Alec+W.

=Wikipost #1 - Genetics= **Alec Wyllie**

February 28th, 2014
=Trisomy 21=

Trisomy 21, commonly known as Down Syndrome, is a genetic condition caused by the presence of a third copy of chromosome 21. It is a type of genetic abnormality known as nondisjunction.



**Symptoms:**

Physical:

Down Syndrome causes distinct physical characteristics, such as a small chin, ears and mouth, slanted eyes, decreased muscle tone, a flattened nose, separation between the joints of the skull, and distinctive creases in the palm of the hand. Most children with Trisomy 21 have eye problems, and require glasses. Heart defects are prevalent. Those with Down Syndrome have greater risk of hip problems and dislocation. Heart defects and sleep apnea are also common symptoms.

//A child with Down Syndrome. Note the distinctive eye shape//.



Mental: Adults with Trisomy 21 do not tend to exceed the mental capacities of an eight year old child. They have intellectual disabilities. They are often slow learners and exhibit impulsive behaviour.

=Causes:= //The older the mother is when the child is conceived, the greater the chance of trisomy 21.//

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**Diagnosis:** Prenatal tests can be performed before a baby is born. There are two types of prenatal test, called screening tests and diagnostic tests. Screening tests often only provide a probability, while diagnostic tests give 100% accuracy. Screening tests are performed using a blood test and an ultrasound. The blood test is used to determine quantities of substances inside the mother. Diagnostic tests are done with chorionic villus sampling and amniocentesis. They have nearly perfect accuracy, but the also carry the 1% odd of causing a miscarriage.

I//mages from a screening test.//



=Treatment:= There is no specific treatment for the syndrome, although heart defects caused by it may require surgery. Individuals with Trisomy 21 can be greatly helped through behavioural training. Due to their differences in brain development, children with Down Syndrome usually require special education.

//Despite its setbacks////, Down Syndrome does not prevent the more than a million people it affects around the world from leading happy, exciting lives.//



=Further reading:=

The National Down Syndrome Society: https://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome/

Down Syndrome Education International http://www.dseinternational.org/en-gb/about-down-syndrome/

The University of Michigan http://www.med.umich.edu/yourchild/topics/downsyn.htm

Patient.co.uk http://www.patient.co.uk/doctor/downs-syndrome-trisomy-21

**Sources:** http://www.nytimes.com/health/guides/disease/down-syndrome/overview.html https://www.ndss.org/Down-Syndrome/What-Is-Down-Syndrome/ http://www.cdss.ca/information/general-information/how-to-talk-about-down-syndrome.html http://ghr.nlm.nih.gov/chromosome/21