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?
Top Related