Explanation About Down Syndrome?
My aunt to all three children have Down syndrome. all I know is the genetic disease down syndrome but why does it only infect third children?
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There are various types of genetic diseases and each type of genetic disease has its own inheritance pattern (some are inherited autosomal dominant, autosomal recessive, and some are related to sex chromosomes). Not even genetic diseases are inherited diseases. There are also genetic diseases that occur spontaneously and Down syndrome is one of them.
Humans normally have 23 pairs of chromosomes (or a total of 46 chromosomes). In Down syndrome, chromosome number 21 is not only a pair (not only 2), but there are 3 or also called trisomy 21. Trisomy 21 most often occurs because of disruption when the division of sex cells occurs in the body of the mother or father. Normally the sex cells (sperm or ovum) each have 23 chromosomes, but disruption during cell division causes one of these sperm or ovum to have 24 chromosomes (on chromosome number 21), so when fertilization occurs, the results of its conception have a total number of chromosomes 47 chromosomes. This disruption of sex cell division occurs spontaneously and randomly, so that not all the results of conception will have this disorder. There are also other mechanisms of Down syndrome that are less common such as mosaic down syndrome and translocation down syndrome.
The main risk factors that increase the likelihood of Down syndrome is the age of the mother who is more than 35 years during pregnancy. Other risk factors that are less common are parents who have certain genetic disorders and a history of having a child with previous Down syndrome.
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