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:
>
> > > > > > > However, it would seem very unlikely that it could act as an error-recovery mechanism.
> > > > > > > When you only have two copies of anything -- and they disagree -- there is no simple
> > > > > > > way to determine which, if either, copy is correct.
> > > > > >
> > > > > > Which raises the question, how is the "correct" gene selected when comparing between the
> > > > > > one that came from mother or the father?
> > > > >
> > > > > Genes are swapped at random. Selection deals with those with more than their fair share of
> > > > > mutations - and rewards those who by chance have a smaller-than-average load.
> > > >
> > > > I think you are talking about selection whereas I was talking about the "error-recovery
> > > > mechanism".
> > >
> > > I was talking about the error-recovery mechanism as well.
> > >
> > > The error recovery mechanism necessarily involves selection.
> > >
> > > Without selection there is no way to tell which gene is the mutated one.
> > >
> > > > What I meant was why is the "correct" gene dominant.
> > >
> > > I never said it was - and it may not be.
> > >
> > > > I read somewhere that a mutated gene will be recessive. Is that correct?
> > >
> > > /Often/ it is. Mutated genes often code for non-functional proteins - which are naturally
> > > recessive.
> > >
> > > > If so, how does it decide which gene is mutated [...]
> > >
> > > "It"? The one that doesn't work is the mutated one.
> >
> > OK. Therefore Wirt Atmar's statement "When you only have two copies of anything -- and they
> > disagree -- there is no simple way to determine which, if either, copy is correct." is false.
>
> He did say "simple".
>
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. Presumably something similar happens on the Y-chromosome. If so I can't
appreciate the difference. Can we think of some examples? What about the gene that causes red-green
colour-blindness? In a female with one normal and one colour-blind gene the normal one is dominant
(there doesn't seem to be any problem picking the right one). What happens in a male? There is only
one X chromosome so only one copy of the gene. If the gene does not code for a "known useful
protein" what happens? Does the colour-blind gene code a useful protein? The gene presumably is used
regardless because I can see colours although not perfectly. If colour-blindness is not a mutation
then what is it? I've used colour-blindness as an example but there could be a new thread about it
as it raises so many interesting questions like why hasn't it been eliminated by selection and why
is it more prevalent in western cultures.
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. I assume that no-one knows for certain as
this is leading edge research.