(a) How does a chromosomal disorder differ from a Mendelian disorder?
(b ) Name any two chromosomal aberration associated disorders.
(c) List the characteristics of the disorders mentioned above that help in their diagnosis.

Explanation

(b) Two chromosomal aberration-associated disorders are Down's syndrome and Klinefelter's syndrome.
(c) (i) Down's syndrome : This is caused by on extra copy of chromosome 21. (trisomy 21). The affected individual is short with a round head. Tongue is furrowed and mouth is partially open. Palmar crease is present. Over all development is retarted.
(ii) Klinefelter's syndrome : It is caused by the absence of an X chromosome. XO. Such females are sterile with rudimentary ovaries. Secondary sexual characters are lacking.