A geneticist is studying a family pedigree for a rare genetic disorder. They observe that the disorder appears in every generation, affects males and females equally, and an affected father always passes the disorder to all of his children. This inheritance pattern is consistent with:
- AMitochondrial inheritance
- BAutosomal dominant inheritance
- CAutosomal recessive inheritance
- DX-linked recessive inheritance
Show answer & explanationAnswer & explanation
Correct answer: B. Autosomal dominant inheritance
Autosomal dominant inheritance is characterized by the disorder appearing in every generation (no skipping), affecting males and females equally, and an affected parent having a 50% chance of passing it to each child. The 'affected father passes to all children' is a key indicator, as it rules out recessive and X-linked patterns, and is consistent with the dominant allele being passed on.
Why the other options are wrong
- A. Mitochondrial inheritance is passed only from mother to all children, not from father.
- C. Autosomal recessive disorders often skip generations and require two copies of the affected allele.
- D. X-linked recessive disorders primarily affect males and affected fathers cannot pass it to sons.
Autosomal Dominant Inheritance
A pattern of inheritance where a single copy of an altered gene on an autosome is sufficient to cause the disorder. Affected individuals typically have at least one affected parent, and the trait appears in every generation, affecting males and females equally.
- Appears in every generation (no skipping).
- Affected individuals have at least one affected parent.
- Males and females are affected equally.
- Affected father transmits to 50% of children on average (or all if homozygous dominant, though rare for disorders).
Memory trick: Dominant: 'Directly' passed, 'Definitely' in every generation.