Mendel"s second law/independent assortment: unlinked, or distantly linked segregating gene pairs assort independently at meiosis. Dihybrid cross: cross between two individuals identically heterozygous at two loci, Dihybrid cross synthesized by mendel produced f2 progeny in ratio 9:3:3:1. Ratios of 1:1:1:1 and 9:3:3:1 are diagnostic of independent assortment in one and two dihybrid meiocytes, respectively. The product rule states that the probability of independent events both occurring together is the product of their individual probabilities. The sum rule states that the probability of either of two mutually exclusive events occurring is the sum of their individual probabilities.