Multifactorial Inheritance Flashcards
1
Q
describe the liability/threshold model
A
- If you have only “good” genes you can have a lot of “bad” environment and still be okay
- But if you start out with some “bad” genes, it does not take much “bad” environment to tip you over the edge
2
Q
describe familial relative risk
A
- the more closely related you are to someone with a complex disorder, the more likely you are to have some of the same alleles
- but that risk drops by half for every degree distance from affected person
3
Q
describe familial aggregation and relative risk
A
- familial aggregation of a disease may be estimated by comparing the frequency (prevalence) of the disease in the relatives of an affected proband with its freq. in the gen. pop.
- this is the relative risk ratio = λ
- λ = (prevalance of disease in relatives of affected person)/(prevalence of disease in general pop)
4
Q
describe characteristics of multifactorial inheritance
A
- trait does not demonstrate a simple Mendelian pattern of inheritance
- familial aggregation
- more common among the close relatives of the proband and less common in relatives who are less closely related
5
Q
describe concordance in MZ twins
A
- concordance means both twins have the same disease
- concordance = 100% if genetically determined
- concordance < 100% if non-genetic factors involved
- discordance means one has it but the other does not
- If concordance similar between MZ and DZ, environment plays a big role
- If concordance different between MZ and DZ, genes play a big role
6
Q
name 2 neural tube defects
A
- Anencephaly
- most severe of the neural tube defects
- rare and fatal
- underdeveloped brain and incomplete skulls
- spina bifida
- incomplete closure of the spine
- repair may be done in utero or postnatally
- BOTH show multifactorial inheritance
- supplementation of the mother’s diet with folate can reduce the incidence of neural tube defects by ~70%
