What are introns?

• A. Noncoding segments removed during RNA processing
• B. Coding segments
• C. Promoters
• D. Exons

Answer: (A)

Introns are the noncoding segments within a gene that are transcribed into RNA but do not encode protein. In many eukaryotic genes, the DNA sequence consists of exons, which carry the protein-coding information, interspersed with introns, which are intervening sequences. After transcription, the resulting pre-mRNA includes both introns and exons. The spliceosome recognizes the boundaries and removes the introns, joining the exons together to form mature mRNA that can be translated into a protein. While introns are not translated themselves, they can play roles in regulating expression and enabling alternative splicing, which allows a single gene to produce multiple protein variants. Promoters are separate regulatory elements that help initiate transcription, and exons are the coding segments that ultimately become part of the protein.