Jolie has sickle-cell trait, a temporary, relatively mild form of sickle-cell anemia, but does not have full-blown sickle-cell anemia. Her condition is most likely the result of
A) incomplete dominance between one allele for normal blood cells and one for sickle-shaped cells.
B) two recessive alleles for sickle-shaped cells.
C) a dominant sickle-shaped cell allele and a recessive normal blood cell allele.
D) two dominant alleles for normal blood cells.

Question

Quizplus · Accepted Answer

Sickle-cell trait is an example of incomplete dominance, which means that the heterozygote (a person with one normal allele and one sickle-cell allele) has an intermediate phenotype between the homozygous dominant (normal blood cells) and homozygous recessive (sickle-shaped cells) genotypes. This is why Jolie has a temporary, relatively mild form of sickle-cell anemia. Option B is not possible because having two recessive alleles would result in full-blown sickle-cell anemia. Option C is also not possible because dominant alleles for sickle-shaped cells do not exist. Option D is not possible because having two dominant alleles for normal blood cells would not result in sickle-cell trait.

Jolie Has Sickle-Cell Trait, a Temporary, Relatively Mild Form of Sickle-Cell