Реферат: Klinefelter Syndrom Essay Research Paper KLINEFELTER SYNDROMETHE
Occasionally, variations of the XXY chromosome count may occur, the most common being the XY/XXY mosaic. In this variation, some of the cells in the male’s body have an additional X chromosome, and the rest have the normal XY chromosome count. The percentage of cells containing the extra chromosome varies from case to case. In some instances, XY/XXY mosaics may have enough normally functioning cells in the testes to allow them to father children.
A few instances of males having two or even three additional X chromosomes have also been reported in the medical literature. In these individuals, the classic features of Klinefelter syndrome may be exaggerated, with low I.Q. or moderate to severe mental retardation also occurring.
In rare instances, an individual may possess both an additional X and an additional Y chromosome. The medical literature describes XXYY males as having slight to moderate mental retardation. They may sometimes be aggressive or even violent. Although they may have a rounded body type and decreased sex drive, experts disagree whether testosterone injections are appropriate for all of them.
One group of researchers reported that after receiving testosterone injections, an XXYY male stopped having violent sexual fantasies and ceased his assaults on teenaged girls. in contrast, Dr. Robinson found that testosterone injections seemed to make an XXYY boy he had been treating more aggressive.
Scientists admit, however, that because these cases are so rare, not much is known about them. Most of the XXYY males who have been studied were referred to treatment because they were violent and got into trouble with the law. It is not known whether XXYY males are inherently aggressive by nature, or whether only a few extreme individuals come to the attention of researchers precisely because they are aggressive
INFERTILITY
The vast majority of XXY males do not produce enough sperm to allow them to become fathers. If these men and their wives wish to become parents, they should seek counseling from their family physician regarding adoption and infertility.
However, no XXY male should automatically assume he is infertile without further testing. In a very small number of cases, XXY males have been able to father children.
In addition, a few individuals who believe themse to be XXY males may actually be XY/XXY mosaics. Along with having cells with the XXY chromosome count, these males may also have cells with the normal XY chromosome count. If the number of XY cells in the testes is great enough, the individual should be able to father children.
Karyotyping, the method traditionally used to identify an individual’s chromosome count, may sometimes fail to identify XY/ XXY mosaics. For this reason, a karyotype should never be used to predict whether an individual will be infertile or not.
Resources
http://www.nih.gov/health/chip/nichd/klinefelter/#xwhat