Mention any six symptoms of disorder caused by trisomy of 21st chromosome.

Answer: Trisomy of chromosome 21 (karyotype 45 + XX or 45 + XY, i.e. 47 chromosomes) causes Down’s syndrome (mongolism). Symptoms:

1. Short stature, small round head and broad flat face.
2. Mental retardation (low IQ) and retarded physical and psychomotor development.
3. Oblique eyelids with epicanthal (Mongolian) fold.
4. Furrowed, protruding tongue and partially open mouth.
5. Broad palm with a single transverse palmar (simian) crease; short stubby fingers.
6. Flat nose and small, low-set ears.
7. Congenital heart defects and weak muscle tone; poorly developed gonads.