Ace the NLN PAX 2025 – Rock Your Nursing Dreams with Confidence!

The relationship described in the question is best represented by epistasis. In this scenario, one gene completely masks or overrides the expression of another gene. This can result in a phenotype that is not reflective of the typical dominance patterns you might expect if both genes were expressing their traits independently.

For example, in the case of coat color in certain animals, one gene may dictate whether pigment is produced at all (the presence of pigment versus no pigment), while another gene determines the type of pigment. If the first gene is recessive and results in no pigment (let's say a Labrador retriever), regardless of the effect of the second gene, the presence of the second gene becomes irrelevant when the first gene is in its recessive form.

In contrast, other concepts like codominance involve both alleles being expressed equally, polygenic inheritance refers to traits controlled by multiple genes affecting a single trait, and incomplete dominance results in a blending effect of the two alleles rather than one completely masking the other. These distinctions clarify the unique nature of epistasis in genetic interactions, making it the correct response to the question about one gene masking the effect of another.