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  1. #1
    Join Date
    Mar. 31, 2006
    Posts
    264

    Default Dumb Question...

    Please forgive me if this has been discussed - I wouldn't even know how to begin a search on it.

    When I see a pedigree, especially on Dream Horse, many times I see the same dam or sire repeated. I have wondered for a long time, does this affect the quality of the animal when it's parents have the same father? Or mother? Does it matter? Or is that a good thing?

    Disclaimer - I don't breed, don't plan on ever breeding. Just looking for education.

    Thanks



  2. #2
    Join Date
    Feb. 3, 2000
    Location
    Nokesville, VA
    Posts
    34,859

    Default

    It depends on the quality of the specific animl that shows up multiple times.

    There is a saying that, when it doesn't work, it is called "inbreeding", when but does work, it is called "line breeding".

    If a horse appears multiple times, you increase the probability of getting genes from that horse. If the horse has "all good" genes, that is good, if the horse has "all bad" genes, that is bad.

    In particular, if a horse has a recessive gene that isn't expressed, then you have an increased probability of getting two copies of the gene, so it will be expressed.

    The "poster child" for this effect is "HYPP" in Quarter Horses. Because the sire, Impressive, had many good features, he appeared many times in the pedigrees of QH "halter" horses. He had one copy of the HYPP gene, which makes the horses "bulk up". But horses that got two copies of the HYPP gene have severe problems. It has now got to the point where people check for the gene befor breeding.

    Conversely, in TBs, the "large heart" X-factor, only appears on the X gene (so a "large heart" sire passes it on to his daughters, not hs sons) . If a mare with two copies of the X-factor appeears multiple times in the pedigree (passed on dam to son or daughter,or sire to daughter, but not sire to son), you increase the chance of getting at least one copy of the X-factor.

    Bottom line (pun intended) it depends on WHO is repeated in the pedigree.
    Janet

    chief feeder and mucker for Music, Spy, Belle and Tiara. Someone else is now feeding and mucking for Chief and Brain (both foxhunting now).


    1 members found this post helpful.

  3. #3
    Join Date
    Mar. 31, 2006
    Posts
    264

    Default

    Janet,
    Thanks for explaining. Now it makes sense.

    While looking for horses, I knew about the Impressive line, in terms of checking back for that name, and the need for HYPP testing, didn't know about "large heart" gene in TB's.

    The more I learn, the more I realize I don't know. Seems to be a science within itself.

    Thanks!!



  4. #4
    Join Date
    Mar. 5, 2007
    Posts
    1,704

    Default

    [QUOTE=Janet;6747309 The "poster child" for this effect is "HYPP" in Quarter Horses. Because the sire, Impressive, had many good features, he appeared many times in the pedigrees of QH "halter" horses. He had one copy of the HYPP gene, which makes the horses "bulk up". But horses that got two copies of the HYPP gene have severe problems. It has now got to the point where people check for the gene befor breeding.

    [/QUOTE]

    Umm. Not exactly.
    Since 2007 or 2008 AQHA will not register a homozygous positive for HYPP (H/H).
    So yeah, it gets checked but not because it's the right thing to do. It's the only way you can get AQHA papers.



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