During eukaryotic gene expression, a primary RNA transcript undergoes several modifications before becoming a mature mRNA. One crucial step involves the removal of non-coding sequences from this transcript. What is the fate of introns during the process of pre-mRNA splicing in eukaryotes?
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The answer
Correct answer: C. Introns are precisely excised from the primary transcript and then rapidly degraded within the nucleus.
Tested concept: RNA processing and splicing
Explanation
During pre-mRNA splicing, introns, which are non-coding sequences, are precisely removed from the primary RNA transcript by the spliceosome. After excision, these introns are typically degraded in the nucleus and are not part of the mature mRNA. Exons, the coding sequences, are ligated together to form the final mRNA molecule. Distractor 1 is incorrect because introns are not translated into protein; they are removed before translation. Distractor 2 is incorrect because exons are retained and translated, while introns are removed. Distractor 3 is incorrect because introns are removed from the mRNA, not incorporated into it to serve regulatory functions in the cytoplasm.
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