Lecture 12 - Linkage And Mapping In Eukaryotes Flashcards
What is linkage?
When 2 genes on the same chromosome indicate that there are only 2 possible combinations instead of 4 (unless recombination occurs)
Who discovered linkage and how?
Bateson, Saunders and Punnett (1905) by seeing that in certain crosses there were a greater number of parental genotypes than expected (more with PpLl and ppll)
What are the non parental genotypes called?
Recombinants
What is the relationship between recombination frequency and distance between genes?
One is dependent on the other: if there is a distance of 2 between them then there are only 2 recombination opportunities
Who discovered linkage maps and how?
T.H Morgan using Drosophila test crosses
What is the equation for measuring % of recombinant offspring?
Total recombinants / total population
What is a centimorgan?
The distance between genes for with 1% of products are recombinant (if it was 11% that is 11 centimorgan)
What can be inferred if map units between genes are low?
The genes are linked since there is a low number of recombinants
What is a limitation of linkage mapping?
Although some genes are linked, they may be very far apart on chromosomes so a value over 50% is presumed to be unlinked when they in fact are
