1. Human Genetic Diseases
(Simple Dominance Inheritance)

2. 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

3. 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

4. Huntington’s Disease Inheritance Pattern: Dominant Symptoms:
Breakdown of brain tissue
Irritability, forgetfulness, loss of coordination

5. Huntington’s Disease (cont.)
Other Important Information:
Rare but lethal
Symptoms show up between years old
May have already had kids
Catfish Hunter
Woody Guthrie

6. 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?

7. Achondroplasia Dwarfism Inheritance Pattern: Dominant Symptoms:
Short arms and legs
Normal skull and torso

8. Achondroplasia (cont.)
Other Important Information:
Inhibits bone growth (cartilage slow to turn to bone)
Most have normal life expectancy

9. Example Problem:
What is the chance of 2 dwarfs that are heterozygous for the disease to have a child that is normal sized?

10. Cystic Fibrosis Inheritance Pattern: Recessive Symptoms:
Overproduction and build-up of mucus in lungs and digestive tract
Difficulty breathing
Salty skin

11. 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

12. Gene Therapy

13. 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?

14. Other Weird Genetic “Conditions”
Vadoma Tribe – Zimbabwe
Ostrich-toed (ectodactyly) – two toes
Dominant inheritance pattern
Blue people of Troublesome Creek
-Recessive inheritance pattern
Result from lack of an enzyme
Causes abnormal hemoglobin

15. 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

16. PKU (cont.) Other Important Information: Treatment:
Babies – diet low in milk until brain is fully developed
Pregnant women – limit milk, diet foods, protein

17. Example Problem:
A woman has PKU. A man is completely normal. What is the chance of their child having PKU?

18. Influence of Gene Expression
Environmental Influence
Human behavior
Phenotype changes
Temperature changes
Family Disease History
Exercise influence
Diet influence
Temperature changes: Warmer temperatures = female turtles vs cooler temperatures = male turtles