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A man with a history of hyperextensible joints and aortic insufficiency presents for a genetic screening. He is discovered to have a homozygous defect in the gene that encodes the glycoprotein fibrillin. What are the chances that his son will have the same disease?

A. 0%
B. 20%
C. 50%
D. 80%
E. 100%

Marfan Syndrome, autosomal dominant, has variable expression, no incomplete penetrance, therefore E.

e??

why not 50%, AD we know only 1 parent having the disease!!!!!!!!!

E is right...since he's homozygous, his son will definitely get a defective gene and manifest..

EE

Thanks samomocos for q&a