Trisomy 21 is -

Ans. is 'a' i.e., Dow n's syndrome Trisomy 21 is synonymous with down's syndrome and is the most common of the chromosomal disorders o Down's syndrome - Trisomy 21 o Edwards syndrome - Trisomy 18 o Patau syndrome - Trisomy 13 o Kleinfelter syndrome - 47XXY o Turner syndrome - 45 XO