Penetrance vs. expressivity
In a family, everyone who carries a dominant disease allele has the disorder, but its severity ranges from mild to severe. This shows:
Answer A: explanation for every choice
A
Correct. Everyone with the allele is affected (complete penetrance), but to different degrees (variable expressivity).
B
Incomplete penetrance means some people with the allele show no phenotype.
C
Codominance is two alleles fully expressed in a heterozygote.
D
Imprinting is expression depending on which parent the allele came from.
TakeawayPenetrance: whether the genotype shows. Expressivity: how strongly.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb60.