Turner syndrome
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
- ↑ Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones & Bartlett Learning International. p273
- ↑ Anthony JF Griffiths et al., 1990, Modern Genetic Analysis, New York : W.H.Freeman, Chapter 8
- ↑ Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones & Bartlett Learning International. p273
- ↑ 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)
- ↑ Hartl D. L., Ruvolo M. (2012) Genetics Analysis of Genes and Genomes, Eighth edition(international edition), London: Jones & Bartlett Learning International. p273