Expert: K Shows - 11/13/2005

Question
I am currently writing a science research paper on the question "Do XYY chromosomes determine criminal behavior?".  Here are my questions:

What causes sex chromosome trisomy?
How have studies indicated that Super Male Syndrome (XYY) causes aggression?
Also, what are other physical and mental effects of Super Male Syndrome?

Thank you very much!

Answer
Tanya,

Trisomy of single chromosomes, such as in XYY syndrome, is caused by a non-disjunction event during cell division in which the chromosomes do not separate so that only one goes to each daughter cell.  This can happen during mitosis or meiosis, but in the case of a genetic condition that is passed to offspring, it happens during meiosis in the gametes.

Try this link, and scroll down to Figure 5 for a diagram of nondisjunction during meiosis:

http://www.knowledgene.com/public/view.php3?db=gene_school&uid=62

XYY syndrome, also called Jacob syndrome is NOT a "super male syndrome".  This is a misconception in the public caused by a report in the 1960's concerning prison inmates that implied that XYY males were taller and produced more testosterone (although they did not measure this) and were more violent; however, this study has since been dismissed by the scientific community because the study had too much "ascertainment bias"-- this means that the study was flawed because the prison population as a whole is taller and more violent than normal people, and XYY is an extremely common chromosome abnormality along with XXY (Klinefelter syndrome) and XO (Turner syndrome).  When the ratio of prisoners with XYY was compared to the actual ratio of XYY in the general population, it was no different than in prisoners.  In fact, XYY is the only chromosomal abnormality that does not have any symptoms: you may know someone who has this condition, but because they are normal there is no reason to test chromosomes.

The only physical condition that may be associated with XYY is decreased fertility in rare cases in which the gonads do not develop properly.  Mental IQ is normal in most cases.

I am sorry to disprove your paper right off the bat, but this has been discussed at length in many publications.  One that I have sitting on my bookshelf is called "In the Name of Eugenics" by Daniel J. Kevles-- you can find a discussion of the original study that led to the "super male" theory on pgs 276-277.  References that the author used for this section are found on p 373.  These are references to the original papers.

In addition, if you continue with your topic, you may want to change the title to , "Does an extra Y chromosome in males determine criminal behavior?" or something like that.

Good luck on your project.