What is the primary function of exons in mature mRNA?

What is the primary function of exons in mature mRNA?

• A. Exons encode the protein-coding sequence retained in mature mRNA.
• B. Exons are noncoding regions removed during processing.
• C. Exons are promoters.
• D. Exons are introns that have been retained.

Answer: (B)

Exons are the portions of a gene that stay in the mature mRNA after RNA processing and carry the information used to make a protein. In eukaryotic cells, the initial transcript contains both exons and introns. During processing, introns (the noncoding segments) are removed and the exons are spliced together. The result is mature mRNA that contains the coding sequence (and often some untranslated regions) used by the ribosome to translate into protein. So the main role of exons is to provide the protein-coding information that will be expressed; introns are the parts that are removed.

Exons are the portions of a gene that stay in the mature mRNA after RNA processing and carry the information used to make a protein. In eukaryotic cells, the initial transcript contains both exons and introns. During processing, introns (the noncoding segments) are removed and the exons are spliced together. The result is mature mRNA that contains the coding sequence (and often some untranslated regions) used by the ribosome to translate into protein. So the main role of exons is to provide the protein-coding information that will be expressed; introns are the parts that are removed.