Final answer:
The "dihybrid ratio" explains the outcome of a dihybrid cross involving two traits and is typically represented by a 9:3:3:1 ratio. Mendel's dihybrid experiments with pea plants, such as those for seed color and texture, demonstrated the law of independent assortment and produced predictable phenotypic ratios.
Step-by-step explanation:
The term dihybrid ratio is used to describe the phenotypic ratio resulting from a dihybrid cross, which involves two gene pairs and shows the inheritance patterns of two different traits. In Gregor Mendel's experiments with pea plants, he demonstrated that when crossing two heterozygous pea plants (F1 generation), the F2 generation exhibits phenotypes in a ratio of 9:3:3:1. This ratio is obtained by performing a Punnett square analysis which predicts the likelihood of offspring phenotypes based on the genotypes of their parents. For instance, crossing individuals with heterozygous genotypes for two traits, such as PpYy (heterozygous for purple flower color and yellow pea shape), demonstrates this ratio clearly.
Mendel observed seven traits in pea plants; one of them was seed texture, which can be round or wrinkled. When he crossed true-breeding parents with contrasting traits (yellow and green seeds, with yellow being dominant), all of the F1 offspring exhibited the dominant trait (yellow seeds).
The principles behind Mendel's findings, including the dihybrid ratio, reflect his laws of inheritance, specifically the law of independent assortment. This law states that alleles for different traits segregate independently during the formation of gametes. This is why yellow peas are not always round, and wrinkled peas are not always green—their inheritance patterns are unlinked.