Klinefelter syndrome: Difference between revisions
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[[Image:KlinefeltersIMG.jpg|left|250x500px|KlinefeltersIMG.jpg]] | [[Image:KlinefeltersIMG.jpg|left|250x500px|KlinefeltersIMG.jpg]] | ||
The karyotype | The karyotype of a normal human male is 46XY<ref>p176.Passarge E.,2007,Color atlas of genetics. 3rd ed.Ludwigsburg: Thieme.</ref>. If an individual has two or more X [[Chromosome|chromosomes]] then he is said to have Klinefelter syndrome | ||
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Symptoms | == Symptoms == | ||
An individual with Kleinfelter syndrome has a male [[Phenotype|phenotype]], however they also possess a number of traits which are absent in a karyotypically normal male which are symptomatic of the disorder, these include: | An individual with Kleinfelter syndrome has a male [[Phenotype|phenotype]], however they also possess a number of traits which are absent in a karyotypically normal male which are symptomatic of the disorder, these include: | ||
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*Usually tall | *Usually tall | ||
*Small testicles | *Small testicles | ||
*Lack of sexual maturation so individuals are usually sterile | *Lack of sexual maturation so individuals are usually sterile (dont produce sperm) | ||
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Cause | == Cause == | ||
Normally sex chromosomes undergo segregation during [[Meiosis|Meiosis]] in gamete producing cells so each daughter cell contains one sex chromosome. However if this fails to occur gametes can be produced with an abnormal number of sex chromosomes (i.e in the case of Klinefelter syndrome an egg cell is produced with two X chromosomes) this process is called[[ | Normally sex chromosomes undergo segregation during [[Meiosis|Meiosis]] in gamete producing cells so each daughter cell contains one sex chromosome. However if this fails to occur gametes can be produced with an abnormal number of sex chromosomes (i.e in the case of Klinefelter syndrome an egg cell is produced with two X chromosomes) this process is called[[Nondisjunction|nondisjunction]]. If such a gamete is fertilised the resulting offspring will in turn have an abnormal number of sex chromosomes, which in this case causes Klinefelter syndrome, though a number of other genetic disorders exist caused by other sex chromosome abnormalities such as [[Turner syndrome|Turner syndrome]] (45,X). | ||
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Variants | == Variants == | ||
Although 47,XXY is the most common karyotype for individuals with Klinefelter syndrome a number of other aberrant karyotypes can cause Klinefelter syndrome. These include 48,XXXY, 48,XXYY and 49,XXXXY. | Although 47,XXY is the most common karyotype for individuals with Klinefelter syndrome a number of other aberrant karyotypes can cause Klinefelter syndrome. These include 48,XXXY, 48,XXYY and 49,XXXXY. | ||
== References == | |||
Revision as of 01:49, 20 November 2011
The karyotype of a normal human male is 46XY[1]. If an individual has two or more X chromosomes then he is said to have Klinefelter syndrome
Symptoms
An individual with Kleinfelter syndrome has a male phenotype, however they also possess a number of traits which are absent in a karyotypically normal male which are symptomatic of the disorder, these include:
- Reduced body hair growth i.e less chest and armpit hair growth than a normal male with less facial hair growth
- Development of breast tissue
- Usually tall
- Small testicles
- Lack of sexual maturation so individuals are usually sterile (dont produce sperm)
Cause
Normally sex chromosomes undergo segregation during Meiosis in gamete producing cells so each daughter cell contains one sex chromosome. However if this fails to occur gametes can be produced with an abnormal number of sex chromosomes (i.e in the case of Klinefelter syndrome an egg cell is produced with two X chromosomes) this process is callednondisjunction. If such a gamete is fertilised the resulting offspring will in turn have an abnormal number of sex chromosomes, which in this case causes Klinefelter syndrome, though a number of other genetic disorders exist caused by other sex chromosome abnormalities such as Turner syndrome (45,X).
Variants
Although 47,XXY is the most common karyotype for individuals with Klinefelter syndrome a number of other aberrant karyotypes can cause Klinefelter syndrome. These include 48,XXXY, 48,XXYY and 49,XXXXY.
References
- ↑ p176.Passarge E.,2007,Color atlas of genetics. 3rd ed.Ludwigsburg: Thieme.