What term describes when a disease can be caused by mutations in two or more different genes?

• A. Phenotypic heterogeneity
• B. Locus heterogeneity
• C. Genetic heterogeneity
• D. Allelic heterogeneity

Answer: (B)

The term that describes when a disease can be caused by mutations in two or more different genes is locus heterogeneity. This phenomenon occurs when mutations at different loci (positions on chromosomes) lead to the same clinical phenotype or disease. This is significant in genetics because it implies that various genetic pathways can disrupt normal function and result in similar outcomes.

For instance, if a particular condition can arise due to mutations in either of two distinct genes, both affecting cellular function but in different ways, those diseases would demonstrate locus heterogeneity. Recognizing this can help in understanding the genetic basis of diseases and in developing targeted therapies or diagnostics.

Other terms like phenotypic heterogeneity refer to different phenotypes resulting from mutations in the same gene, while genetic heterogeneity can include both loci and alleles contributing to the same disease. Allelic heterogeneity pertains specifically to different mutations within the same gene causing a similar disease phenotype. Each of these concepts highlights a different aspect of genetic variability, but for the specific scenario of mutations across different genes, locus heterogeneity is the most accurate term.