Down syndrome is a genetic disorder caused by the presence of an extra chromosome 21, known as trisomy 21, which accounts for 95% of cases. It can also be caused by translocations involving chromosome 21 or mosaicism, present in 4% and 1% of cases respectively. Common physical traits include low muscle tone, small stature, an upward slant to the eyes and a flat facial profile. Cognitive impairment and developmental delays are also associated with Down syndrome.

1. Down syndrome

2. Down syndrome)

3. 1
21 3 2
TRISOMY 21 95%
TRANSLOCATION
14 21
4%
46 47 1%
MOSAIC

4. karyotype

5. Embryo

7. http://www.student.chula.ac.th/~53370663
http://downsyndromeubu.exteen.com/200802
17/entry-3
http://www.ideaforlife.net/health/disease/do
wn_syndrome/index.html
http://downsyndromeubu.exteen.com/200802
17/entry-1

8. Down syndrome