This happens during the production of sex cells, and its effect is to halve the number of chromosomes in a cell (the number returns to normal when two sex cells combine during fertilisation).

ECONOMIST: Genetic engineering

But Sir John showed the wisdom of Dr Brenner's choice when he discovered that (sex cells aside) adult worms all have 959 cells in them, and that the pattern of cell differentiation which leads from egg to adult is the same in every individual.

ECONOMIST: This year, the Nobel authorities have shown a deft touch