Dublin displaying his sire line
In pedigree analysis, the Sire Line is the singular branch of a family tree that looks only at the transmission of the Y chromosome. Because the sex chromosomes don’t recombine (much) each generation, the X and Y allosomes are largely conserved intact over many generations changed only by mutations and transcription errors. This also means that normal selective pressures for and against genes work differently for alleles on the Y chromosome.
Inefficient Selection
Without the ability to recombine during meiosis, the Y chromosome is unable to expose individual alleles to natural selection. Deleterious alleles are allowed to “hitchhike” with beneficial neighbors, thus propagating maladapted alleles in to the next generation. Conversely, advantageous alleles may be selected against if they are surrounded by harmful alleles (background selection).
The Y chromosome also provides insufficient coverage with the X chromosome, creating a pattern of disease expression and transmission that is different from autosomal genetics.
Sex linkage is the phenotypic expression of an allele related to the chromosomal sex of the individual. This mode of inheritance is in contrast to the inheritance of traits on autosomal chromosomes, where both sexes have the same probability of expressing the trait. Since humans have many more genes on the X than the Y, there are many more X-linked traits than Y-linked traits.
Given these unique properties of the Y chromosome and the sire-focused culture in dog breeding, particular attention should be paid in managing disease and conserving diversity in the sire lines.
There are two unique points of canine pedigree diversity that are not always paid much attention. These are the topmost and bottommost lines of the pedigree – the tail-male or sire-line and the tail-female or dam-line. They represent unique genetic content, held by the mitochondrial DNA and the sex chromosomes, much of which is transmitted only by those pedigree lineages. Given the intense preoccupation among breeders with both stud dogs and brood bitches, what I am going to say may seem surprising: diversity in sire and dam lines is often quite scarce in purebred dog genomes.
Since these lines are not consistently scrutinised and conserved by breeders (because they are unknown if the breeder has not researched the pedigree all the way back to breed foundation), they are subject to changes in the frequency of their occurrences, exactly similar to the changes in gene frequency that occur due to random drift. Most breeds begin with a fair number of unique sire and dam lines. But some drift into prominence and others into obscurity, scarcity, and finally extinction.
As predicted, there isn’t a lot of diversity in sire lines in the Border Collie. I traced the pedigrees of the most popular sires (by number of puppies) in the ISDS and found that 7 of 10 carried the same line leading back to Old Hemp.
Sires are blue, Dams white. Lines show parentage. Glen 3957 and Glen 3940 are full siblings.Glen 3510 and Jigges 2378; Spot 3624 and Drift 4380; Ben 56646 and Mirk 52844 are half-siblings.
Although all Border Collies can be traced back to Old Hemp ISDS 9, it’s significant that so many of the top producing dogs trace directly back to his sire line. He’s often called the figurative “father of the breed” but if the pattern holds across the breed like it does with the top producing dogs, he’s quite literally the father of the breed. If Border Collies had last names, 22 of the top 30 dogs would share the same surname and the Wiston Cap branch of that family would own the lion-share.
It’s also worth noting that what diversity we do have in sire lines {McCaskie’s Moss, Crozier’s Toss, Kep 13, Anderson’s Spot and Hill’s Haigh} might not represent separate lines. The stud books do not actually list any offspring for Old Hemp, and later research has only revealed 3 surviving lines to Hemp. I’ve named the sire lines after the dog at or near the terminus, and it’s possible that any or all of the separate lines could be carrying the same Y chromosome as Old Hemp, either through him or a common unknown ancestor. Genetic testing could verify this.
I took me years of pedigree research before I could trace Dublin and Celeste back to Old Hemp through any line, not just the singular sire line, and when I first made the 30 generation connection I was thrilled that I had bridged a century of time and shown a direct link to the famous founding dog. I was so happy I printed up a pedigree chart and kept it in the car just in case I found an opportunity to show off all the hard work. Today after several more years of research, I can trace Dublin back to Old Hemp 1.2 million times. Some paths are as short as 14 generations and others as long as 55; even though so many generations separate them, Hemp still accounts for 2.67% of Dublin’s blood. It’s possible that Dublin’s sire line includes Old Hemp, and it it’s true, you can add ~1.35% blood to that (dogs have 37 pairs of chromosomes and the Y would come from Hemp unadulterated).
SIRE LINE for: Dublin Rex – ABCA 280570 AKC DN14512501
Date of Birth: 1/14/2006
Colour & Markings: Black and White Tri
Owner: Christopher LandauerSIRE LINE
SIRE DAM
Yippee Kye Yay – ABCA 214956 …………………Jazz – ABCA 256411
Tweed – ABCA 96669 ………………………….Tali – ABCA 154233
Tweed – ABCA 35308 ………………………….Two Dots – ABCA 38909
Craig – ISDS 153167 …………………………Fly – ISDS 142527
Spot – ISDS 115367 ………………………….Scot. Team Member Nell – ISDS 97285
Moss – ISDS 50511 …………………………..Nell – ISDS 102053
Don – ISDS 30938 ……………………………Midge – ISDS 28849
Cap – ISDS 13754 ……………………………Meg – ISDS 15602
Hemp – ISDS 8822 ……………………………June – ISDS 6901
Int Aggr Ch 1949, Scot Aggr Ch 1949 Moss – ISDS 5176 June – ISDS 6901
Int Sup Ch 1950, Scot Nat Ch 1950 Mirk – ISDS 4438 Nell – ISDS 3514
Spot – ISDS 3369 ……………………………Chris – ISDS 4065
Moss – W. Amos ……………………………..Meg – J. McDonald
[possible continuation]
Moss – ISDS 131 …………………………….Lassie – Courtney
Glen – ISDS 603 …………………………….Lassie – ISDS 68
Int Sup Ch 1924 Spot I – ISDS 308 …………….Fly – ISDS 165
Ben – ISDS 249 ……………………………..Ruby – ISDS 207
Don – ISDS 217 ……………………………..Fan – ISDS 208
Int Sup Ch 1911/1914 Don I – ISDS 17 ………….Old Meg – ISDS 27
Don – W. Burns ……………………………..Trim – ISDS 37
Old Hemp – ISDS 9 …………………………..Ancrum Jed – J. Scott
Roy – A. Telfer …………………………….Meg – A. Telfer
I’ve traced Dublin’s sire line back to Amos’ Moss, no ISDS number. When you get into the first stud book, you’ll often have situations where a dog is listed as a sire with an owner but no number associated, but that owner will have a dog with the same name that has a number listed under their dogs. This dog could be the same or it could be an entirely different animal. The listing for dogs owned by W. Amos lists Moss ISDS 131, so if this is the same dog, Dublin’s sire line does trace back to Old Hemp. If not, we must assume it ends with the unnumbered Moss.
