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 13 has Huntington’s Disease! 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?

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

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

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

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?

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

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

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

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