Genetic Disorders Downs Syndrome Caused by nondisjunction of

Genetic Disorders

Down’s Syndrome • Caused by non-disjunction of the 21 st chromosome. • This means that the individual has a trisomy (3 copies of the 2 lst chromosomes).

Down’s Syndrome or Trisomy 21

Symptoms of Down Syndrome • • Upward slant to eyes. Distinctive facial features Low muscle tone Usually mild to moderate mental retardation. In some cases, mental issues are severe.

Kleinfelter’s syndrome XXY • Non-disjunction of the X chromosome. • Males with some development of breast tissue normally seen in females. • Little body hair is present, and such person are typically tall, have small testes. • Infertility • Evidence of mental retardation may or may not be present.

Kleinfelter’s syndrome

Turner’s Syndrome

Sickle Cell Anemia • Autosomal Recessive • Results in crescent or “sickle” shaped red blood cells. • Homozygous recessive condition is fatal. • Heterozygous condition provides some protection against malaria.

Cystic Fibrosis (CF) • Autosomal Recessive • Cause: deletion of only 3 bases on chromosome 7 • Fluid in lungs, potential respiratory failure • Common among Caucasians… 1 in 20 are carriers

Tay-Sachs disease • Autosomal recessive • Central nervous system degrades, ultimately causing death. – Normally before 3 years old • Most common among people of Jewish, eastern Europe descent.

Hemophilia, the royal disease • Recessive – Sex linked (on the X chromosome) • One can bleed to death with small cuts. • Known as the royal disease (very important in Russian history)

Huntington’s Disease • Autosomal Dominant • Rare – most common among white Europeans • Brain tissue is destroyed leading to loss of motor control and severe mental deficiency. • Symptoms usually appear between age 30 -50 with death 12 years later.

Phenylketonuria or PKU • Autosomal Recessive • People with PKU cannot consume any product that contains phenylalanine until after they have reached physical maturity. • Caused by a deficiency of an enzyme which is necessary for proper metabolism of the amino acid phenylalanine.

Color Blindness • Recessive – Sex linked (on the x chromosome) • 1/10 males have, 1/100 females have. • Individuals are unable to distinguish shades of red-green.