Down's Syndrome

An error in number of chromosomes is called Aneuploidy. Among all the aneuploidies , trisomy of the 21st chromosome or Down's syndrome is the most common autosomal aneuploidy with an extra 21 chromosome due to nondisjunction.

How common -Down's syndrome ( DSynd ) is the most common chromosomal disorder It is estimated to affect approximately in 1 in 700 live births ( Kanamori et al 2000 ) DSynd is the most commonly identified genetic form of mental retardation and the leading cause of specific birth defects and medical conditions ( Sherman et al ) CDC ( USA ) reports that between 1979 and 2003 the number of babies born with DSynd increased by about 30 % Most common figure in literature quotes that DSynd occurs in 1 out of 600-800 births DSynd happens in people of all races and socio economic status No sex preponderance.

Trisomy happens due to non-separation or non-disjunction ( NDJ ) of chromosome ( Ch21 ) during gametogenesis - leading to disomic gametes with two copies of a particular chromosome being formed which upon fertilization by a haploid gamete from opposite sex leads to the formation and implantation of trisomic fetus Three subtypes have been described...