What are introns?

What are introns?

• A. Non-coding sequences removed during mRNA processing.
• B. Sequences coding for tRNA.
• C. Protein-coding sequences.
• D. Regions that code for rRNA.

Answer: (A)

Introns are non-coding segments within a gene that are transcribed into RNA but not translated into a protein. In the initial RNA transcript, introns lie between coding portions called exons. The cell’s splicing machinery—the spliceosome—removes these introns and joins the exons together to form mature mRNA, which then carries the instructions to make a protein. This processing step, along with adding a 5' cap and a poly-A tail, prepares the transcript for export and translation. Introns also enable alternative splicing, producing multiple protein variants from a single gene. Sequences that code for tRNA, rRNA, or protein-coding regions describe different kinds of transcripts, so those options aren’t what introns are.

Introns are non-coding segments within a gene that are transcribed into RNA but not translated into a protein. In the initial RNA transcript, introns lie between coding portions called exons. The cell’s splicing machinery—the spliceosome—removes these introns and joins the exons together to form mature mRNA, which then carries the instructions to make a protein. This processing step, along with adding a 5' cap and a poly-A tail, prepares the transcript for export and translation. Introns also enable alternative splicing, producing multiple protein variants from a single gene. Sequences that code for tRNA, rRNA, or protein-coding regions describe different kinds of transcripts, so those options aren’t what introns are.