Multifactorial Inheritance Flashcards
Relative risk ratio (lamda)
Lamda=(prevalence of disease of affected person)/(prevalence of disease in general population)
- the greater the lamda the greater the familial aggregation.
- lamda=1 means individual and population get disease equally
- the greater the population prevalence the more difficult it is to observe familial aggregation and the more likely hood of impact from environment
Familial relative risk
The more closely related to someone with a disorder the more closely you are to some alleles.
1st degree : 1/2 chance
-parents, siblings, children
2nd degree: 1/4
-Nieces and nephews, grand parents, grandchildren, half siblings
3rd degree 1/8
-first cousins, great-grand parents, great-grandchildren
Liability/theshold model
Model attempts to describe a population’s genetic and environmental susceptibility.
All factors that contribute to disease
-produces normal distribution
Characteristic of multifactorial Inheritance
- Trait does not demonstrate a simple mendelian pattern of inheritance
- Famillial aggregation
- Common among relatives of proband and less common in relatives who are less closely related.
- Environment also interacts with genotype to produce the final phenotype
Tools for determining Genetics Vs environment
- Population/migration
- Family studies
- Twin studies
- association studies
Concordance
both twins have the same disease
if Concordance = 100% then genetically determined disorder
If concordance < 100% then non-genetic factors are involved
Disconcordance
one twin has the disease and the other does not.
the greater the discordance = the greater environmental input
Association Analysis
Identify SNP’s then ask whether you see more alleles more commonly in individuals with disease than individuals without disease, arguing that there is some association with some allele with disease.
Association studies do not analyze familial inheritance patterns; they are instead case-control studies.
