Turner syndrome: Difference between revisions

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Turner Syndrome is a [[Monosomic|monosomic]] condition in which only one [[X chromosome|X chromosome]] is present (XO). This presents itself as 45,X in terms of karyotype.
Turner Syndrome is a [[Monosomic|monosomic]] condition in which only one [[X chromosome|X chromosome]] is present (XO). This presents itself as 45,X in terms of karyotype.  


=== Karyotype  ===
=== Karyotype  ===


Instead of having a set of 44 [[Autosomes|autosomes]] + 1 pair of sex [[Chromosome|chromosomes]] (either XX or XY) - the normal [[Human_karyotype|human karyotype]], the person has only 44 [[Autosomes|autosomes]] + 1 X [[Chromosome|chromosomes]]. A person with Turner syndrome will have no [https://teaching.ncl.ac.uk/bms/wiki/extensions/FCKeditor/fckeditor/editor/Barr_Body barr bodies] due to them only have 1 X chromosome.
Instead of having a set of 44 [[Autosomes|autosomes]] + 1 pair of sex [[Chromosome|chromosomes]] (either XX or XY) - the normal [[Human karyotype|human karyotype]], the person has only 44 [[Autosomes|autosomes]] + 1 X [[Chromosome|chromosomes]]. A person with Turner syndrome will have no [[Barr_Body|barr bodies]] due to them only have 1 X chromosome.  


=== Cause ===
=== Cause ===


Turner syndrome occurs as a result of [[Nondisjunction|nondisjunction]], which is when chromosomes do not separate successfully during meiosis. It happens in about 1 in 5000 female births.
Turner syndrome occurs as a result of [[Nondisjunction|nondisjunction]], which is when chromosomes do not separate successfully during meiosis. It happens in about 1 in 5000 female births.  


=== Phenotype ===
=== Phenotype ===


The&nbsp;affected person is phenotypically female but does not undergo sexual maturation<ref>Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp; Bartlett Learning International. p273</ref>.&nbsp;This leads to&nbsp;poor breast development (with the nipples spread a distance apart)&nbsp;<ref>Anthony JF Griffiths et al., 1990, Modern Genetic Analysis, New York : W.H.Freeman, Chapter 8</ref>. Other phenotypes present include being short in stature, having a low hairline and having small finger nails. But mental abilities are typically within the normal range<ref>Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp; Bartlett Learning International. p273</ref>. Furthermore different karyotypes found in patients with Turner Syndrome will manifest themselves as different phenotypes of the disease<ref name="null">Al Alwan, Khadora M et.al. 2014. Turner Syndrome Genotype and phenotype and their effect on presenting features and timing of Diagnosis.(www.ncbi.nlm.nih.gov/pmc/articles/PMC4166992/) (22/10/2014)</ref>.&nbsp;However more than 99 percent of (turner syndrome) foetuses undergo spontaneous abortion. this indicates that&nbsp;the condition has profound deleterious effects on&nbsp;development<ref>Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp; Bartlett Learning International. p273</ref>.&nbsp;
The&nbsp;affected person is phenotypically female but does not undergo sexual maturation<ref>Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp;amp; Bartlett Learning International. p273</ref>.&nbsp;This leads to&nbsp;poor breast development (with the nipples spread a distance apart)&nbsp;<ref>Anthony JF Griffiths et al., 1990, Modern Genetic Analysis, New York : W.H.Freeman, Chapter 8</ref>. Other phenotypes present include being short in stature, having a low hairline and having small finger nails. But mental abilities are typically within the normal range<ref>Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp;amp; Bartlett Learning International. p273</ref>. Furthermore different karyotypes found in patients with Turner Syndrome will manifest themselves as different phenotypes of the disease<ref name="null">Al Alwan, Khadora M et.al. 2014. Turner Syndrome Genotype and phenotype and their effect on presenting features and timing of Diagnosis.(www.ncbi.nlm.nih.gov/pmc/articles/PMC4166992/) (22/10/2014)</ref>.&nbsp;However more than 99 percent of (turner syndrome) foetuses undergo spontaneous abortion. this indicates that&nbsp;the condition has profound deleterious effects on&nbsp;development<ref>Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp;amp; Bartlett Learning International. p273</ref>.&nbsp;  


= References  =
= References  =

Revision as of 17:02, 25 November 2014

Turner Syndrome is a monosomic condition in which only one X chromosome is present (XO). This presents itself as 45,X in terms of karyotype.

Karyotype

Instead of having a set of 44 autosomes + 1 pair of sex chromosomes (either XX or XY) - the normal human karyotype, the person has only 44 autosomes + 1 X chromosomes. A person with Turner syndrome will have no barr bodies due to them only have 1 X chromosome.

Cause

Turner syndrome occurs as a result of nondisjunction, which is when chromosomes do not separate successfully during meiosis. It happens in about 1 in 5000 female births.

Phenotype

The affected person is phenotypically female but does not undergo sexual maturation[1]. This leads to poor breast development (with the nipples spread a distance apart) [2]. Other phenotypes present include being short in stature, having a low hairline and having small finger nails. But mental abilities are typically within the normal range[3]. Furthermore different karyotypes found in patients with Turner Syndrome will manifest themselves as different phenotypes of the disease[4]. However more than 99 percent of (turner syndrome) foetuses undergo spontaneous abortion. this indicates that the condition has profound deleterious effects on development[5]. 

References

  1. ↑ Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp; Bartlett Learning International. p273
  2. ↑ Anthony JF Griffiths et al., 1990, Modern Genetic Analysis, New York : W.H.Freeman, Chapter 8
  3. ↑ Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp; Bartlett Learning International. p273
  4. ↑ Al Alwan, Khadora M et.al. 2014. Turner Syndrome Genotype and phenotype and their effect on presenting features and timing of Diagnosis.(www.ncbi.nlm.nih.gov/pmc/articles/PMC4166992/) (22/10/2014)
  5. ↑ Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones &amp; Bartlett Learning International. p273


  

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