Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

Karyotype of people suffering from Down's syndrome has 47 chromosomes ( $45+\mathrm{XY}$ in males, $45+\mathrm{XX}$ in females) instead of 46 . It is caused due to the presence of an extra chromosome number 21 , thus it is also known as 21 trisomy.