Good evening Andreas and everyone in H and D,
Here is a quotation from a feature in todays Daily Mail [ a UK newspaper..] on 21st July 2008. I have abridged this from the lengthy article by David Derbyshire.
WHY EVERY WHITE HORSE CAN TRACE ITS ROOTS BACK TO JUST ONE ANCESTOR THOUSANDS OF YEARS AGO.
They have been favoured by kings and emporers, in the form of Desert Orchid they became the housewives' choice and in Billy the police horse they helped clear the Wembley pitch and make history.
Now scientists have identified the genetic mutation that turns horses grey and then white - and it could mean that they all trace their ancestors back to just a single mare or stallion more than 2,500 years ago.
Grey horses are typically descended from Arabian ancestors, including the famous purebred Lipizzaner stallions that are trained for classical dressage, and have been selected by humans for their striking appearance. Born with dark hair greys gradually lose pigmentation. As their hair becomes white between six and eight years old they take on a grey appearance due to their black skin underneath.
Dr Leif Andersson and colleagues at Uppsala University, Sweden, found mutated genes in more than eight hundred grey horses from eight different breeds. Crucially the variants are not present in horses of other hues and through further DNA mapping the phenomenon was nailed down to the over expression of two neighbouring genes, known as STX17 and NR4A3. It is not known if one, or both of the genes is responsible for the loss of hair pigmentation, according to the study published online in Nature Genetics.
Dr Anderssons team also point out between 70 and 80 percent of grey horses older than 15 years have melanomas, the most serious form of skin cancer that reduces their lifespan. They believe the defective genes trigger both the disease and the loss of hair colour through reducing protective pigment containing cells in the skin and hair follicles.
Dr Andersson analysed the coat colours and skin of thoroughbreds from five national studs in Austria, Croatia, Hungary, Slovakia and Slovenia. He said the grey provides a notable example of how humans have cherry-picked mutations that produce attractive appearances in domestic animals. He said, " The manifestation of this mutation as a white horse has had a strong impact on human culture and has left numerous traces in art and literature from Asia and Europe, such as Pegasus and the unicorn."
The oldest written record is by the Greek historian Herodotus, who describes the Persian emporer Xerxes who reigned from 485 to 465 BC as keeping sacred white horses.
Dr Andersson said, " The prestige of riding a white horses has thus led to the selection of the grey causing mutation by humans. This mutation is by far the most common cause of white colour in horses."
For the full article and pictures [ Desert Orchid / Billy / Lipizzan in Courbette / Saxon horse carvings ] please go to
http://www.dailymail.co.uk/sciencetech/article-1036871/Why-white-horse-trace-roots...
Karen MacKenzie,
Manchester, England.
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