In fruit flies, white eyes are produced by a dominant X-linked mutation, with the wild-type being red-eyed. If a white-eyed male is mated with a red-eyed female, what will be the phenotype of the resulting offspring?
Correct answer: D. All the females have white eyes
- A. Half the females will have white eyes
- B. All the males will have white eyes
- C. Half the males will have white eyes
- D. All the females have white eyes
Explanation
As the male has the genotype XwY, with Xw coding for the gene of white eyes. The female, being homozygous recessive would have the genotype XrXr. Crossing them would give us the following Punnett Square;
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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