• Most affected children have unaffected parents
• Heterozygotes (carriers) are unaffected

• Affected children usually have an affected parent
• Heterozygotes are effected
• Two heterozygotes (Hh x Hh) can produce a normal (hh) child

Tay - Sachs Disease

• More common among Jewish populations
• Young children begin showing signs of slowed development
• Severe impairment and death

Cystic Fibrosis

• More common in Caucasion
• Mucus in respiratory tract, difficulty breathing
• extreme salty sweat
• Mucus may cause secondary infections

Phenylketonuria (PKU)

• Lack enzyme for normal metabolism
• Phenylalanine builds up and causes brain damage
• Newborns are routinely tested
• Changes in diet lead to normal life

Sickle Cell Disease

• More common in Africans (African-Americans)
• Causes blood to be sickle shaped
• Affects oxygen flow to organs, causing weakness, pain, anemia, etc
• Heterozygotes are resistant to malaria

Neurofibromatosis

• Tumors form under skin and
• Can cause skeletal deformities, blindness

Huntington Disease

• Neurological disorder, progressive degeneration of the brain
• Symptoms appear later in life

Achondroplasia

• Common form of Dwarfism
• Short arms and legs, normal torso
• Homozygotes (AA) do not survive