In Drosophila, gray body color is dominant to ebony body color, while long wings are dominant to vestigial wings. Assuming that the P₁ individuals are homozygous, work the following crosses through the F₂ generation, and determine the genotypic and phenotypic ratios for each generation.
gray, long x ebony, vestigial

Verified step by step guidance

1. Identify the alleles and their dominance relationships: gray body color (G) is dominant to ebony (g), and long wings (L) are dominant to vestigial wings (l). Since the P₁ individuals are homozygous, the gray, long parent is GGLL and the ebony, vestigial parent is ggll.
2. Set up the P₁ cross: GGLL (gray, long) × ggll (ebony, vestigial). Since both parents are homozygous, all F₁ offspring will be heterozygous for both traits (GgLl), showing the dominant phenotypes gray body and long wings.
3. Determine the F₁ genotype and phenotype: All F₁ individuals have the genotype GgLl and display gray body color and long wings because of dominance.
4. Set up the F₁ cross to produce the F₂ generation: Cross GgLl × GgLl. Use a dihybrid Punnett square to find all possible genotype combinations for the two traits.
5. Calculate the genotypic and phenotypic ratios in the F₂ generation by analyzing the Punnett square results. The phenotypic ratio will reflect the dominant and recessive traits' combinations, typically following a 9:3:3:1 ratio for two independently assorting traits.

Key Concepts

Mendelian Inheritance and Dominance

Mendelian inheritance describes how traits are passed from parents to offspring through dominant and recessive alleles. A dominant allele masks the expression of a recessive allele in heterozygotes, resulting in the dominant phenotype. In this question, gray body and long wings are dominant traits, while ebony body and vestigial wings are recessive.

Dihybrid Cross and Independent Assortment

A dihybrid cross involves two traits, each with two alleles, to study how they are inherited together. According to Mendel’s law of independent assortment, alleles of different genes segregate independently during gamete formation, producing a variety of genotype combinations in offspring. This principle helps predict phenotypic and genotypic ratios in the F2 generation.

Genotypic and Phenotypic Ratios

Genotypic ratios describe the frequency of different allele combinations in offspring, while phenotypic ratios describe the frequency of observable traits. Calculating these ratios involves determining all possible allele combinations from the parents and predicting the resulting traits, which is essential for understanding inheritance patterns in the F1 and F2 generations.