codominant or dominant spiders

New to BP's but not new to genetics.

The question that needs to be asked is the phenotype (the way it looks) different between the heterozygous Spider and the homozygous Spider. Since as far as I know there is no living homozygous Spider. I would have to say that there is a big difference. Het Spiders look awesome and homozygous spiders start to smell bad really quickly and don't move much.

So I would say that the Spider mutation is a codominent one with its super form being lethal. This is not unheard of in other species. If a living homozygous spider can be produced that looks the same as a heterozygous spider and all previous failures turn out not to be related to the genotype of the animal then its a dominant mutation.

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Originally Posted by littleindiangirl

If each animal receives one copy of a gene from the parents, using the heterozygous spider as an example, what guarantees that this "dominant" gene is the one that gets passed along to the offspring and not the normal gene?

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Fair enough.I'm going to Play devils advocate here for a sec. So help me out here Pastel's are Hets also only needing one copy of the gene to be expressed. The homozygous form of the mutation is a super pastel correct or a visual difference between the two. Now you breed any two animals together say pastel for example you get a 1:4 shot at producing a homozygous pastel. Now lets look for a moment at spiders you breed two spiders together and does each parent still pass half of its genetic material on to the offspring? If so then 1:4 animals will be Homozygous. Now where is it written that the Homozygous form of a mutation must look different that the Het. If the mutation only effect the scales to a certain extent or the super is so subtle we can't tell the difference from the Het form how would you know.

Just fun to think that just because some body said so doesn't mean that other possibility's don't exist

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Originally Posted by Egapal

New to BP's but not new to genetics.

The question that needs to be asked is the phenotype (the way it looks) different between the heterozygous Spider and the homozygous Spider. Since as far as I know there is no living homozygous Spider. I would have to say that there is a big difference. Het Spiders look awesome and homozygous spiders start to smell bad really quickly and don't move much.

So I would say that the Spider mutation is a codominent one with its super form being lethal. This is not unheard of in other species. If a living homozygous spider can be produced that looks the same as a heterozygous spider and all previous failures turn out not to be related to the genotype of the animal then its a dominant mutation.

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So far, the current theory is that the spider gene is dominant, in that it does not need to be homozygous for the full expression of the phenotype.

Meaning, there very well could be homozygous spiders out there, but no one has proven it.

BHB believes he has a homozygous Pinstripe, and it also does not look any different from any other pin. ;)

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Originally Posted by Freakie_frog

So help me out here Pastel's are Hets also only needing one copy of the gene to be expressed. The homozygous form of the mutation is a super pastel correct or a visual difference between the two.

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A pastel is an incomplete dominant. When an animal carries one copy, it is only showing a partial expression of the gene.

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Now you breed any two animals together say pastel for example you get a 1:4 shot at producing a homozygous pastel. Now lets look for a moment at spiders you breed two spiders together and does each parent still pass half of its genetic material on to the offspring?

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Yes, the inheritance is still the same. Each animal is going to give one of the copies of it's gene. It could be the normal gene it gives, or the pastel gene.

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If so then 1:4 animals will be Homozygous. Now where is it written that the Homozygous form of a mutation must look different that the Het. If the mutation only effect the scales to a certain extent or the super is so subtle we can't tell the difference from the Het form how would you know.

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Exactly my point. So far as we know it, the spider gene is a dominant in that only one copy of the gene is needed for the FULL expression of the phenotype. ;) So a het spider would look exactly the same as a homozygous spider.

No one has come forward about their homozygous spider as of yet, so it is still very possible it is homozygous lethal.

Like I said, BHB believes he has a homozygous pin, because when bred to normals, he gets all pins. ;)

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Originally Posted by Freakie_frog

Fair enough.I'm going to Play devils advocate here for a sec. So help me out here Pastel's are Hets also only needing one copy of the gene to be expressed. The homozygous form of the mutation is a super pastel correct or a visual difference between the two. Now you breed any two animals together say pastel for example you get a 1:4 shot at producing a homozygous pastel. Now lets look for a moment at spiders you breed two spiders together and does each parent still pass half of its genetic material on to the offspring? If so then 1:4 animals will be Homozygous. Now where is it written that the Homozygous form of a mutation must look different that the Het.

