Comparison of genetic profiles – determination of inbreeding/diversity coefficient – selection of optimum breeding pair
Diversity or inbreeding coefficient = a number that shows the genetic similarity of the given breeding pair. The smaller the number, the greater is the difference between the male and the female. The coefficient can be determined for dogs and cats from their DNA profiles.
At present, by testing genetic profiles the breeder gains a lot of benefits. Besides the possibility to determine the paternity and the clear identification of an individual it is also possible to use the genetic profile for selection of a breeding pair. The inbreeding coefficient is determined by comparing the variability of genetic profiles of the chosen individuals and according to this the breeder can choose the most suitable breeding pair from the genetic point of view.
Obviously, the selection of an optimum breeding animal is based on many factors. The most important are the breeding standard, health, temperament, working abilities, appearance or coat colour and length....
However, today the breeder can choose from a great variety of top individuals of a given breed from all over the world. How to decide between two or more selected breeding animals?
Just this comparison of genetic profiles of a breeding female and of some potential partners or of a breeding male and several potential females can make the choice of the correct partner easier. For ideal crossing it is suitable to choose genetically most variable individuals who will keep the highest level of genetic diversity of the offsprings.
Thanks to the specialized breeding of individual canine and feline breeds the genetic variability (heterozygozity) of many breeds has been substantially reduced. The reduced genetic variability of the given breed often results in occurrence of genetic diseases and reduced number of healthy young animals in a litter. In general, the risk of occurrence of genetic diseases reduces with higher genetic diversity in the breed population. Therefore the current breeding practices are focused on keeping or gradual increasing the genetic variability of the given breed.
The genetic profiles of the potential breeding pair can be compared by calculation of so-called inbreeding coefficient of the given pair. The inbreeding coefficient of an ideal breeding pair is as low as possible – such a pair produces most probably a litter with high level of genetic variability.
Genomia laboratory determines the genetic profiles of individuals according to ISAG.
Overview of canine DNA-profiles and chromosomes tested
In dogs, 22 markers with high informative power localized on many key chromosomes are analysed. The inbreeding coefficient is calculated from 21 markers (Amelogenin has no informative power for the coefficient calculation; it only determines the sex of the animal).
Example of the inbreeding coefficient calculation for a canine breeding pair
F = a genetic profile of a female dog we are looking an ideal partner for; the genetic variability of the breeding pair shall be as high as possible, i.e. the inbreeding coefficient shall be as low as possible
P1 = genetic profile of the first potential partner
P2 = genetic profile of the second potential partner
|Marker||Value (F)||Value (P1)||Value (P2)|
Calculation of the inbreeding coefficients of potential canine breeding pairs:
|Marker||F versus P1||F versus P2|
The table shows individual inbreeding coefficients at 21 determined markers of a female genetic profile and of two potential partners. If the values at a given marker differ between the female and the male, so the inbreeding coefficient is 0. If the value of inbreeding coefficient is 0.25, it means that there is 25% probability that the offspring will be homozygous with regard to this marker. If the inbreeding coefficient equals 0.5, the probability of the homozygosity at this marker is 50%. If the inbreeding coefficient equals 1, so the homozygosity of the offspring at this marker is 100%. The total inbreeding coefficient is a sum of the individual coefficients at all markers. The maximum value is 21 and the minimum value is 0. The lower the value of the inbreeding coefficient is the better.
In the above example, we would choose the partner no. 2 from the two potential breeding mates, whose inbreeding coefficient equals 7.25 on contrary to the partner no. 2 whose total inbreeding coefficient after comparing with the female is 9.
The diversity of the individual markers differs among various breeds and depends on the genetic basis of the given breed.