The discovery of the genetic basis of Down syndrome is based on which study
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Treatment for Down syndrome is based on the person's physical problems and intellectual challenges. Many babies who have Down syndrome do not have good muscle tone, which makes it harder for them to roll over and walk. Physical therapy can help with these problems. Show About 40 - 60 percent of babies born with Down syndrome have a heart defect. Therefore, all newborns with Down syndrome have their heart checked with an electrocardiogram and an echocardiogram. When there is a heart defect present in an infant with Down syndrome, the infant is referred to a pediatric cardiologist for medical management or to a pediatric cardiac surgeon for early surgical repair. Some infants with Down syndrome have difficulties with swallowing or they may have blockages in their bowels. Surgery can be performed to correct these problems. Once corrected, they usually cause no further health issues. Children with Down syndrome may have frequent colds and sinus and ear infections. These are treated early and aggressively to prevent hearing loss and chronic infections. Low thyroid levels are more common in infants who have Down syndrome. It is recommended that thyroid level testing be performed at least yearly. Some infants with Down syndrome have eye problems such as cataracts (cloudy lenses) or crossed eyes (strabismus). Surgery can help with these problems. Sucking problems related to low muscle tone or heart problems may make breast feeding difficult initially. Occupational therapists, speech therapists, breast feeding consultants and support groups usually have specific resources for the mothers of infants with Down syndrome. Intelligence in individuals with Down syndrome ranges from low normal to very slow to learn. At birth it is not possible to tell the level of intelligence a baby with Down syndrome will have. All areas of development including motor skills, language, intellectual abilities, and social and adaptive skills are followed closely in children with Down syndrome. Early referral, beginning at birth, to an early intervention program will help enhance development. Preschool programs for children with Down syndrome include physical, occupational, speech and educational therapies. Many adults with Down syndrome have jobs and live independently. DescriptionDown syndrome is a chromosomal condition that is associated with intellectual disability, a characteristic facial appearance, and weak muscle tone (hypotonia) in infancy. All affected individuals experience cognitive delays, but the intellectual disability is usually mild to moderate. People with Down syndrome often have a characteristic facial appearance that includes a flattened appearance to the face, outside corners of the eyes that point upward (upslanting palpebral fissures), small ears, a short neck, and a tongue that tends to stick out of the mouth. Affected individuals may have a variety of birth defects. Many people with Down syndrome have small hands and feet and a single crease across the palms of the hands. About half of all affected children are born with a heart defect. Digestive abnormalities, such as a blockage of the intestine, are less common. Individuals with Down syndrome have an increased risk of developing several medical conditions. These include gastroesophageal reflux, which is a backflow of acidic stomach contents into the esophagus, and celiac disease, which is an intolerance of a wheat protein called gluten. About 15 percent of people with Down syndrome have an underactive thyroid gland (hypothyroidism). The thyroid gland is a butterfly-shaped organ in the lower neck that produces hormones. Individuals with Down syndrome also have an increased risk of hearing and vision problems. Additionally, a small percentage of children with Down syndrome develop cancer of blood-forming cells (leukemia). Delayed development and behavioral problems are often reported in children with Down syndrome. Affected individuals can have growth problems and their speech and language develop later and more slowly than in children without Down syndrome. Additionally, speech may be difficult to understand in individuals with Down syndrome. Behavioral issues can include attention problems, obsessive/compulsive behavior, and stubbornness or tantrums. A small percentage of people with Down syndrome are also diagnosed with developmental conditions called autism spectrum disorders, which affect communication and social interaction. People with Down syndrome often experience a gradual decline in thinking ability (cognition) as they age, usually starting around age 50. Down syndrome is also associated with an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function. Approximately half of adults with Down syndrome develop Alzheimer disease. Although Alzheimer disease is usually a disorder that occurs in older adults, people with Down syndrome commonly develop this condition earlier, in their fifties or sixties. FrequencyDown syndrome occurs in about 1 in 700 newborns. About 5,300 babies with Down syndrome are born in the United States each year, and approximately 200,000 people in this country have the condition. Although women of any age can have a child with Down syndrome, the chance of having a child with this condition increases as a woman gets older. CausesMost cases of Down syndrome result from trisomy 21, which means each cell in the body has three copies of chromosome 21 instead of the usual two copies. Less commonly, Down syndrome occurs when part of chromosome 21 becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) in a parent or very early in fetal development. Affected people have two normal copies of chromosome 21 plus extra material from chromosome 21 attached to another chromosome, resulting in three copies of genetic material from chromosome 21. Affected individuals with this genetic change are said to have translocation Down syndrome. A very small percentage of people with Down syndrome have an extra copy of chromosome 21 in only some of the body's cells. In these people, the condition is called mosaic Down syndrome. Researchers believe that having extra copies of genes on chromosome 21 disrupts the course of normal development, causing the characteristic features of Down syndrome and the increased risk of health problems associated with this condition. InheritanceMost cases of Down syndrome are not inherited. When the condition is caused by trisomy 21, the chromosomal abnormality occurs as a random event during the formation of reproductive cells in a parent. The abnormality usually occurs in egg cells, but it occasionally occurs in sperm cells. An error in cell division called nondisjunction results in a reproductive cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 21. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 21 in each of the body's cells. People with translocation Down syndrome can inherit the condition from an unaffected parent. The parent carries a rearrangement of genetic material between chromosome 21 and another chromosome. This rearrangement is called a balanced translocation. No genetic material is gained or lost in a balanced translocation, so these chromosomal changes usually do not cause any health problems. However, as this translocation is passed to the next generation, it can become unbalanced. People who inherit an unbalanced translocation involving chromosome 21 may have extra genetic material from chromosome 21, which causes Down syndrome. Like trisomy 21, mosaic Down syndrome is not inherited. It occurs as a random event during cell division early in fetal development. As a result, some of the body's cells have the usual two copies of chromosome 21, and other cells have three copies of this chromosome. Other Names for This Condition
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What is the genetic basis of Down syndrome?The genetic basis of Down syndrome
In Down syndrome, there is an additional copy of chromosome 21, resulting in three copies instead of the normal two copies. Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21.
How was Down syndrome discovered?The chromosome aberration was discovered in 1959 by the French human geneticist Jérôme Jean Louis Marie Lejeune (1926–1994). Dr. Jérôme Lejeune discovered that Down syndrome was caused by an extra chromosome on the 21st pair while working in Raymond Turpin's laboratory In 1958.
Who discovered the genetic cause of Down syndrome?In 1959, the French physician Jérôme Lejeune identified Down syndrome as a chromosomal condition. Instead of the usual 46 chromosomes present in each cell, Lejeune observed 47 in the cells of individuals with Down syndrome.
Who studied Down syndrome?John Langdon Down studied medicine in England in the nineteenth century and was one of the first people to develop a complete description of the disorder that would later be known as Trisomy 21, or Down Syndrome.
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