Genetics and Human Disease Flashcards
(22 cards)
Pleiotropism
a mutation in a single gene can lead to many effects
genetic heterogeneity
a mutation in multiple genetic loci may produce the same trait
Autosomal dominant disease
late age of onset
only need one parent to carry defective gene
autosomal recessive
earlier age of onset
BOTH parents must carry defective gene
Examples of autosomal dominant diseases
- Huntington’s disease
- Familial hypercholesterolemia
- Marfan syndrome
Huntington’s disease
triplet repeat on chromosome 4 –> excessive # of glutamine residues –> dysfunctional protein builds up –> toxic to GABA neurons
Familial hypercholesterolemia
defective LDL receptor –> very high LDL levels in the blood
Marfan syndrome
mutation in fibrillan protein –> weak extracellular matrix
Examples of autosomal recessive diseases
- Phenylketouria (PKU)
- Cystic fibrosis
- Sickle Cell Anemia
Phenylketouria (PKU)
defective phenylalanine hydroxylase –> phenylalanine is not catabolized –> buildup in CNS causes mental retardation in infants
Cystic fibrosis
defective chloride ion channel –> thickened mucus secretions
protects against typhoid
Sickle Cell Anemia
defective hemoglobin which precipitates at low O2 tension –> sickling of RBC’s –> buildup and hypoxia
X-linked recessive diseases
males most affected
- hemophilia
- G6PD deficiency
- Diabetes insipidus
- Fragile X Syndrome
Hemophilia A & B
defect in clotting factors VIII and IX –> prolonged bleeding due to inability to form fibrin clot
Diabetes insipidus
mutation in AVPR2 receptor –> defective vasopressin receptor
G6PD deficiency
most common enzyme defect in humans
usually asymptomatic until hemolysis is triggered –> RBC’s unable to repair
Fragile X Syndrome
triplet repeat in FMR1 gene
affects brain development
Non-dysjunction
chromosomes do not separate normally
Examples of diseases from non-dysjunction
- Down’s syndrome (trisomy 21)
- Turner’s syndrome (X0)= only one X chromosome
- Klinefelter’s syndrome (XXY)= extra X
positive selection
confers a survival advantage
ex: alcohol tolerance, lactose tolerance
ex. Sickle Cell carriers are protected from malaria, Tay Sach’s protected against TB, Type AB blood resistant against cholera
multiple sclerosis
incidence is higher in countries far from the equator (US, Canada, Northern Europe)
Venous thrombosis
increased risk in pts who are oral contraceptive users with the Factor V Leiden mutation (majority are AA substitution at position 506) –> makes them more predisposed to having blood clots
most frequent CV event in young women
