In fruit flies, yellow body (y) is recessive to gray body , and the trait of body color is inherited on the X chromosome. Vestigial wing (v) is recessive to full-sized wing (v⁺), and the trait has autosomal inheritance. A cross of a male with yellow body and full wings to a female with gray body and full wings is made. Based on an analysis of the progeny of the cross shown below, determine the genotypes of parental and progeny flies.
[Table below appears at this point containing crosses and results]

Verified step by step guidance

1. Step 1: Identify the inheritance patterns and alleles involved. The yellow body (y) is recessive and located on the X chromosome, while gray body (Y⁺) is dominant. Vestigial wing (v) is recessive and autosomal, with full wing (v⁺) being dominant.
2. Step 2: Determine the genotypes of the parental flies based on the problem statement. The male has yellow body and full wings, so his genotype for body color is X^yY (since males have one X chromosome) and for wings is v⁺v⁺ or v⁺v (we will confirm this later). The female has gray body and full wings, so her genotype for body color is X^Y⁺X^Y⁺ or X^Y⁺X^y (to be determined) and for wings is v⁺v⁺ or v⁺v.
3. Step 3: Analyze the progeny phenotypes and numbers from the table. Notice that the numbers of males and females with each phenotype are roughly equal, suggesting autosomal inheritance for wings and X-linked inheritance for body color. The presence of vestigial wings in both sexes indicates that the vestigial allele is segregating in the parents.
4. Step 4: Use the phenotypic ratios to deduce the genotypes of the parents. For the X-linked body color, since the male parent is yellow (X^yY) and the female is gray, the female must be heterozygous (X^Y⁺X^y) to produce both yellow and gray offspring. For the autosomal wing trait, the presence of vestigial wings in offspring suggests both parents are heterozygous (v⁺v).
5. Step 5: Assign genotypes to the progeny based on the parental genotypes and inheritance patterns. Males inherit their X chromosome from the mother and Y from the father, so their body color depends on the mother's alleles. Females inherit one X from each parent. Wings follow Mendelian autosomal inheritance, so use a Punnett square to determine the expected genotypes and phenotypes of the progeny.

Key Concepts

X-linked Inheritance

X-linked inheritance refers to genes located on the X chromosome, which affects males and females differently due to their sex chromosome composition (XY in males, XX in females). In this case, the yellow body trait is X-linked recessive, meaning males express the trait if they inherit the recessive allele, while females require two copies. Understanding this helps predict phenotypic ratios in progeny.

Autosomal Inheritance

Autosomal inheritance involves genes located on non-sex chromosomes, inherited equally by males and females. The vestigial wing trait is autosomal recessive, so individuals must inherit two recessive alleles to express the trait. This concept is crucial for analyzing the segregation of wing phenotypes independent of sex.

Dihybrid Cross and Phenotypic Ratios

A dihybrid cross examines the inheritance of two traits simultaneously, predicting offspring phenotypes based on parental genotypes. The table shows four phenotypic classes with roughly equal numbers, indicating independent assortment of the X-linked and autosomal traits. Understanding how to interpret these ratios is key to deducing parental and progeny genotypes.