Down syndrome is a genetic defect that occurs as the result of
Down syndrome results when abnormal cell division involving chromosome 21 occurs. These cell division abnormalities result in extra genetic material from chromosome 21, which is responsible for the characteristic features and developmental problems of Down syndrome. Down's syndrome is a genetic condition that occurs as a result of an extra chromosome (chromosome 21). The human body is made up of cells that contain genes. Down 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. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability. Usually, cells contain 46 chromosomes. A child inherits 23 from the mother and 23 from the father. In people with Down's syndrome, all or some of the cells in their bodies contain 47 chromosomes, as there is an extra copy of chromosome 21. Ninety-five percent of Down syndrome results from trisomy 21. Occasionally, the extra chromosome 21 is attached to another chromosome in the egg or sperm; this may result in what is called translocation Down syndrome (3 to 4 percent of cases). Down Syndrome. Down 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. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability. In 90% of Trisomy 21 cases, the additional chromosome comes from the mother's egg rather than the father's sperm. Down syndrome is the most common genetic disorder caused by a chromosomal abnormality. It affects 1 out of every 800 to 1,000 babies. Causes of Down's syndrome. Down's syndrome is a genetic condition that occurs as a result of an extra chromosome (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. 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.
Abnormal cell division involving chromosome 21 occurs.