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A karyotype of an individual with trisomy 21, showing three copies of chromosome 21. An abnormal number of chromosomes is known as aneuploidy, and occurs when an individual is either missing a chromosome from a pair (resulting in monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy, etc.).
Complete trisomy 8 causes severe abnormalities in the developing fetus and can be a cause of miscarriage. [2] [3] Complete trisomy 8 is usually a gestational lethal condition, whereas trisomy 8 mosaicism is less severe and individuals with a low proportion of affected cells may exhibit a comparatively mild range of physical abnormalities and developmental delay. [4]
DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. [7] While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent infections, developmental disability, intellectual disability and cleft palate. [7]
Symptoms may include, but are not limited to, swelling, edema, or hypertension. [ medical citation needed ] Infants may show facial abnormalities, micrognathia , cleft lip , spina bifida , as well as other birth defects that result from kidney, limb, and umbilical cord complications.
The extra chromosome is provided at conception as the egg and sperm combine. [16] In 1–2% of cases, the additional chromosome is added in the embryo stage and only impacts some of the cells in the body; this is known as Mosaic Down syndrome. [17] [15] Translocation Down syndrome is another rare type.
Trisomy 18 is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on the 18th chromosome, either in whole (trisomy 18) or in part (such as due to translocations). The additional chromosome usually occurs before conception. The effects of the extra copy vary greatly, depending on the extent of the extra ...
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
We will explore chromosome specific cases in the chromosome specific section. Type of chromosome abnormality: The factor that had the highest predictive value as to whether the fetus was affected or not was the type of chromosome abnormality. Marker chromosomes were more often confirmed in the fetus than trisomies.