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If the homozygous white-eyed Drosophila female is crossed with red-eyed Drosophila male, what is the probability of the male offspring having white colour eyes:

Correct answer: D. 100%

  • A. 0%
  • B. 25%
  • C. 50%
  • D. 100%

Explanation

After crossing between white-eyed female (XWXW) with red-eyed male (X+Y), in the F1 generation, all the females flies were red-eyed and all the male flies were white-eyed. This result obtained is not the same as expected from the normal Mendelian ratio. This shows that the pattern of inheritance of eye color is dependent on X-chromosome. Therefore, it was concluded that the gene for eye color is located on the X-chromosome.

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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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