LOD scores
The LOD (logarithm of odds) score is the statistical test most used in genetic linkage calculations (indicating the likelihood of linkage vs. non-linkage).
Specifically:
If two markers are unlinked, then the odds (Ou) of getting exactly x recombinant progeny and y parental-type progeny is: (0.5x)(0.5y).
If the markers are linked, with a recombination frequency of r, then the odds ratio (OL) is given by (rx)[(1-r)y].
The odds ratio is OL/OU and the LOD score is log10 (OL/OU).