Re: Why 64 codons?

On Tue, 30 Aug 2005, lamoran@xxxxxxxxxxxxxxxxxxxxxxx (Larry Moran) wrote:

> On 29 Aug 2005 16:41:24 -0700,
> chris.linthompson@xxxxxxxxx <chris.linthompson@xxxxxxxxx> wrote:
>> Frank Sullivan wrote:
>>> If only 20 amino acids are needed, then why 64 different codons? Why
>>> not have 25 codons instead (5 nucleotides + 2 per codon). Is there any
>>> physical reason why this would have been impossible, if a designer
>>> wanted to be a little more efficient about things and make his code a
>>> little easier to read?
>>
>> I would think that if you are working with a double-stranded molecule,
>> you might want an even number of codons. The rationale should be fairly
>> obvious. Don't ask me why RNA is limited that way, though. Check with
>> Larry Moran. He knows everything.
>
> There are four different bases; A, G, T, C. If your code consist of
> only two nucleotides then there are 16 possibilites. This isn't
> enough. A three nucleotide codon gives 64 possibilites. That's too
> much but there are no intermediate choices.
>
> There are at least 23 different amino acids and you need at least one
> stop codon.

23 _possible_ amino acids, or 23 actually used by biology AWKI?

--
Bobby Bryant
Austin, Texas

.

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