In Drosophila, the X-linked echinus eye phenotype disrupts formation of facets and is recessive to wild-type eye. Autosomal recessive traits vestigial wing and ebony body assort independently of one another. Examine the progeny from the three crosses shown below, and identify the genotype of parents in each cross. <image>

Verified step by step guidance

1. span>1. Understand the genetic traits involved: The echinus eye phenotype is X-linked and recessive, while vestigial wing and ebony body are autosomal recessive traits that assort independently.</span
2. span>2. Analyze the progeny from each cross: Look at the phenotypic ratios of the offspring to determine the possible genotypes of the parents. Consider how the X-linked and autosomal traits are inherited.</span
3. span>3. For the X-linked echinus eye trait, remember that males have one X chromosome and females have two. Use this information to deduce the genotypes of the parents based on the presence or absence of the echinus phenotype in male and female offspring.</span
4. span>4. For the autosomal traits (vestigial wing and ebony body), use Mendelian inheritance patterns to determine the genotypes of the parents. Consider the phenotypic ratios of the offspring to infer whether the parents are homozygous or heterozygous for these traits.</span
5. span>5. Combine the information from the X-linked and autosomal traits to construct the most likely genotypes for each parent in the crosses. Ensure that the genotypes are consistent with the observed phenotypes in the progeny.</span

Key Concepts

X-linked Inheritance

X-linked inheritance refers to the pattern of inheritance for genes located on the X chromosome. In Drosophila, traits such as the echinus eye phenotype are determined by alleles on the X chromosome. Since males have one X chromosome, they express X-linked traits more readily, especially if the trait is recessive, as they lack a second X to mask the effect.

Independent Assortment

Independent assortment is a fundamental principle of genetics stating that alleles for different traits segregate independently of one another during gamete formation. In the context of the Drosophila traits mentioned, the autosomal recessive traits vestigial wing and ebony body do not influence each other's inheritance, allowing for a variety of combinations in the progeny.

Genotype and Phenotype

The genotype refers to the genetic constitution of an organism, while the phenotype is the observable expression of that genotype, influenced by both genetics and the environment. Understanding the genotypes of the parent Drosophila in the crosses is crucial for predicting the phenotypes of their offspring, particularly in the context of dominant and recessive traits.