h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I am looking for information concerning life forms that do not share DNA with the majority of life on Earth. Many years ago, in a college course, I was introduced to this idea. Recently I have been following the human genome progect and with all the focus upon how similar the DNA of most life is I remembered that some very small portion of life does not share evidence of commonn origins with most life. Does anyone have information on this topic to share?

The origins of life is a huge debate right now because we can't agree on the definition of life. A few months ago Scientific American did a cover story on self-replicating molecules. I've missplaced it (too lazy to look) but you might go their website.

This is a thread that I'd like to keep going as I have very radical views on it. Thanks for starting it.

http://www.science-frontiers.com/sf081/sf081c17.htm

Some bacteria have an extra thingmy, U, as well as the A,C,G,T that the rest of us have. I don't think that's looked on as evidence of anything in particular though.

It's the June '07 issue. There are self replicating molecules much simpler than either DNA or RNA. I'm not too good with biochemistry so I won't try to explain it. Explaining things on HooToo always gets me smacked down.

"Explaining things on HooToo always gets me smacked down."

That's only because everyone here knows everything.

Twice.

And, thanks, lil, for the link. Been having some fun with it this morning.

-Twice- ?

There is supposed to be some deep sea fish that have a vertebrae based on silicon instead of carbon. I don´t know more than that though.

Last time I did any indepth reading on this (which I've since forgotten about due mainly to alochol nictoteen caffine and barbituit and... overuse), anyhow, the last time I was reading anythingn on this. hang on didn't I just say that?
Right.
The last time I remember reading anythign much on this, the recieved opinion at that time* was that life (or the precursors of life), independantly evolved several times, though probably about the same timeish, so there isn't a single 'egg' from which all the chicken came, but rahter a range of differnt eggs that then gave rise to all the various chickens.
hang on... does that analagy even work
Of course, things are somewhat complicated by many of those initial lines of evolution most probably never getting very far and goign the way of the doda art movement. I mean dodo.
Also there has been a fair bit of genetic exchange between these lines, most especially I think brought about by virus and bacterial influences on their insurting DNA in to host DNA.

The 'U' mentioend above is Urasil, It was* at a one point as far I as I recall thought that life would have origionally been in the RNA as opposed to DNA state, and U is used in RNA instead of T (I think), and we still use U as far as I recall in DNA replication/production of MRNA
A lot of the simularity between E.G. Human and single celled organisms genetics, is in really quinteressential genes coding for molecules/proteins who's function is so tied up with their exact shape/conformation, that these haven't been able to evolve and change since the genes first arrose, as the substrates their bind E.G., Oxygen etc., havne't changed, so a mutation in that gene woudl be pretty fatal for the unlucky blighter invovled
I've entirely forgotten waht we were talking about now

That post was a wonderful illustration of Dawkin's idea of memes acting like genes. You have all these ideas mashing around and gettin' it on and new and strange offspring..well..ah, springing off.

Someone frame post 10 - classic 2legs.

And thanks for the paragraphs, 2legs