Final answer:
A homozygous dominant AA crossed with a homozygous recessive aa results in all Aa offspring in the F1 generation, expressing the dominant phenotype. An F2 generation from Aa x Aa crosses leads to a genotypic ratio of 1:2:1 and a phenotypic ratio of 3:1, with dominant traits appearing three times as often as recessive ones. A Punnett square can be used to visualize these genetic outcomes.
Step-by-step explanation:
When considering a cross between two homozygous parents, one with dominant alleles (AA) and the other with recessive alleles (aa), Mendelian inheritance principles can be applied to predict the outcomes of future generations. The offspring of the P generation (AA x aa) will inherit one dominant allele and one recessive allele, resulting in a genotype of Aa. Therefore, all the offspring (F1 generation) will express the dominant phenotype, which gives a probability of 100 percent.
In the F2 generation, resulting from an Aa x Aa cross, the gametes produced by the parents will be 50 percent A and 50 percent a. Following Mendel's principle of random segregation, the resulting combinations lead to a genotypic ratio of 1:2:1 (AA: Aa: aa). However, since AA and Aa exhibit the dominant phenotype, we see a phenotypic ratio of 3:1 for the dominant to recessive phenotype.
The use of a Punnett square can illustrate and predict the possible genotypic outcomes of these genetic crosses, given the randomness of segregation and fertilization. Thus, Mendelian genetics helps us understand how dominant and recessive traits are passed down to offspring, providing a foundation for classical genetics and inheritance patterns.