Trisomy 13

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  • Topic: Chromosome, Cytogenetics, Aneuploidy
  • Pages : 3 (803 words )
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  • Published : January 5, 2013
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Trisomy 13

Trisomy 13, also known as Patau Syndrome, is a chromosomal abnormality where an individual has an extra chromosome 13. Trisomy 13 was first recognized by Patau and his colleagues in 1960 (Matthews, 1999). It affects approximately 1 in 12,000 births and is the least common of the trisomy syndromes, after trisomy 18 and trisomy 21 (Down syndrome). An abnormality of the chromosome occurs when mitosis or meiosis does not happen correctly. During mitosis, when the cells are dividing, chromosomes are either lost or gained. The chromosomes do not separate evenly. When the distribution of chromosomes during cell division occurs after the egg is fertilized by the sperm, mosaicism occurs. The fetus will have 47 chromosomes in some cells and 46 chromosomes on other cells. There are three variations of trisomy 13; full trisomy 13, which is the presence of an extra chromosome 13 in all cells, trisomy 13 mosaicism, which is the presence of an extra chromosome 13 in some of the cells, and partial trisomy 13, which is the presence of a part of an extra chromosome 13. The chromosomal abnormality usually begins with the egg cell, therefore there are more female fetuses affected with trisomy 13 than males. Women over the age of thirty-five are at greater risk of having a child with trisomy 13 (Genetics.edu, 2007). Roughly one out of 3-4 eggs fertilized are considered to have a chromosomal abnormality, but our bodies usually react with a miscarriage.

There are several ways that trisomy 13 can be detected during pregnancy such as: ultrasound, amniocentesis, or maternal serum screening. While these tests can pick up on the genetic likelihood that the fetus will have a trisomy defect, many parents chose not to get this testing done. The severity of the symptoms associated with trisomy 13 depends on the portion of the chromosome that is affected, as well as the percentage of cells that have an abnormality. If an infant presents with mosaic trisomy 13, the...
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