Re: In the news: Researchers Predict Infinite Genomes

Glenn wrote:

> <rja.carnegie@xxxxxxxxxx> wrote in message
> news:1127613914.409390.187040@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
>>Glenn wrote:
>>
>>>http://www.sciencedaily.com/releases/2005/09/050923075708.htm
>>>"TIGR scientists have concluded that researchers might never fully describe
>
> some
>
>>>bacteria and viruses--because their genomes are infinite. Sequence one strain
>
> of
>
>>>the species, and scientists will find significant new genes. Sequence another
>>>strain, and they will find more. And so on, infinitely."
>>>"Many scientists study multiple strains of an organism," says TIGR President
>>>Claire Fraser. "But at TIGR, we're now going a step further, to actually
>
> quantify
>
>>>how many genes are associated with a given species. How many genomes do you
>
> need
>
>>>to fully describe a bacterial species?"
>>
>>Once all possible combinations of DNA codes are exhausted,
>
>
> How many are there?

Hard to say. In theory, there are infinitely many possibilities. But
this requires that a string of DNA can exist that's infinitely long.
Obviously, that's absurd, but neither can we easily say what the longest
possible DNA string is. So the boundary of possible lengths is nebulous.
But if we have the longest possible string figured out as N, then the
number of distinct genomes of that length is 4^N. Shorter genomes are
all subsets of those, but if we count them as distinct then we have to
add 4^(N-1), 4^(N-2), etc. There's a simple mathematical description of
the resulting number, which I leave as an exercise for the reader.

>>the Designer
>>will no longer consider, "What creature shall I create today?" But
>>"Which creature shall I create today?"
>>
>>After Lewis Carroll, _Sylvie and Bruno Concluded_.
>>
>>"But lunatics would always write new books, surely?" she went on. "They
>>couldn't write the same books over again!"
>>
>>"True," said Arthur. "But their books would come to an end, also. The
>>number of lunatic books is as finite as the number of lunatics."
>>
>>On reflection, Carroll's Lunatic Book Conjecture actually runs into a
>>Turing Machine Halting Problem, but I don't think that applies to
>>bacteria or viruses, which have an upper size limit.
>>
>
> What's the limit?

It's not a logical limit but a physical limit, and there's no simple way
to decide it. What limits are we placing on bacterial metabolism? Could
there be a bacterium as big as a pea, with room for a very big genome
indeed? I doubt it, but who knows what tricks of metabolism might make
it possible? Would the largest known bacterial genome do? The biggest
one I can find is a Nostoc genome at 10 megabases.

.

Relevant Pages

  • Re: In the news: Researchers Predict Infinite Genomes
    ... > thus a finite number of different genomes. ... I'm talking about species concepts here. ... > bacteria have trouble coming up with meaningful criteria for defining ... I thought that nothing in biology makes sense except in light of evolution. ...
    (talk.origins)
  • Copes rule and bacterial evolution
    ... There is an old idea about mammal and dinosaur evolution known as ... Most species get bigger over time, ... genomes", Trends in Genetics 17, 589. ... It is the generalist bacteria with the ...
    (sci.bio.evolution)
  • Re: In the news: Researchers Predict Infinite Genomes
    ... >>>the species, and scientists will find significant new genes. ... thus a finite number of different genomes. ... bacteria have trouble coming up with meaningful criteria for defining ...
    (talk.origins)
  • Re: Part 1 (of 3): What are major aspects of evolutionary theory?
    ... sequence comparison will show ... >>few species have had their entire genomes sequenced. ... > twenty large genomes so-far) already fully sequenced. ... If we see a large number of indels ...
    (talk.origins)
  • Re: Evolution increases the computational ability of organisms.
    ... They are as complex as they can be for the environments they are in. ... the bacteria have maximized the amount of information stored in their genomes vis-a-vis the environment. ... reason to believe that fitness ever achieves a maximum. ...
    (talk.origins)