Autosomal and Recessive Inheritance Flashcards
Characteristics of Autosomal Dominant Inheritance
Direct transmission from affected parent to affected child
Affected children always have an affected parent
No gender bias
50% chance of inheriting the gene
No skipped generations
Examples of Autosomal Dominant Disorders
Achondroplasia Adult dominant polycystic kidney disease Marfan syndrome Neurofibromatosis Huntington's disease Hypercholesterolemia
Characteristics of Autosomal Recessive Inheritance
No gender bias
Usually two normal parents produce an affected child
25% chance of inheriting the gene (when both parents are carriers)
Skips generations
Examples of Autosomal Recessive Disorders
Cystic Fibrosis PKU Thalassemia Tay-Sachs Hereditary Hemochromatosis Sickle Cell Anemia
Achondroplasia
Most common cause of dwarfism Mutation in FGFR3 Normal intelligence Recurrence risk is low with unaffected parent Homozygous dominant is lethal
Adult Dominant Polycystic Kidney Disease
Adult onset
Fairly common (1:900)
Accounts for 10% of all dialysis patients
Cysts form throughout kidney
Causes progressive renal dysfunction and ultimately renal failure
Less than 5% of nephrons become cystic
Neurofibromatosis 1
2 or more criteria: Neurofibromas Cafe au lait macules Freckling in axillary or inguinal area Optic glioma Iris hamartomas (Lisch nodules) Sphenoid dysplasia Affected first degree relative Due to mutation in chromosome 17 About 50% of cases are due to spontaneous mutations
Marfan syndrome
Tall with long extremities Arachnodactyly Hyperextendible joints Dissecting aortic aneurysms Subluxation of lens Mutation in FBN1 gene on chromosome 15
Hemochromatosis
Most common single-gene inherited disease (1/200)
Iron overload
Symptoms begin in mid adulthood
Type 1 diabetes, liver sclerosis, cardiovascular problems
Sickle cell anemia
Most common genetic disease of African Americans (1/12 AA carriers)
Mutation in Hemoglobin B subunit (glutamate–>valine)
Skeletal problems
Infarctions
Anemia and repeated infections
Examples of X-linked recessive disorders
Hemophilia
G6PD deficiency
Duchenne muscular dystrophy
Characteristics of X-linked recessive
More affected males than affected females
Affected grandfather–>carrier mother–>affected grandson
No male to male transmission
Hemophilia
Primarily affects males
Mutations in Factor VIII or Factor IX
Clotting disorder causing bleeding into soft tissues
Duchenne muscular dystrophy
Most common form of MD
Mutation in the dystrophin gene–largest gene
Gower’s sign
X-linked dominant inheritance
50% of children of an affected mother will be affected
None of the sons of an affected man will be affected
Males affected more than females (mosaic inheritance)
