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Message: <blockquote data-quote="imhotep" data-source="post: 30731104" data-attributes="member: 562115">Two independent teams identified a DNA deletion that causes pigment cells to produce a yellow-red color rather than the default brown-black, solving a mystery that has stumped scientists for decades.Researchers knew the genetic instructions for ginger fur resided in the X sex chromosome. Most orange cats are male because they usually have just one X chromosome, which is active in each cell. Because female cats normally have two X chromosomes, both X chromosomes would need to carry the orange trait for a girl to be fully ginger. If just one X contains the trait, her coat would likely become a patchwork of orange and black because only one of her X chromosomes is turned on in each cell.But most other mammals — even big cats like tigers — don’t acquire ginger hair based on sex, hinting domestic cats possess an unusual mutation, says geneticist Chris Kaelin of Stanford University.Kaelin and colleagues analyzed DNA from about 30 cats to find variations shared exclusively by those with orange fur. That revealed a deletion near a gene called Arhgap36.The deletion boosts production of the protein encoded by Arhgap36, but only in pigment cells, the team found. There, the protein prevents genes needed to create the brown-black pigment from turning on, leaving the more easily made yellow-red pigment to be produced instead, says geneticist Greg Barsh of Stanford University. (Mammals produce just two pigments, so different shades come from other genetic factors.)A team in Japan identified the same deletion by examining DNA from almost 60 cats. They also found that the more Arhgap36 protein gets made, the less active genes involved in brown-black pigment production become, says geneticist Hiroyuki Sasaki of Kyushu University in Fukuoka. </blockquote>

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