List any four symptoms of Down's syndrome. What is the basis of this disorder?

Explanation

(ii) Four symptoms of Down.s syndrome are : (a) feeble minded (b) retarded growth (c) rounded face and broad forehead (d) permanently open mouth It is an autosomal aneuploidy (hyperploidy) or 21-trisomy. In this case, the egg possesses 24 chromosome instead of 23 and the offspring has 47 chromosomes (45 + XY in male, 45 + XX in female) instead of 46.