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A homozygous form of a mutation does not have to be different than the Het. Thats what we are talking about. If its a recessive mutation you need a pair of the genes, if its a codominant mutation then a single gene gets you something and a pair gets you the super form. If its Dominant then a single gene gets you the mutation and a pair of the genes gets you the same thing but when you breed an animal that's homozygous for a dominant trait you are guaranteed the offspring will show that trait. Whether they are homozygous or heterozygous then depends on the other parent and luck if the other parent is heterozygous for the same trait.

The question is whether the Spider mutation is codominant or dominant and that depends entirely on whether the phenotype of the homozygous is different than the heterozygous. I would still have to assert that since the homozygous spiders all die they are a super form.

The answer is unknown and can only be proven by a living homozygous spider (something that can only be proven by multiple breedings to normals throwing only spiders or a genetic test).

Or else it comes down to a strict definition of whether or not a lethal homozygous gene is considered a super form despite no visible difference. I am not sure on that one.

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Originally Posted by littleindiangirl

So a het spider would look exactly the same as a homozygous spider.

No one has come forward about their homozygous spider as of yet, so it is still very possible it is homozygous lethal.

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So if the spider mutation is homozygous lethal would you then say that its codominant or would you say that the lethal/non lethal question is irrelevant.

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Originally Posted by littleindiangirl

Like I said, BHB believes he has a homozygous pin, because when bred to normals, he gets all pins. ;)

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My understanding is that the pinstripe is a separate mutation from the spider. Pinstripe may be a true dominant mutation this would not prove anything regarding the spider mutation. The fact that a spinner has been produced and its is yet another phenotype would help validate that they are separate mutations.

so the pastel gene is codominant and does not become dominant in the super form. the super form is just two copies of the codominant gene, right? just like mojaves and lucys? one is codom and the other is two copies of the codom gene. so what morph is truely dominant? the normal wild type?

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Originally Posted by Egapal

So if the spider mutation is homozygous lethal would you then say that its codominant or would you say that the lethal/non lethal question is irrelevant.

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I'm majorly sorry, but that is a very confusing question.

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My understanding is that the pinstripe is a separate mutation from the spider. Pinstripe may be a true dominant mutation this would not prove anything regarding the spider mutation. The fact that a spinner has been produced and its is yet another phenotype would help validate that they are separate mutations.

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Yes, I know they are separate mutations. That was not my point, I'm sorry to have confused you.

The reason I used the pin as an example is because the spider and pinstripe are the two BP mutations that are unknown to whether or not it is possible there are homozygous animals out there. We DO know that if there are, they do not look any different from a heterozygous animal.

The question is and always has been, is it lethal, or are their homozygous animals out there. Since all the animals from a pin x pin or spider x spider pairing all look the same, meaning they have no "super".

so many people told about the lethal homozygot Spider´s.
or when breeding 2 Spiders there will be nearly 25% "death snakes"

Is there someone who can show us such an 25%-Snake(Superspider)?

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Originally Posted by bigballs

so what morph is truely dominant? the normal wild type?

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Good question.

And it's very muddy waters. :oops:

When I think of dominant, I think in terms of this gene is dominant over another gene, or a recessive gene.

When I think of codominant, I think of the same thing, but in the sense that only one copy is needed for the full expression of the gene. (heterozygous)

(I could very well have codominant and dominant wrong)

When I think of incomplete dominant, I always think of the partial expression when heterozygous, and complete expression when homozygous.

I know, I'm terrible about explaining terminology, so usually when it gets ugly in these threads, I leave them alone from sheer exhaustion at trying to get people to understand simple inheritance VS. dominant/recessive expressions.