As women grow older, their chances of becoming pregnant become slim. However if a woman over the age of forty happens to finally get pregnant, the chances of the baby having birth imperfections tend to increase. Although some disorders occur through unhealthy lifestyles that the mother involves herself in, Down Syndrome is usually not identified as such. The age of the mother is not the only thing that may cause Down Syndrome to occur. The reasoning for this is because it’s a rather “sporadic” disorder and “the majority of children with Down's syndrome are born to younger mothers” (Down’s syndrome 1). The high number of younger women having children with Down Syndrome may be because they become pregnant more frequent to begin with. The only known cause of Down Syndrome is the genetic mutation of having an extra copy of chromosome 21, however there is still much more that needs to be done to figure out why this mutation happens.
Since the 1800’s there have been cases of people with symptoms relating to that of Down Syndrome except then the people were merely called “mongoloids” named after the people of Mongolia (Jilg 1). However, the first known case of Down Syndrome is not exactly known. Eventually in 1959, a French physician named Jermone Lejeune discovered the obvious difference between those diagnosed with Down Syndrome and the normal biological make-up. He found that Down Syndrome patients had, “47 chromosomes, whereas the cells of people without the syndrome only had 46 chromosomes” (Jilg 1). This later became labeled as the medical term Trisomy 21 (Down Syndrome 1).
There is more than one way a person can be affected through mutations on chromosome 21. Through the process of Trisomy 21, all cells in the body will have three copies of chromosome 21. Trisomy 21 occurs in a developing fetus, the body and brain development of the baby begins to go down a separate path. As the body changes physically, the brain begins to change more rapidly. In some rare instances those diagnosed with Down Syndrome only have three copies of chromosome 21 in some of their body cells, but not all. In this case, the name of the disorder is then identified as Mosaic Down Syndrome (Down Syndrome1 1). This may happen before conception even occurs, however once the cell containing an extra chromosome 21 fertilizes something happens causing only one of the copies to receive the extra chromosome. Children with Mosaic Down Syndrome will have disabilities just as those with Down Syndrome may struggle with, however in both cases there is no way to predict the severity of the case early on.
A third (and even rarer) case of Down Syndrome known as translocation Down Syndrome has the usual two copies of chromosome 21. However a part of chromosome 21 “becomes attached (translocated) to another chromosome during the formation of reproductive cells (eggs and sperm) or very early in fetal development” (Down Syndrome1 1). In addition to the normal two copies, leftover material will then form next to the pair. The pair of chromosome 21 may also be connected to each other (Translocation Down Syndrome).
Pattern of Inheritance
In the majority of cases pertaining to Down Syndrome, there is no indication of inheritance. However there is a slight chance that inheritance may be involved. This is seen in when, “a mother or father may have a balanced translocation of chromosome 21” (Down’s syndrome 1). As seen in the section above titled “Genetic Basis” and third and rare condition is named translocation Down Syndrome. If it appears that both the mother and father have a translocation of chromosome 21, then there is a good chance the child’s case of Down Syndrome comes through inheritance. However cases of inheritance are highly rare. This is because most people with translocation...
Cited: "Facts About Down Syndrome." National Down Syndrome Congress. National Down Syndrome
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