In jacob's syndrome, where did the extra Y chromosome came from?

Question:i can't figure it out..

Best Answer - Chosen by Asker: i can't figure it out..

Actually it is possible for a MALE to have two Y chromosomes, in fact, that is just what Jacob's syndrome is.

But the male with Jacob's syndrome also has an X from the Mother (because she only has two X's). So while normal females are XX and normal males are XY, a person with Jacob's syndrome is typed XYY.

It is very rare and of course both Y chromosomes come from the father. The exact cause of this symdrome though is currently unknown.

It might be from an abnormal something that occured. Which gave the extra chromosome

I really wish people would stop mixing up genealogy with genetics. They are NOT the same thing! Genealogists are not geneticists! Genealogy is a historical body of research of one's ancestors. Genetics is a science related to biology. You posted this question in the wrong category.