Are Mutations in the Coding Regions of DNA Primarily Favored

Question

Are mutations in the coding regions of DNA primarily favored or selected against?
A) They are always selected for because they always increase fitness.
B) They are often selected against because they often make the mutated organism less fit.
C) They are generally maintained at a level of 50% throughout a population.
D) Selection does not act on this part of the genome.

Accepted Answer

Mutations in the coding regions of DNA, which affect the amino acid sequence of proteins, are often selected against because they can result in non-functional or deleterious proteins that decrease the fitness of the organism. While some mutations may be beneficial and increase fitness, they are much rarer than deleterious mutations. Therefore, the selective pressure on coding regions is generally to maintain the existing functional protein rather than to generate new variants.