Klinefelter syndrome

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[[Image:KlinefeltersIMG.jpg|left|250x500px|KlinefeltersIMG.jpg]]  
 
[[Image:KlinefeltersIMG.jpg|left|250x500px|KlinefeltersIMG.jpg]]  
  
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<ref>National Centre for Biotechnology Information, 2011,Pub Med (online)Available at ;http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001420/[accessed 19th November 2011]</ref><br>
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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<ref>National Centre for Biotechnology Information, 2011, PubMed (online)Available at ;http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001420/[accessed 19th November 2011]</ref>.
  
 
== Symptoms  ==
 
== Symptoms  ==
  
An individual with Kleinfelter syndrome has a male [[Phenotype|phenotype]]&nbsp;<ref>p269,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett</ref>, however they also possess a number of traits which are absent in a [[Karyotypical|karyotypically]] normal male which are symptomatic of the disorder.
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An individual with Kleinfelter syndrome has a male [[Phenotype|phenotype]]<ref>p269,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London, Jones and Bartlett</ref>, however, they also possess a number of traits which are absent in a [[Karyotypical|karyotypically]] normal male which is symptomatic of the disorder.  
  
 
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Physical signs include:  
 
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Physical signs include:
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*Reduced body hair growth i.e less chest and armpit hair growth than a normal male with less facial hair growth  
 
*Reduced body hair growth i.e less chest and armpit hair growth than a normal male with less facial hair growth  
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*Lack of sexual maturation, so individuals are usually sterile (do not produce sperm)
 
*Lack of sexual maturation, so individuals are usually sterile (do not produce sperm)
  
<ref>National Centre for Biotechnology Information, 2011,Pub Med (online)Available at ;http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001420/ [accessed 19th November 2011]</ref><ref>Image of Klinefelter suffer taken from Andrology Australia, November 2005.Available at &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;http://www.andrologyaustralia.org/pageContent.asp?pageCode=KLINEFELTERSSYNDROME#WHATARETHEEFFECTSOFK&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; [accessed 19 November 2011]</ref>  
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<ref>National Centre for Biotechnology Information, 2011,Pub Med (online)Available at ;http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001420/ [accessed 19th November 2011]</ref><ref>Image of Klinefelter suffer taken from Andrology Australia, November 2005.Available at http://www.andrologyaustralia.org/pageContent.asp?pageCode=KLINEFELTERSSYNDROME#WHATARETHEEFFECTSOFK; [accessed 19 November 2011]</ref>.
  
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Behavioural signs in developing boys include:
  
 
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*Quietness  
Behavioural signs in developing boys include:
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*Lacking in self-confidence  
 
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*Anxious or restless  
*Quietness
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*More complacent than other children  
*Lacking in self-confidence
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*Anxious or restless
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*More complacent than other children
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*Less physically active
 
*Less physically active
  
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Learning and language signs:
  
 
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*Slow language development where there is a delay in learning to talk  
Learning and language signs:
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*Problems communicating their wants and requirements  
 
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*Reading dfficulties, and often leading to difficult reading comprehension  
*Slow language development where there is a delay in learning to talk
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*Issues with processing what they hear - which can lead to fidgeting or 'tuning out'. This may be made worse by noisy settings, whereby they may have extreme difficulty to concentrate<ref>What are common symptoms of Klinefelter syndrome (Ks)?.(2016) https://www.nichd.nih.gov/health/topics/klinefelter/conditioninfo/symptoms (Last accessed: 12/1/16)</ref>.
*Problems communicating their wants and requirements&nbsp;
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*Reading dfficulties, and often leading to difficult reading comprehension
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*Issues with processing what they hear - which can lead to fidgeting or 'tuning out'. This may be made worse by noisy settings, whereby they may have extreme difficulty to concentrate.<ref>What are common symptoms of Klinefelter syndrome (Ks)?.(2016) https://www.nichd.nih.gov/health/topics/klinefelter/conditioninfo/symptoms (Last accessed: 12/1/16)</ref>
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== Cause  ==
 
== Cause  ==
  
Normally [[Sex chromosomes|sex chromosomes]] undergo segregation during [[Meiosis|Meiosis]] in [[Gamete|gamete]] producing cells so each daughter cell contains one sex chromosome<ref>p268,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett</ref>. 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) &nbsp;this process is called&nbsp;[[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. A number of other genetic disorders exist which are caused by other sex chromosome abnormalities, such as [[Turner syndrome|Turner syndrome]] (45,X)&nbsp;<ref>p269,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett</ref>.  
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Normally [[Sex chromosomes|sex chromosomes]] undergo segregation during [[Meiosis|Meiosis]] in [[Gamete|gamete]] producing cells so each daughter cell contains one sex chromosome<ref>p268,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett</ref>. 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. A number of other genetic disorders exist which are caused by other sex chromosome abnormalities, such as [[Turner syndrome|Turner syndrome]] (45,X)<ref>p269,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett</ref>.  
  
