What is Down's syndrome ?

Explanation

Down.s Syndrome Down.s syndrome is associated with the trisomy of 21st chromosome. It was described by ] Langdon Down (1886). The person suffering from this have broad forehead, short and broad neck, short and stubby fingers, a simian line in the palm and a wide gap between first and second fingers in feet. The face is moon-like with widely separated eyes, flattened nose, permanently open mouth, projecting lower lip and long protruding tongue. The person also suffers from severe mental retardation because of malformation of central nervous system. The patient has 47 chromosomes (i.e. an extra 21st chromosome). Trisomy arises due to the non-disjunction (non-separation) of 21st chromosome during oogenesis. Thus, the egg has 24 chromosomes instead of fertilisation of such egg with a normal sperm results in trisomy of 21st chromosome,