Multifactorial Disorders Flashcards
chromsomal and genomic disorders affect what percentage of the poplaution
0.38%
single gene disorders affect what percentage of the popluation
2%
disorders with multifactorial inheritance affect what percentage of the population
60%
the more genes are involved …
the lower the probabiliy of an offspring inheriting all or none of the contributing alleles
higher number of genes involved…
lower the fraction of extreme phenotypes at the fringes of the bell curve
what do we assume during the analysis of quantitiative traites
many genes are invovled with the development of disease
alleles can be contriubting or noncontributing to disaes phenotupes
liability distribtuion
bell curve of phenotype distrubtion
threshold of liabity
can be differnt for men and women
influenced by environment
once you pass this point you ge tthe disease
recurrene risk is higher than what in multifactorial disorders
occurrence risk
is pyloric stenosis imore common in men or women
males
why does pyloric stenosis affect more males
they need fewer contributing alleles to exxpress the disease
who has a higher risk of an affected sibling with pyloric stenosis, an affected male or female
female
falconer’s formula (twins)
hertibility H2 = ( concordance MZ- concordance DZ) x 2
concordant trait
triat shared by both twins
disease with a signifcant genetic compoentn will show waht
high concordance rate in MZ twins than DZ twins
MZ twin
identical
linkage analysis
mapps an unknown number o fcontributin glici
model free linkage analysis
insensitive and imprecise but doesn’t amke possible incorrect assupmtions about the number of genes inboled
why is model free linkage insensitive
needs a very large sample size
why is model free linkage imprecise
maps the contributing allele to a very alrge chormsomal region
incidence
how many new cases are recorded in a given time
prevalence
what proportion of the population has the disease
relative risk ratio
prevalence of the diseas in r of affeccted person / precvalence in general population
what is the risk of multifactorial birth defec ting eneral population
0.5
what is the risk of multifactorial birth defect in 2nd degree relative
0.7 -2%
what is the first of multifacotiral birth defect if 1sst degree relative is affected
3-4%
what is the rist of multifactorial birth defect if 2 first degree relatives are affected
5-8%
what is the risk of multifactorial birth defect if 3 first degree relatives are affected
9-12%
what is the risk o fmultifacotiral birth defect if identifcal twin is affected
20-30
disease association of allele
how the allele in question influecnes the risk for the disorder
relative risk
percentage of people with the allele who develop the trait with the percentage of people without the allele who develope it
4 charactersitcs of multifactorial disease tha tset them apart from single gene disorders
- don’t follow mendelian patterns of inheritance
- familial aggegration
- incomplete penetrance
- much more common amoung close relatives than less closely related
where is MHC locus found
chromsome 6
fucntion of MHC class I and II
encode cell surface proteins that play role in iniation of immuen resposne
HLA gene charactersiti
polymorphic
how are HLA haplotypes expressed
codominat manner
if parent and child share 1 haplotype waht is the chance of 2 sibling expressing identical haplotypes
25%
what types of disease does HLA haplotypes tend to favor
immuen system disease
what is unqieua bout DR-DQ haplotypes and T1D
some are susceptibiliy alleles and some are protective alleles
HLA-B haplotypes determine risk for waht
spondyloarthropathy
HLA-C haplotypes predict risk for what
psoriatic arthritis
