The coding portions of a gene that are joined together during mRNA processing are called:

• A. promoters
• B. enhancers
• C. introns
• D. exons

Answer: (D)

Verified step by step guidance

1. Understand the structure of a gene, which includes coding and non-coding regions. The coding regions are the parts that actually code for proteins.
2. Recognize that during mRNA processing, the initial RNA transcript (pre-mRNA) contains both introns (non-coding regions) and exons (coding regions).
3. Know that introns are removed through a process called splicing, and the exons are joined together to form the mature mRNA.
4. Identify that promoters and enhancers are regulatory DNA sequences, not parts of the mRNA or coding regions.
5. Conclude that the coding portions of a gene that are joined together during mRNA processing are called exons.