Maharashtra Class 9 Answered

Down’s syndrome is an aneuploid, trisomic disease caused by the presence of extra chromosome No. 21. The egg has 24 chromosomes instead of 23 and the offspring has 47 chromosomes (45 + XY/45 + XX) instead of 46 chromosomes. The presence of three chromosomes of the same kind is called trisomy.

Symptoms

• Characterised by rounded face, broad forehead, a Mongolian type of eyelid fold, flattened nasal bridge, permanently open mouth, projecting lower lip, protruding tongue, short neck, flat hands and stubby fingers.
• The victim has little intelligence due to malformation of the brain.
• Heart and other organs may also have deformities.
• Gonads and genitalia are under developed.