Down Syndrome
Name Origin:
Down Syndrome (previously Down's Syndrome), was named after the man who first discovered this genetic disorder, John Langdon Down. In his work at a children's asylum for mental retardation, he thought children with this syndrome looked like people from Mongolia, who were thought to be very unintelligent at the time. Because of this, he originally called the disorder Mongolism. The scientific community later noted the racism in his judgement and corrected the name to what it is today, Down Syndrome.
The scientific name for Down Syndrome is Trisomy 21.
The scientific name for Down Syndrome is Trisomy 21.
Causes:
Down Syndrome is often caused by non-disjunction; a chromosome failing to separate during meiosis. The chromosome that fails to separate is usually chromosome 21. When this egg/sperm with 2 chromosome 21's joins with another normal sperm/egg with only 1 chromosome 21, the resulting embryo will have 3 chromosome 21's instead of 2.
There are two other ways that this embryo can receive three chromosomes. In Robertsonian Translocation, part of chromosome 14 breaks off and becomes an extra chromosome 21. In mosaicism, some tissues in the developing embyro have an extra chromosome 21, while others don't. For example, blood cells might be normal, but skin cells might have Trisomy 21. Mosaicism and Robertsonian Translocation are much less common, however, and only make up about 5% of all cases of Trisomy 21.
There are two other ways that this embryo can receive three chromosomes. In Robertsonian Translocation, part of chromosome 14 breaks off and becomes an extra chromosome 21. In mosaicism, some tissues in the developing embyro have an extra chromosome 21, while others don't. For example, blood cells might be normal, but skin cells might have Trisomy 21. Mosaicism and Robertsonian Translocation are much less common, however, and only make up about 5% of all cases of Trisomy 21.
Effects:
Chromosomes help control the production of cells in the body. Having an extra chromosome 21 results in over expression. This means that there is an increased production of the things in the body that are controlled by the genes that are affected by chromosome 21. Chromosome 21 is thought to hold 250 genes. Over expression's effects are widespread and vary tremendously from patient to patient. Some of these effects include premature aging, decreased function of the immune system, heart defects, skeletal abnormalities, damaging DNA synthesis, disruption of metabolism and DNA repair, mental retardation, cataracts, and interference with the immune system.
Treatments:
There are many treatments for Down Syndrome, but sadly it cannot truly be cured. There are many diseases and conditions caused by Down Syndrome that can be treated, however. Lots of research is going on about chromosome 21 and the genes it controls in the hope that a cure for Down Syndrome can be created.