Enigma Genetics help

[Sandra]

Double post

 

[Sandra]

Marcia I think you slipped a bit there... Let me explain.

I agree with this 100%. I think where we get so much confusion is when we start thinking in terms of textbook genetics definitions, which simply does not apply all the time... especially with gecko morphology!

Textbook genetic definitions apply most of the time in leopard gecko morphology. It's the made up definitions used by hobbyists which can or cannot be applied to some cases. That's why I insist, that is important to learn proper genetics.

You definitions of phenotype and genotype are perfect, I have nothing against them.

But...

So what this means is, that if a gecko has an enigma parent (dominant gene) and let's say, a tangerine parent (line bred trait), we know that half of the offspring will be Enigmas (dominant) and the other 50% will be tangerines. Right? Well, technically speaking, all of the tangerine offspring will be heterozygous for Enigma... which simply means that the genetic copy of the Enigma parent's genes are in there somehwere, even if not expressed.

One the flip side, all of the Enigma offspring should therefore be 'heterozygous' tangerines because the other parent was a tangerine. Right? WRONG! How come? Well, in leopard geckos, only recessive traits actually work like that, because ther are inheritable!

So by scientific textbook standards, an Enigma 'sibling' would be technically heterozygous Enigma, it is not heterozygous for Enigma. An Enigma sibling will never be able to express the enigma gene in any of it's offspring because the Enigma gene is dominant. A geckos is either and Enigma or it is not an Enigma. An Enigma sibling is NOT an Enigma, so it cannot produce Enigmas because it is NOT inheritable!

WRONG! An Enigma sibling is not an heterozygous enigma, it's normal! In this case the parent enigma and the offspring would be the heterozygotes.

I'm not going to explain this because it has been said over and over in this thread and some others. There was one thread some time ago where it was explained and people seemed to understand it quite well.

Here are some useful posts:
http://www.geckoforums.net/showpost.php?p=81630&postcount=13
http://www.geckoforums.net/showpost.php?p=81726&postcount=26
http://www.geckoforums.net/showpost.php?p=81768&postcount=32
http://www.geckoforums.net/showpost.php?p=81771&postcount=34
http://www.geckoforums.net/showpost.php?p=81840&postcount=50

The whole thread:
http://www.geckoforums.net/showthread.php?t=8167

If people don't understand it with this, then I give up :main_laugh:

Sorry, Sandra. I wasn't meaning to imply you were expressing yourself badly.

You don't have to apologize, cause it's true :main_laugh: Haha no, really, I didn't take it the wrong way.

i didn't mean for it to go this far. i'm very sorry for my lack of understanding.

Oh please don't apologize. The sentence in your signature is very true, and we are all here to teach and learn. I was in a bad mood that day and maybe I let it show in my posts somehow, it won't happen again.

It's not about your own personal interpretation of what het or homo mean. The definition of homozygous and heterozygous is well documented and not subject to interpretation.

+1. This is so true, it should have it's own sticky. In fact, we could do a sticky post with some basic genetic terms as I'm sure that most of us are a little tired of answering always the same questions.

Well, having said this, I'll add that this all applies with the premise that the enigma gene is dominant. And the meaning of dominant is like that of heterozygous and homozygous, it doesn't change, our understandig of morphs does.

At this point I venture to say that either the enigma is dominant or it is incomplete dominant being the homozygote form lethal. Both things can be proven with time.

 

[paulh]

Textbook genetic definitions apply most of the time in leopard gecko morphology. It's the made up definitions used by hobbyists which can or cannot be applied to some cases. That's why I insist, that is important to learn proper genetics.

Agree with this 100%.

Sticking my oar in on the "variable pertinence" part of this thread. The correct spelling is "incomplete penetrance", and it can be found using a Google search. Here's one I found.

http://www.netwellness.org/question.cfm/34242.htm

Recessive, codominant, and dominant mutant genes can show incomplete penetrance.

 

[paulnj]

That is not how the term(I very well mis spelled) was discribed to me, but I will recheck as to whether I misquoted or not.

