I have a filly by Escudo II; she’s out of a mare by Art Deco and out of a TB.
I’ve looked at the pedigrees of the “E boys” and Art Deco, but haven’t seen the blood percentage listed; and then how does one factor in the TB contribution? (Obviously said filly is at least 25% blood, yes?)
Any help would be appreciated, and since (ahem) math is not my strong suit, any sort of simple way to calculate this would be most helpful 
[QUOTE=Dr. Doolittle;7433780]
I have a filly by Escudo II; she’s out of a mare by Art Deco and out of a TB.
I’ve looked at the pedigrees of the “E boys” and Art Deco, but haven’t seen the blood percentage listed; and then how does one factor in the TB contribution? (Obviously said filly is at least 25% blood, yes?)
Any help would be appreciated, and since (ahem) math is not my strong suit, any sort of simple way to calculate this would be most helpful :)[/QUOTE]
The quickest way would be for you to enter your fillies pedigree into http://www.horsetelex.com// It’s free to register and free to use. Both Escudo II and Art Deco are already entered so you would just need to enter the Tb mare line. Once the pedigree is entered fully the database will provide you with an XX/0X percentage 
Someone please check my math, but my rough calculations show an Escudo II / Art Deco / TB offspring would have 43.0% blood.
Per HorseTelex, Art Deco had 30% blood. Combined with a TB mare at 100% blood would produce a foal with 65.0% blood (30% + 100% = 130%, divided by 2 = 65.0%).
Escudo II has 21% blood. So 21% from Escudo II, plus 65.0% from the dam = 86.0%, divided by 2 = 43.0%.
[QUOTE=DownYonder;7433987]
Someone please check my math, but my rough calculations show an Escudo II / Art Deco / TB offspring would have 43.0% blood.
Per HorseTelex, Art Deco had 30% blood. Combined with a TB mare at 100% blood would produce a foal with 65.0% blood (30% + 100% = 130%, divided by 2 = 65.0%).
Escudo II has 21% blood. So 21% from Escudo II, plus 65.0% from the dam = 86.0%, divided by 2 = 43.0%.[/QUOTE]
BUT. They do not simply average the parents, they use the average of the last 9 generations in the pedigree so you can have blood drop off. Example http://www.horsetelex.com/horses/pedigree/2924 If both parents have the Tb in the first 8 gens, than an average will work but if they are in the ninth gen for a parent, you will not get an average of the parents.
[QUOTE=stoicfish;7434030]
BUT. They do not simply average the parents, they use the average of the last 9 generations in the pedigree so you can have blood drop off. Example http://www.horsetelex.com/horses/pedigree/2924 If both parents have the Tb in the first 8 gens, than an average will work but if they are in the ninth gen for a parent, you will not get an average of the parents.[/QUOTE]
Yes, I understand that. And that is why I said, “my rough calculations…” Or maybe I should have said, “my quick and dirty calculations…” :lol:
Thanks, guys I did register and log onto horsetelex, but was unable to find any obvious link to where I would enter the pedigree??
Am I missing something? (The answer is probably “yes”…
I am interested in finding out, but if 43% is a good approximation, I’m willing to run with it.
Click on database, choose Add a Horse.
There may be a few hours waiting time before registering and being allowed to add a horse.
rodawn–I did add the horse (she’s in there!), so where do I go from there to determine the blood percentage?
ETA, just checked; now she is no longer in there 
Drat. I know I “saved” the info and she showed up afterwards when I checked…
Do y’all want a long, but clear historical tutorial on this topic? It goes back to Francis Galton and the marriage of Mendelian genetics and biometry (a mathematical approach to the study of heredity). That union produced 20th century population genetics-- used for evolution as well as livestock breeding.
I’ll explain if you want, but the circa-1900 way of thinking is what you mean in talking about “how much blood” in the way you are.
(I think I need that lecture.)
[QUOTE=mvp;7443142]
Do y’all want a long, but clear historical tutorial on this topic? It goes back to Francis Galton and the marriage of Mendelian genetics and biometry (a mathematical approach to the study of heredity). That union produced 20th century population genetics-- used for evolution as well as livestock breeding.
I’ll explain if you want, but the circa-1900 way of thinking is what you mean in talking about “how much blood” in the way you are.[/QUOTE]
They are just using simple percentages on Horse Telex.
You would need DNA testing to determine the amount of genetics actually transferred to the horse in question.
You can use marbles for a simple explanation of why the percentages are not necessary accurate.
