Having correctly established the F₂ ratio in Problem 18, predict the F₂ ratio of a 'dihybrid' cross involving two independently assorting characteristics (e.g., P₁ = WWWWAAAA x wwwwaaaa).

Verified step by step guidance

1. Identify the two independently assorting characteristics and their alleles. For example, consider the alleles W and w for the first trait, and A and a for the second trait.
2. Determine the genotypes of the parental (P₁) generation. In this case, one parent is homozygous dominant for both traits (WWWWAAAA) and the other is homozygous recessive for both traits (wwwwaaaa).
3. Predict the F₁ generation genotype by crossing the P₁ parents. Since each parent is homozygous, all F₁ offspring will be heterozygous for both traits (WwAa).
4. Set up the F₂ generation by crossing two F₁ individuals (WwAa x WwAa). Use a Punnett square or the product rule to determine the genotypic and phenotypic ratios.
5. Calculate the expected phenotypic ratio for the F₂ generation by considering the independent assortment of each trait. For two traits with dominant and recessive alleles, the classic dihybrid phenotypic ratio is 9:3:3:1, representing the combinations of dominant and recessive phenotypes.

Key Concepts

Dihybrid Cross

A dihybrid cross involves two traits, each with two alleles, crossed between two individuals. It examines how alleles for different genes segregate and combine in offspring, typically resulting in a phenotypic ratio that reflects independent assortment.

Independent Assortment

Independent assortment is Mendel’s principle stating that alleles of different genes segregate independently during gamete formation. This leads to new combinations of traits in offspring, which is key to predicting phenotypic ratios in dihybrid crosses.

F₂ Generation and Phenotypic Ratios

The F₂ generation results from crossing two F₁ individuals. In a dihybrid cross with independent assortment, the typical F₂ phenotypic ratio is 9:3:3:1, representing the distribution of combined traits among offspring.