GED Science TestLife ScienceHard
A genetic counselor is explaining the inheritance pattern of a specific trait to a couple. She states that if a child inherits just one copy of the affected allele, they will express the trait, regardless of the other allele. This means that the trait appears in every generation and an affected individual has a 50% chance of passing it to each child. Which of the following inheritance patterns is being described?
- AAutosomal recessive
- BAutosomal dominant
- CX-linked recessive
- DX-linked dominant
Show answer & explanationAnswer & explanation
Correct answer: B. Autosomal dominant
Autosomal dominant inheritance is characterized by the expression of the trait with only one copy of the affected allele, its appearance in every generation (vertical transmission), and a 50% chance of transmission from an affected parent to each child.
Why the other options are wrong
- A. Autosomal recessive traits require two copies of the affected allele to be expressed and often skip generations.
- C. X-linked recessive traits primarily affect males and have a distinct inheritance pattern related to the X chromosome, not appearing in every generation from a single affected allele in both sexes.
- D. X-linked dominant traits also appear in every generation, but they have specific patterns of inheritance concerning sex (e.g., affected fathers pass to all daughters, no sons), which is not fully captured by the general '50% chance to each child' statement for both sexes.
Autosomal Dominant Inheritance
A pattern of inheritance where a single copy of an altered gene on a non-sex chromosome is sufficient to cause the trait or disease.
- Trait appears in every generation (vertical transmission).
- Affected individuals have a 50% chance of passing the allele to each child.
- Affects males and females equally.
Memory trick: Dominant is 'D' for 'Direct' transmission, no skipping generations.