Rick <[email protected]> wrote or quoted: > Tim Tyler <[email protected]> wrote in message news:<[email protected]>... > > Rick <[email protected]> wrote or quoted: > > > Tim Tyler <[email protected]> wrote in message news:<[email protected]>... > > > > Rick <[email protected]> wrote or quoted: > I'm not trying to win points - just trying to understand. > > > Selection can tell which genes have been zapped - but to do that it has to grow them into a > > whole organism and see how well they reproduce compared to their fellows - hardly a *simple* > > process. > > > > I human watcher can sometimes tell whether a gene has been mutated by seeing if it codes for a > > known useful protein - or comparing it with expected data - but again, this isn't a *simple* > > process. > > > > It's true that - given two copies of a gene you can't /easily/ tell which one is the right one. > > > > Selection can tell, though - and a "backup copy" may well allow an organism with a mutation on > > one bit of their Y chromosome to still be able to have some offspring without that mutation. > > In paired chromosomes there is a gene on each chromosome and somehow one is switched on and the > other switched off. [...] Sort of. Often both are translated into protein. Dominance and recessiveness is a consequence of the resulting proteins on the organism. If one codes for something important - and the other is a dysfunctional mess, then a double-dose of the latter might have dire consequences - which would have been masked if there was a single copy of the good gene around. This is the "hallmark" of a "recessive" gene. > When I originally read the phrase "error correction mechanism" I thought it meant that the good > gene would be dominant instead of the faulty gene or that when the Y-chromosome has recombination > with itself it corrects the faulty gene. But you interpretted it as meaning that the faulty gene > is weeded out by selection. I don't see why you haven't considered that error correction could > happen in the Y-chromosome because if a correct gene can be chosen for dominancy then it could be > chosen to correct an error on the other copy in the Y-chromosome. [...] That seems more like "error hiding" than "error correction". The error is still there - it's just its effect is mostly masked. It is not *completely* masked - if another mutation happens in the remaining good copy of the gene, things go wrong. FWIW, it's not yet clear to me whether the second copy of these "palindrome" genes is expressed at all. It may not be - in which case, dominance may not be relevant at all. -- __________ |im |yler http://timtyler.org/ [email protected] Remove lock to reply.