Final answer:
We predict the ratios of offspring's traits using Mendelian genetics, where a single trait cross between heterozygous parents yields a 3:1 phenotypic ratio. With two traits, a dihybrid cross typically shows a 9:3:3:1 phenotypic ratio. These predictions assume large sample sizes to mitigate the influence of chance.
Step-by-step explanation:
We can model and predict the ratios of traits in the offspring of parents with two different versions of a trait by using principles discovered by Gregor Mendel. For a single trait, Mendel found that if both parents are heterozygous (carrying two different alleles for a trait, such as Yy for seed color), the offspring genotype ratios are expected to be 1 YY: 2 Yy: 1 yy, which leads to a phenotypic ratio of approximately 3 yellow seeds to 1 green seed. This is because yellow is the dominant trait.
For traits that exhibit continuous variation, the offspring appear as a blend of the parent's traits. However, in Mendelian genetics, traits segregate in specific ratios, not as blends. In dihybrid crosses, where two traits are analyzed, the phenotypic ratio can be more complex. For example, crossing two individuals heterozygous for two traits (TtIi × TtIi) will result in a phenotypic ratio of 9 tall/inflated: 3 tall/constricted: 3 dwarf/inflated: 1 dwarf/constricted. This is derived from Mendelian principles of independent assortment and dominance, with the dihybrid phenotypic ratio systematically collapsed into two separate 3:1 monohybrid ratios.
It is important to understand that these are statistical predictions and real-life genetics can show variation from these expected values due to chance, especially in small sample sizes.