Question

Suppose a gene has three exons, with 570 nucleotides in exon 1, 420 in exon 2, and 810 in exon 3. there is a variant in which exon 2 is also spliced out from the mature mrna. the protein translated from this genetic variant is _______ amino acids long.

Answer 1

Exon one has 570 nucleotides. Exon three has 810 nucleotides. We are not concerned about exon two because it is spliced out in the variant. There are 1380 nucleotides (570+810).  Each amino acid requires three nucleotides. One codon, or three nucleotides, codes for one amino acid. So 1380/3=690 amino acids.