BTW, Hemochromatosis runs in my mom's side ofthe family. I am suprised to see that term, for it's quite rare for most doctors to know it from my experience.

 

[Golden Gate Geckos]

WRONG! An Enigma sibling is not an heterozygous enigma, it's normal! In this case the parent enigma and the offspring would be the heterozygotes.

I agree! An Enigma sibling IS a normal... not a homozygous Enigma, and it does not carry the Enigma loci fraction since it is a dominant trait. Essentially, the Enigma sibling is a heterozygous Enigma because it has one copy of the Enigma parent's genes. If you look at the definition of 'heterozygous' by textbook standards:

"Homozygous is possessing two different forms of a particular gene, one inherited from each parent.

Heterozygous is in contrast to homozygous, the possession of two identical copies of the same gene."

Since the normal sibling has one parent that is an Enigma, it could be defined as heterozygous Enigma... BUT! Since it does not have the allele FOR Enigma, it would not be considered a heterozygote, or carrier of the Enigma gene.

 

[Sandra]

Isn't it just the opposite? I looked for the source you took those definitions from as they are just the contrary I have always heard, and I think you got it wrong.

From http://www.medterms.com/

Heterozygous: Possessing two different forms of a particular gene, one inherited from each parent. A person who is heterozygous is called a heterozygote or a gene carrier.

Heterozygous is in contrast to homozygous, the possession of two identical copies of the same gene.

Homozygous: Possessing two identical forms of a particular gene, one inherited from each parent.

I think that when they said "Heterozygous is in contrast to homozygous, the possession of two identical copies of the same gene." they didn't mean that was the definition of heterozygous, but the definition of what is contrary to heterozygous. It isn't very well written but they must mean that, if not it would contradict the previously and following definition they are giving.

Essentially, the Enigma sibling is a heterozygous Enigma because it has one copy of the Enigma parent's genes.

That doesn't make it an heterozygous enigma / enigma heterozygote. That's not what it means to be a heterozygote. It means that you are receiving from one of your parents an allele that is mutated and from the other one an allele that is normal. The normals from enigma x normal or enigma x enigma crosses posses two normal alleles (homozygote normal), they HAVE TO, because if one of the alleles was enigma, the normal allele would be dominated by the enigma allele and the phenotype of the gecko would be enigma.

It's obvious that a normal would transmit one of the normal alleles, but how come that an enigma can transmit a normal allele to the offspring? Being heterozygous as well! That is, having an enigma allele and a normal allele. There is a 50% chance to transmit one or another to the offspring. Then the hatchlings can either get an enigma allele or a normal allele from one parent, and only normal alleles from the other parent.

I'll try to explain using my sucky schemes again :main_laugh:

This are the alleles of the parents and all the possible combinations in the offspring (padre=father, madre=mother).

Yellow = Normal allele
Orange = Mutant allele

Two yellow = Homozygote normal
Two orange = Homozygote mutant
One yellow one orange = Heterozygote

That's why (het) enigma x (homo) normal = 50% (het) enigmas, 50% (homo) normals. In the same way, het. albino x (homo) normal would throw 50% het. albinos 50% (homo) normals. The difference is that het albinos look like normals and het enigmas look like enigmas.

What would happen if there was an homozygous enigma? Even if we bred it to an homozygous normal, all hatchlings would receive one enigma allele. That why we say that homozygous enigma x normal = 100% enigmas.

In short, the thing is, that having received a normal allele from an enigma parent doesn't make it heterozygous. Maybe I'm not understanding what you mean.

Again, that's how it would work if it is dominant.

The thing about incomplete penetrance is very interesting, it was also described to me some time ago as a possible explanation to what might be happening with enigma's variable color and issues, but also mispelled and I couldn't find any information on it afterwards. Maybe Paul(nj) and I have the same sources :main_laugh: But Paul(h) is right, that doesn't have anything to do with a mutation being dominant or recessive. It's not what we are discussing here, although it may deserve it's own thread :main_thumbsup: