Re: [MLUG - DISCUSSION] cloning

[Mike Miller <EMAIL:PROTECTED>]

On Thu, 5 Oct 2006, Jonathan King wrote:

> On 10/5/06, Mike Miller <EMAIL:PROTECTED> wrote:
>
> > I don't know if the planets issue is related to the cloning issue, but 
> > I can say that we know that clones will not behave identically.  We 
> > know this because so-called identical twins (actually called 
> > monozygotic or MZ twins) are clones of one another (identical nuclear 
> > DNA except for somatic mutations) and they are not identical in 
> > behavior.  They have correlations of about .40 on some personality 
> > tests and correlations in IQ of around .70.  So they are similar but 
> > not exactly alike.
>
> Acutally, to me the really interesting thing is that identical twins 
> really are virtually identical in things like height, appearance, and 
> even the shape and depth of major brain sulci (when quantified, these 
> are all over 0.9) ...but once you get into behavior, the correlations 
> fall pretty dramatically. Now, an interesting thing is that correlations 
> of IQ are rather higher than those for personality tests, which is 
> particularly striking once you consider that MZ (and DZ) twins share 
> much of their environment as well. I don't have a deep meaning to 
> extract on this at the moment, but it does make me wonder sometimes.

It's pretty hard to understand.  Some traits show a lot of non-shared 
environmental influence, some of which is measurement error.  Personality 
traits have plenty of this kind of environmental effect, part measurement 
error and part environmental sensitivity (I guess).  IQ tests have less 
measurement error in them than do personality tests -- that would be part 
of the effect.

It is interesting that MZ twins are very similar looking -- many 
anthropometric traits are highly correlated.  I guess this means that (1) 
we can measure such traits with very high precision and (2) those traits 
are very highly genetically influenced.

Mike

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