"Split for X" - what does it mean? ARAUCANA question

Discussion in 'General breed discussions & FAQ' started by BlazeJester, Feb 16, 2012.

  1. BlazeJester

    BlazeJester Chillin' With My Peeps

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    Ok, genetics folks - my genetics professor told me to drop the class and consider a change in profession, so I'm not even going to try to interpret what is meant by a "split" gene in chickens.

    Someone explain this to me (and other clueless non-geneticists) please? I have an Araucana cockerel who I was told is "split for tufts". I have also seen the term used widely for color. Any insights into what this term refers to is quite appreciated.

    I am a chemist with some microbiology experience so highly capable of understanding technical explanations, it's just unclear to me outside of common usage what this means in terms of breeding.

    ETA: From what I understand of Araucana genetics, tufts are dominant and homozygous lethal, so it is completely unclear to me how a cockerel can be split for tufts.
     
    Last edited: Feb 16, 2012
  2. To me a split gene simply means they don't know who his daddy is.
     
  3. AinaWGSD

    AinaWGSD Chillin' With My Peeps

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    Being split has nothing to do with not knowing the parentage! Split for X simply means that you know the bird is carrying a recessive gene (heterozygous) but has the dominant phenotype. I don't know that much about Araucana genetics, but like you I thought that tufts were dominant and heterozygous lethal so there's no way for a bird to be "split" for tufts.
     
  4. BlazeJester

    BlazeJester Chillin' With My Peeps

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    This is what I thought as well - homo- or heterozygous dominant over expressed recessive.

     
  5. tadkerson

    tadkerson Chillin' With My Peeps

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    Ear tufts is lethal in homozygotes. Heterozygous embryos also have a good chance of dieing. Even heterozygous ( Et/et+) adults can die from the trait. A low percentage of heterozygous individuals will not express the trait ( penetrance ).

    Tim
     
  6. AquaEyes

    AquaEyes Chillin' With My Peeps

    In "genetics-speak", the simple explanation of "split" is that in a description of an animal, what you see is listed first, then comes the word "split", and then comes the recessive traits that are not seen but for which the animal carries one copy of the gene(s). Recessive traits need to be expressed on each member of the pair of chromosomes on which they exist in order for them to be visible.

    For example, if you take a Lavender roo and cross it with a Black hen, the offspring would be Black split to Lavender -- you see Black, but the birds also carry the gene for Lavender.

    As others have said, you really can't have a bird that is "split" for a dominant gene. If it has only one copy, it should show. If for some reason it doesn't (variable penetrance), genetically it is no different with respect to that trait than an individual who does show it, and shouldn't be listed as being "split" to the trait.
     
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  7. nicalandia

    nicalandia Overrun With Chickens

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    Not if they are Sex Linked...[​IMG]
     
  8. cashdl

    cashdl Chillin' With My Peeps

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    Some say that their birds could be tufted and not show the tufts. That is fairly rare. Tufted birds may have very small tufts but the tufting is still evident. I have had tufted birds get their tufts pecked out for a short period of time but they grow back. A bird cannot be split for tufts. It either has them or does not. I do have one tufted hen that you really have to look at closely to see her tufts. Tufts are not recessive they are dominant, and a bird cannot get tufts unless at least one of their parents had tufts. By the same token, they cannot pass them on unless they themselves have them.

    To make it more difficult. 99.99% of every bird that has two copies or is homozygous for the tufting gene dies before it is hatched or shortly after. There has been one person who said their bird was homozygous tufted but I don't believe it was genetically tested. They said every chick it fathered was tufted. I can neither prove or disprove this.

    So if every living bird only has one copy of the tufting gene, then there is a 50% chance it will not pass that gene on.

    Lanae
     
  9. Sonoran Silkies

    Sonoran Silkies Flock Mistress

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  10. Sonoran Silkies

    Sonoran Silkies Flock Mistress

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    I wonder if the person who made the original statement simply meant that the bird was heterozygous? And just had an incomplete understanding of genetic terminology? OP, did hte bird in question display tufts? Of were they not apparent?
     

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