What is the risk of a color-blind baby boy in a family when the mother is color-blind but the father is normal?
Correct answer: D. 100%
- A. 25%
- B. 50%
- C. 75%
- D. 100%
Explanation
Color blindness is a sex-linked genetic disorder carried on the X chromosome. Females have two X chromosomes, while males have one X and one Y chromosome. In this scenario, the mother is color blind, which means she has one X chromosome with the color blindness allele. The father is normal, which means he has one X chromosome without the color blindness allele and one Y chromosome. Therefore, the father cannot pass on the color blindness allele to his son, but the mother can pass on the color blindness allele to her son. Since the son only has one X chromosome, he will express the color blindness phenotype if he inherits the color blindness allele from his mother. Therefore, the risk of a color-blind baby boy in this family is 100%.
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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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