--- title: "6.11: Additive genetic relationship when the common ancestor is inbred" canonical: "https://wiki.groenkennisnet.nl/space/TAB/288719128/6.11%3A%20Additive%20genetic%20relationship%20when%20the%20common%20ancestor%20is%20inbred" format: markdown --- Animals that are inbred are homozygous for more loci (genes) than animals that are not inbred. Consequently, the chance that they pass the same allele on to two of their offspring is larger than in non-inbred animals. The more inbred an animal is, the larger the probability that it is homozygous, thus the larger the probability that it passes the same allele on to two of its offspring. An inbred common ancestor thus results in a higher additive genetic relationship between two animals. How much higher? Proportionally to how much more likely the common ancestor is passing the same allele on to the offspring, which is equal to the level of inbreeding. Below you see the same formula for the additive genetic relationship between X and Y as before, but now including the inbreeding level (F) of the common ancestor. F indicates how much more likely it is that the same allele is passed on to two offspring. ![image](media://ca522fd4-0f96-4fb1-aad6-afa6020d75c0) *If we go back to our example with pedigree 2 we have no information on the inbreeding of the animals F and G. The additive relationship between J and K is 0.125 in case F and G are not inbred. The question is: how would it make a difference for the additive genetic relationship between J and K if G was inbred?  Let’s assume that the inbreeding coefficient of G = 0.23, so F**G** = 0.23. That implies that the probability that H and I receive the same allele from G is 23% larger than before. So the probability that the same allele is passed on to J and K is 23% larger than before. Before it was ½**4** * 1 = 0.0625 and now it becomes ½**4** * (1+0.23)  = 0.0769. If F was not inbred, then the additive genetic relationship between J and K becomes ½**4** + ½**4***1.23 = 0.0625 + 0.0769 = 0.139. Animals J and K are more related because common ancestor G was inbred.* ![image](media://9217574c-fb0d-419b-b0d2-3d39659d0460) > Macro (children)