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Multiple Choice
How do small nuclear RNAs (snRNAs) in the spliceosome initiate the splicing of pre-mRNA?
A
They base-pair with specific sequences at the intron-exon boundaries to guide the spliceosome to the correct splice sites.
B
They transport the pre-mRNA out of the nucleus after splicing.
C
They degrade introns by acting as ribonucleases.
D
They directly catalyze the addition of a 5' cap to the pre-mRNA.
Verified step by step guidance
1
Understand the role of small nuclear RNAs (snRNAs) in the spliceosome. These are RNA molecules that are part of the spliceosome complex, which is responsible for removing introns from pre-mRNA during RNA processing.
Recognize that snRNAs function by base-pairing with specific sequences at the intron-exon boundaries. This helps the spliceosome identify the correct splice sites on the pre-mRNA.
Learn that the spliceosome uses snRNAs to guide the splicing process. The snRNAs help align the pre-mRNA in a way that allows the spliceosome to catalyze the removal of introns and the joining of exons.
Clarify that snRNAs do not transport pre-mRNA out of the nucleus, degrade introns as ribonucleases, or catalyze the addition of a 5' cap. These are separate processes unrelated to the splicing function of snRNAs.
Conclude that the correct mechanism involves snRNAs base-pairing with intron-exon boundary sequences to guide the spliceosome to the correct splice sites, ensuring accurate splicing of pre-mRNA.