Question

The list of events below describes intron removal and splicing during pre-mRNA processing. Please select the choice that lists the events in the correct sequential order.

1.Attachment of snRNP U1 to the 5′ splice site
2.Transcription of the DNA template into the pre-mRNA molecule
3.Release of lariat structure 4. Splicing together of exons 5. Transesterification reaction at the branch point adenine
a) 2, 1, 4, 3, 5
b) 2, 1, 3, 4, 5
c) 1, 2, 3, 4, 5
d) 2, 3, 1, 4, 5
e) 2, 1, 3, 5, 4

Answer 1

In pre-mRNA processing, splicing involves the accurate and precise removal of introns and joining of exons, facilitated by the spliceosome complex. The right order of events is the transcription of DNA into pre-mRNA, the attachment of snRNP to the splice site, transesterification at the branch point, the release of the lariat, and the splicing of exons, making option e) the correct sequence.

Step-by-step explanation:

The process of splicing during pre-mRNA processing in eukaryotic cells is a crucial step that ensures the removal of non-coding sequences (introns) and the correct joining of coding sequences (exons). To achieve this, several steps occur in a specific order: the transcription of DNA into pre-mRNA, the recognition of splice sites by the spliceosome components such as small nuclear ribonucleoproteins (snRNPs), the transesterification reaction at the branch point adenine, the formation of a lariat structure of the intron, the removal of the intron, and finally the ligation of the exons.

The chronological sequence of these events as per the options given would be:

1. Transcription of the DNA template into the pre-mRNA molecule.
2. Attachment of snRNP U1 to the 5′ splice site.
3. Transesterification reaction at the branch point adenine.
4. Release of lariat structure.
5. Splicing together of exons.

Considering this information, the correct option that lists these events in the appropriate sequence is option e) 2, 1, 5, 3, 4.