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
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.
Based on the provided amino acid sequences, the species that would be considered the most evolutionarily related to humans is B: Species 3: Val-Gly-Thr-Ser-Tyr-Pro. This is because it has the most similar sequence to the active site of the DNA polymerase gene in humans, differing by only one amino acid (Tyr instead of Cys). The similarity in amino acid sequence indicates a closer evolutionary relationship.
To determine which species is most evolutionarily related to humans based on the amino acid sequence of the active site, we need to compare the sequences and look for similarity.
The active site sequence of the DNA polymerase gene in humans is Val-Gly-Thr-Ser-Cys-Pro.
Now, let's compare this sequence to the options:
A: Species 1: Gly-Leu-Ser-Thr-Cys-Pro
In this sequence, the first amino acid (Val) is replaced with Gly. The other amino acids remain the same, except for Leu, which is not present. Therefore, this option is not as similar to the human sequence.
B: Species 3: Val-Gly-Thr-Ser-Tyr-Pro
This sequence is quite similar to the human sequence, with only one difference: Tyr instead of Cys. However, since there is only one difference, this option is a strong contender for being the most evolutionarily related.
C: Species 2: Val-Gly-Phe-Tyr-Asn-Pro
In this sequence, the third and fourth amino acids (Thr and Ser) are replaced with Phe and Tyr. Again, this option is significantly different from the human sequence.
D: Species 4: Leu-Val-Met-Thr-Tyr-Pro
This sequence is entirely different from the human sequence, with no matching amino acids.
Based on the comparison, option B (Species 3: Val-Gly-Thr-Ser-Tyr-Pro) is the most similar to the human sequence. Therefore, Species 3 would be considered the most evolutionarily related to humans in terms of the DNA polymerase gene's active site amino acid sequence.