Post by Admin on May 18, 2023 11:35:58 GMT
Down syndrome
en.wikipedia.org/wiki/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.[3] It is usually associated with developmental delays, mild to moderate intellectual disability, and characteristic physical features.[1][12] There are three types of Down syndrome, all with the same features: Trisomy 21, the most common type; Mosaic Down syndrome, and Translocation Down syndrome.[13][14]
The parents of the affected individual are usually genetically normal.[15] The probability increases from less than 0.1% in 20-year-old mothers to 3% in those of age 45.[4] The extra chromosome is provided at conception as the egg and sperm combine.[16] A very small percentage of 1-2% gets the additional chromosome in the embryo stage and it only impacts some of the cells in the body; this is known as Mosaic Down syndrome.[17][18] Usually, babies get 23 chromosomes from each parent for a total of 46, whereas in Down syndrome, a third 21st chromosome is attached.[18] It is believed to occur by chance, with no known behavioral activity or environmental factor that changes the probability.[2] Down syndrome can be identified during pregnancy by prenatal screening, followed by diagnostic testing, or after birth by direct observation and genetic testing.[6] Since the introduction of screening, Down syndrome pregnancies are often aborted (rates varying from 50%-85% depending on maternal age, gestational age, and maternal race/ethnicity).[19][20][21]
There is no cure for Down syndrome.[22] Education and proper care have been shown to provide good quality of life.[7] Some children with Down syndrome are educated in typical school classes, while others require more specialized education.[8] Some individuals with Down syndrome graduate from high school, and a few attend post-secondary education.[23] In adulthood, about 20% in the United States do paid work in some capacity,[24] with many requiring a sheltered work environment.[8] Support in financial and legal matters is often needed.[10] Life expectancy is around 50 to 60 years in the developed world, with proper health care.[9][10] Regular screening for health issues common in Down syndrome is recommended throughout the person's life.[9]
Down syndrome is the most common chromosomal abnormality.[25] It occurs in about 1 in 1,000 babies born each year.[1] In the US this figure is given as one in 700 births.[13] In 2015, Down syndrome was present in 5.4 million individuals globally and resulted in 27,000 deaths, down from 43,000 deaths in 1990.[11][26][27] It is named after British doctor John Langdon Down, who fully described the syndrome in 1866.[28] Some aspects of the condition were described earlier by French psychiatrist Jean-Étienne Dominique Esquirol in 1838 and French physician Édouard Séguin in 1844.[29] The genetic cause of Down syndrome was discovered in 1959.[28]
en.wikipedia.org/wiki/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.[3] It is usually associated with developmental delays, mild to moderate intellectual disability, and characteristic physical features.[1][12] There are three types of Down syndrome, all with the same features: Trisomy 21, the most common type; Mosaic Down syndrome, and Translocation Down syndrome.[13][14]
The parents of the affected individual are usually genetically normal.[15] The probability increases from less than 0.1% in 20-year-old mothers to 3% in those of age 45.[4] The extra chromosome is provided at conception as the egg and sperm combine.[16] A very small percentage of 1-2% gets the additional chromosome in the embryo stage and it only impacts some of the cells in the body; this is known as Mosaic Down syndrome.[17][18] Usually, babies get 23 chromosomes from each parent for a total of 46, whereas in Down syndrome, a third 21st chromosome is attached.[18] It is believed to occur by chance, with no known behavioral activity or environmental factor that changes the probability.[2] Down syndrome can be identified during pregnancy by prenatal screening, followed by diagnostic testing, or after birth by direct observation and genetic testing.[6] Since the introduction of screening, Down syndrome pregnancies are often aborted (rates varying from 50%-85% depending on maternal age, gestational age, and maternal race/ethnicity).[19][20][21]
There is no cure for Down syndrome.[22] Education and proper care have been shown to provide good quality of life.[7] Some children with Down syndrome are educated in typical school classes, while others require more specialized education.[8] Some individuals with Down syndrome graduate from high school, and a few attend post-secondary education.[23] In adulthood, about 20% in the United States do paid work in some capacity,[24] with many requiring a sheltered work environment.[8] Support in financial and legal matters is often needed.[10] Life expectancy is around 50 to 60 years in the developed world, with proper health care.[9][10] Regular screening for health issues common in Down syndrome is recommended throughout the person's life.[9]
Down syndrome is the most common chromosomal abnormality.[25] It occurs in about 1 in 1,000 babies born each year.[1] In the US this figure is given as one in 700 births.[13] In 2015, Down syndrome was present in 5.4 million individuals globally and resulted in 27,000 deaths, down from 43,000 deaths in 1990.[11][26][27] It is named after British doctor John Langdon Down, who fully described the syndrome in 1866.[28] Some aspects of the condition were described earlier by French psychiatrist Jean-Étienne Dominique Esquirol in 1838 and French physician Édouard Séguin in 1844.[29] The genetic cause of Down syndrome was discovered in 1959.[28]