Which gene interaction involves a modifier gene masking the expression of another gene?

The concept of gene interaction where one gene masks the expression of another is known as epistasis. In epistasis, the effect of a gene at one locus hides or modifies the phenotypic expression of a gene at a different locus. This interaction is particularly important in understanding genetic traits and how they manifest in an organism.

For example, consider a scenario in which one gene controls the production of pigments that contribute to color, while another gene may modify how these pigments are expressed. If the modifier gene is dominant and suppresses the pigment production gene, the organism will display a phenotype that reflects the modified expression rather than the expected trait from the unmasked gene.

In contrast, codominance refers to a situation where both alleles in a heterozygote contribute to the phenotype distinctly without one overshadowing the other. Pleiotropy occurs when a single gene influences multiple phenotypic traits, while inversion is a type of chromosomal mutation where a segment of DNA is reversed within the chromosome. Each of these concepts represents a different aspect of genetic influence, but they don't describe the specific mechanism of one gene masking another, which is unique to epistasis.