An amino acid analysis of the DNA polymerase gene in humans determines that the sequence of the active site is: Val-Gly-Thr-Ser-Cys-Pro. Based on this information, which species below would be considered the most evolutionarily related to humans?

A: Species 1: Gly-Leu-Ser-Thr-Cys-Pro

B: Species 3: Val-Gly-Thr-Ser-Tyr-Pro

C: Species 2: Val-Gly-Phe-Tyr-Asn-Pro

D: Species 4: Leu-Val-Met-Thr-Tyr-Pro

1 answer

B: Species 3: Val-Gly-Thr-Ser-Tyr-Pro

This species has the same first four amino acids in the active site as humans (Val-Gly-Thr-Ser) and only differs by one amino acid (Tyr instead of Cys) which is a conservative substitution. The other species have more differences in their active site sequence.