Science: Gene behind orange fur in cats found at last
"But when the researchers looked at Arhgap36’s genetic sequence in orange cats, they didn’t find any mutations in the DNA that encodes the Arhgap36 protein. Instead, they found the orange cats were missing a nearby stretch of DNA that didn’t affect the protein’s amino acid components but might be involved in regulating how much of it the cell produced. Scanning a database of 188 cat genomes, Barsh’s team found every single orange, calico, and tortoiseshell cat had the exact same mutation.
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No one previously knew Arhgap36 could affect skin or hair coloration—it is involved in many aspects of embryonic development, and major mutations that affect its function throughout the body would probably kill the animal, Barsh says. But because the deletion mutation appears to only affect Arhgap36 function in melanocytes, cats with the mutation are not only healthy, but also cute."
https://www.science.org/content/article/gene-behind-orange-fur-cats-found-last
@akuchling the "... cats with the mutation are not only healthy, but also cute." part is my favorite