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Aneuploidy is a change in the number of chromosomes that can lead to a chromosomal abnormality. In humans, in every cell of our bodies, we typically will have 46 chromosomes. The only exception to this is that our egg and sperm cells will only have half the number of chromosomes (23). The 46 chromosomes can be arranged into 23 pairs. From each pair, we typically will inherit one chromosome from our mother and one from our father. The first 22 pairs of chromosomes are referred to as autosomes, or body chromosomes. They are numbered from 1 through 22 from largest to smallest. The last pair of chromosomes are the sex chromosomes. Females will typically have two X chromosomes, while males will typically have one X chromosome and one Y chromosome.
Changes in chromosome number may not necessarily be present in all cells in an individual. It may be detected in just a specific tissue or within different cells in a tissue. When the presence of chromosomal abnormalities occurs differentially within an individual, it is called chromosomal mosaicism. In general, as we would expect, individuals who are mosaic for a chromosome change tend to have a less severe form of the syndrome present than full trisomy individuals. Critical examples of mosaicism are found in leukemia cases, specifically; chronic lymphocytic leukemia (CLL) which is a trisomy of chromosome 12 and acute myeloid leukemia (AML) prognosis which is a trisomy of chromosome 8. Aneuploidy is common in cancerous cells.
Aneuploidy is typically detected through karyotyping, a process where a picture of the chromosomes of an individual is analyzed. Other techniques include Fluorescence In Situ Hybridization (FISH), Quantitative Polymerase Chain Reaction (PCR) of Short Tandem Repeats, Quantitative Fluorescence PCR (QF-PCR), Quantitative Real-time PCR (RT-PCR) dosage analysis, Quantitative Mass Spectrometry of Single Nucleotide Polymorphisms, and Comparative Genomic Hybridization (CGH). These tests can also be done prenatally to detect aneuploidy in a pregnancy, either through amniocentesis or chorionic villus sampling.
Pregnant women over the age of 35 are typically offered various tests for aneuploidy in the fetus because the chance of these syndromes increases as the mother's age increases. For more information, see prenatal diagnosis.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Aneuploidy". A list of authors is available in Wikipedia.|