Human Genetic Diseases

(Simple Dominance Inheritance)

Dominant Human Diseases

• Only have to inherit it from one parent

• Having disease is dominant to not having disease

• If child has it, a parent must have it also

Huntington’s Disease• Inheritance Pattern: Dominant

• Symptoms:– Breakdown of brain tissue– Irritability, forgetfulness, loss of coordination

Huntington’s Disease (cont.)

• Other Important Information:– Rare but lethal– Symptoms show up between 30-50 years old

• May have already had kids

Catfish Hunter Woody Guthrie

Example Problem:

• A man who is homozygous for HD and a woman that does not have HD have a child. What is the chance that the child will have HD?

Achondroplasia

• Dwarfism

• Inheritance Pattern: Dominant

• Symptoms:– Short arms and legs– Normal skull and torso

Achondroplasia (cont.)

• Other Important Information:– Inhibits bone growth

(cartilage slow to turn to bone)

– Most have normal life expectancy

Example Problem:

• What is the chance of 2 dwarfs that are heterozygous for the disease to have a child that is normal sized?

Recessive Human Diseases

• Not having disease is dominant over having the disease

• Have to inherit the recessive allele from both parents (i.e. 2 little letters)

• A person can be a CARRIER (heterozygous) for the disease and not show symptoms

• If two carriers have a child, the child has a 25% chance of having the disease

• A child can have it without either parent having it

Cystic Fibrosis• Inheritance Pattern:

Recessive

• Symptoms: – Overproduction and build-

up of mucus in lungs and digestive tract

– Difficulty breathing– Salty skin

Cystic Fibrosis (cont.)• Other Important Information:

– Avg. life expectancy 30 – 40 years– Most common genetic disease in white

Americans– Treatment: physical therapy, gene therapy,

special diet

Gene Therapy

Example Problem:

• A child’s mom is completely normal. His dad is a carrier for CF. What is the chance that the child will also be a carrier?

Other Weird Genetic “Conditions”

Blue people of Troublesome Creek-Result from lack of an enzyme-Causes abnormal hemoglobin

Vadoma Tribe – Zimbabwe- Ostrich-toed (ectodactyly)

Old Slides

Phenylketonuria (PKU)• Inheritance Pattern: Recessive

• Symptoms:– a.a. phenylalanine accumulates in body and

damages CNS → brain damage– Now can be detected at birth before brain

damage occurs

PKU (cont.)

• Other Important Information:– Treatment:

• Babies – diet low in milk until brain is fully developed

• Pregnant women – limit milk, diet foods, protein

Example Problem:

• A woman has PKU. A man is completely normal. What is the chance of their child having PKU?