down syndrome definition

This accomplishment opened the door to great advances in Down syndrome research. Chromosomes contain hundreds, or even thousands, of genes. ©1996-2020 MedicineNet, Inc. All rights reserved. Down syndrome (DS), also called Trisomy 21, is a condition in which a person is born with an extra chromosome. The blood tests (or serum screening tests) measure quantities of various substances in the blood of the mother. Genetic counseling can determine the origin of translocation. By examining the karyotype, doctors can diagnose Down syndrome. Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. Unfortunately, most adults with Down syndrome eventually develop Alzheimer's disease as they grow older. Genes carry the information that determines your traits (features or characteristics passed on to you from your parents). The American College of Obstetricians and Gynecologists recommends offering the option of screening tests and diagnostic tests for Down syndrome to all pregnant women, regardless of age. NDSS uses the preferred spelling, Down syndrome, rather than Down’s syndrome. Definition Down syndrome (DS) is the most common cause of mental retardation and malformation in a newborn. Diagnostic tests, on the other hand, can provide a definitive diagnosis with almost 100% accuracy. Down syndrome is a chromosomal disorder characterized by recognizable facial features, multiple malformations, and mental impairment. It was first described in 1866 by Dr. John L. H. Down (1828 – 1896), an English physician.. Down syndrome occurs about once in every 800 births. It can occur in any racial or ethnic group. The risk of recurrence of translocation is about 3% if the father is the carrier and 10-15% if the mother is the carrier. With the discovery of antibiotics, the average survival age increased to 19 or 20. Although other people had previously recognized the characteristics of the syndrome, it was Down who described the condition as a distinct and separate entity. Mosaicism is the least common form of Down syndrome and accounts for only about 1% of all cases of Down syndrome. Instead of the usual 46 chromosomes present in each cell, Lejeune observed 47 in the cells of individuals with Down syndrome. At age 45 the incidence becomes approximately 1 in 30. But these tests can't tell for sure or diagnose whether the baby has Down syndrome. Each person with Down syndrome is an individual — intellectual and developmental problems may be mild, moderate or severe. They photograph the chromosomes and then group them by size, number, and shape. These blood tests are often performed in conjunction with a detailed sonogram to check for “markers” (characteristics that some researchers feel may have a significant association with Down syndrome). It's one of the most common genetic birth defects (a birth defect is a problem that happens while a baby is still growing inside their mother). Down syndrome (sometimes called Down’s syndrome) is a condition in which a child is born with an extra copy of their 21st chromosome — … People with Down syndrome may also be born with various health concerns such as heart defects or digestive abnormalities, as … Now you know that Down syndrome is caused by a … It wasn’t until the late nineteenth century, however, that John Langdon Down, an English physician, published an accurate description of a person with Down syndrome. There is no definitive scientific research that indicates that Down syndrome is caused by environmental factors or the parents’ activities before or during pregnancy. Typically, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. Once a woman has given birth to a baby with trisomy 21 (nondisjunction) or translocation, it is estimated that her chances of having another baby with trisomy 21 is 1 in 100 up until age 40. Merriman, A. Beccles, UK: The Down’s Syndrome Association. A 35 year old woman has about a one in 350 chance of conceiving a child with Down syndrome, and this chance increases gradually to 1 in 100 by age 40. “Intellectual disability” or “cognitive disability” has replaced “mental retardation” as the appropriate term. Increasingly important karyotype is done to confirm the diagnosis have ” Down syndrome on to you from parents! Lejeune identified Down syndrome have distinct facial features babies with Down syndrome should always be referred to as people.. Syndrome research, A. Beccles, UK: the history of a disability great advances in and... Individual — intellectual and developmental delays this extra genetic material is stored in.. 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