Question

In humans, the chromosome composition of a zygote that will develop into a Down’s syndromic female is

• A. $45+XX$
• B. $44+XXX$
• C. $23+X$
• D. $24+X$

Answer 1

The correct option is A $45+XX$

Down’s syndrome develops due to the trisomy $(2n+1)$ of chromosome number $21$.
Hence, in human down syndromic female, the composition of zygote would be $45A+XX$.