Genetic Epidemiology Flashcards
What is genetic epidemiology?
Studies the influence if genes and environment on measures of health and disease susceptibility in populations.
What is the purpose of genetic epidemiology?
Uncover the role of genetic factors in determining health and disease through the detection of inheritance patterns.
What are the advantages of studying genetic epidemiology?
Genetic contribution
Risk estimates
Disease mechanism
Targets for intervention
Impacts of environment and lifestyle
What is a gene?
A portion of a DNA molecule (basic unit of hereditary?
How identical are unrelated human DNA?
99.9%
What is a genotype?
Combination of alleles at a locus
What is a haplotype?
Combination of alleles at different loci
What are regulatory sequences?
When, where and how much protein is made.
What types of SNPs are there?
Deletions, Inversions, Copy Number Variants and Short Tandem Repeats
What is the difference between a polymorphism and mutation?
Mutations are rare
What are the objectives of genetic epidemiology?
Establishing a genetic component
Size of genetic effect about other factors of disease risk
Finding responsible genes for component
What is the purpose of descriptive epidemiology?
Disease characteristics
What is the purpose of family aggregation studies?
Familial clustering, (clustering of certain traits, behaviours or disorders within a family)
What is the purpose of twin/adoption/half-sibling/migrant studies?
Genetic?
or
Enivironmental
What is the purpose of Segregation analysis?
Mode of inheritance
What is the purpose of linkage analysis?
Disease susceptibility loci
What is the purpose of association studies?
Disease susceptibility markers
In which order does classic research genetic epidemiology flow?
Draw it
What is the first step of familial aggregation studies?
Identification of hereditary disease
What is the general approach of familial aggregation studies?
To sample proband(s), and obtain their detailed family history of disease
What is proband in relations to genetics?
The patient or member of the family that brings a family under study
What is familial aggregation is measured by?
Relative recurrence risk (RRR) or Familial risk ratios (FRRs)
How to calculate relative recurrence risk?
What is KR?
The risk or probability of getting the disease to the relatives of type R
What is K?
Population risk
What is R?
Relationship
What does the value of λ mean?
The higher the value of λ the stronger the genetic effect
What is the issue of familial aggregation studies?
Not sufficient to infer the importance of genetic susceptibility
What is the purpose of twin studies?
Estimating heritability
Comparison of monozygotic and dizygotic twins
What is heritability?
Proportion of the phenotypic variance accounted for by genetic factors
What are monozygotic twin pairs?
Share all of their genes
What are dizygotic twin pairs?
Share half of their genes in common
What does the similarity between MZ and DZ twins mean?
The greater similarity in correlation or concordance of MZ twins than DZ twins is considered evidence of genetic factors
What is cocordance?
Probability that a pair of individuals will both have a certain characteristics given that one of the pairs have the characteristics
What does segregation analysis require?
Multigenerational family trees preferably with more than one affected member
What are genetic linkage studies used for?
Associate functionality of genes to their location on chromosomes
What are genetic association studies used for?
Find candidate genes or genome regions that contribute to a specific disease status and genetic variation
What is linkage analysis?
A small set of large pedigrees each containing several affected individuals
Disease phenotype and alleles at one or more genotyped genetic marker loci
What does linkage analysis test for?
Testing the hypothesis that a particular locus is linked to a locus that causes the disease
What is co-segregation?
Alleles at markers that are physically close together tend to be transmitted together, this can be individual in families.
What is the aim of genetic association analysis?
The aim is to determine whether a particular genetic variant influences risk of developing disease.
How is association deemed present?
A particular allele will be seen more often than expected by chance in an individual carrying the trait
What is association?
Statistical findings which usually require investigating the functional relationship
What can genetic association analysis indicate?
Direct causal relationship
Indirect relationship
What are the main types of genetic association study?
Family-based studies
Case/control studies
Total association studies
What are family-based studies?
Investigate transmission of particular high risk alleles through a number of pedigrees
What is the advantage of family-based studies?
Avoid problems of population heterogeneity
What are case/control studies?
Compare the distribution of alleles or genotypes at a locus in affected individuals (controls) or a population -based control sample
What are total association studies?
All individuals with quantitative trait
What is the differences between linkage and association?
While linkage implies a physical connection on a chromosome, the association is based on observation of how variations in genes correlate with certain traits or conditions.
What is genome-wide association studies (GWAS)?
The examination of many common genetic variants in a group of individuals to see if any variant is association with a trait
What is linkage disequilibrium (LD)?
Corresponds to correlation between alleles at two or more loci.
What is a haplotype?
Set of SNPs on a single chromatid of a chromosome pair that are statistically association
What are haplotype blocks?
Sizable regions over which there is little evidence for historical recombination and within which only a few haplotypes are observed
What does it mean is 2 SNPs are in strong linkage disequilibrium?
The genotype at SNP2 will be well-predicted by the genotype at SNP1
What is tagging SNP?
A representative genetic variant that is used to capture the genetic variation in a region of interest.
How are tagging SNP selected?
Due to linkage disequilibrium with other SNPs in that region,
Why are tagging SNP important?
Simplifies the analysis of genetic association without testing each variant.
What is mendelian randomization?
Investigating the casual relationship between an exposure and an outcome.
Relies on mendelian inheritance and the random assortment of genetic variants during gamete formation.
What are the steps of mendelian randomization?
- Identification of genetic variants
- Random Allocation of genetic variants
- Association with outcome
- Casual inference
When is mendelian randomization used?
Overcome some limitations of observational studies such as confounding and reverse causation.