In-breeding coefficients for Pika, Jojo and Elwood
Homozigosity in dogs

Computing the in-breeding coefficients for our dogs [1], we find that for Pika there are no repeated ancestors across four generations.  Adding the fifth and sixth, the coefficient becomes equal to 1.0% due to the presence of famous dogs born in the 70's: Shargleam Blackcap contributes 0.7%, his parents 0.2% and Wizardwood Sandpiper 0.1%. At this level, Pika may be described as "outcrossed". (A coefficient of inbreeding of 2.7% is computed for Pika in the british database www.flatcoatdata.com, based on eight complete generations and considering the inbreeding coefficients of the common ancestors.)

Jojo does not have repeated ancestors up to the fifth generation, and at the sixth generation Shargleam Blackcap (probably the most recurrent names in pedigrees extending enough backward),  Wizardwood Tawny Owl and Claverdon Lysander add altogether to a negligible 0.5%. (With eight full generations, www.flatcoatdata.com provides for Jojo an inbreeding coefficient of 1.1%.)

The results would be different for the four parents of our dogs (Bob, Lianga, Thor and Zorra), with coefficients ranging between 1.5 and 7% (1.8% to 8.5% in www.flatcoatdata.com with seven or eight complete generations). Values in this range are common and can be described as moderate line-breeding. Values larger than about 15% would instead be described as in-breeding and are less frequent.

A litter from Pika and Jojo, Elwood is an example, si also out-crossed, with the coefficient equal to zero in five generations, 0.4% at the 6th, and 1.2% at the 7th generation (2.0% in www.flatcoatdata.com with eight complete generations).

Discussing line-breeding and in-breeding we should not neglect that for dogs, and in particular for selected breeds from small founder populations, the genetic diversity is limited by the small number or different alleles that concur to specify each gene, and therefore a significant amount of homozygosity (equal alleles) is observed also for dogs not related via pedigre. Typical frequencies range between 40 and 50%, and  48% has been observed in Flat Coated Retrievers [2]. These values are significantly larger than the amount of homozygosity obtained by line-breeding or in-breeding.

Dog and parentage identification by genetic markers has become relatively common and can provide additional information on this subject. In a typical analysis, 21 markers pairs, on 19 chromosomes, are classified [3]. (The 22nd pair is on the X-X/Y gender-related chromosomes and no additional information is provided). As an example, for dogs like Jojo and Elwood, both "out-crossed" in their pedigree, the number of pairs of equal markers is 9 and 10 respectively, out of a total of 21, which is fully compatible with the large homozigosity frequencies mentioned above.  

[1] Tools for fast computation of in-breeding coefficients from large data-sets are available on the web, e.g.: FSpeed and PedigreeViewer.
[2] S. DeNise et al., Animal Genetics 35, 14-17 (2004)
[3] e.g. the test available through Antagene SA, made according to the ISAG 2006 norms.

[Back to the description of the line-breeding coefficient]     [Pika's Pedigree]     [Jojo's pedigree]     (Last update: 25/08/2011)