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Human Genetic Diseases
(Simple Dominance Inheritance)
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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
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Huntington’s Disease Inheritance Pattern: Dominant Symptoms:
Breakdown of brain tissue Irritability, forgetfulness, loss of coordination
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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
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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?
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Achondroplasia Dwarfism Inheritance Pattern: Dominant Symptoms:
Short arms and legs Normal skull and torso
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Achondroplasia (cont.)
Other Important Information: Inhibits bone growth (cartilage slow to turn to bone) Most have normal life expectancy
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Example Problem: What is the chance of 2 dwarfs that are heterozygous for the disease to have a child that is normal sized?
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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
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Cystic Fibrosis Inheritance Pattern: Recessive Symptoms:
Overproduction and build-up of mucus in lungs and digestive tract Difficulty breathing Salty skin
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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
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Gene Therapy
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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?
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Other Weird Genetic “Conditions”
Vadoma Tribe – Zimbabwe - Ostrich-toed (ectodactyly) Blue people of Troublesome Creek Result from lack of an enzyme Causes abnormal hemoglobin
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Old Slides
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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
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PKU (cont.) Other Important Information: Treatment:
Babies – diet low in milk until brain is fully developed Pregnant women – limit milk, diet foods, protein
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Example Problem: A woman has PKU. A man is completely normal. What is the chance of their child having PKU?
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