Although all but 1 X chromosome is condensed into a [[Barr_bodies|Barr body]], this is incomplete and some genes are expressed on both X chromosomes; males with Klinefelter produce more X linked genes that normal males resulting in a different phonetype. &nbsp;However the symptoms are not as severe as other trisomies as most of the extra X chromosomes are silenced.&nbsp;<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2008) Molecular Biology of the Cell, 5th Edition, New York, Garland Science (p272)</ref>
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Although all but 1 X chromosome is condensed into a [[Barr bodies|Barr body]], this is incomplete and some genes are expressed on both X chromosomes; males with Klinefelter produce more X linked genes that normal males resulting in a different phenotype. However, the symptoms are not as severe as other trisomies as most of the extra X chromosomes are silenced.<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2008) Molecular Biology of the Cell, 5th Edition, New York, Garland Science (p272)</ref>.
  
 
== 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&nbsp;<ref>National Centre for Biotechnology Information, 2011,Pub Med (online)Available at http://www.ncbi.nlm.nih.gov/pubmed/21540567 [accessed 19th November 2011]</ref>.<br>
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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<ref>National Centre for Biotechnology Information, 2011,Pub Med (online)Available at http://www.ncbi.nlm.nih.gov/pubmed/21540567 [accessed 19th November 2011]</ref>.  
  
 
== References  ==
 
== References  ==
  
 
<references />
 
<references />

Latest revision as of 06:49, 5 December 2018

KlinefeltersIMG.jpg

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[2].

Contents

Symptoms

An individual with Kleinfelter syndrome has a male phenotype[3], however, they also possess a number of traits which are absent in a karyotypically normal male which is symptomatic of the disorder.

Physical signs include:

[4][5].

Behavioural signs in developing boys include:

Learning and language signs:

Cause

Normally sex chromosomes undergo segregation during Meiosis in gamete producing cells so each daughter cell contains one sex chromosome[7]. 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. 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. A number of other genetic disorders exist which are caused by other sex chromosome abnormalities, such as Turner syndrome (45,X)[8].

Although all but 1 X chromosome is condensed into a Barr body, this is incomplete and some genes are expressed on both X chromosomes; males with Klinefelter produce more X linked genes that normal males resulting in a different phenotype. However, the symptoms are not as severe as other trisomies as most of the extra X chromosomes are silenced.[9].

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[10].

References

  1. p176.Passarge E.,2007, Color Atlas of genetics. 3rd ed.Ludwigsburg: Thieme.
  2. National Centre for Biotechnology Information, 2011, PubMed (online)Available at ;http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001420/[accessed 19th November 2011]
  3. p269,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London, Jones and Bartlett
  4. National Centre for Biotechnology Information, 2011,Pub Med (online)Available at ;http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001420/ [accessed 19th November 2011]
  5. Image of Klinefelter suffer taken from Andrology Australia, November 2005.Available at http://www.andrologyaustralia.org/pageContent.asp?pageCode=KLINEFELTERSSYNDROME#WHATARETHEEFFECTSOFK; [accessed 19 November 2011]
  6. What are common symptoms of Klinefelter syndrome (Ks)?.(2016) https://www.nichd.nih.gov/health/topics/klinefelter/conditioninfo/symptoms (Last accessed: 12/1/16)
  7. p268,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett
  8. p269,Hartl,D.L et al, 20009. Genetics Analysis of Genes and Genomes. London,Jones and Bartlett
  9. Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P (2008) Molecular Biology of the Cell, 5th Edition, New York, Garland Science (p272)
  10. National Centre for Biotechnology Information, 2011,Pub Med (online)Available at http://www.ncbi.nlm.nih.gov/pubmed/21540567 [accessed 19th November 2011]
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