Chromosomal Disorders

Down Syndrome

• 47 chromsomes• 1/700 births• 3 x #21 nondisjunction of chromosome 21• Short, broad hands with palmar crease, short

stature, hyper-flexibility of joints, mental retardation, broad head with round face, open mouth with large tongue.

Cri-du-Chat

• 46 total chromosomes• Upper arm deletion on chromosome #5• “Cry of the cat” severely impaired- both

mentally and physically, their plaintive, catlike crying gives the syndrome its name.

Edwards Syndrome

• 47 chromosomes• 1/8000 births• Nondisjunction of chromosome # 18. • Congenital malformation of many organs. Low-

set malformed ears, receding mandible, small mouth and nose with general elfin appearance, mental deficiency, horseshoe or double kidney, short sternum, 90% die within the first 6 months after birth

Patau Syndrome

• 47 chromosomes• 1/20,000 births• Nondisjunction of chromosome #13.• Mental deficiency and deafness, minor

muscle seizures, cleft lip and/or palate, cardiac anomalies, posterior heel prominance

Turner Syndrome

• 45 chromosomes• 1/2500 female births• Monosomy of chromosome X. • Female, but almost always sterile. Short in

stature, webbing in neck region, hearing deficiencies, and significant cardiovascular abnormalities

XXX- Triplo X Syndrome

• 47 chromosomes• 1/700 female births• Trisomy of chromosome 23• Female, phenotypically normal, limited

fertility, may have slight mental retardation

Klinefelter Syndrome

• 47 chromosomes• 1/500 male births• Nondisjunction of chromosome 23. XXy• Male, subfertile with small testes, developed

breasts, feminine pitched voice, knock knees, long limbs.

Jacob’s Syndrome

• 47 chromosomes• 1/1000 male births• Xyy- nondisjunction of chromosome 23• Male- tend to be taller than normal. Most have

normal sexual development and able to father children. May have increased risk of learning disabilities, delayed speech and gross motor skills. Some linked to Autism. Not inherited.