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

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

5. 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?

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

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

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

9. 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

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. Tay-Sachs Inheritance Pattern: Recessive Symptoms:
Lipids accumulate in cells of CNS
Loss of motor skills, blindness, paralysis, death

15. Tay-Sachs (cont.) Other Important Information:
Life expectancy = 5 years
Most common in Jews and Amish

16. Example Problem
Two carriers for Tay-Sachs have a child. What is the chance that the child will have Tay-Sachs?

17. 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

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

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

20. Albinism Inheritance Pattern: Recessive Symptoms:
Little or no pigment (melanin) in eyes, skin, hair
Most have blue eyes, pale skin, and blond hair
Vision problems

21. Albinism (cont.) Other Important Information:
Have to be careful of sun exposure

22. Example Problem:
Is it possible for 2 albino people to have a child with normal pigment?

23. Other Weird Genetic “Conditions”
Vadoma Tribe – Zimbabwe
- Ostrich-toed (ectodactyly)
Blue people of Troublesome Creek
Result from lack of an enzyme
Causes abnormal hemoglobin