GGG and GGC Are Codons for the Amino Acid, Glycine

GGG and GGC are codons for the amino acid, glycine. A mutation caused the insertion of a cytosine in place of the guanine during DNA replication. Over many generations the DNA changes so that the frequency of GGC is similar to that of GGG. What is this phenomenon called and what affect does
this mutation have on the population?

A) directional selection; that has resulted in genetic uniformity in the species.
B) a bottleneck effect; decreases the number alleles in the population.
C) stabilizing selection; that reduced genetic diversity within the species.
D) adaptive variation; resulting in reduced genetic diversity in females because the GGC coded for . bright feather color instead of the mottled brown feather color coded for by GGG.
E) neutral variation; the change in genetic code does not cause a change in phenotype therefore there is . no change in reproductive success. This mutation then does not affect the population.