Asked in Premeth Test 27 — InheritanceModerate

Haemophilia is more commonly seen in human males than in human females because:

Correct answer: B. This disease is due to an X-linked recessive mutation

  • A. A greater proportion of girls die in infancy
  • B. This disease is due to an X-linked recessive mutation
  • C. This disease is due to a Y-linked recessive mutation
  • D. This disease is due to an X-linked dominant mutation

Explanation

Hemophilia is more commonly seen in males than females due to its inheritance pattern as an X-linked recessive disorder. Males have one X chromosome and one Y chromosome, so if they inherit an X chromosome carrying the mutation, they will exhibit the disease because they lack a second X chromosome to mask the effect of the mutation. Females, on the other hand, have two X chromosomes, so they would need to inherit two copies of the mutant allele to express the disease, making it less common among females. Option B accurately describes this inheritance pattern. Options A, C, and D are incorrect as they do not appropriately account for the genetic mechanism behind the prevalence of hemophilia in males.

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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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