3rd litter born today- 25 big healthy babies

[Jeff B]

Nice explanation.
So anerythristic and axanthic are both recessive, and when both genes are present it is the axanthic trait that is expressed.

We know anerythristic is a simple recessive, that has been well characterized. Which means that one copy of the anerythristic gene is dominated by the wild type counterpart or respective wild type allele. It appears that anerythristic and the axanthic gene are co-dominant to each other which when one copy of each are present it creates a 3rd phenotype, which we call blue axanthic. It is likely that the axanthic gene is recessive as well, but does it produce a distinguishable phenotype on its own without a copy of anerythristic being present is the question. I think some of Scotts past breedings says it can't, but I am not completely certain that anerythistic has ever been completely taken out of the equation, but it is and het axanthic x het axanthic produces all normals in large sample size with no axanthic phenotype expressed, then the question becomes does xx just look normal or is it lethal?

[chris-uk]

It is likely that the axanthic gene is recessive as well, but does it produce a distinguishable phenotype on its own without a copy of anerythristic being present is the question. I think some of Scotts past breedings says it can't, but I am not completely certain that anerythistic has ever been completely taken out of the equation, but it is and het axanthic x het axanthic produces all normals in large sample size with no axanthic phenotype expressed, then the question becomes does xx just look normal or is it lethal?

That is probably impossible to answer without genetic sequencing of all offspring from a het axanthic x het axanthic pairing, and testing of any stillborns and slugs (I'm assuming a slug can be an undeveloped fertilised egg).
I suspect that if that pairing has consistently produced normal offspring that two axanthic genes are incompatible with life.

[Steveo]

That is probably impossible to answer without genetic sequencing of all offspring from a het axanthic x het axanthic pairing, and testing of any stillborns and slugs (I'm assuming a slug can be an undeveloped fertilised egg).
I suspect that if that pairing has consistently produced normal offspring that two axanthic genes are incompatible with life.

You wouldn't necessarily have to test any of the nonviable pairings - just check the parents vs. the living offspring and see if the ratios line up i.e. if Yy x Yy doesn't ever produce yy, there's something wrong with the yy pairing.

Some lethal gene pairings are lethal from the start so you'd never see anything from them. In that situation, humans tend to spontaneously abort so early that the woman never even knows about it. I'm not sure how it works in herps but I would suspect it's something similar, possibly a very small ovum excreted with normal digestive waste.

It's possible a lethal gene could be located near the gene in question and so they tend to travel together... but to tease that out using mendelian methods could require a tremendous sample size.

[Jeff B]

You wouldn't necessarily have to test any of the nonviable pairings - just check the parents vs. the living offspring and see if the ratios line up i.e. if Yy x Yy doesn't ever produce yy, there's something wrong with the yy pairing

The problem with that is if xx is not phenotypically discernable from normal (wild type) phenotype.

[chris-uk]

You wouldn't necessarily have to test any of the nonviable pairings - just check the parents vs. the living offspring and see if the ratios line up i.e. if Yy x Yy doesn't ever produce yy, there's something wrong with the yy pairing.

Yes with a large enough sample you could just test the living and identify whether there are any yy individuals with a statistical confidence.

Some lethal gene pairings are lethal from the start so you'd never see anything from them. In that situation, humans tend to spontaneously abort so early that the woman never even knows about it. I'm not sure how it works in herps but I would suspect it's something similar, possibly a very small ovum excreted with normal digestive waste.

I don't know how the mechanism for this works in herps either. I'd assume either expelled shortly after conception, or retained and expelled during the birth.

It's possible a lethal gene could be located near the gene in question and so they tend to travel together... but to tease that out using mendelian methods could require a tremendous sample size.

I think it could be a case of missing genetic material. In that a axanthic mutation has some vital genetic material from a nearby loci missing, this would explain why you don't get yy and also why a axanthic phenotype is only displayed when paired with an anerythristic gene - the anery expression is "weak" enough that the axanthic can dominate, but the anery genes aren't missing the genetic material that the axanthic gene does so the combination is viable.

Sorry for diverting your new litter thread Jeff. The genetics are quite interesting with this one.

[Steveo]

Sorry for diverting your new litter thread Jeff. The genetics are quite interesting with this one.

I apologize as well. This is just a neat topic and it's nice to discuss with others who are literate in genetics.

[Jeff B]

Sorry for diverting your new litter thread Jeff. The genetics are quite interesting with this one.

Not diverted one bit, that's what this post is all about. I welcome the ideas and the input. My hypothesis is that it is a minor mutation that alone, one copy or two doesn't have any major effect and thus results in normal wild type phenotype, but combined with the anery gene it somehow interacts in a truncated fashion. So phenotypically, the axanthic is somewhere between anerythristic and normal in effect or appearance (maybe 75% toward anerythristic). The evidence is in the fact that the axanthic look like an anerythristic that didn't quite loose all the brown and yellow color, just greatly reduced, compared to the anerythristic that has the full effect and makes a black and gray snake.