TWA - Pedigree Analysis
We now offer an extensive pedigree analysis page for each dog stored in the TWA database. This analysis contains the inbreeding coefficient (Wright's formula), ancestor loss, the partial inbreeding coefficient, the blood quota and more.
Please note: The pedigree analysis is based on the information in the database and is only accurate to that extent. These calculations are very complex, so the page might take longer to load than other pages on TWA.
You can find a link to the pedigree analysis page on each dog's detail page and on the testmating page, see screenshots:
The pedigree analysis page calculates the inbreeding coefficient, ancestor loss, blood quota and the partical inbreeding coefficient (only up to the 5th generation) for a particular dog or testmating, see screenshots:
For details on the calculations read the following sections:
Partial inbreeding coefficient
Ancestor loss, maximum ancestors, actual ancestors
Using the pedigree analysis page
The Inbreeding Coefficient (IC) or Coefficient of Inbreeding (COI) or Coefficient of Kinship of an individual is defined as the probability that the two genes this individual has in a locus are identical by descent, i.e. they are both inherited from a common ancestor.
The calculation of the inbreeding coefficient is done to a given pedigree depth (number of generations): the greater the depth of the pedigree, the greater the chance of finding new common ancestors, and the higher the inbreeding coefficient.
It only makes sense to compare the inbreeding coefficients of different pedigrees if the number of generations used for the calculation are the same and the pedigrees are complete for the generations!Follow these links for more details on genetics and inbreeding:
- For an introduction to genetics, see this Wikipedia article.
- For information on inbreeding, see KC Online Services.
Partial inbreeding coefficient
The partial inbreeding coefficients, Fij , measure the probability that the alleles at an arbitrary locus in individual i are identical by descent and that the alleles were derived from an allele in founder j.
The partial inbreeding coefficients of the ancestors of an individual can be seen as their "contribution" to this individual's COI, i.e. in a full pedigree the sum of all partial COIs of all ancestors of the individual must equal the individual's COI!
Ancestors contributing the most to an individual's COI do not automatically have the highest inbred percentage. By being a closer relative (grandparent, great-grandparent) a dog with a low inbred percentage might have a larger contributing factor than other dogs with a higher inbred percentage. The dog you selected for pedigree analysis will have most in common with the ancestors having the highest partial inbreeding coefficient.
Please note: The partial COI calculation is available only up to the 5th generation as computational requirements are too high for larger pedigrees.
Ancestor loss, maximum ancestors, actual ancestors
The maximum number of possible ancestors in a pedigree is 2^(number of generations+1)-2. The ancestor loss is calculated by comparing the number of possible ancestors in a pedigree with the actual number of different ancestors.
e.g. a four-generation pedigree contains 30 dogs and if a particular pedigree consists of 30 unique dogs then this pedigree has no ancestor loss at all; but in a pedigree with some inbreeding there might only be 26 unique dogs in these four generations meaning an ancestor loss of 13.3%.
Blood quota is the percentage of a pedigree that is made up by any one ancestor. Sire and dam, obviously, each make up 50% of a pedigree; grandsires and granddams 25%; great-grandparents contribute 12.5%, etc.
e.g. a dog that appears in the grandparent generation contributes with 25%, if it also appears in the great-grandparent generation (12.5%) then it has a blood quota of 37.5%(25 + 12.5).
Using the pedigree analysis page
Use the dropdown list at the top right to set the number of generations for the inbreeding calculation. You can choose from 1 to 10 generations, but due to performance issues, the partial COI calculation is only available up to the 5th generation. We have chosen seven generations as the default setting – on the one hand, it is accurate enough and on the other fast enough, and there is a good chance that a large percentage of the pedigrees will be complete for that number of generations.
Use the arrow up and down icons in each column header to sort the ancestor list according to the particular header's measure (default is to sort by blood quota in descending order).
