Genome [antikvár]

PREFACE The human genome — the complete set of human genes — comes packaged in twenty-three separate pairs of chromosomes. Of these, twenty-two pairs are numbered in approximate order of size, from the largest (number i) to the smallest (number 22), while the remaining pair consists of the sex chromosomes: two large X chromosomes in women, one X and one small Y in men. In size, the X comes between chromosomes 7 and 8, whereas the Y is the smallest. The number 23 is of no significance. Many species, including our closest relatives among the apes, have more chromosomes, and many have fewer. Nor do genes of similar function and type necessarily cluster on the same chromosome. So a few years ago, leaning over a lap-top computer talking to David Haig, an evolutionary biologist, I was slightly startled to hear him say that chromosome 19 was his favourite chromosome. It has all sorts of mischievous genes on it, he explained. I had never thought of chromosomes as having personalities before. They are, after all, merely arbitrary collections of genes. But Haig's chance remark planted an idea in my head and I could not get it out. Why not try to tell the unfolding story of the human genome, now being discovered in detail for the first time, chromosome by chromosome, by picking a gene from