The figure shows aligned homologous gene sequences from two species. What is the dominant evolutionary force acting on this gene in these species?
A) positive selection
B) recombination
C) genetic drift
D) purifying selection

Question

The figure shows aligned homologous gene sequences from two species. What is the dominant evolutionary force acting on this gene in these species? 
A) positive selection 
B) recombination 
C) genetic drift 
D) purifying selection

Quizplus · Accepted Answer

The homologous gene sequences in the two species are nearly identical, suggesting that the gene is under purifying selection, which acts to remove deleterious mutations and preserve functional sequences. Recombination can contribute to sequence diversity but is not the dominant force acting on this gene. Genetic drift can lead to random changes in allele frequencies over time but is unlikely to be the dominant force acting on this gene given the high sequence conservation. Positive selection would result in an increase in sequence divergence between the two species, but this is not observed in the aligned gene sequences.

The Figure Shows Aligned Homologous Gene Sequences from Two Species