Question

Exons are parts of genes that:

a. are present in the mature mRNA.
b. contain protein coding sequences of a gene.
c. sometimes can be spliced out of a functional mRNA.
d. often encode entire protein domains
e. all of the above

Answer 1

Exons are the segments of a gene that are included in the mature mRNA and code for proteins. They remain after the introns are spliced out from the pre-mRNA. The presence and proper combination of exons in mRNA are essential for synthesizing functional proteins.

Step-by-step explanation:

Exons are parts of genes that:

1. Are present in the mature mRNA.
2. Contain protein coding sequences of a gene.
3. Sometimes can be spliced out of a functional mRNA.
4. Often encode entire protein domains.

In eukaryotic cells, genes are composed of exons and introns. Exons correspond to the parts of a gene that are expressed and are kept in the final processed mRNA that leaves the nucleus to be translated into proteins. Introns, on the other hand, are intervening sequences that do not encode for functional proteins and are removed from the pre-mRNA during splicing. This splicing process is imperative for creating a functional mRNA that can correctly code for proteins. The mature mRNA, which exclusively contains exons, is then translated into a protein. Sometimes, a process known as alternative splicing occurs, where different combinations of exons are assembled, allowing for the generation of diverse protein variants from a single gene.