Condition

Karyotype

Frequency

Traits

Down Syndrome

47, XX or XY, +21

1/700

Mental retardation, heart defects, high risk of leukemia.

Edward Syndrome

47, XX or XY, +18

1/10,000

Mental retardation, elfin appearance.

Patau Syndrome

47, XX or XY, + 13

1/20,000

Cleft palate/lip, heart defects, polydactyly, mental retardation.

Turner Syndrome

45, X

1/10,000

Underdeveloped ovaries, abnormal jaw, webbed neck, shield-like chest.

XYY Karyotype

47, XYY

1/1,000

Often taller, maybe lower in intelligence.

Klinefelter Syndrome

47, XXY

1/1,000

Taller and often infertile.

Metafemale

47, XXX(+)

1/1,000

Mild mental retardation, possible infertility.

Fragile-X syndrome

46, XX or XY

1/1,250 m

1/2,000 f

Mental retardation, altered speech patterns, large testis in males (macroorchidism).

Cri-du-Chat Syndrome

46, XX or XY, 5p-

Microcephaly, Severe mental retardation, heart defects.

Familial Down Syndrome

46, XX or XY, +21p

Same as Down’s Syndrome.