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Let's say we are talking about a complex being with many variations. Let's take coat colour as an example and pretend we have a creature with codominant genes to do with coat colour (for example BR (B for black and R for red, assuming they're both dominant and visible). We now breed said animal to a co dominant coat type of a different variation (for example, YW (Y for yellow and W for white, assuming again that they're both dominant).

Assuming all 4 dominant genes are as dominant as each other (so red isn't going to appear over yellow, for example) What comes out of said breeding?

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    $\begingroup$ I believe you are mistaking co-dominance with semi-dominance. What is the color of BR individuals? Do they have red and black hairs? $\endgroup$ – user24284 May 28 '17 at 1:22
  • $\begingroup$ The animal will have both colours present and visible in its coat. If it helps, we can assume the parents had the genes Bg (black (dominant) and green (recessive)) and and Rp (red dominant and purple recessive) the 25% would have been BR which is what we got $\endgroup$ – user32745 May 28 '17 at 1:25
  • $\begingroup$ Well, I just posted an answer but now you're talking about recessive alleles, which render my answer useless. I just deleted it. $\endgroup$ – user24284 May 28 '17 at 1:33
  • $\begingroup$ Well, assuming we have 2 parents with the genes Bg and Rp, there is a 25% chance of an offspring with the gene BR. folkweing the same pattern we have another of the same species with the genes YW. If we bred those two, what happens? If all 4 genes are dominant, do they separate to create a new variation (such as the chance of BY) or do they mutate to create a whole new type of colour (perhaps YWRb (yellow white and red, with the black carried as recessive?) $\endgroup$ – user32745 May 28 '17 at 1:39
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    $\begingroup$ Reading your comments I strongly suggest you study monofactorial inheritance first, and then ask your question here. Don't get me wrong, but there are a lot of things in your comment that make no sense and show us that you have a wrong concept of genetics. $\endgroup$ – user24284 May 28 '17 at 1:54
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I am not sure I understood your question. I will try to rewrite your question below with my own words and you will let me know if I udnerstood your question correctly.

Description of the genetic of interest

There is only one locus for coat color. Individuals are diploid. At this locus, there exists 4 alleles in the population. B, R, Y and W. BR individuals are both black and red (as B and R are codominant). Another individual is YW and its phenotype is yellow and white (as W and Y are codominant)

Question

What phenotype do BY, BW, RY and RW have?

Answer

There is no way to know! Relationships between alleles, say Y and B in determining a given phenotype cannot be extrapolated from relationship B and Y have with other alleles. A relationship between two alleles in determining a phenotype is specific to a pair of alleles.

It is for example theoretically possible that A is dominant over B and B is dominant over C and C is dominant over A.

In your case, as you only have codominant relationship, it is tempting to expect that BY would be both black and yellow but there is really no way to be sure of that from the "Description of the genetic of interest"

EDIT

You have now changed your post. I don't really understand the new question either. You seem to imply that two alleles may be both dominant. This is impossible. They can be co-dominant.

I think your issue is that you are trying to associate a property of relationship between alleles as a property of an allele itself. Keep in mind, that saying that an allele is dominant only makes sense in a particular context that is in relationship to another allele who will therefore necessarily be recessive.

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  • $\begingroup$ Could the crossossing of all those dominant genes create a mutation? (Or make a mutation more Likely?) also even if we get let's say a RW (red and white), is it possible for the other genes to have been carried over still and be present in said offspring? $\endgroup$ – user32745 May 28 '17 at 1:36
  • $\begingroup$ It does not mean anything to say that a gene is dominant. An allele can be called dominant when considered in its relationship to another allele at the same locus. Relationship between allele have no causal effect on mutation production so I don't understand why you ask if it would "create a mutation". Specific alleles may affect the mutation rate though but I don't think this is where you are trying to go. $\endgroup$ – Remi.b May 28 '17 at 1:40
  • $\begingroup$ I do apologise if I don't make much sense, I'm really struggling to understand co dominance and how it affects breeding and mutations into new variations. To put it more into a sort of context we can look at horses. There's a colour called piabald (black and white patches on black skin). Did that colour originate from a BW (black white co dominant) and mutate into one gene (call it P for dominant piabald, which can now be carried with any other recessive (such as b for buckskin (a recessive colour)) $\endgroup$ – user32745 May 28 '17 at 1:47
  • $\begingroup$ No worries. I know what it is to enter into a new subject. It can be very challenging to ask clear questions. I don't really understand your question again and don't really understand what's unclear to you. You might want to review the definitions of mutation, gene, allele and locus. $\endgroup$ – Remi.b May 28 '17 at 2:26

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