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  1. #41
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    Re: How can a male snake be a "female maker" or "male maker"?

    Quote Originally Posted by TessadasExotics View Post
    lol I forgot that reptiles and birds were backwards.

    That is a great article and interesting to see that morphology (and faster evolution/genetic drift) is caused by the males.
    Pretty sure this is what caused your misconception about it being sex-linked when most people think it's not. Plus, the fact that bananas are codominant pretty much renders the sex-linked theory impossible. It's still pretty perplexing why mutations in the male would cause a skewed ratio assuming that the same number of babies are produced (ie. assuming females or males don't die before they're hatched).

  2. #42
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    Re: How can a male snake be a "female maker" or "male maker"?

    Do you know who produced a 'super banana' and what gender it was?

    It's still possible that the trait is sex-linked because Z and W may be able to engage in crossing over (I can't find anything in the literature 'for' or 'against' this - anyone know of any studies? birds or reptiles. insects do crazy stuff, so not usually as applicable).
    Cross-over events are rarer as two genes get closer together, so a 'banana male maker' producing 95% male/banana & 5% female/banana ratio would be really neatly explained by two neighboring genes crossing over. statistically beautiful, really.

    Science studies mammals more often, but X and Y don't really crossover (the size difference keeps them from hooking up properly), so 'what's there is there'. e.g. you can't get calico cat coat color genes "orange" and "black" off of the X and on to the Y (Y doesn't have a color locus at all, so there's nothing for X to trade with = no crossing over); you have to have non-disjunction events (resulting in XXY) to get a 'male calico' but the calico male is sterile (because making gametes with 3 copies of a chromosome is not pretty and hormone dosage in mammals is tricky and must be perfect in order to get proper adult genitalia - you're sterile without fully functional testes).

    There is no 'model reptile' (there is a 'model' plant, bacterium, fungus, and mammal - where basic questions like this are first answered). Back in 2007, a research group found that temperature could influence sex ratio EVEN IN genotypic (ZZ male / ZW female) species (http://www.sciencemag.org/content/316/5823/411.short).
    If "W" isn't 100% necessary for functional females, then banana may well be 'sex-linked'. It's also possible ZZW females aren't sterile (and Z_ males for that matter) - lots of organisms tolerate genetic mishaps far better than mammals.

    Since so little is known about sex determination in the snake clade, it's also possible there are other factors involved we haven't even fathomed.

    The ratios are super cool and the whole mystery is really intriguing.

    Right now, my money's still on crossing over between Z and W, but my heart wants it to be something TOTALLY UNKNOWN!!
    Last edited by PeterPieBaldPython; 08-07-2015 at 12:20 AM.

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  4. #43
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    Re: How can a male snake be a "female maker" or "male maker"?

    Sorry if this has already been asked, but are there other morphs that "female makers" and "male makers" occur with?

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    Re: How can a male snake be a "female maker" or "male maker"?

    Quote Originally Posted by chosen2030 View Post
    Sorry if this has already been asked, but are there other morphs that "female makers" and "male makers" occur with?
    nope

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    a few related questions:

    So, one of the problems with solving this may be that we assume all fertile females are zw, and all fertile males are zz, which may not be the case?

    Is there an easy, cheap test for determining if breeding animals are, in fact, standard zw or zz?

    Do these fertile anomalies produce standard zw's and zz's, in 50/50 ratio, or does the anomalous gene tend to propagate down the line? That is, for example, are zzw females producing more zzw's?

    Agree, cross-over would seem to be the simplest explanation, but I'm wondering about some odd ball possibilities as well (unintentional pun). Unfortunately, my college biology was a LONG time ago!

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    Last thing I read about it, which was quite a few years ago so things might of changed, but I read something about looking at the burm genome and they were just happy they figured out which was Z and which was W. they didn't see too far along in having a good base line to figure things out. Maybe things have changed though.

    Problem with crossing over or not, is females produce normal ratio as far as we know, if it sits on a sex chromosome we shouldn't see that. sitting on Z of the female would lead to no female bananas and all males being bananas. Those males would be the ones producing the 50/50 split we see in females. If it sat on the W, we would only see female bananas. Now obviously cross over could come into play, but to think a crossover would happen to replicate a 50/50 split is a little far fetched. Also even with cross over the males should still be doing the 50/50 split.

    Some have brought up the possibility of males being the ZW and females being the ZZ in ball pythons. But banana gene is the only evidence toward it, but we have burms that are definitely ZW female ZZ male as far as we know, which i would say is pretty close to the ball python, and a swap like that would be pretty extraordinary, not to say it is impossible tho. there just no reason to think it besides the banana gene. I don't know of any case of an XY reptiles, just ZW and temp determined ones.

    The ZZW scenario might be something to think about, but I still can't seem to make it work off the top of my head, even with crossing over. Perhaps you could lay out a theory for it?

  9. #47
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    "The ZZW scenario might be something to think about, but I still can't seem to make it work off the top of my head, even with crossing over. Perhaps you could lay out a theory for it?"

    Ha! Just shots in the dark, that's all.
    My understanding of this is too vague to support anything more than the basic recessive/dominant, etc. Mendelian grids. I'm not attached to any theories, I just find the outcomes VERY peculiar. There has to be a reason, and the possibility of the zzw's, or even a complete flip for sex expression, etc. just looks like the most promising angle at present.

    Off to do some net searches.
    Last edited by distaff; 08-16-2015 at 08:08 PM.

  10. #48
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    Re: How can a male snake be a "female maker" or "male maker"?

    I have been looking at the "male maker" vs "female maker" and just want to know if i got this right
    If i have a female my sex ratio will be even, but all males she has will be "female makers"
    if i have a "male maker" male, I will get 95% or higher males
    If i have a "female maker" male, I will get 95% or higher females
    If I do get a male form my "female maker" male, the new male will then be a "male maker" male
    is that about right?

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    Re: How can a male snake be a "female maker" or "male maker"?

    Quote Originally Posted by StillBP View Post
    I have been looking at the "male maker" vs "female maker" and just want to know if i got this right
    If i have a female my sex ratio will be even, but all males she has will be "female makers"
    if i have a "male maker" male, I will get 95% or higher males
    If i have a "female maker" male, I will get 95% or higher females
    If I do get a male form my "female maker" male, the new male will then be a "male maker" male
    is that about right?
    Nope. Not "about right". Right.
    Find me on Facebook: E.B. Ball Pythons and Instagram: @EBBallPythons

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