Models of single-gene inheritance: Punnett squares

Most characteristics are influenced by multiple genes, but some are determined by just one. An individual will inherit two alleles for each gene, the alleles for a gene may be dominant or recessive. A Punnett square models inheritance of alleles showing possible genotypes of offspring as homozygous or heterozygous. Punnett squares are used to predict proportion of genotypes/phenotypes, or probability of occurrence in the offspring. Each instance of sexual reproduction is independent, so does not affect the probability for subsequent offspring.