Klinefelter syndrome (KS) is a sex chromosome disorder and occurs due to the presence of an extra X chromosome in males
Posted: Thu Jun 09, 2022 11:48 am
Klinefelter syndrome (KS) is a sex chromosome disorder and occurs due to the presence of an extra X chromosome in males (XXY). It is estimated that 1 in 700 to 1 in 900 live male births are affected by KS. Early research linked KS with psychiatric disorders, criminal behavior, and mental retardation.
Down syndrome (DS), an important cause of intellectual disability (‘mental retardation’), results from the presence of three copies of human chromosome 21. The trisomy, affecting more than 300 genes, is associated with a variety of manifestations, including cardiac anomalies, thyroid dysfunction, leukemia, digestive disorders, and intellectual disabilities
Down syndrome is a genetic syndrome, occurring in from 1 in 650 to 1 in 1000 live births. In 95% of cases, Down syndrome is caused by nondisjunction during cell division, resulting in an extra chromosome 21 (trisomy 21). Most cases of Down syndrome involve a nondisjunction during the first meiotic cell division, with mothers contributing the extra chromosome in 85% of cases. When nondisjunction occurs after fertilization, this leads to mosaic Down syndrome, where one line of cells in the developing fetus contains the extra copy of chromosome 21 and a second line of cells in the developing fetus does not. In a small percentage of cases, Down syndrome is caused by a translocation of genetic material on chromosome 21.
Down syndrome (DS), an important cause of intellectual disability (‘mental retardation’), results from the presence of three copies of human chromosome 21. The trisomy, affecting more than 300 genes, is associated with a variety of manifestations, including cardiac anomalies, thyroid dysfunction, leukemia, digestive disorders, and intellectual disabilities
Down syndrome is a genetic syndrome, occurring in from 1 in 650 to 1 in 1000 live births. In 95% of cases, Down syndrome is caused by nondisjunction during cell division, resulting in an extra chromosome 21 (trisomy 21). Most cases of Down syndrome involve a nondisjunction during the first meiotic cell division, with mothers contributing the extra chromosome in 85% of cases. When nondisjunction occurs after fertilization, this leads to mosaic Down syndrome, where one line of cells in the developing fetus contains the extra copy of chromosome 21 and a second line of cells in the developing fetus does not. In a small percentage of cases, Down syndrome is caused by a translocation of genetic material on chromosome 21.