A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance do you suggest for this disease?
Correct answer: B. Sex-linked recessive
- A. Sex-linked dominant
- B. Sex-linked recessive
- C. Sex-limited recessive
- D. Autosomal dominant
Explanation
The correct answer is Sex-linked recessive. In this inheritance pattern, the disease is carried on the X chromosome. Males, having only one X chromosome, will express the disease if they inherit an affected X. Females, with two X chromosomes, can be carriers if only one X is affected, which aligns with the scenario where the sons are affected and daughters are not. The other options are inconsistent with the given information: Sex-linked dominant would mean affected daughters if a parent was affected, Sex-limited recessive would require expression limited to one sex only, and Autosomal dominant would require one affected parent.
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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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