Down Syndrome

Abstract:  Downs syndrome is a syndrome of psychic retardation accompanied by abnormal facial features, which firmness of purposes when a baby inherits troika copies of chromosome 21 instead of the normal two copies. This chromosome abnormality, c every(prenominal)ed trisomy 21, may be detect prior to present by culturing some cells from the fetus and examining the chromosomes straight off (karyotyping). However, this trial run is time-consuming and costly, and is norm bothy speechless only for women at the sterling(prenominal) jeopardy of exposure. Generally, this risk is determined by the mothers be on; women over 36 be considered to be at the highest risk. However, Downs syndrome is the most well-known(prenominal) of all chromosome abnormalities and affects virtually 1 in 700 births. Women over 36 account for only nearly 30 percent of all Downs syndrome births and, at present, only about 15 percent of the cases of Downs syndrome atomic come up 18 find before birth. It would be very valuable, therefore, to develop a screening method that would result in the prenatal lore of many fetuses with Downs syndrome without excessive cost. In a review of 3,436 pregnancies, 5 percent were karyotyped because of the mothers age and transmitted history.

A entirety of octad affected fetuses were identified; the total may be considered 11, if triple cases born shortly aft(prenominal) the close of the study summit in time atomic number 18 also considered. Only adept of the affected fetuses was detected by conventional screening procedures. However, a new particularise of risk factors was designed that included the measure of alpha fetoprotein and chorionic gonadotrophin in the mothers blood. The congenial ranges were defined so that the number of karyotypes that would be recommended on the keister of these risk factors would be 5 percent, about the same as when maternal age is apply as the predominant risk factor. Using these criteria, 8 of the 11 affected pregnancies would piss been recommended for karyotyping, which would have yielded a espial say of 73 percent. The adoption of this method of using risk...If you indispensableness to pull out a full essay, array it on our website: Orderessay

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