Multifactorial Diseases Flashcards
What does the threshold of liability indicate/?
how many contributing alleles are required for a patient to be affected by a disease
What is a concordant trait?
a trait shared by both twins
What is a discordant trait?
a trait not shared by twins
What does high heritability indicate?
that a disease is mainly determined by genetic factors
What is incidence?
describes how many new cases are recorded in a given time
What is prevalence?
describes the proportion of the population that is affected by the disease at any given time
What are the most common genetic diseases?
multifactorial inheritance
How can one estimate the number of genes involved in a multifactorial disease?
shape of bell curve
Regarding a multifactorial disease, the higher number of genes involved does what to the shape of the bell curve?
lower the fraction of extreme phenotypes
What is a liability distribution?
shape of bell curve of phenotypes for multifactorial diseases
Why does the recurrence risk of a multifactorial disease increase with each diagnosis of a relative?
more disease contributing alleles likely present
Which sex is more likely affected by pyloric stenosis?
male
Which sex requires fewer contributing alleles to develop pyloric stenosis?
males
If a female develops pyloric stenosis, what does this mean for the number of contributing alleles she possesses?
she likely has a larger number
What is a concordant trait?
a trait shared by two twins
What is the term for a trait not shared by twins?
discordant
What is the equation for heritability?
(concordance MZ - concordance DZ)*2
What is incidence?
how many new cases are recorded in a given time divided by the size of the population
What is prevalence?
proportion of population that is affected at any given time
What is the equation for relative risk ratio?
prevalence of disease of relatives / prevalence of the disease in the general population
Do multifactorial diseases follow Mendelian inheritance?
No
Do multifactorial diseases show complete or incomplete penetrance?
incomplete
On what chrmosome is the MHC gene found?
chromosome 6
What are MHC class I and II genes involved in?
initiating immune response
How are HLA genes transmitted? Why is this?
as a whole unit
very little meiotic recombination
What is a compound heterozygote?
two mutant alleles are not identical
What is the genetic transmission of the HLA genes classified as?
haplotype
How are the HLA haplotypes expressed?
co-dominant
What is the percentage of MHC haplotypes shared by parent and child?
half
What are the changes of two siblings sharing identical haplotypes?
25%
In order to find an organ donor, what must one do?
match the HLA haplotypes
What haplotype affects T1D?
DR-DQ
What is HLA-B associated with?
Spondyloarthropathy
What is HLA-C associated with?
Psoriatic Arthritis
