Which type of gene interaction occurs when one gene masks or suppresses the expression of another gene at a different locus?

• A. Codominance
• B. Complementation
• C. Incomplete dominance
• D. Epistasis

Answer: (D)

Verified step by step guidance

1. Understand the concept of gene interaction, which occurs when the expression of one gene affects or modifies the expression of another gene at a different locus.
2. Review the definitions of the given options: Codominance (both alleles expressed equally), Complementation (two different genes compensate for each other's mutations), and Incomplete dominance (heterozygote shows intermediate phenotype).
3. Recognize that the key phrase 'one gene masks or suppresses the expression of another gene at a different locus' describes a specific type of gene interaction called epistasis.
4. Recall that epistasis involves one gene (the epistatic gene) overriding or hiding the effect of another gene (the hypostatic gene), which is different from dominance that occurs between alleles at the same locus.
5. Conclude that the correct answer is epistasis because it specifically refers to the masking or suppression of gene expression at a different locus.