Essay Archive - Down Syndrome Report
Down Syndrome Report
The chromosomal abnormality involved in most cases of Down syndrome is
trisomy-21, or the presence of three copies of the 21st chromosome. As a result,
the affected person has 47 chromosomes in all body cells instead of the normal
46, although how this causes the condition's symptoms is not yet known.
Scientists assume that the reason for the abnormal chromosomal assortment is the
fertilization of an ovum having 24 chromosomes by a sperm with a normal
assortment of 23, but they have also found that the sperm can carry the extra
chromosome as well. The abnormal ovum or sperm is derived from a germ ....
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