الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
In 1866 Langdon-Down gave the first description of
mongloism, shortly afterwards different terms such as
fetalism, peristatic amentia and congenital acromica designated
the same clinical entity.
In 1959 Lejuene et al., discovered that the cellular
karyotype of Mongols carries 47 and not 46 as the cell of
normal individual.
An exira chromosome means that a large number of
genes are present 3 times rather than the balanced two. Since
the genes on particular chromosome may be quit unrelated in
their primary action, trisomy would disturb, many apparently
unrelated functions (Sutton, 1975).
Uniparental disomy involving several different
chromosomes has been described in several cases of human
aneuploidy. Patermal uniparental isodisomy for chromosome
21 (PUPID 21) is not associated with abnormal phenotypes
and that there are probably no imprinted genes on
chromosome 21. (Jean et aL, 1993).
The criteria, set forth for the diagnosis of mongolism are
classified into major or macro signs and minor or micro signs.
The major signs include the classic Mongolian facies (small
depressed nose and slanting plapebral fissures) coupled with
varying grades of mental deficiency and somatic growth
retardation. These major signs are considered essential and
constant features