Tiaris wrote: 12 Dec 2017, 05:56
Ross,
How on Earth do you know which position on the Gouldian Finch's genome, any of the genes for various known colour mutations are located, let alone determine which of certain mutations are located in different positions and others are situated in the same gene pair?
Morning Tiaris,
I did not say I, or anyone else, knows the positions of gene pairs or chromosomes in the genome; I don't think any finch's genome has been decoded yet like the human genome. The question is not whether we know the exact positions, it is whether certain mutations (like red and yellow mutations in Gouldians) are affected by the same position or different positions in the genome (i.e., different chromosomes). You have been arguing that the yellow head gene is at the same position as the red head gene. And that (in the case of the Star finch) the fawn gene is at the same location as the cinnamon gene. And therefore, because [red split black split yellow] "triple splits" in Goulds, and [normal split fawn split cinnamon] "triple splits" in Stars are possible, then [purple split lilac split white] "triple splits" in Goulds must also be possible (because, indeed, those three mutations occur at the same gene location). Please correct me if I did not summarise your position accurately.
My argument has been that the mutation that changes a red head to black, and the mutation that changes a red head to yellow, are affected by gene pairs in different locations, as are the fawn and cinnamon mutations in Star finches produced by genes/chromosomes in different locations. I've come to that conclusion via what I have read and, based on that information, "logical dedution". For example, (as I have explained previously in this thread) the red head mutation is a sex-linked trait. That means it must be located in a chromosome that is sex-linked. The yellow mutation is autosomal, and that means it must be located in a chromosome that allows autosomal inheritance. And by logical deduction, these two chromosomes must be different chromosomes, i.e., with different locations. A sex-linked chromosome cannot also be autosomal.
Similarly, the Star finch fawn mutation is autosomal and thus must be located in a chromosome that allows autosomal inheritance. The cinnamon mutation is located in a sex-linked chromosome. Thus those two chromosomes must be located at different positions in the genome.
It is for this reason, (chromosomes located at different positions in the genome) it is possible to get your "triple splits", i.e., red split black split yellow for Goulds, and normal split fawn split cinnamon for star finches. Triple splits can only occur when the mutations are at different location in the genome.
This is why, I feel, your assertion that a "triple split" for breast colour is incorrect. Breast color is affected at a single chromosome location, i.e., a single pair of genes. Each of the two genes in that pair can take on one of three colours: purple, lilac, or white. So, as a gene pair, they can only take on two of those three colours, for example purple & purple, or lilac & white, or white & white, etc. That gene pair, being a pair, cannot take on purple & lilac & white, simultaneously, thus a triple split of purple/lilac/white is a genetic impossibility, in my humble opinion. Lilac is,. after all, a modification of the white gene; that one gene cannot be both lilac and white simultaneously. Yes one gene in the pair can be lilac and the other gene in the pair white, but that still leaves you missing the purple in your triple split.
Further evidence that red and yellow mutations are located at different positions in the genome can be found here:
http://www.gouldianfinches.eu/en/geneti ... -coloring/
Specifically:
We will assume that red color is dominant and sex linked, black color is recessive and sex linked. In this case we consider black to be a recessive allele to a red dominant allele. The mechanism of pigment production is described elsewhere, so I will mention it only briefly. If, in the process of red pigment – canthaxanthin production, a change occurs, yellow lutein is created. The gene that causes interruption of red pigment production is present in an autosomal chromosome, it is therefore not sex linked and is inherited freely. This gene is a modifier, that is either active and thus disables red pigment production, or is inactive and red pigment is produced.
As I said before, Marek knows his genetics, and here he is clearly stating that the gene pair responsible for red and black, and the gene pair responsible for yellow, are located in different chromosomes, i.e. red in a sex-linked chromosome, and yellow in an autosomal chromosome.
Cheers,
Ross
