Re: DNA, RNA and Protein questions

On Mar 19, 1:01 pm, wf3h <w...@xxxxxxxxxxxxxxx> wrote:
On Mar 19, 12:04 pm, Bill <spintro...@xxxxxxxxxxx> wrote:

On Mar 19, 12:28 am, Free Lunch <lu...@xxxxxxxxxxxxxx> wrote:

On Wed, 18 Mar 2009 11:46:16 -0700 (PDT), Bill <spintro...@xxxxxxxxxxx>
I said conditions were more favourable now for RNA based life now than
in a RNA world.

So you did. You failed to back up your claim.

Woops. Forgetful me..

"One handed" free floating nucleotides.

How do you make primidine into cytosine or urasil?

you mean uracil?

And he also probably means 'pyrimidine' (I don't know no primidine)?

At any rate, the basic pyrimidine ring, in contrast to purines (de
novo rather than salvage synthesis of purines is done directly on
ribose), is synthesized first in the form of orotate. The first step
is the synthesis of N-carbamoylaspartate from which then undergoes
dehydration to cyclize it into dihydroorotate. A second
dehydrogenation produces orotate, the precursor pyrimidine. This,
then, is the pyrimidine ring that gets added to 5-phosphoribosyl-1-
pyrophosphate (PRPP) with loss of the pyrophosphate to generate
orotidylate monophosphate. This then is decarboxylated to produce UMP
(uridine monophosphate). Amination of UTP produces CTP. And, as
previously mentioned, thymidine is accomplished by first changing the
sugar to deoxyribose (at the diphosphate level), removing a phosphate,
and then methylating dUMP to dTMP.

If you want the biochemistry of purines, I would recommend you look at
a biochem book. It is not clear, in the case of purines, whether the
evolutionarily older mechanism is salvage synthesis or de novo
synthesis. In salvage synthesis, free purines are added to PRPP (like
in pyrimidine synthesis). In de novo synthesis, the first purine
nucleotide made is inosinate (IMP). This is then differently modified
to generate either GMP or AMP.


Ribose would have to be of the same enantimer,

you mean enantiomer?

and how does any of this answer the question?

you left out the world.

other than that, it's a great answer.

.