Down syndrome, also called Trisomy 21, is a medical condition which causes delays in the development and growth of a child. Named after the first doctor to document it, Dr John Langdon Down, it is the most common abnormality in humans with 1 in every 800 babies born in the US having Down syndrome. The extent to which Down syndrome affects the child varies from person to person. Some people with Down syndrome require a lot of medical attention whilst others live a mostly healthy life. Whilst Down syndrome itself cannot be cured many of the medical problems associated with the syndrome can be treated.
What causes Down syndrome?
When a baby is conceived genetic material is received from both the mother and the father. Each of the parents contributes 23 chromosomes, making a total of 46. In a Down syndrome conception an extra chromosome makes up part of the genetic structure leading to a baby with 47 chromosomes instead of 46. It is the extra copy or part copy of the chromosome 21 that leads to the physical and developmental differences in a Down syndrome child. 95% of Down syndrome is caused by this extra chromosome that is present in all cells in the body. The other 5% of Down syndrome is caused by either mosaicism or translocation. Mosaic Down syndrome comes about when only some of the cells in the body have the extra chromosome 21, whilst the others are normal. Translocation Down Syndrome occurs when part of Chromosome 21 breaks off and adheres to another chromosome (usually Chromosome 14), this cause Down syndrome characteristics. People with this type of Down syndrome may not show the physical signs of Down syndrome but are more likely to produce children with Down syndrome.
So far scientists have been unable to determine what causes the chromosomal error to occur, but have found a common factor that makes it more prevalent. Women over the age of 35 are more likely to conceive a child with Down syndrome as the chances increase dramatically with age.