Flame-haired fancies

It's been a tough year for redheads. Not as bad as 2007, though, when a report surmised that anti-ginger prejudice was driving "mate avoidance" behaviour that would eventually lead to their extinction. Just 4 per cent of Europeans express the reddish pigment called pheomelanin, in preference to eumelanin, found in dark hair.

A gene called MC1R determines hair colour. Some MC1R variants allow pigment-producing cells to produce eumelanin; others don't, leaving them richer in pheomelanin. Because eumelanin blocks out the ultraviolet rays in sunlight necessary to make Vitamin D, redheads are more prominent in the sunlight-starved north (they also run a higher risk of skin cancer in sunnier climes). We have two MC1R genes, one from each parent. The "red-haired" variant is recessive, so we are ginger only if both sides are redhead types. The laws of genetics dictate that, in principle, Harriet Harman would bear non-ginger children with Danny Alexander, unless her brown locks disguise a recessive red MC1R type - in which case, the chances rise to 50 per cent. Those wishing to stamp out auburn locks by means of mate avoidance would need to hack into the genome of prospective partners to check their MC1R type. So, in spite of all that's happened at the News of the World, I'm happy to say that red tops are here to stay.