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Euploidy and aneuploidy describe having a number of chromosomes that is an exact multiple of the number of chromosomes in a normal gamete; and having any other number, respectively. For example, a person with Turner syndrome may be missing one sex chromosome (X or Y), resulting in a (45,X) karyotype instead of the usual (46,XX) or (46,XY).
Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human somatic cell having 45 or 47 chromosomes instead of the usual 46. [ 1 ] [ 2 ] It does not include a difference of one or more complete sets of chromosomes .
The unequal distribution of DNA to daughter cells upon mitosis results in a failure to maintain euploidy (the correct number of chromosomes) leading to aneuploidy (incorrect number of chromosomes). In other words, the daughter cells do not have the same number of chromosomes as the cell they originated from.
euploidy The condition of a cell or organism having an abnormal number of complete sets of chromosomes , possibly excluding the sex chromosomes . Euploidy differs from aneuploidy , in which a cell or organism has an abnormal number of one or more specific individual chromosomes.
Aneuploidy of autosomes is not well tolerated and usually results in miscarriage of the developing fetus. Fetuses with aneuploidy of gene-rich chromosomes—such as chromosome 1 —never survive to term, [ 9 ] and fetuses with aneuploidy of gene-poor chromosomes—such as chromosome 21 — are still miscarried over 23% of the time. [ 10 ]
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XXXY syndrome is a genetic condition characterized by a sex chromosome aneuploidy, where individuals have two extra X chromosomes. [3] People in most cases have two sex chromosomes: an X and a Y or two X chromosomes. The presence of one Y chromosome with a functioning SRY gene causes the expression of genes that determine maleness. Because of ...
Abnormalities arising from nondisjunction events can cause cells with aneuploidy (additions or deletions of entire chromosomes) in one of the parents or in the fetus. In 1959, Lejeune [20] discovered patients with Down syndrome had an extra copy of chromosome 21. Down syndrome is also referred to as trisomy 21.