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The Language of the GenesTwo thousand years later the English wit Sydney Smith had the same idea, although his three sexes were men, women and clergymen. To define sex is easy enough. It makes individuals who contain genes from more than one line of descent, so that inherited information from different ancestors is brought together. In an asexual lineage everyone has one mother, one grandmother, one great-grandmother and so on in an unbroken chain of direct descent from the ur-mother who began the lineage. Sexual organisms are different, because the number of ancestors doubles each generation. Everyone has two parents, four grandparents and so on. Each sperm or egg has half the number of genes present in body cells and in each the genes are scrambled into new arrangements by recombination. When they meet, the novel arrays come together to produce a new and unique individual. Reshuffling the genetic message is at the heart of sexual reproduction. The nature of sex is illustrated by two eponymous heroes of British history, King Edward VII (who flourished in the years before the First World War) and the King Edward variety of potato (which has fed the British working class for almost as long) ...» |
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