Which of the following disorders is caused by a defective recessive allele?

A) Down syndrome
B) neurofibromatosis
C) sickle-cell anemia
D) Turner syndrome

Sickle-Cell Anemia

a genetic blood disorder characterized by red blood cells that assume a sickle shape, leading to various complications including pain and anemia.

Recessive Allele

A version of a gene that does not produce a dominant phenotype when paired with an identical allele; it expresses its effects only in a homozygous state.