Put 20 blue marbles and 20 white in a bag. Shake up the bag and blindly draw out 20 marbles. You will get any combination from 20 white to 20 blue and every combination in between. Some genes are linked so this is a simplification but you get the point. Say you got 15 blue and 5 white, this would be the contribution of the mare to the foal, say the stallion was yellow. So in total the foal would have 15 blue, 5 white and 20 yellow. If that foal grows up and has an offspring, you randomly pick 20 marbles out from the 40 and it could be 2 white, 8 yellow and 10 blue. The white could be the Tb ancestor, so in this scenario it is 10% but in Telex it would be 25%.
No, you don’t need DNA for the purposes of this discussion.
Yes, linkage (not yet clearly conceived of by 19th-century biometricians) is important.
But there’s a thing about linkage and the OP’s question.
If all ancestors of a given individual are all absolutely unrelated to one another, the math and logic is relatively simple. However, there is more than one way to calculate the amount of influence each relative has on an individual. That was related to a mistake made by Karl Pearson, I believe. I’ll check it out if you guys want the historical lecture.
But here’s how all this matters for the OP’s question.
Most pedigrees, however, are complicated by the fact that individuals appear in them more than once. So imagine a stallion how shows up more than once in a 5-generation pedigree. In a qualitative sense, you can see that that stallion’s influence is greater than is any other individual and you want a way to acknowledge that in your math. Early 20th-century population geneticists worked on this kind of problem all the time.
To get to the modern and more complicated question: If you wanted to know how much, say, TB or Oldenburg or Appy blood was in some complexly-bred horse, you can’t treat any of those breeds as you would the individual stallion. That’s because the stallion is has a single genome and will transmit what he has reliably; that’s all he can do. But does a breed similarly transmit it’s heritable features reliably? Well…… depends how true-breeding (and more or less inbred) it is. And what we now think of as linkage-- genes we know about appearing near- or far from one another on a chromosome can get established by a combination of selective- and inbreeding practices.
Let’s say for the TB/Oldenburg/Appy pedigree you knew how inbred each “breed” was. Then knowing what percentage of each breed’s blood was in the individual horse at the end of the pedigree would be worth knowing.
That’s not the historical lecture, but it might help you guys think about this.
The point is that the way Galton and the circa-1900 biometricians conceptualized inheritance was to talk about the amount of influence any given ancestor had on the individual in question.
One could calculate that for people/animals in the direct line-- so you could, for example, say how much your great, great, great grandfather contributed to your heritable features. And one can do this for relatives off that line, too-- uncles, cousins and such. (That all presumes you could also parse our inheritance and environment. That was a huge, huge question at the time, of course.)
In this kind of math-- very useful and very influential in livestock breeding for a long, long time-- you didn’t need to know diddly about individual genes. It did, however, create a basis for those interested in physiological genetics (figuring out which genes must exist or be in play behind a pattern of phenotypes seen in generations of relatives) a way to conceptualize genes in the way most people talk about them now.
IMO, most livestock breeding is still done more with that circa-1900 biometry-style genetics than with the kind where we talk about getting individual genes for this and that feature.
mvp
Common ancestors is an issue for calculation in the sense that it does increase the chance of any one ancestor passing on genes but it does not change the outcome, if that makes sense. The same TB multiple times in the pedigree would have the same input as different Tb’s.
But how is recombination not one of the biggest factors?
I’m not sure I get what you mean. But I’ll try to speak to you, using the colored marbles thing.
First, I take the different colored marbles to be alleles of a single gene. By the way, there can be more than two. But each parent contributes one of those to its offspring. That’s part of the version of Mendelian genetics taught to every high schooler.
In this scenario, it would seem that the mare with her blue and white marbles, plus the stallion with all yellow marbles, is one in which there are three alleles? So the mare is heterozygous, (white and blue) and the stallion is homozygous for the third allele (yellow)? Is that what you mean?
But as I said in my other post, there’s a difference between an individual organism and a breed. That’s because an individual organism has, in fact, only two versions of a gene, no matter how many alleles are possible.
Yes, one can speak of him in terms of averages. In fact, that’s how the Punnett Square (named for the British mathematician, Reginald Punnett who wrote a short book that helped popularize Mendel’s system) works. It’s dirt simple in those high school systems we were taught because each gene is posited to have just one allele and where no selective breeding has happened.
But the logic of alleles discussed in quantitative terms was really about explaining how fast change could happen in a population where various patterns of selection, inbreeding and outcrossing was happening. Change, then, could be expressed in several ways.
How many of one allele or another would be present in a closed population after lots of selection for or against that allele, assuming you knew how many of it were there in the first place.
And therefore, one could also predict the likelihood that one individual in that population would hold the allele. This is how you can speak of that stallion in terms of being a representative of the population.
