18 Gene mapping Flashcards
Why gene map?
ID disorders, new Dx/Tx
What is linkage analysis?
Close genes linked = less likely separated, distance in centimorgan
How can numbers of crossovers determine what may occur to an allele?
Single crossovers may alternate all alleles before the crossover point but a double crossover may bring back the original allele if it is not involved in the region of crossover
How is centimorgan equate to recombination chance?
1 cM = 1% chance of recombination(alleles touching). 50 cM = 50% max chance of recombo (alleles at opposite ends)
When does chromosomes reorganize?
Meiosis
What is a linkage phase?
Description of where alleles are located in a pedigree
What is a LOD score?
Statistical result to calculate likelihood of two alleles are linked
What LOD score indicates linkage? What score for no linkage?
3 or higher is significant for linkage. -2 or below is no linkage
What are commonly used for markers in linkage phase?
Microsatellites are useful as they are polymorphic and located everywhere on genome. Can be followed if close enough to allele and unimproved even when likely
What is uninformative mating?
Markers that cannot determine linkage due to not enough polymorphisms
How does linkage relate with time?
Linked alleles/markers will initially stay together but eventually become unlinked
What is linkage disequilibrium?
Mutation with linked allele being inherited together
How is age determined for linked mutations?
Linked mutations estimated by time to equilibrium (close link = longer time)
What is genetic association?
Allele’s effect = increased risk of disorder
How does genetic association compare with linkage?
Association = specific allele found = increased risk but can be anywhere on chromosome
