Unlocking the mystery of the orange cat: Gene discovery revealed
Two independent research teams have finally determined what causes cats to be orange. A special gene is responsible for the unique coloration of domestic cats, ending years of searching for the answer to the mystery of these ginger quadrupeds.
These teams found that a missing segment of DNA in the non-coding part of the cat's genome is what causes these animals to have their distinctive orange coloration. “It's been a genetic mystery, a conundrum,” said geneticist Greg Barsh from Stanford University in an interview with Science Alert.
Details of the Arhgap36 gene discovery
Barsh and his colleagues discovered that skin cells of cats with orange patches of fur express 13 times more RNA from a gene called Arhgap36 compared to the skin cells of non-orange cats. Rather than a mutation in the protein-coding section, they found a deletion in the preceding sequence that affects gene expression.
"The 5 kilobase deletion was present in every orange cat the researchers examined out of a database of 188 cats," described the research team in the analysis. Their work is available online and is awaiting review on bioRxiv.
Does orange fur equal male cat?
The gene mutation is located on the X chromosome, explaining the differences in coloration between male and female cats. Most orange cats are males, while females with orange fur often have patches of various colours. “Taken together, these observations provide strong genetic and genomic evidence that the 5 kb deletion causes sex-linked orange,” wrote Barsh and his team.
For thousands of years, people have wondered how a black and orange cat could be the parents of kittens with diverse colours. Males from this pairing are usually orange or black, while females can have calico or tortoiseshell colouring. The research confirmed that the mutation responsible for orange fur is located on the X chromosome, leading to differences in coloration between sexes.
Orange cats have a reputation for being less intelligent, but there is no scientific evidence linking fur colour to intelligence. The Arhgap36 gene is known to cause developmental issues in other animals, but in orange cats, it is over-expressed only in pigment cells.
