Question on XY stuff, please help?

Keith Robison robison1 at
Sun Apr 24 19:48:48 EST 1994

gcamp1 at (Geoff Camp) writes:

>Hello bio people,

>I'm sorry if this is not the exact place for this question, but I was
>wondering if someone could answer a simple question...

>I was talking with a group of people about people whose XY chromosomes are
>"screwy," like XXY, etc, and someone recalled hearing about men who were
>for some reason EXTRA-masculine.  That is to say, they were very hairy and
>extremely aggressive, very MALE.  We wondered if it were in ANY way
>possible to get an set of chromosomes that were XYY, or how genetically
>this could happen.  Could someone be XYY, or maybe just Y ?  Thanks in
>advance to anyone who answers!

XYY males exist.  The most obvious explanation is meiotic non-disjunction
in the father.  Studies were published which purported to show a link
between XYY and aggressiveness & criminal behaviour; it is generally
regarded that these studies were poorly conducted and used biased samples.

Most genetics textbooks cover this subject.  Griffiths et al
"An Introduction to Genetic Analysis" is good; a human genetics textbook
might be even better.

Y only is impossible -- many essential genes reside on the X (otherwise,
dosage compensation via Barr bodies would be unnecessary).

Keith Robison
Harvard University
Department of Cellular and Developmental Biology
Department of Genetics / HHMI

krobison at 

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