Lecture 5: Segregation analysis and genetic mapping Flashcards
Purpose of segregation analysis
Testing of models formulated through aggregation and Heritability
What do you get out of a segregation analysis?
1) Estimates for penetrance probabilitis
2) *Estimates of allele frequencies
What can you use the output of segregation analysis for?
1) Necessary input in parametric linkage analysis
Autosomal dominant disease rules:
1) All affected individuals have at least one affected parent
2) The disease appears in every generation
3) Males and females are equally affected
What type of matings are used to test a dominant model in segregation analysis?
Only Dd x dd
DD x DD and dd x dd we know the outcome of. They provide no thing we can test for.
Dd x Dd very unlikely in rare diseases - leaves us with Dd x dd.
What type of distribution is used for testing segregation analysis?
Binomial - to calculate the likelihood of offspring probability.
This log likelihood is then used to perform a log likelihood test - which is chi squared distributed.
Why is a recessive mendelian disease harder to perform a segregation analysis on?
Because the genetype status of unaffected individuals is unknown.
What is the purpose of gene mapping?
To find the location of a gene (DSL)
Name two methods for gene mapping:
1) linkage analysis
2) Association mapping
What is the overall concept of gene mapping based on?
Identify areas of the genome associated with DSLs by looking at genetic markers.
What is the difference between linkage analysis and association mapping?
Linkage = related individuals
Association mapping = unrelated individuals.
What forms the biological basis for gene mappingn
the biological distance between DSL and the markers
Genetic recombinations
Recombination fraction
theta = (1-p0)/2
When are two loci unlinked?
When the recombination fraction is 1/2
What is linkage disequlibrium?
When two loci are associated - the recombination fraction is smaller then 0.5.
