genetic variability with no unifactiral mechanism ( there is no single things that contributes to these inheritance)
environement play a BIG roll
quantitative trait
polygenic
quantitative trait loci
there is always variability
how are quantitative traits measured?
a bell curve
liability districution
threshold model
what does the threshold model tell you
if you are below the treshold you have unexpressed genetic varaiation if you are above you have expressed variability
what does a higher threshold mean?
have less disease because you have to reacha certain amount until it is expressed
what are the neural tube defects
Spina bifida and anencephaly
what environmental factors can cause neural defects
folic acid intake
what is the recurrence risk of NTD
1 child= 5%
2 children=10%
3 child=21%
what is the general pop risk for neural tube defects?
.1%
empirical risk
what has been exactly observed in a population because we cannot calculated multifactorial inheritance
they are disease specific and based on family studies
specific to population
principles of multi factorial inheritance
segregation does not fit mendelian inheritance patterns ( they are more complexed)
recurrent risk within a family is larger than general pop
inverse relationship btwn recuurence risk and distanc eof family members
risk increase with affected individuals
increased roisk comes with increase severity
may have a sex bias
cleft palate
congenital malformation
.1% if non of the parents have this malformation ut risk increases with siblings and 1st and 2nd degress relatives
Pyloric stenosis
congenital defect
male biased
fathers pass on reccurent risk higher to son
what is significant about maternal passing on of the pyloric stenosis gene
females have higher threshold and they have greater contribution to creating the gene because there has to be more thing factoringin forthe disease to manifest
Diabetes Type II
major risk is family history
second is obesity
cancer genetics
there must be genetic changes
rare ocurance
genetic predisposition and environemtnal risk
uncontrolled cell divison and proliferation that can lead to tumor
protooncogenes
normal role if to promote cell proliferation e.g. growth factors, transcription factos, receptor, and signal transduction
when it is mutated it becomes an oncogene which is the bad stuff
oncogenes
increase in function mutation
enhance function
tumor suppressors
genes involved in suppressing the cycle .g.
p53
retinoblastoma
mutationin RB1 gene ( a tumor supressor)
Rb1 has twp alleles and you need mutation in both
two types
two hit hypothesis
you need mutation in both alleles of a tumor suppressor in order to progress to cancer phenotype
loss of heterocygosity
what mutations cause familial and ovarian cancer
BRCA1 and BRCA2 genes
what mutation is found in 30% of all cancers?
Ras mutation
what does p53 normal function
there to induce apoptosis in a damaged cell
environmental factors that can contribute to cncers