Buckpasser in the X

[Pan Zareta]

~50% is reasonable. Deviaton of about 15% either way is well within textbook norms. Much wider deviations have been documented anecdotally.

[Pan Zareta]

Dink found that Buckpasser ranked first among all the major sires in various positions in the pedigree.

Including in topline although Dink remarks that accomplishment as based on very low numbers and mainly dependent on stakes wins of foals of his tail male descendant Lil E Tee.

[stancaris]

Pan Zareta:
What about this quote from Dink on page 181 of the book Racehorse Breeding Theories? He says the following---

"That Buckpasser ranks best at P6 and P8 is no surprise at all. He is known as a great broodmare sire and was leading broodmare sire four times."

Position P6 is the maternal grandsire of the broodmare sire and position P8 is the sire of the third dam.

Both of the above positions are X passing positions and lend support to the X linked theory. Buckpasser is transmitting important genes on his X chromosome which contributes to his success in those above positions where he was the best of the major stallions studied by Dink.

Another Dink quote on page 181 follows: "As a sire of females in the fourth generation his overall results are 5.36 from a much larger number of foals."

Then he says, his overall results at P4, P6, and P8 (the other three positions as the sire of a female) are 7.30.

The data from Dink clearly shows the importance of position in a pedigree. Particularly position P6 and P8 which is an X passing position on the dam side.

Looking at the third generation sire we find that Buckpasser is strongest in the P4 position with an index of 7.05 and that is the only position shown in the third generation that is an X passing position. HMM! Now thats interesting and serves as further support for the importance of the X chromosome.

[Pan Zareta]

Stan, if the X "dictates" or is a primary contributing factor to BMS success I'd expect to see a bit more skew between Buckpasser's non-X passing P5 result (5.91%, highest of all sires surveyed in that position) and X passing (~25% +/-) P6 result (7.08%, again, highest in that position).

The fact that so many of the 4th gen. sires, including Buckpasser, had much higher results in the P8 3d BMS position says a lot about the pressure against males remaining in the top tier of the TB breeding population and the direct effect that has on where you're apt to find most sires in future pedigrees. The results at P1 and P5 ought to tell you how absurd it is to reduce Buckpasser's genetic excellence to a single chromsome.

ETA - all the above observations pertain to sires in 4th gen.

[stancaris]

Pan Zareta: The fact that Buckpasser had the absolute highest number (11.99) in the P8 position of all 20 sires in Table 2 on pages 178-180 and also had the absolute highest number in the P8 position (7.08) of all 20 stallions is strong evidence that he is transmitting an X chromosome that contributes to that success because both of these positions are X passing positions. He is better than all 20 stallions that Dink lists in Table 2 in the P6 and P8 positions. Thats saying a lot for two X passing positions.

The results of P6 and P8 ought to tell you how absurd it is to say that Buckpasser's X chromosome plays a minor role at best.

[stancaris]

Pan Zareta: I typed P8 in the last part of the second line in my above post. That was meant to be the P6 position that had 7.08.

[Pan Zareta]

The results of P6 and P8 ought to tell you how absurd it is to say that Buckpasser's X chromosome plays a minor role at best.

When you are informed of genome-based evidence that does anything other than contradict your inane notions about the "power of the X", please do post it here.

[stancaris]

Pan Zareta: I take it that you cannot really respond with a negative about the P6 and P8 highest numbers for Buckpasser. The highest numbers for all 20 stallions listed. And these pedigree places are in X passing positions.

P

[Pan Zareta]

I take it that you cannot really respond with a negative about the P6 and P8 highest numbers for Buckpasser.

I've already done that Stan. Would you also like for me to point out that in 3d pedigree generation Buckpasser's numbers were not the highest in any pedigree position including the mandatory X passing P4 position and therefore by your reasoning the X chromosomes of Northern Dancer, Mr. Prospector, Bold Reasoning, and Never Bend were superior to Buckpasser's?

In full context the numbers prove nothing and don't really even suggest much about what's going on at the genetic level except, apparently, to someone desperately in search of validation for a false premise.

[xfactor fan]

Pan Zareta,

I never claimed that any conformation type presents a racing advantage. Just that forehand conformation seems to be X linked, or pseudo X linked ( On the autosome, but only expressed via the maternal chromosome)

What I suspect counts is how well any given set of body parts work together, and how all the other systems: cardio. proportion of muscle types, reaction time, plus any of the other factors that make up a great racehorse.

If this is correct then it goes a long way to explain why mare shows one phenotype, is mated with a stallion with a compatible phenotype, and out pops a foal that expresses her hidden genotype. Which may or may not be what the breeder had in mind.

One observation, and this will have to have more study, is that successful broodmares tend to have sires and damsires that have similar conformation. This may increase the chance that the same or very similar forehand conformation being passed on by the mare for each breeding. Which would increase the chance that she is bred to the correct type of stallion to produce quality runners.

Buckpasser was a great racehorse, and it doesn't matter that he had a particular type of forehand conformation, what matters is that his forehand was in balance with the hind end, and all the other systems worked with the basic structure to produce a great racehorse.

[stancaris]

Pan Zareta: Take another look at the P4 position in the third generation as compared to the numbers in the P1, P2, and P3 in the third generation.

