Aneuploidy

 

ANEUPLOIDY

This product is intended to determine the DNA copy number of eight DNA sequences on each of four human chromosomes (13, 18, 21, X) and four sequences on chromosome Y as a means to detect an aneuploidy for one of these chromosomes in prenatal and postnatal DNA samples. Purified DNA from prenatal samples should be from (1) amniotic fluid obtained in week 16 of the pregnancy or later and free from blood contamination, (2) uncultured chorionic villi free from maternal contamination, or (3) fetal blood. Purified DNA from postnatal samples should be from blood or buccal swabs. This probemix can be used for initial diagnosis or confirmation of results from other techniques. This probemix cannot distinguish between normal (46,XX) and triploid females (69,XXX).

 

Clinical background: Germline aneuploidy of a complete chromosome usually results in a miscarriage. The most common cases of an abnormal chromosome copy number at birth concern the presence of an extra chromosome 13, 18 or 21, each resulting in mental retardation and other disorders, or the presence of an extra or missing sex chromosome (e.g. X0, XXY, XYY) - with much less severe consequences. Full trisomies account for the majority of cases, while a minority results from partial chromosome duplications or mosaicism.

 

Methods used to detect aneuploidies include karyotyping, FISH, quantitative PCR (in particular QF-PCR of short tandem repeats), MLPA, (array)-CGH, and high throughput sequencing. Not restricted to any particular detection method, aneuploidies can be diagnosed prenatally in samples from amniotic fluid, chorionic villi, fetal blood or from free circulating fetal DNA in the maternal plasma (NIPD). For analysis of postnatal samples, blood or buccal swap derived DNA is commonly used.