Not at all.
Aparently my previous post is completely wrong, newer studies have revealed that XYY's are found at the same level in the general population as they are in prisons. Also, the XYY's have been found to not be overtly aggressive.
Here's a brief synopsis...
"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."
and according to Wikipedia..
"First case
The first published report of a man with a 47,XYY chromosome constitution was by Dr. Avery A. Sandberg, et al. in 1961. It was an incidental finding in a normal 44-year-old, 6 ft. [183 cm] tall man of average intelligence.
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Effects
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Physical traits
XYY syndrome typically causes no unusual physical features or medical problems. Males with this syndrome may be slightly taller than average and are typically a few centimeters taller than their father and siblings.
Skeletal malformations may also accompany XYY syndrome at a higher rate than in the general population. Severe facial acne has occasionally been reported, but dermatologists specializing in acne (Plewig & Kligman, 2000) now doubt the existence of a relationship with XYY. Several other physical characteristics, including large hands and feet, have been associated (although not definitively) with XYY syndrome. Any physical characteristics, however, are usually so slight that they are insufficient evidence to suggest a diagnosis.
Most males with XYY syndrome have normal sexual development and are able to conceive children.
Since there are no distinct physical characteristics, the condition usually is only detected during genetic analysis for other reasons.
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Behavioral characteristics
A fellow editor requested that someone provide references or some sources for the information in this section.
XYY boys have an increased risk of minor speech and motor skill delays and learning disabilities with roughly half requiring some special education intervention. Behavior problems are common, but are not unique to XYY boys and are managed no differently than in XY boys. There have been suggestions of elevated frequency of XYY genotype in inmates and delinquents. A common myth is that the Y Chromosome (male sex chromosome) adds to the aggression and antisocial behavior of people who have this syndrome. No clear evidence exists of it leading to aggression. However, scientists have noticed that an abnormal amount of prison inmates in comparrison to the general population have the XYY chromosome (still some think this is no proof of a link).
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Cause and prevalence
XYY syndrome is not inherited, but usually occurs as a random event during the formation of sperm cells. An error in cell division called nondisjunction can result in sperm cells with an extra copy of the Y chromosome. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra Y chromosome in each of the body's cells. In some cases, the addition of an extra Y chromosome occurs as an accident during cell division in early fetal development.
The incidence of this condition is approximately one in 850 males.
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See also
Turner syndrome
Klinefelter syndrome
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References
Public domain text from NLM Genetics Home Reference: 47,XYY syndrome.
Sandberg, A. A.; Koepf, G. F.; Ishihara, T.; Hauschka, T. S. (August 26, 1961) "An XYY human male". Lancet 2, 488-9.
Milunsky, Jeff M. (2004). Prenatal Diagnosis of Sex Chromosome Abnormalities. In Milunsky, Aubrey (Ed.), Genetic Disorders and the Fetus : Diagnosis, Prevention, and Treatment (5th ed.), pp. 297-340. Baltimore: The Johns Hopkins University Press. ISBN 0801879280.
Allanson, Judith E.; Graham, Gail E. (2002). Sex chromosome abnormalities. In Rimoin, David L.; Connor, J. Michael.; Pyeritz, Reed E.; Korf, Bruce R. (Eds.), Emery and Rimoin's Principles and Practice of Medical Genetics (4th ed.), pp. 1184-1201. London: Churchill-Livingstone. ISBN 0443064342.
Plewig, Gerd; Kligman, Albert M. (2000). Acne and Rosacea (3rd ed.). Berlin: Springer-Verlag. ISBN 3540667512.
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The higher rate of African American incarcerations seems to be due to socio-economic conditions. To suggest otherwise is irresponsible and baseless.