To : Lane Lester Subj: Adaption=evolution? LLYou said to DAVID BUSHARD: LLJM I thought tha

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From: Neal Eldred 3 Oct 94 10:31 To : Lane Lester Subj: Adaption=evolution? LL>You said to DAVID BUSHARD: LL>JM> I thought that multiple LL>JM> identical DNA molecules in the nucleus of each germ cell are LL>JM> carried on different chromosomes and that any one of these LL>JM> molecules determines the physiology of the resulting offspring. LL>No, if this were true, then it would be impossible to "map" the genes LL>to specific chromosomes, and this is done. In fact, there's a research LL>project, I think it's called the Human Genome Project, to map the LL>locations of each gene both as to chromosome and location on the LL>chromosome. You might be interested in Christopher Wills' _Exons, Introns, and Talking Genes_ (1991) about the Human Genome Project. Starting on page 95 is a discussion of how multiple copies of genes are placed in the genome to allow for mutational experimentation, sort of like scratch paper. "These genes [nine sequences coding for different human hemoglobins] all arose from a very distant common ancestor through a process called *gene duplication.* [italics] In this rare occurrence, an extra copy of a gene gets placed elsewhere in the genome, sometimes even on a different chromosome. The two copies are then free to evolve separately. They will accumulate different mutations, and as they diverge they will be shaped by selection and chance to take up different tasks. The end products can be similar or very different, depending on the amount of time that has passed and the selective pressures involved." Examples - fetal and adult hemoglobins; the hormones glucagon and secretin are related by a common ancestor gene (regulating sugar in the blood and secretion of pancreatic enzymes, resp.); the gene that results in cystic fibrosis when mutated is related to a number of others involved in membrane transport. "One relative of the CF gene repairs damage to DNA caused by UV light in bacteria. Another helps to make eye pigment in fruit flies. Yet another is involved in cell division." Life--it's a family thing. One *big* family.


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