Which sequences are removed during splicing?

Which sequences are removed during splicing?

• A. Exons
• B. Promoters
• C. UTRs
• D. Introns

Answer: (D)

During RNA processing in eukaryotes, the initial transcript (pre-mRNA) contains coding sequences called exons and intervening noncoding sequences called introns. The spliceosome recognizes intron boundaries and the branch point, removes the intron as a looped structure, and joins the adjacent exons together. This yields mature mRNA that contains only exons, with any untranslated regions (UTRs) still residing within those exons. Promoters, by contrast, are DNA regulatory elements upstream of a gene and are not part of the RNA transcript or its splicing, so they aren’t removed or processed in this step. Thus, introns are the sequences removed during splicing.

During RNA processing in eukaryotes, the initial transcript (pre-mRNA) contains coding sequences called exons and intervening noncoding sequences called introns. The spliceosome recognizes intron boundaries and the branch point, removes the intron as a looped structure, and joins the adjacent exons together. This yields mature mRNA that contains only exons, with any untranslated regions (UTRs) still residing within those exons. Promoters, by contrast, are DNA regulatory elements upstream of a gene and are not part of the RNA transcript or its splicing, so they aren’t removed or processed in this step. Thus, introns are the sequences removed during splicing.