Question

During the post transcriptional processing of pre-mRNA, a 5′ cap is added to an mRNA. Arrange the following events in correct order for the capping process.

1. Addition of guanine nucleotide via 5′-5′ bond
2. Removal of a phosphate from a ribonucleotide triphosphate at the 5′ head of pre-mRNA
3. Methylation to the 2′ position of the sugar in the second and the third nucleotide
4. Methylation at the 5′ end and addition of methyl group to the position 7 of the terminal guanine base

a. 1, 2, 3, 4
b. 2, 4, 1, 3
c. 4, 1, 3, 2
d. 2, 1, 4, 3
e. 3, 2, 4, 1

Answer 1

The correct sequence for the 5' capping process of pre-mRNA is: Removal of a phosphate (2), addition of a guanine nucleotide (1), methylation at the 5' end (4), followed by methylation at the 2' sugar position (3).

Step-by-step explanation:

The correct order of events during the 5' capping process of pre-mRNA is the addition of a guanine nucleotide via 5′5′ bond, removal of a phosphate from a ribonucleotide triphosphate at the 5′ head of pre-mRNA, methylation at the 5′ end and addition of a methyl group to the position 7 of the terminal guanine base, and methylation to the 2′ position of the sugar in the second and the third nucleotide. Therefore, the proper sequence of these events is option (d): 2, 1, 4, 3.