Downs syndrome was discovered by an English physician named John Langdon down in 1866.
Downs syndrome is an autosomal , trisomic disease caused by the presence of extra chromosome number 21.
The offspring has 47 chromosomes instead of 46 chromosomes .
The presence of three chromosomes of the same kind is called trisomy .
The defective chromosomes for downs syndrome is originated in two ways .
When an abnormal egg containing the chromosomes 23A+X fertilized with the normal sperm containing the chromosomes 22AA+XX .
When an abnormal sperm containing the chromosome 22A+Y resulting in the karyotype 45A + XY .
The symptoms include round 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 . Hence they are called mongolian idiocy .
Heart and other organs may also have deformities gonads and genitalia are under developed.
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