Texas A&M University (TAMU) ANSC 305 Animal Breeding Exam 1 Practice

The main idea is additive genetic relationship: how much genetic material two individuals share on average due to common ancestry. The additive relationship coefficient (often laid out in the A matrix) represents the probability that a randomly chosen allele from one individual and a randomly chosen allele from another are identical by descent because they came from the same ancestors, averaged over all possible ways genes can segregate. This captures how closely related their additive genetic effects are, which is exactly what the covariance of their additive breeding values depends on. It’s different from dominance relationships (non-additive gene interactions), environmental variance (non-genetic factors), or phenotypic covariance (which mixes genetics with environment). So this option correctly describes the additive genetic relationship.