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 a methyl group to the position 7 of the terminal guanine base
a) 2, 1, 3, 4
b) 2, 1, 4, 3
c) 1, 2, 3, 4
d) 1, 3, 2, 4
e) 1, 3, 4, 2

Answer 1

The correct order for the capping process of pre-mRNA is option b) 2, 1, 4, 3 where a phosphate is removed, guanine nucleotide is added, methylation occurs at the 5' end and guanine base, followed by methylation of the second and third nucleotides.

Step-by-step explanation:

During the post-transcriptional processing of pre-mRNA, specifically in the 5' capping process, the correct order of the events is as follows:

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

Therefore, the correct sequence for the capping process is option b) 2, 1, 4, 3.