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

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

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?

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” 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

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?

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