Re: Minimum Cell?


"The Last Conformist" <andreasj@xxxxxxxxx> wrote in message news:1194865068.754393.27060@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Nov 12, 3:05 am, Rich Townsend <r...@xxxxxxxxxxxxxxxxxxx> wrote:
spintronic wrote:
What are the requirements for a "minimum cell"? I.E, what is the
minimum amount of genes required for a fully functional cell?

What do you mean by 'fully functional'? What must the cell be able to do?

My immediate reaction was "it must be able to survive and reproduce
without help of other cells, duh!", but on a moment's reflection that
would exclude not only parasites also all heterotrophs, as well as all
autotrophs that depend on symbiosis or biologically fixed nitrogen or
anything else produced by other cells. This seems somewhat overly
restrictive definition ...

The spinmeister's intention here seems to be in the area of abiogenesis.
And I think there is something to be learned about abiogenesis by looking
at it both restrictively and non-restrictively.

Personally, I am convinced that the Last Universal Common Ancestor
was a fully capable autotroph, 'beholden to no one'. It fixed its own
nitrogen, its own carbon, made its own coenzymes from scratch, and
had time left over to study flower arranging with Martha Stewart. So,
identifying a 'minimal' full autotroph seems to me to be a useful step
in sketching the steps of the origin.

But there is also something to be learned by trying to identify a minimal
heterotroph. For example, how much complexity can be saved by
becoming an intracellular parasite? Are mitochondria "fully functional"?
Note that mitochondria have only a half-dozen genes related to
metabolism, but they have a mimimal set of 50 or so related to protein
synthesis just to be able to express those half-dozen metabolic genes.

Well, if you count mitochondria as 'fully functional', what about
hydrogenosomes? It is generally believed that hydrogenosomes are
organelles descended (like mitochondria) from bacterial endosymbionts.
But, hydrogenosomes have lost all of their nucleic-acid genes. They
are totally dependent on their hosts for all protein synthesis. But it
is still the case that they reproduce - "Every hydrogenosome from a
hydrogenosome". Is this an example of 'minimal cellular life' without
self-contained genetics?

.

Relevant Pages

  • Article: Evidence for organelle origin
    ... Evidence for organelle origin ... triphosphate -that evolved from mitochondria is reported by Dutch and ... hydrogenosomes," coauthor Johannes Hackstein of Radboud University Nijmegen ... guts might possess genes. ...
    (sci.bio.evolution)
  • Re: epigenetics
    ... production of a pine tree but when put into a human egg cell would ... PAX gene into leg cells of a fly causes the formation eyes in the leg. ... It's because of the other genes ... "responsible" for producing eyes of whatever type. ...
    (talk.origins)
  • Re: epigenetics
    ... production of a pine tree but when put into a human egg cell would ... PAX gene into leg cells of a fly causes the formation eyes in the leg. ... It's because of the other genes ... "responsible" for producing eyes of whatever type. ...
    (talk.origins)
  • Re: Where does information come from?
    ... in the cell. ... describe the sequences of bases in DNA. ... You can describe blood vessels as pipes. ... that genes cause the expression of certain molecular building blocks, ...
    (talk.origins)
  • See the future of biotechnology
    ... genes inside the bean are deleted and medicinal gene are inserted in it ... genome was made compatible to photosynthesis as Plants in sun light. ... There is no such industry which was looking in the past. ... Any living cell can be made totipotent now. ...
    (sci.bio.ecology)