Multifactorial Inheritance Flashcards
What are the classic single gene disorders?
Sickle cell
cystic Fibrosis
duchenne dystrophy
what is a characteristic of Multifactorial traits?
- Trait does not demonstrate a simple mendelian pattern
- Familial aggregation
- More common among the close relatives of the proband and less common in relatives who are less closely related
- Environment also interacts with genotype to produce the final phenotype
What is the model that tries to explain multifactorial traits?
Liability/threshold
attempts to describe a populations genetic and environmental susceptibility.
What is liability?
all factors that contribute to the disease
What is threshold?
The limit to which normal is defined.
Passing threshold will make them affected
Liability in multifactorial diseases
Disease state is determined by both genes and environment
What is this image of?
Liability model and familial aggregation
What happens when there are bad genes in the liability and threshold model?
The curve is moved to the right- more of the population is above the threshold point
The threshold line moves to the left-in essence the same thing as more of the population is under the affected portion of the curve
Relative Risk ratio
Prevalence of disease in relatives of affected person / prevelance of disease in general population
What does the liability threshold model explain?
Explains the pattern of recurrence risk in families
What is Pyloric stenosis? What does it mean is a female has it in regards to recurrence risk?
Hypertrophy of the muscle between the stomach and intenstines,causing it to narrow(stenosis) impeding gastric emptying.
More common in male babies
If a female child gets it, that means there is a higher reccurence risk f because the parents have more of the bad gene
Symptoms of pyloric stenosis
Severe vomiting
palpation of the abdomen may reveal a mass in the epigastrium
may cause other problems such as dehydration and salt fluid imbalances
What are tools for determing the effects of genetic versus environment?
- Population/migration studies
- Family studies
- twin studies
- adoption studies
- Association studies
Population/Migration studies
Indicative of environmental factors.
Disease incidences differences between populations suggest a genetic basis for that disease.
Could be due to cultural/lifestyle differences.
It is known that Asian women have a lower incidence of breast cancer than American women. The Asian women move to America and within two generations, their incidence increased to near american levels. What experiment/study is this an example of?
Population/Migration study.