Lecture 4: Random genetic drift, aggregation and heritability analysis Flashcards
What is random genetic drift?
Change in allele frequency as a function of random genetic sampling.
What model can be used to model random genetic drift?
Binomial - we can then model the probability of different frequencies of the allele frequencies.
Explain the principle of the wright fisher model:
The wright fisher model is an adaptation of the HWE assumptions when we assume the sample size is not infinite.
When this is the case the inheritance of alleles can bo thought of as a stochastic process that behaves binomially. That is the amount of alleles in the next generation is a function of the previous one.
This is kind of like a markov chain.
What kind of equilibrium can occur with the wright fisher model?
Either everything is A or everything is not A.
Why does allele fixation not happen in the real world?
1) Mutations
2) Selection
3) Migration
What is the purpose of aggregation and heritability analysis?
Used to uncover if genetic basis for a given phenotype exists.
What is the purpose of segregation analysis?
To find support for specific genetic models.
What does aggregation, heritability and segregation have in common?
They don’t have any genetic data.
What kind of trait is associated with a DSL?
A dichotomous one.
What kind of trait is associated with a QSL?
A quantitative one
What kind of trait is associated with a aggregation analysis?
Dichotomous traits
What kind of trait is associated with a heritability analysis?
Quantitative traits
What are the assumptions for aggregation, heritability and segregation analysis?
1) HWE
- alleles are given as binomial
2) Phenotypic independence
3) Full genetic information (all information that affects phenotype is in the genotype)
Principle of aggregation analysis:
Related people are more likely to share genetic information. Individuals related to diseased individuals are more likely to be sick. Compare the probability of sickness in people related to a sick person with the overall prevalence of disease.
