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

Down's Syndrome is caused due to the presence of an additional copy of the chromosome number 21 (trisomy of 21). This disorder was first described by Langdon Down (1866). The affected individual is short statured with small round head, furrowed tongue and partially open mouth. Palm is broad with characteristic palm crease (simian crease). Physical, psychomotor and mental development is retarded.