Author:
Wade A. Tisthammer
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Date Posted: 10/31/04 1:53pm
In reply to:
Damoclese
's message, "RNA thoughts" on 10/16/04 6:00pm
For the record, I'm not a biochemist. I don't know much more than what I've read.
>. For instance,
>>while some RNA strings have catalytic properties (one
>>of the reasons why DNA requires enzymes) the vast
>>majority don't.
>
>Assuming that RNA strings that have deoxyribozymes in
>them are small, approximately how many would it take
>in order to bring about evolution so that other RNA
>strands could evolve?
The problem is that without evolution it seems unlikely to get a self-replicating ribozyme, but without self-replication you can't conduct an evolutionary search for the first, primitive self-replicating ribozyme. Molecular Biology of the Cell talks about this in pages 551-651. Basically, a big problem with the RNA world scenario is this: how to get the RNA strings to begin with?
> High-fidelity replication is also a
>>problem.
>
>I'm not sure "high fidelity" replication is a problem
>in the beginning. So long as it was close enough
The problem is the "close enough" part. From what I've read, without high fidelity it won't be "close enough" to keep its self-replicating properties.
> Also the RNA-world hypothesis certainly it
>>doesn't solve the problem of biological information
>>necessary to code the relevant enzymes for DNA.
>
>So you think that given enough time, RNA that self
>replicates leading into proteins which produce DNA
>could NOT have lead to enzymes for DNA?
I'm not saying could not have, more like probably not. The RNA-world hypothesis doesn't solve the problem of biological information. Furthermore, a real problem for the RNA world hypothesis is getting the self-replicating RNA in the first place (e.g. the chemical incompatibility in getting the nucleotide components), thus not really solving the problem even if we did ignore the concept of biological information.
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