Down syndrome is a genetic disorder that occurs in approximately 1 to 800 live births. It is the leading cause of cognitive impairment. It is named after Doctor Langdon Down, who in 1866 first described the syndrome as disorder. But he could not identify what causes the disorder. It was in 1959 that Lejune discovered the genetic origin of Down’s Syndrome.
Genes on an extra copy of chromosomes 21 are responsible for all characteristics of Down Syndrome. At conception, individual inherits 23 chromosomes each from mother and father. However, sometimes a person inherits an extra chromosome from one parent, in this, both the chromosomes of pair 21 pass into single egg due to nondisjunction during oogenesis. Due to this individual inherits two copies of chromosomes 21 from mother and one chromosome 21 from father for a total of 3 chromosomes 21. Thus the offspring possess 47 chromosomes because down syndrome is caused by inheritance of three chromosome 21, the disorder is called trisomy 21.
SYMPTOMS OF DOWN SYNDROME :-
A flattened face and nose, a short neck, a small mouth, protruding and furrowed tongue, small ears, upward slanting eyes that may have small skin folds at the inner corner, coarse and straight hairs.
White spots may be present on coloured pairs of iris.
The hands are short and broad with short fingers, with many loops on finger tips, characteristic palmer crease that runs all the way across palm.
Poor muscle tone and loose ligaments are also common.
Development and growth is usually delayed and often average height and development milestones are not reached.
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