ASCP Specialist in Blood Banking (SBB) Practice Exam

The scenario described indicates an inheritance pattern where both a son and a daughter in one generation have an inherited genetic disorder, but this condition is not present in the subsequent generation (the grandchildren). This can be analyzed through the lens of autosomal recessive inheritance.

In autosomal recessive inheritance, a child must inherit two copies of the mutated gene (one from each parent) to express the disorder. If both parents are carriers, they can pass the gene to their children, resulting in an affected child. However, if the parents do not carry the gene or if it skips a generation, it is not unusual for their children (the grandchildren) to show no signs of the disorder. This explains why the grandchildren do not exhibit the inherited condition even though their parents (the son and daughter) do.

In contrast, other inheritance patterns would typically present differently in this scenario. For example, in autosomal dominant inheritance, the condition would likely show up in every generation, as one affected parent can pass the trait to approximately half of their offspring. For sex-linked dominant inheritance, affected males can pass the trait to all daughters but none to sons, which does not match the results observed in this family study. Non-paternity, or questioning the biological relationship of the