Red-green color-blindness is an X-linked recessive disorder. Jacob's paternal grandfather and father are both color-blind, but his mother has two normal alleles. What is the probability that Jacob is red-green color-blind?
Correct answer: A. 0%
- A. 0%
- B. 25%
- C. 50%
- D. 75%
Explanation
In humans, red-green color-blindness is an X-linked recessive trait. Males (XY) will be color-blind if the gene is present on only their single X chromosome. Therefore a color-blind boy can't receive a color-blind gene from his father, even if his father is color-blind because his father can only pass an X chromosome to his daughters.
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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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