But! (And) “Allele frequency” (how common or uncommon an allele is in a population) really is also about the amount of genetic variability that population holds at that locus (literally, a place on a chromosome, but also one gene).
So while a (sexually reproducing) individual really only does transmit one allele to his offspring, an entire population can’t be conflated with an individual. That’s because it can hold different degrees of variability than can an individual organism.
So far, the variability of the population and an individual’s likelihood of holding this or that allele are expressed the same way in mathematical terms.
But! (And therefore) what someone like the OP really needs to know about any of the breeds in question is how much variability is within the breed. To put this in terms of single loci and alleles, you need to know just how “fixed” that allele is.
In other words, has it been selected for enough that just about every individual in the population holds it? If so, there’s little genetic variability. Put in terms of an individual, that means he is homozygous for that allele. If the rules of simple dominance hold for that gene and it’s the only one involved, he’ll be “prepotent” for that trait and stamp his offspring with it.
I’m not sure I see what you mean by relating linkage to this discussion. Maybe try to explain again?
Oh… and all this gets worse with an open studbook where phenotype is still pretty well regulated. So WB registries mess up the whole Mendelian/quantitative population genetics thang because those “breeds” are not closed populations.
[QUOTE=mvp;7444524]
I’m not sure I get what you mean. But I’ll try to speak to you, using the colored marbles thing.
First, I take the different colored marbles to be alleles of a single gene. By the way, there can be more than two. [/QUOTE]
No. The marbles in this scenario represent chromosomes, not genes or alleles. And a diploid cell always has two alleles for every gene. A haploid cell has one. Alleles are specific versions of genes. We all have the same genes; it’s the alleles of those genes that vary among individuals.
[QUOTE=Dr. Doolittle;7443117]
rodawn–I did add the horse (she’s in there!), so where do I go from there to determine the blood percentage?
ETA, just checked; now she is no longer in there Drat. I know I “saved” the info and she showed up afterwards when I checked…[/QUOTE]
She’s there. The percentage is 41.02%
[QUOTE=L&L;7444706]
She’s there. The percentage is 41.02%[/QUOTE]
Thanks, L&L!
Bottom line, it’s nice to know–though the discussion above was definitely interesting–as well as educational…
[QUOTE=L&L;7444706]
She’s there. The percentage is 41.02%[/QUOTE]
Excellent! It is interesting to see that the HorseTelex computation was close to my own rough calculation of 43%.
I wonder if that “margin for error” of 2% would hold true for other calculations of this sort, or if there would be a much greater (or lesser) spread in some cases. Any math nerds out there want to weigh in?
DownYonder, I think your rough calculation would generally work pretty well as long as there was thoroughbred up close in the pedigree. If there wasn’t you would really have to know your bloodlines to know thoroughbred content to be able to come up with the percentage. I just tried putting my youngster in HorseTelex and although in the first 3 generations there isn’t 1 thoroughbred listed (you can find his pedigree in the sale ad I bought him off of http://www.warmblood-sales.com/SoldHorseDetail.asp?HorseID=32649&UserID=6400), when you go back 9 generations he comes out at 38.28%. I think he would be an example of a tough one to do a rough calculation for percentage of thoroughbred in him, however pedigree guru’s might disagree.
[QUOTE=ynl063w;7444690]
No. The marbles in this scenario represent chromosomes, not genes or alleles. And a diploid cell always has two alleles for every gene. A haploid cell has one. Alleles are specific versions of genes. We all have the same genes; it’s the alleles of those genes that vary among individuals.[/QUOTE]
Yes.
And I get the whole population view point. However, the original discussion was about TB influence and my example was to show that regardless of the individual traits that a Tb may bring to a population, a) you would need a genetic test to actually see what any one horse has inherited from it’s ancestors (you could have 30 very different horses with 100% common ancestors) and b) and more importantly to show that horse telex is using a very simplified calculation of the percentage of genes that could have been inherited from a Tb…because of the marble thing. That that the percentage is not really indicative of the amount of blood the horse might actually have.
To try and model a whole population when you are just looking at an individual is not necessary. Population genetics is a predictive tool of the trends of a population but an individual already has those results in tact and can be quantified.
I guess the bottom line is to look at the horse itself as it my not either have the desired genetics of it’s pedigree or it may have it but not express it in the phenotype but is able to pass it on to the offspring.
PS population genetics was used to try and explain evolution. Domestic herds are a results of human selection of traits and most of the theories that were traditionally relevant are not so much with domestic herds. And now I would think with genetic testing and the identification of individual traits (alleles) that population genetics becomes obsolete. But even without testing any breeder is looking at only 2 animals at a time and the frequency of passing on desirable traits.
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