Trisomy 21 is one of the most common chromosomal abnormalities in live born children and causes Down syndrome. Trisomy 13, also called Patau syndrome, is a chromosomal condition that is associated with severe mental retardation and certain physical abnormalities. Trisomy 18 causing Edwards syndrome is the second most common autosomal trisomy after trisomy 21. The disorder/condition is characterized by severe symptoms. Turner syndrome occurs when females inherit only one X chromosome; their genotype is X0. Metafemales or triple-X females, inherit three X of more chromosomes. Klinefelter syndrome males inherit one or more extra X chromosomes; XYY syndrome males inherit an extra Y chromosome.
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