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.