yes it causes childlike symptoms
Down syndrome is caused by the presence of a third chromosome 21
I'm not sure but being around people with down syndrome, it seems like they are over emotional like they can get mad easily and if they don't get what they want they get upset. Like if they are older, they seem more childlike
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There are many causes of retardation. These includes Down syndrome, velocariofacial syndrome, fetal alcohol syndrome, problems during pregnancy and other genetic disorders.
Having an extra copy of chromosome 21. You are supposed to have 2; when you have 3 (trisomy 21), Down's Syndrome is the result.
See the Related Link to a very good FAQ on the causes of Down syndrome.
Down syndrome is purely genetic. There are no known environmental causes of the disorder. It is not a disease that is passed from parent to child. It is simply an disorder when the chromosomes split during cell division during development. The mayoclinic describes the causes: http://www.mayoclinic.com/health/down-syndrome/DS00182/DSECTION=causes
Down Syndrome is a the addition of an extra chromosome and not really related to evolution. It is more of a genetic mutation that causes this event to occur.
Quote from Wikipedia: "Irukandji syndrome is a condition induced by envenomization through the sting of Carukia barnesi, the Irukandji jellyfish, and other cubozoans.[1]"Note: Irukandji Syndrome has nothing to do with Down Syndrome and this question should NOT be placed in the Down Syndrome category!
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There are no mental or behavioral abnormalities, but people who have Down's Syndrome have rounded shoulders, a thicker skull, and a spongy tongue which causes speech impediment.
Mistakes in meiosis may cause Down syndrome. The error happens when the chromosomes segregate into the gametes. The egg or sperm may have too many or too few chromosomes. Down syndrome has an extra chromosome in the 21st pair.