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Down Syndrome

 Down Syndrome

Down syndrome is also known as trisomy -21, because the cells of the affected individual contain an extra copy of chromosome 21. The syndrome shows characteristic facial features, short body, heart defects (which can be corrected) and developmental delays. They have a high risk of developing leukemia and Alzheimer disease. Almost all males and half of the females with Down syndrome are sexually under developed and sterile. Their life span is shorter than normal, but can live past middle age with proper medical treatment. However, they have a lower risk of high blood pressure, atherosclerosis (hardening of the arteries), strokes and many types of solid tumors. Despite their abnormalities, many live independently and are employed. The risk of having a baby with Down syndrome increases with the age of the mother. This is caused by nondisjunction in meiosis-I. While Down syndrome is due to trisomy of an autosome, there are human genetic disorders due to aneuploidy in sex chromosomes as well. The aneuploidy conditions in sex chromosomes cause Turner syndrome due to monosomy and Klinefelter syndrome due to trisomy.




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