Which part of a gene is typically non-coding?

• A. Introns.
• B. Exons.
• C. Regulatory regions.
• D. Coding sequences.

Answer: (A)

When a gene is transcribed in a eukaryotic cell, the initial transcript includes both the parts that will code for protein and the parts that won’t. The non-coding portions inside the gene are introns. They’re transcribed into RNA but are removed during RNA splicing before the RNA is translated, so they don’t contribute to the amino acid sequence. Exons are the segments that remain and form the coding sequence that gets translated into protein. Regulatory regions control when, where, and how much the gene is expressed and are typically separate from the gene’s coding sequence, while coding sequences are the exons that actually code for amino acids. So introns are the typical non-coding parts of a gene.