a positive charge) and sometimes other nucleotides, creating different 5' caps.