Co-Dominance

[Myron Tay]

Any co-dominant genes in bettas?

quote:Originally posted by Ramon

giant: from what I have read (not sure though), co-dominance, ~2 genes, whereas size in general is certainly a multi-factorial trait, but the giant gene brings it to other levels
blue: 1 gene, co-dominant
opaque: most likely 1 gene co-dominant ?

What is blue or opaque gene co-dominant to?

[Ramon]

errmm, to itself Myron, to itself ;)

dominant / recessive gene: 1 gene has 2 alleles (expressions) A and a, where AA and Aa lead to the same phenotype: A is dominant over a, a is recessive to A. aa leads to a second phenotpye.

co-dominance means, that each combination AA, Aa, aa results in a distinct phenotype.

The problem is in understanding, that alleles and genes are very generally spoken the same (biologists, don't kill me ;) ) here is why:
When speaking about the cambodia-gen, we actually refer to the mutated, recessive allel that, if present on both alleles, causes the cambodian phenotype. An allele is a copy of a gene, and diploid beings store 2 copies per gene.

Usually 1 gene consists of 2 alleles (one from father, one from mother). A single dominant allel is responsible for a certain trait (it's the construction plan for a certain protein), it overrides the recessive allel. When 2 recessive alleles are present, there is nothing overriding the information, the recessive allele can do it's job. dominant / recessive genes with 2 alleles can yield 2 geno/phenotypes. We must not gorget, that a gene can also consist of more than 2 alleles.

the interesting thing about co-dominance is, that each allel has the same "rights", in this case we have 3 distinct geno/phenotypes. Just like blue, green and steel.

If I get the intention of your post right, you think about the interaction of 2 different and independent genes, this is called epistasis.

For example, c (cambodia) is epistatic to b (blond). It just overrides the information in blond. (We "could" say, c is dominant over b. This is dangerous and the the term dominant is just used for explanation, since it implies that they are related in locus and function. Epistasis is the right term here. )
Nr should be epistatic to Er.

Regards
Ramon

[Myron Tay]

Thanks for the clarification, Ramon. Don't think that intense study has been conducted on co-dominance in bettas. It certainly makes for interesting study.

[sylwester]

co-dominance: if the hetrozygote has a phenotype not equal to either two homozygotes.

Think I understood the word epistatic but how can you say nr is epistatic to Er? Nr changes red to yellow. Without Er it will result in yellow fins only - with heavy Er the entire body will be yellow. Er function is not changed one bit and is never overridden by nr rather than just the colour of the spread is changed and as far as I understand that are two completely different functions unlike c and b which actually reduce the same pigments.

[Ramon]

Sylwester, you are right, replace Er with Red.
But here is my theorie:
If the yellow layer is below the red and xanthophores produce yellow pigments, how come we all talk about NR "changing" red to yellow ?
There is no need to change red to yellow, because yellow is there, there is a layer for yellow. erythrophores and xanthophres co-exist, why are we talking about changing from red to yellow ?

I think this is why Lucas called the gene "non red" rather than "red to yellow" ;)

What if yellow is omnipresent in red but only covered by red ?

[sylwester]

I think it has something to do with the fact that the inner yellow layer is totally abstent in domestic fish or so pale that you wouldn't be able to call it yellow. non-red and red-loss would be very simular if non-red didn't have any colour. I think intense yellow fish are the product of a high degree of extended red.

In printing; a perfect red is made out of yellow and magenta(red colour used in printing). A warm red colour has much yellow while a cold has more blue. A fish pigmentation works a lot like printing I guess so you may be right. (as it's spots of colour on surface that reflect light)

[Ramon]

hmm, but I can't believe that a single recessive gen (Nr) is responsible for that.

We have eryhtophores, producing erythopterin as the red pigment, and we have xanthophores, producing lutein as the yellow pigment.


My initial thought was that Nr-gene avoids the creation of a certain hormone/protein/whatever that is needed on the pathway from yellow (maybe over orange) to red. Hmm... Yellow pigments are different from red pigments, and the locations were they can be found differ as well.

It is hard for me to believe that one gene alone causes this. And if you look at most yellow lines, they are not what I call yellow, they are more pale than yellow.

All this should be the work of a single gene ? We must be kidding ;)

Myron, don't you have anything in your magical TA-Box ? ;)

Regards
Ramon

[sylwester]

I think red and yellow are very related. Dr. Goldstein writes about several solutions to both yellow and red colour, but the pigments are basicly the same.

I belive diet has an important role in colour production as well and I have seen good yellows, but they are very rare. More rare than good reds.

[Ramon]

Sylwester,

I do totally agree, nutrition is very important, especially for reds and yellows.

Found a very interesting article
http://www.eeb.ucla.edu/Faculty/Grether/pdfs/Grether_et_al_Biol_Rev_2004.pdf on Chromatophores and the relationship between erythrophores, xanthophores and the respective carotenoids and pterins.

From what I understood, carotenoids (for yellow) must be supplied from food, whereas pterins (for red) can be created out of carotenoids.

If that is true for betta splendens, my initial thought on Nr was the right one...the pathway from yellow to red is interrupted...well, need more input...
Lucas says about yellow, "it shows yellow where it would normally be red". My second thought on that was that Er affects both, xanthophores and erythrophores, since they are pretty much in the same layer of the dermis.

On the other hand, does that mean that the large variety in yellow lines is equivalent to the large variety of red lines ? Because of the continous variation of the Er gene ? Or is it because of the lack of carotenoids, because breeders are afraid to feed red wash into yellows ?

I am not afraif, I have fed my yellows tremendous amounts of cyclop-eeze, and they still show not the slightest sign of red. But they have a nice and quite intense yello...


Maybe the whole qualitative vs quantitative genetic thing was too much for my wee brain and I need a break ;)


Regards
Ramon

[Myron Tay]

quote:Originally posted by Ramon

hmm, but I can't believe that a single recessive gen (Nr) is responsible for that.

We have eryhtophores, producing erythopterin as the red pigment, and we have xanthophores, producing lutein as the yellow pigment.


My initial thought was that Nr-gene avoids the creation of a certain hormone/protein/whatever that is needed on the pathway from yellow (maybe over orange) to red. Hmm... Yellow pigments are different from red pigments, and the locations were they can be found differ as well.

It is hard for me to believe that one gene alone causes this. And if you look at most yellow lines, they are not what I call yellow, they are more pale than yellow.

All this should be the work of a single gene ? We must be kidding ;)

Myron, don't you have anything in your magical TA-Box ? ;)

Regards
Ramon

Ramon

There are a couple of factors in a good yellow. They basically need to be good red bettas, but carry and exhibit the "nr" gene. As we all know, there are many elements to a good red, such as must carry the extended red gene (so that there would be a good spread of red), no black (caused by either the cambodian or blonde genes or by a complete coverage of the red to block out all black on the black layer entirely) and little irridescence. All these genes, plus the 'nr' one, is one way to produce a good yellow.

An alternative would be to rediscover the yellow layer. Even in that situation, you would still need to have minimum irridescence on the blue layer, the "non-red" gene on the red layer and the cambodian gene on the black layer. So many genes involved.