Down Syndrome : A Genetic Disorder

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Down syndrome is a genetic disorder that affects a person’s facial features and intelligence. Down syndrome is also commonly known as Down’s syndrome, Trisomy 21, Trisomy G, 47,XX,+21, or 47,XY,+21. In 1866, English physician John Langdon Down is known as the “father” of Down syndrome. He was given that title for his publication of an accurate description of a person with Down syndrome, hence the reason why the disorder was named after him; although, this disorder was known as “Mongolism” until the 1970s. More information was learned about Down syndrome in 1959 when French physician Jérôme Lejeune identified that the disorder was caused by a chromosomal error. Then in 2000, a team of scientists was able to classify roughly 329 genes on chromosome 21, opening the door to many more advancements in the world of research for Down syndrome. Down syndrome is inherited because of a chromosomal error. It occurs when someone gains an extra 21 chromosome. Usually, an individual will inherit two copies of chromosome 21, one from each parent. The extra 21 chromosomes can be inherited in three different ways, which results in three different types of Down syndrome: trisomy 21 (nondisjunction), mosaicism, and translocation. Trisomy 21 or nondisjunction is the most common form of Down syndrome; responsible for 95 percent of all the cases of Down syndrome. In this type of Down syndrome, the embryo contains three 21 chromosomes which is the result of the sperm or egg cell failing to
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