Kearns-Sayre Syndrome is caused by a mutation on a gene in the mitochondrial [my-tuh-KON-dree-uh] DNA. Both males and females can have the disease, but the disease can only be transmitted to a child by the mother, never the father. Why is this so?

W) The gene is on the X chromosome, and females are XX

X) The sperm that fertilizes the egg contributes only its chromosomes and none of its mitochondria

Y) The mutant protein is only active in the egg, not the sperm

Z) The disease is sex-limited
X) THE SPERM THAT FERTILIZES THE EGG ONLY CONTRIBUTES ITS CHROMOSOMES AND NONE OF ITS MITOCHONRIA