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Re: Mosquitoes in Jurrasic Park



>> to find a female mosquito that hasn't just fed on flowers alone,
>
>.. which they only do if they can't *find* a blood source during the
>egg developmental period...
>

They always feed on nectar for their own nourishment, regardless of
whether they find a blood meal or not.

>> *and* fed on a dinosaur
>> with nucleated red blood cells (and no other animal)
>
>1) There are other nucleated celltypes in  blood (which should be
>thought of as a fluid tissue). Dinosaurs presumably had a similar
>complement of immune system cellular components floating around in
>addition to the RBC's.
>
Point well taken.  DNA could be derived from these blood elements, but is
it as easily extracted as from nucleated RBCs?

>2) Mosquitos generally require only a single blood meal to stock up on
>the protein neccessary to build eggs, if I recall correctly.>

Which means the window for that mosquito being caught in amber with that
single blood meal unprocessed is narrow.

>3) Even if a given mosquito contained blood from several species, the
>PCR amplification of the extracted sample would selectively hit
>sequences from the target type, since that is what the primers would
>be tailored towards...>

If we knew exactly how to tailor the primers.  Would you use avian or
reptilian-based primers?

>> *and* hasn't already
>> completely processed the blood meal for her developing eggs and* 
>became
>> entombed in amber *and* the amber fossilizing intact.  What are the
>> incredible odds of anyone finding this and getting viable DNA at 
>all?
>> Pretty nil, I'd say.
>
>It's strange to hear an argument from personal incredulity from
>someone who has obviously accepted evolutionary history: its usually
>the creationists who can't imagine huge numbers an amounts of time. We
>are looking at the entire world population of female mosquitos for the
>untold millenia that dinosaurs were available as a blood source as a
>base population from which to derive enough amber-fossilised
>candidates to give us a reasonable chance of finding a well-enough
>preserved sample. To my mind, thats not as unlikely as you put it.
>
My incredulity was for the entire sequence to happen, not for just the
mosquito part.  Granted there were tons of mosquitoes in the Mesozoic. 
How many fed on dinosaurs? Lots of the females.  How many of those
females got caught in amber? A fair number.  How many amber pieces
fossilized with the mosquito intact, preserved the DNA inside, and were
actually found?  This part of the chain is just as dicey to me as the
first part.

How much DNA has survived from the Mesozoic?  Nothing confirmed as yet,
from what I have read.  Anybody with references?

>
>However, there are many better-based reasons to think any kind of
>revivification of a dinosaur genome is possible, mostly relating to
>the limitations DNA preservation and to the technology available to
>pull out authentic sequences...
>

Nothing is impossible.  But lots of things are improbable.

Judy Molnar
Education Associate, Virginia Living Museum
vlmed@juno.com
jamolnar@juno.com
All questions are valid; all answers are tentative.