If a Disease is Caused by a Dominant Allele, It

Question

If a disease is caused by a dominant allele, it means that a person with the disease:
A) will always pass it on to all their children.
B) will pass it on to one-fourth of their children.
C) must be homozygous dominant for the allele.
D) must be heterozygous for the allele.
E) could be either homozygous or heterozygous for the allele.

Accepted Answer

If a disease is caused by a dominant allele, a person with the disease could have one copy of the allele (heterozygous) or two copies (homozygous dominant). Both scenarios would result in the expression of the disease, as only one copy of a dominant allele is needed for its phenotype to be expressed.