The SOX10 protein that’s made from it switches the Tyrp1 gene on, and TYRP1 protein is made (or in the case of the brown allele, not made). The gene is normally turned on in melanocytes. The ‘not recessive red’ allele is a “normal” version of the Sox10 gene. When genes are switched on, proteins are made from them, and the proteins are available to do their jobs. The SOX10 protein’s normal function is to switch other genes ‘on,’ including Tyrp1. (For more details, visit color.) The recessive red gene is called Sox10, and it codes for the SOX10 protein. The color gene is Tyrp1, and it codes for the TYRP1 protein. But the two genes code for proteins that work on different steps of melanin synthesis. The color and the recessive red genes both affect the synthesis of pigments called melanins, which are made in structures called melanosomes in cells called melanocytes. But the parts we do understand are interesting and worth the effort to learn. Inside a bird’s cells, the molecular mechanism of recessive red is fairly complex and not completely understood. Second, the melanin is distributed evenly in all feathers, disrupting any underlying pattern or spread genotype. First, the feathers have mostly red melanin, with very little black and brown. On the surface, we can see two things are happening with the melanin pigments in recessive red birds. Genes that interact epistatically are often parts of the same biochemical pathways. The interactions among these genes are what cause their epistatic relationships. The genes that control recessive red, spread, color, and pattern all affect the synthesis and distribution of pigment molecules called melanins. It is important to remember that even though recessive red birds show no color, spread, or pattern phenotype, they always have two alleles for each of those genes (except remember that females have just one color allele). Because pigment in recesive red birds is distributed evenly in all feathers, any underlying pattern is hidden. Notice the illustration to the right: both of the recessive red birds look the same, regardless of whether they have a spread allele or not.Īlso shown on the right, recessive red is epistatic to pattern. Recessive red is also epistatic to spread. (Spread ash-red birds are a very light reddish shade recessive red birds are much darker.) In fact, the recessive red phenotype is different from any of the spread phenotypes, regardless of the underlying color–even ash-red. While the two look the same, they are controlled by separate genes. You may have noticed that the recessive red color distribution looks similar to the spread phenotype. That is, whatever the underlying color alleles, a bird with two recessive red alleles will always have recessive red coloring. Also, recessive red is epistatic to color. For one, color is sex-linked and recessive red is not. The gene that controls recessive red is seperate from the gene that controls color.
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