This was initially an exciting revelation, “Dublin would have the same last name as Old Hemp! Border Collie royalty,” but when you see that 77% of the puppies produced by the top 30 ISDS stud dogs also share this distinction, I’d actually prefer if Amos’ Moss is a unique sire line. It’d be better for the breed if it were.
* * *
Comments and disagreements are welcome, but be sure to read the Comment Policy. If this post made you think and you'd like to read more like it, consider a donation to my 4 Border Collies' Treat and Toy Fund. They'll be glad you did. You can subscribe to the feed or enter your e-mail in the field on the left to receive notice of new content. You can also like BorderWars on Facebook for more frequent musings and curiosities.
* * *
Years ago I traced Zephyr’s lines back as far as I could just for fun (back to the beginning of the ISDS #’s)…I never thought at the time about all the implications. There is a real trend in our area even in the sport world to use the same few sires MANY MANY times, and all that they bring to the lines good and bad.
And thanks for your visit.
Erin (Zephyr’s Zoo) recently posted..52 Weeks of Zephyr
I’ve got a decent number of dogs in my DB now if you ever want a more complete pedigree, I’d be happy to run it for you. It is fascinating being able to connect these dogs with the history of the breed.
Popular sires seem to be the inevitable consequence of any competitive venue, I think we’re lucky in Border Collies that at least we have dogs that are so good in so many venues that we increase the number of sires being vetted.
While the sport, show, and trial worlds might all have their own limited set of popular sires and sire lines, and even though it’s my guess that genetic diversity is being lost in each sector, I would guess that we’re losing different lines and blood in each such that over all the rate of loss is slower and we can make good “outcross” breedings even within Border Collies.
This is what I’ve done with my first litter and I hope to continue the trend in the future.
Yes I would love it you could run it for me! Let me know the best way to get the pedigree to you.
Zephyr’s lines are a mix, very much working lines on his sire’s side and a bit further back on the dam’s to find working lines. However I am happy with what that produced 🙂
I think it must be a very daunting thing to breed dogs….for someone who wants to breed overall healthy, sound minded dogs, much to consider and there will always be that element of crap shoot even with all the care into a breeding! I don’t feel I would ever have the knowledge or nerve!!!
Erin (Zephyr’s Zoo) recently posted..52 Weeks of Zephyr
I’ve traced some of my Afghans back to the founders, but really, I kept ending up on the same few dogs so I stopped. I did COIs on of my Salukis on complete (as possible) pedigrees as well and it just ended up being depressing, too.
Jess recently posted..A Note About the History Posts
Since negative recessive traits cannot be hidden on the Y chromosome (or in the genes animals receive solely from their mother) the need for this kind of genetic diversity is dramatically reduced. However, if the male and female lines of a breed are not diverse it seemingly implies a serious lack of diversity in the entire gene pool.
My understanding is that X-linked genes are more likely to show up in men, even if they are recessive, because the Y chromosome is deficient in providing coverage. So, if there’s a gene that a male only has one copy of it’s most likely on the X chromosome. For example, Hemophilia in humans.
This would speak to greater Dam-line diversity so there are options to avoid diseases that can’t be covered up by being carried. Queen Victoria was a hemophilia carrier and we see how that effected global political history. Dam-line diversity is also critical because mitochondrial DNA doesn’t recombine and is an essential aspect of so many critical cell processes.
The issue on both lines is that there is no recombination to selectively eliminate bad mutations. You have to throw the entire baby out with the bath water or live (if you can) with the mutation.
I don’t think this suggests that there is a dramatically reduced need for diversity in these genes, I think it means the opposite. Our ability to “fix” these problems are limited so we need choices. Bad genes on autosomal chromosomes can be changed with great specificity, not so with the sex chromosomes.
When I was talking about the genes that can only be passed along by a female I was talking about the genes that are not in the DNA. I think in humans about two percent of our genetic information comes solely from our mother and can never be passes along by the father. These “female” genes are just like the Y chromosome genes since they do not get recombined at all. I do think diversity of these genes is good since it allows for more variability, but it is not nearly as important as genetic diversity for the x chromosome or the numbered chromosomes.
I think ‘X’ chromosomes do mix and match in the creation of a female’s genetics. But I could be wrong about this. Another point is that it is harder to loose diversity for the ‘X’ chromosome than the ‘Y’. The reason is because a female holds two ‘X’s and the male has one ‘X’. But by comparison the ‘y’ is only held by the male once and not at all by the female. Therefore there is three times as much potential genetic diversity for the ‘X’s than the ‘Y’s. And practically speaking the X chromosomes end up with more diversity because they can be combined with each other allowing for new combinations of genes and they also have more potential for mutations since they contain more genetic data.