Genetics & Inheritance MCAT Practice Question
A geneticist analyzes a pedigree showing an autosomal dominant trait affecting multiple family members across generations. An affected heterozygous individual (Aa) has children with an unaffected homozygous individual (aa). Among their four children, two show the trait and two do not. Does this result follow expected Mendelian ratios, and why or why not?
Answer choices
- ANo, because all offspring should show the trait regardless of genotype
- BNo, because dominant traits always produce 3:1 ratios
- CYes, a 1:1 ratio is expected, though small sample sizes can cause deviation from expected ratiosCorrect answer
- DYes, because only affected offspring survive to birth in autosomal dominant crosses
- ENo, because homozygous recessive individuals cannot have affected children
- FNo, because the trait should skip generations in autosomal dominant inheritance patterns
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