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

검증된 단계별 안내

Identify the genotypes of the parents: The attached-X female has two X chromosomes attached together and one Y chromosome (genotype: XXY), and she expresses the recessive white-eye mutation on her X chromosomes. The male has one X chromosome with the recessive miniature-wing mutation and one Y chromosome (genotype: X^m Y).

Determine the possible gametes produced by each parent: The attached-X female produces gametes with the attached X chromosomes together (X^w X^w) or a Y chromosome, while the male produces gametes with either the X chromosome carrying the miniature-wing mutation (X^m) or the Y chromosome.

Set up a Punnett square to combine the female and male gametes: The female gametes are either X^w X^w or Y, and the male gametes are X^m or Y. Cross these to find all possible offspring genotypes.

Analyze the genotype of each offspring to determine their sex and phenotype: Offspring with two X chromosomes (one from each parent) will be female, and those with one X and one Y will be male. Use the presence of recessive alleles on the X chromosomes to determine eye color (white if recessive) and wing size (miniature if recessive).

Summarize the phenotypes of the offspring by sex, eye color, and wing size based on the genotypes obtained from the Punnett square.

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주요 개념

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X-linked Inheritance

X-linked inheritance refers to genes located on the X chromosome. Since males have one X and one Y chromosome, recessive mutations on the X chromosome are expressed in males if present. Females have two X chromosomes, so recessive traits are expressed only if both X chromosomes carry the mutation.

Attached-X Chromosome Configuration

An attached-X female has both X chromosomes physically connected and inherited together as a unit. This affects the segregation of sex chromosomes during meiosis, influencing the sex and genotype of offspring differently than typical XX females.

Phenotypic Expression of Recessive Mutations

Recessive mutations, such as white-eye and miniature-wing, are only phenotypically visible when no dominant allele is present. Understanding which offspring inherit these recessive alleles on the X chromosome helps predict their eye color and wing size.