Genetic Disorders Like Down Syndrome Are Caused by

Genetic disorders like Down syndrome are caused by

A) genes on the X-chromosome; females express this less often than males.
B) a recessive allele, that if passed on by both parents, causes disease.
C) errors in meiosis that cause a gamete to receive an extra chromosome.
D) a dominant allele, that if passed on by one or both parents, causes disease.