If a color blind woman marries a normal visioned man, their sons will be:
Correct answer: A. All color blind
- A. All color blind
- B. All normal visioned
- C. One-half color blind and one-half normal
- D. Three-fourths color blind and one-fourth normal
Explanation
Color blindness is a recessive, sex-linked trait carried on the X chromosome. When a color blind woman (XXc) marries a normal-visioned man (XY), each son receives the Xc chromosome from the mother and the Y chromosome from the father. This results in all sons being color blind, as they lack a normal X chromosome to mask the recessive trait. Daughters, however, will be carriers, inheriting one normal X from their father and one Xc from their mother. The incorrect options suggest other outcomes, but based on sex-linked inheritance, all sons will inherit the Xc chromosome from their mother and be color blind.
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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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