Polygenetic Disorders Flashcards
Polygenetic
Trait where there is variation caused by combined effect of multiple genes
Multifactorial
When environment factors cause variation in trait
Quantitative traits
Traits that are also multifactorial (2 alleles A and a)
What happens when environmental factors are added?
We approach a bell shaped curve if the representation of the alleles
What is the threshold model?
Most diseases don’t follow the bell shaped curve. they are either present or absent
What is the threshold of liability?
The line that must be crossed before a disease is expressed.
What is the significance of males having a lower threshold of liability?
It requires fewer disease-causing factors to generate the disorder in males.
Proband
The person that has the disorder/disease
Why are the risk estimations for multifactorial disease so complex?
Because the number of genes are not known.
Neural Tube Defect
1/1000, highest in Chinese populations
Anencephaly
Partial or complete absence of the cranial vault. Or complete abscence of the cerebral hemispheres
How do you detect Neural Tube Defects?
Prenatally through US and elevated alpha-fetoprotein in the maternal serum or amniotic fluid.
How do we best prevent Neural Tube defects?
Supplement the mothers with folic acid during pregnancy development.
What makes the recurrence risk higher for NTD?
if more than one family member is affected, if the expression is more severe, or if the proband is of the less commonly affected sex.
How can you distinguish between single gene mutations and multifactorial?
single gene is a mutation in ONE location. where multifactorial is from many more things. Ex. Environmental, inbreeding, diet. etc.
