A normal woman, whose father was red-blind, marries a red-blind man, what proportion of their children can have normal color vision?
Correct answer: D. 50%
- A. 100%
- B. 33%
- C. 25%
- D. 50%
Explanation
The proportion of children with normal color vision is 50%. Color blindness is an X-linked recessive trait, which means that it is carried on the X chromosome and only expressed in males. Females need to have two copies of the mutated gene to be color blind, while males only need one copy. In this case, the woman is normal, but her father is colorblind. This means that she is a carrier of the colorblind gene. When she marries a colorblind man, one of their daughters will be a carrier the other will be colorblind, and one of their sons will be colorblind.
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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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