Pedigrees Transitional Reasoning Download PDF

Questions

1. 1.

   A geneticist evaluates a three-generation pedigree of a family affected by a metabolic syndrome linked to mitochondrial energy production. In Generation I, an affected mother and an unaffected father have four children—two daughters and two sons—all of whom display the syndrome. In Generation II, each affected daughter passes the condition to all of her offspring, whereas neither of the affected sons passes the condition to any of their children with unaffected partners. Based on these pedigree observations, which mode of inheritance explains this transmission pattern?

   • A) Autosomal dominant inheritance, because the trait appears in both male and female offspring across multiple consecutive generations.
   • B) Mitochondrial inheritance, because the condition is inherited exclusively through the maternal cytoplasm, affecting all offspring of affected mothers but none from affected fathers.
   • C) X-linked dominant inheritance, because affected mothers transmit the responsible dominant allele located on the sex chromosome to both sons and daughters.
   • D) Y-linked inheritance, because the trait is carried on non-homologous regions of the sex chromosomes and affects all generations.