Question

An attached-X female fly, XXY (see the "Insights and Solutions" box), expresses the recessive X-linked white-eye phenotype. It is crossed to a male fly that expresses the X-linked recessive miniature wing phenotype. Determine the outcome of this cross in terms of sex, eye color, and wing size of the offspring.

Short answer

Answer: The offspring's phenotypes will be: 1. Female flies with wild-type eyes and miniature wings. 2. Male flies with white eyes and wild-type wings. 3. Male flies with wild-type eyes and miniature wings.

Step-by-step solution

Write down the genotypes of the parents

The female fly has attached-X chromosomes, with genotype XXY = XX^wY (the superscript "w" indicates the white-eye allele). The male fly has a genotype XY with one miniature wing allele, which can be represented as XmY.

Perform the cross

To find out the possible combinations of alleles in the offspring, we should perform the cross between the female and the male flies. This can be done by creating a Punnett square. We should focus on the possible combinations of X and Y chromosomes first. The Punnett square will look like this: X^w X^w Y Xm X^wXm X^wXm XmY Y X^wY X^wY YY Note that since YY is not a viable genotype for flies, we can ignore this outcome.

Determine the sex, eye color, and wing size of the offspring

Now, we can analyze the resulting genotypes to determine the sex, eye color, and wing size of the offspring. 1. X^wXm: This offspring is female (XX), it will have wild-type eyes (X-linked recessive trait, one dominant allele is enough), and miniature wings (X-linked recessive trait, two recessive alleles required for a female). 2. X^wY: This offspring is male (XY), it will have white eyes (X-linked recessive trait, only one allele required for a male), and wild-type wings (X-linked recessive trait, one dominant allele is enough). 3. XmY: This offspring is male (XY), it will have wild-type eyes (X-linked recessive trait, one dominant allele is enough), and miniature wings (X-linked recessive trait, only one allele required for a male).

Summarize the results

In the offspring of this cross between a female fly with the attached-X condition and a recessive X-linked white-eye phenotype, and a male fly with the X-linked recessive miniature wing phenotype, we can expect the following combinations: 1. Female flies with wild-type eyes and miniature wings. 2. Male flies with white eyes and wild-type wings. 3. Male flies with wild-type eyes and miniature wings.