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Re: Rconstructing DNA (was Re: Dino-fuzz found in amber?)

On Tue, Sep 20, 2011 at 7:19 AM, David Marjanovic
<david.marjanovic@gmx.at> wrote:
> You are. You have neornithean sequences (or even just one), yet you don't
> merely reconstruct the ancestral neornithean sequence -- you reconstruct the
> ancestral tyrannoraptoran sequence! That's extrapolation.

Actually not. It is *eukaryotic* sequences. They share the same
nuclear genetic code and it is that characteristic that I've used. Or
more proximally, they are coelurosaurs (which share the same nuclear
genetic code too). It is not strictly interpolation too.

Of course that, more distant is the pair compared, more noise is
expected - and that differences must be taken into account.

>>  We do similar things when we find a incomplete fossil. We know that
>>  the ancestral dinosaur is a tetrapod with all four limbs (and it is
>>  known by comparative analysis of the descendants). We find a
>>  dinosaur skeleton with three limbs: we could infer that the
>>  individual used to have four limbs (unless we find information that
>>  lead us to conclude other way).
> First, this is, again, interpolation. Second, information reconstructed this
> way is _never_ used in phylogenetic analysis -- is that what you mean?

Not a strict interpolation: we are reconstructing a terminal unit, not
the common ancestor, in this example.

No one is suggesting using the reconstructed T-rex DNA sequence in
phylogenetic analysis - it is just the opposite: using the
phylogenetic information (obtained in other ways) to reconstruct the
T-rex DNA sequence.

We could make other comparisons with some extant bird protein and DNA
sequences and extant crocodile protein sequence (and verify the
predicted DNA sequence with the actual one).


Roberto Takata