Question

Human protein X is encoded by human gene X. Gene X consists of 4 exons of 200 bp each, interspersed with introns of 1,000 bp each.
An mRNA cap will be found on ____________.
a. the primary transcript
b. the mRNA
c. at least one of the lariats
d. the poly(A) tail.
e. exon 1
f. all exons
g. some introns

Answer 1

Answer:

a. the primary transcript

Explanation:

The first step in RNAm maturation is the modification of the 5' end of the transcript via the addition of a structure called a cap or 7-methyl guanosine cap. The enzymes responsible for the formation of this cap are recruited to the phosphorylated C-terminal domain after the addition of the first twenty to thirty nucleotides of ARN. The formation of the cap is started by the addition of a GTP molecule oriented inversely to the 5' end nucleotide on RNA. Then methyl groups are added to this G residue and to the ribose forms of one or two nucleotides located on the 5' end. All these reactions take place in the nucleus when the mRNA is found as a primary transcript.