Which syndrome involves a common sex chromosome defect?

A) Down
B) Turner
C) Marfan
D) Hemophilia

Turner syndrome is caused by an absence of one of the X chromosomes. Down syndrome is caused by trisomy 21, three copies rather than two copies of chromosome 21. Marfan syndrome is a connective tissue disorder inherited in an autosomal dominant pattern. Hemophilia is a disorder of blood coagulation inherited in an X-linked recessive pattern.