Hi Griff,
Personally at least, I don't think Plus/Minus % is adequate to convey the differences.
For instance, the difference between a 60% Arab and a 80% Arab is probably more important than the difference between a 0% Arab and a 20% Arab as the first difference is big enough to push the Arab Gene Combinations into a securely dominant position.
In contrast, when you go from 0% to 20% and if the other 80% are from one breed, it won't push the Arab Blood into a securely dominant position by a long shot (of course, its a VERY complex question which is, for sure, the more important difference but my point is that there's a significant difference between the two differences that would be unduly ignored if I just reported the Plus/Minus %).
Anyway, what I'm trying to get at here is that Gene Effects are cumulative.
For instance, one "Arab Gene" is EXTREMELY unlikely to make a horse more like the typical Arab for the simple reason that
to a great extent it is NOT Individual Genes that are unique to the races within a species but instead gene combinations that are.
For instance, lets say there was a Gene called SHYR-43 and that there were four variants in the Species under consideration: A, B, C, and D.
What we'd see with Arabs and even a unrelated Breed will almost certainly NOT be this:
Arabs = 40% Variant A
Arabs = 60% Variant B
Arabs = 0% Variant C
Arabs = 0% Variant D
Chinese Plow Horses (or whatever) = 0% Variant A
Chinese Plow Horses (or whatever) = 0% Variant B
Chinese Plow Horses (or whatever) =75% Variant C
Chinese Plow Horses (or whatever) = 25% Variant D
In THAT case, then yes, One Gene could tell you if a horse was an Arab or a Chinese Plow Horse. However, reality will be closer to something like this:
Arabs = 10% Variant A
Arabs = 20% Variant B
Arabs = 40% Variant C
Arabs = 30% Variant D
Chinese P.H. = 20% Variant A
Chinese P.H. = 35% Variant B
Chinese P.H. = 30% Variant C
Chinese P.H. = 15% Variant D
In this Scenario, you see, one gene won't be enough to determine breed origin to a meaningful degree of certainty.
Nonetheless though; these discrepancies are
EASILY great enough to produce Gene Combinations unique to each of the two breeds and those Gene
COMBINATIONS will produce very meaningful differences in Phenotype.
Therefore we can see that one (and even to an extent some numbers larger than one) Arab Gene(s) are not enough to really matter and as a result we can conclude that at least to an extent;
the effects of Genes are cumulative.
How about a thoroughbred onto a real mustange, one from spanish horses. You think we might have another 60% vs 80% or maybe 60% vs 70% here???
I have a feeling the Mustangs are more Barb descended than Arab descended and as best I can tell (please correct me if I'm wrong), Barbs and Arabs are two essentially distinct breeds.
For this reason I don't think I have enough info at this point to make a meaningful attempt at an estimate.
-llbean
