kinship and related concepts
resources
I am no geneticist at all, so all information in this section comes straight from external sources. If you have any questions about it, ask your local guru, not me! (If you notice anything seriously wrong, then please let me know.)
The most complete source of information I found on the web, were lecture notes by Elizabeth Thompson. I found these at http://www.stat.washington.edu/thompson/Stat578C/chap2.ps. Though the Thompson document is very clear, it was a bit steep for me at first (knowing nothing whatsoever about genetics). Then I found lecture notes apparently by Dag Lindgren, which helped me climb the first part of the learning curve.
definitions
The following definitions are based on those in the documents by Thompson and Lindgren.
A gene is the DNA segment that is copied from parents to offspring.
Genes that are identical by descent (ibd) are identical copies of a gene segregating from a common ancestor.
The kinship coefficient between two individuals is the probability that genes, taken at random from each of the individuals, are identical by descent.
Or, in more precise terms, kinship coefficient is the probability that homologous genes on gametes segregating from two individuals are identical by descent.
Coefficient of coancestry is a synonym for coefficient of kinship.
The inbreeding coefficient of an individual is the probability that homologous genes on the two gametes uniting to form it are identical by descent.
The kinship coefficient of two mating individuals is the inbreeding coefficient of their offspring.
