Anthony AllisonBMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2243 (Published 24 March 2014) Cite this as: BMJ 2014;348:g2243
- Laura Spinney, Lausanne
I vividly remember the day I learnt about balanced polymorphisms in biology class. The teacher illustrated the concept with the classic textbook example—the case of the carriers of the sickle cell trait, who are protected from malaria.
The lesson stayed with me because of its pleasing symmetry—that beautiful bell curve that describes so many things in nature. The sickle cell mutation—lethal in homozygote individuals before they reach puberty—maintains itself in the gene pool because people with only one copy don’t get the disease, and are less likely to contract malaria too.
Tony Allison saw the distressing tail ends of the curve: the children’s wards in Mombasa on the Kenyan coast, and at Kisumu on Lake Victoria. Here half of the young patients were suffering the agonising crises of sickle cell anaemia—pain …