In the P1 which is a NON X passing position Buckpasser gets 2.32
In the P2 which is another NON X passing position he gets 4.75
In the P3, another NON X passing position Buckpassser gets 3.32

In the P4 the only X passing position (2nd damsire) he gets 7.05

Now lets see the benchmark according to Dink is 3.74 and anything below that is not good. Buckpasser is below the average (not good) in two of the 4 positions in the third generation, both of which are non X passing positions.

However Buckpasser gets a 7.05 in the P4, the only X passing position in the third generation and that is higher than the average for Dink's study and that is Buckpasser's highest number in the third generation.

In summary, Buckpasser gets the absolute highest numbers for all 20 stallions in the P6 and P8 of the fourth generation (both X passing positions) and he also gets his highest number in the P4 an X passing position in the third generation.

Despite the above statistics of David Dink, you still are of the view that I have no basis whatsoever for thinking that the X chromosome is important to broodmare sire success or the success of Buckpasser in Dink's study which clearly shows strength in the X passing position.

[Linda_d]

DDT: I need broodmare sire lists not just sire lists and there are no listings like that on the left hand side of the first page of the bloodhorse.

It is the broodmare sire that transmits his X chromosome to all his daughters but none of his sons. My first post in this thread dealt with the last three years listing of the top 20 leading broodmare sires not the top leading sires. I compared the presence of Buckpasser in the X passing position of these top broodmare sires versus the frequency of Buckpasser in the X passing position of horses in the general population.

So, then while all of his daughters get a stallion's X, there's only about a 50% chance that his daughters pass on his X, and that is likely to be at least partly recombined so it's not necessarily much of his genetic material anyways. The chances of the exact X chromosome from any stallion being passed to a maternal grandson and influencing his ability as a broodmare sire are slim and none. And you don't have to be particularly well versed in genetics to realize that.

FTR, Buckpasser was only bred to very select mares for his entire career, so a great deal of his success as a broodmare sire stems from the fact that the Phipps family had a great band of broodmares. Those of his daughters not retained by the Phipps were also bred to the very best stallions and their offspring given every opportunity to excel at the highest level. There's not one Buckpasser son or maternal grandson that does not come from a long line of top producing mares, and for Buckpasser's grandsons and great grandsons on the leading sire list, those bottom line pedigrees are even more impressive.

You are totally ignoring the bottom side of the pedigree except for how it relates to your theory about Buckpasser. Great broodmares make great sires ... and great broodmare sires.

[louis finochio]

Buckpasser was a great BMS, because of his 79 crosses of FFI, 45 of those crosses, are from the great mare Pocahontas.

[stancaris]

Linda_d

You said, "So, then while all his daughters get a stallion's X, theres only a 50% chance that his daughters pass on his X, and that is likely to be recombined so its not much of his genetic material anyways."

That's not true. When Buckpasser transmits his X to a daughter that daughter gets near 100% of his X. When his daughter transmits an X chromosome to her progeny that X has undergone recombination so that it contains genes from Buckpasser's X and also genes from the daughters dam's X. So, regardless of which X is transmitted from Buckpasser's daughter to her progeny, that X contains around 50% of Buckpasser's X chromosome. In some cases that X may contain 65% of Buckpasser's X or it may contain around 35% of Buckpasser's X. (15% deviation one way or the other). On the average every son or daughter that is born from a daughter of Buckpasser will receive on the average 50% of Buckpassser's X chromosome. (they may get as much as 65% of Buckpassers X or as little as 35% of Buckpasser's X).

Refer to my post of May 27th 2013 at 2:00AM where I have made reference to David Dink's statistical studies of Buckpasser in various X passing positions in a pedigree. The stats from that study clearly shows that the X chromosome is important because the numbers are highest for Buckpasser in positions P4, P6 and P8 and they are the ONLY X passing positions that Dink analyzed in his study.

[Pan Zareta]

I never claimed that any conformation type presents a racing advantage. Just that forehand conformation seems to be X linked, or pseudo X linked ( On the autosome, but only expressed via the maternal chromosome)

Parent-of-origin dependent gene activation could quite plausibly be mistaken for X or Y linked inheritance.

Despite the above statistics of David Dink, you still are of the view that I have no basis whatsoever for thinking that the X chromosome is important to broodmare sire success or the success of Buckpasser in Dink's study which clearly shows strength in the X passing position.

As usual, you're cherry-picking only the bits and pieces that confirm your bias. When present in 4th gen mandatory X passing positions P6 and P8 Buckpasser's numbers are inversely correlated to the amount of his X chromosome contribution. His highest number (11.99%) is in the 4th gen P8 position (3d BMS) where he contributes ~12.5% of the X and ~6.25% of each autosome. In 4th gen P6 position (BMS of the BMS), where he contributes the same amount of autosomal DNA but double the amount of X DNA, Buckpasser posts an impressive but lower number (7.05%). Hardly what would be expected if his X is doing the genetic heavy lifting.

Overall, Dink's findings speak to the quality of Buckpasser and of his consorts and in regard to the latter demonstrate that their descendants in tail female stood a far better than average chance of remaining in the top tier of the TB breeding population. No surprise there.