Down syndrome is a disorder due to having extra 21st chromosome i.e. an individual will have 47 chromosomes instead of normal 46. This is known as trisomy 21. Its occurrence can be prevented by genetic testing. Genetic code determines functioning and structure of an organism. A minute alteration in the genetic code leads to a huge physical or mental disorders. Mostly these deficiencies are dormant for a period.
Down’s syndrome is the condition where the symptoms of the disease don’t appear in the initial stages but the problems are found later. Genetic testing is the only method which can determine it. 
The characterizes of Down syndrome;

 

• Stunned growth, abnormal features like flat facial may be developed.
• Acute or obtuse mental retardation is possible

Though one in many hundreds come across genetic disorders, it is very important to perform genetic testing to allay the possibility of the disease.
Tests for Down syndrome;
This is the all important basic procedure for screening down’s syndrome. It is a series of steps which begins with a collection of blood sample.
Aminiocentesis – in this test, a needle is used to puncture abdomen. The amniotic fluid which is drawn out is tested for chromosomal analysis. It is also performed during fifteenth to twenty week of gestation.

AFP - the test is also known as expanded AFP. It is performed during fifteen to twenty weeks of gestation period.
CVS – this is chorionic villus sampling (CVS) where a tissue sample from the placenta of the mother is collected and genetic test is conducted.