Richard Holmes, of Lower Hutt, asks :-
Do plants and bacteria have DNA and RNA? If so, does this imply both evolved at a very early stage in the development of life, before animals, plants and bacteria went their separate ways?
Anthony Poole, a geneticist at the University of Canterbury's School of Biological Sciences, responded.
Yes, both plants and bacteria have DNA and RNA. In fact, all cellular life forms possess these molecules.
All cellular life uses DNA as its genetic material. RNA is used for a wide range of processes. Scientists agree that RNA evolved earlier than DNA and before protein synthesis. A stunning piece of evidence to support this is the recent discovery that RNA lies at the heart of the ribosome, the machinery used to synthesise proteins, using instructions coded on DNA.
As all cellular life shares a common genetic code, and all cells carry ribosomes, the fact that the machinery for making proteins is an RNA machine at its core is consistent with the view that RNA predates proteins.
If you look up nobelprize.org and look for the chemistry winners in 2009 you will find more information on this.
In addition, ribosomal RNA carries an incredible evolutionary history. It was the first molecule used to build a tree of life, and it shows that the broad evolutionary history of life can be read from this molecule. One of the main surprises was that plants and animals and bacteria comprise only a part of the diversity of life.
So, yes RNA did evolve before modern life forms diverged. It's harder to say for DNA - it's likely to be old, but its evolutionary history is partly hidden by horizontal gene transfer (gene swapping between species) - most stunningly, the basic machinery for copying DNA is not the same between bacteria and plants/animals. So DNA may have evolved once or twice or these different machine ties could be the result of replacement via gene swapping - the jury is still out on that.
A good article to give a brief overview of the reconstruction of early life, though slightly dated, can be found at www.actionbioscience.org then evolution then poolearticle.