What are the factors that determines the IBD of pairs of individuals?

Question

[MAPK]

I am trying to figure out how Identity by descent (IBD) values of pair of individuals is dependent on. Is it the proportion of homozygote (reference), heterozygotes and homozygotes(non-reference) alleles shared? Can someone please explain me the determinant factors on which IBD calculations is based upon?

[John]

Just Google "How is Inherited By Descent calculated?", and you'll get plenty of examples :) http://ibgwww.colorado.edu/workshop2005/cdrom/ScriptsA/evans/IBDestimation/IBD--2005.pdf