Final answer:
Pre-mRNA is processed in multiple ways before leaving the nucleus, including the addition of a 5' cap, splicing, and 3' polyadenylation. RNA splicing is critical for removing introns and joining exons. The correct answer to the question is A) Splicing, and the sigma subunit of RNA polymerase in bacterial transcription is involved in initiation.
Step-by-step explanation:
Pre-mRNA Processing
Pre-mRNA can be processed in multiple ways by means of splicing. In eukaryotes, pre-mRNA undergoes several modifications before it can leave the nucleus and be translated into a protein. This includes the addition of a 5' cap, splicing to remove introns and ligate exons, and 3' polyadenylation. RNA splicing is particularly important as it allows for the removal of non-coding sequences (introns) and the joining of coding sequences (exons), which can generate multiple protein variants from a single gene through alternative splicing. This processing happens after transcription but before translation, making it a key aspect of post-transcriptional control of gene expression.
The answer to the question about pre-mRNA processing is A) Splicing.
Initiation in Bacterial Transcription
In bacterial transcription, the σ (sigma) subunit of the RNA polymerase is involved in initiation, where it helps the polymerase to recognize the promoter regions on the DNA template and commence transcription. The correct answer is A) initiation.