Nondisjunction Disorders

Down Syndrome (trisomy 21)47, XX, +21 / 47, XY, +21• the result of an extra copy of chromosome 21• characteristic facial features, short stature; heart defects, shorter

lifespan • often sexually underdeveloped and sterile, usually some degree

of mental retardation • Down Syndrome is correlated with age of mother but can also be

the result of nondisjunction of the father's chromosome 21

Patau Syndrome (trisomy 13): 47, XY, +13 / 47, XX, +13

• serious eye, brain, circulatory defects as well as cleft palate

• children rarely live more than a few months

Edward’s Syndrome (trisomy 18): 47, XX, +18 / 47, XY, +18• almost every organ system affected • children with full Trisomy 18 generally do not live more

than a few months.

Turner's syndrome (Monosomy X ): 45, XO• the only viable monosomy in humans • genetically female - they do not mature sexually during

puberty and are sterile• short stature and normal intelligence (98% of these fetuses die before birth)

Klinefelter’s Syndrome: 47, XXY • genetically male• individuals have male sex organs, but usually small testes and

are sterile• may have breast enlargement and other feminine body

characteristics• normal intelligence

Trisomic Females: 47, XXX

healthy and fertile - usually cannot be distinguished from normal female except by karyotype

XYY Males: 47, XYY • individuals are somewhat taller than average and

sometimes have below normal intelligence• increased amounts of acne• normal sexual development