Any evidence that some organisms use bases other than A T C & G?

  • Thread starter Thread starter Nereid
  • Start date Start date
  • Tags Tags
    Bases Evidence
Click For Summary

Discussion Overview

The discussion centers on the genetic bases of life forms, specifically whether any organisms utilize nucleobases other than adenine (A), thymine (T), cytosine (C), and guanine (G) in their DNA. Participants explore the implications of this question for the evolution of life, particularly in the context of archaea and potential synthetic life forms.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that all known life forms, including archaea, bacteria, and eukaryotes, are based on DNA composed of A, T, C, and G, and questions if there are any current counter-examples, excluding viruses.
  • Another participant mentions that uracil (U) replaces thymidine in RNA but does not directly answer the original question about DNA bases.
  • A participant raises the question of whether new base pairs could evolve, suggesting that gradual changes might allow for this possibility.
  • In response, another participant references an article about engineered new base pairs, indicating that synthetic biology may eventually explore alternatives to the traditional DNA bases.
  • One participant expresses skepticism about finding evidence of alternative genetic codes in the history of life, given the dominance of the ATCG system over billions of years.
  • There is an acknowledgment that synthetic life could potentially reveal whether alternative bases could serve as a foundation for life on Earth-like planets in the future.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether any organisms use bases other than A, T, C, and G. There are multiple viewpoints regarding the potential for alternative genetic systems and the implications of synthetic biology.

Contextual Notes

Participants discuss the limitations of current knowledge regarding alternative genetic codes and the historical absence of evidence for such systems. The conversation also touches on the speculative nature of future discoveries in synthetic biology.

Nereid
Staff Emeritus
Science Advisor
Gold Member
Messages
3,392
Reaction score
3
Yet another question about the evolution of life, likely in the Archaen or Proterozoic eons.

As I understand it, the genomes of all life - archaea, bacteria, eukaryotes - is based on DNA, even that of eukaryote organelles, such as plastids and mitochondria. Are there any counter-examples, in forms of life with us today (i.e. not fossils)? Viruses excluded.

Is the DNA of all forms of life based on only A, T, C, and G? Or are there some other bases, used by some weird archaea, say?

If so, details please!
 
Biology news on Phys.org
I actually have an addition to that question. Would it ever be possible for new base pairs to evolve?
 
Monique said:
U (urasil) replaces thymidine in RNA, but this doesn't answer your question. I'm not sure about a genetic code based on a divergent system, but on a higher level there is: some organisms have alternative codon usage (http://www.genetics.org/cgi/content/full/170/2/831).

This article might be of interest to you:
http://www.ncbi.nlm.nih.gov/pubmed/14746991
Thanks Monique.

I knew about U in RNA, and that, at a higher level, codon usage does not follow a single, universal, scheme.

I'm interested in the fact that, in 3+billion years of evolution, just one basic DNA code (ATCG) seems to be used. It would seem exceedingly unlikely that, had there been alternatives in the history of life*, we would be able to find any evidence of them.

On the other hand, with 'synthetic life' almost within reach, it may be possible - several decades or more from now - to determine if any such alternatives could have been, or could be!, the basis for life on an Earth-like planet.

* not counting pre-DNA life
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
9K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
5
Views
3K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 10 ·
Replies
10
Views
13K
  • · Replies 6 ·
Replies
6
Views
16K