GED Science TestLife ScienceHard
A genetic counselor is explaining the inheritance pattern of a specific trait to a couple. The trait appears in every generation, affects males and females equally, and an affected parent always has at least one affected offspring. This pattern is characteristic of:
- AAutosomal recessive inheritance
- BAutosomal dominant inheritance
- CMitochondrial inheritance
- DX-linked recessive inheritance
Show answer & explanationAnswer & explanation
Correct answer: B. Autosomal dominant inheritance
Autosomal dominant inheritance is characterized by the trait appearing in every generation (no skipping), affecting males and females equally, and an affected individual having at least one affected parent (vertical transmission). If an affected parent always has at least one affected offspring, it further supports this pattern.
Why the other options are wrong
- A. Autosomal recessive traits often skip generations and may not affect males and females equally if penetrance varies.
- C. Mitochondrial inheritance is passed only from mother to all offspring, which doesn't fit the 'males and females equally' and 'affected parent always has at least one affected offspring' from either parent criteria.
- D. X-linked recessive traits typically affect males more frequently than females and can skip generations.
Autosomal Dominant Inheritance
A pattern of inheritance where an affected individual has one copy of a mutant allele and one normal allele on a non-sex chromosome, and the mutant allele is expressed, affecting offspring even if only one parent is affected.
- Trait appears in every generation (vertical transmission)
- Affected individuals have at least one affected parent
- Males and females are affected equally
- Affected heterozygotes transmit trait to ~50% of offspring
- Unaffected individuals do not transmit the trait
Memory trick: Dominant means it shows up, Recessive means it hides.