Question

f a protein is coded for by a single gene and this protein has six clearly defined domains, which number of exons below is the gene likely to have? A) 1 B) 5 C) 8 D) 12 E) 14

Answer 1

Answer:

The correct answer is C) 8 exons.

Explanation:

If we assume that each domain matches with an exon, and we have a 6 domain protein (domain= the functional regions of the protein that include the active site), there must be at least 6 exons in the gene. Also, remember that exons include the 5'- and 3'- untranslated regions or UTR. So, assuming that each unstraslated region is equivalent to an exon, there must be at least 8 exons in the gene (6 exon for each domain and one 2 exons for UTR).

Anyway, be careful, because this is a simple exercise where we assume a lot of things. In the real world, the first exon tends to include the 5'-UTR and it is already proved that one exon is not always equivalent to one protein domain.