Genetic Disorders

PKU

Inability to produce proper enzymes for phenylalanine breakdown —> degradation product phenylpyruvic acid accumulates —> mental retardation

• Autosomal recessive

Cystic fibrosis

Thick mucus buildup in respiratory tracts

• Autosomal recessive

Tay-Sachs

Lysosome defect: cannot breakdown lipids for normal brain function (fatal within the first 5 years of life)

• Autosomal recessive

Sickle-Cell Anemia

Defective hemoglobin due to substitution

• Autosomal recessive

Galactosemia

Cannot breakdown galactose properly

• Autosomal recessive

Huntington’s Disease

Degenerate nervous system disease

• Autosomal dominant

Achondroplasia

Dwarfism

• Autosomal dominant

Hypercholesterolemia

Excess cholesterol in blood —> heart disease

• Autosomal dominant

Hemophilia

Abnormal blood clotting

• X-linked recessive

Color blindness

Inability to distinguish between different colors

• X-linked recessive

Duchenne

Muscular dystrophy

• X-linked recessive

Fragile X syndrome

Intellectual disability

• X-linked dominant

Downs Syndrome

Trisomy 21; causes mental retardation

• Chromosomal

Turner Syndrome

XO; sterility; typically doesn’t cause mental retardation

• Chromosomal

Klinefelter Syndrome

XXY; sterility; causes mental retardation

• Chromosomal

Cri du Chat

Deletion on chromosome 5; causes mental retardation

• Chromosomal

Genetic disorder testing

A fetus can be tested for genetic disorders via amniocentesis or chorionic villus sampling (CVS)

Autosomal recessive disorder tips

Usually “skips” generations

Autosomal dominant tips

Does not skip generation

X-linked tips

If a father doesn’t have the phenotype, neither will any of his daughters