Miller/ Urey Experiment

[valich]

Current experiments, related to Miller/Urey, were carried out by Dr. Albert Eschenmoser. Are you familiar with his experiments?

RNA is supposed to be the predecessor to DNA. So Eschenmoser asked "what is the ancestor of RNA?" He suggests that it may be a nucleic acid called (L)-a-threofuranosyl oligonucleotides, also known as TNA.

"Dr. Albert Eschenmoser chemically synthesized TNA and found that complementary TNA strands can form stable double helices. The TNA strands can also pair up with complementary strands of RNA and DNA. This ability is thought to be one of the requirements of any system that would be considered a possible ancestor of RNA.

Eschenmoser is creating nucleic acids that are structurally similar to RNA. They study the properties of the alternatives, such as TNA, and compare them with corresponding properties of RNA."

http://nai.arc.nasa.gov/news_stories/news_detail.cfm?ID=189

Carl R. Woese way back in the 60's also thought that RNA came first.

 

[CharonZ]

Yups, it is in general consensus that RNA predates DNA. However, a few argue that due to its instability RNA is not a likely candiate.

Well, I didn't want to go off-topic, but if you really are interested in newer phylogenetic analyses (the book you provided deals more with comparative anatomy, from what I've seen, and does not deal with prokaryotes in depth at all) check this for instance. if you are in an uni you should be able to get the full text easily.:

Proc Natl Acad Sci U S A. 2005 May 3;102 Suppl 1:6608-13. Epub 2005 Apr 25. Related Articles, Links
Click here to read
Decoding the genomic tree of life.

Simonson AB, Servin JA, Skophammer RG, Herbold CW, Rivera MC, Lake JA.

Molecular Biology Institute, Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, 90095, USA.

Genomes hold within them the record of the evolution of life on Earth. But genome fusions and horizontal gene transfer (HGT) seem to have obscured sufficiently the gene sequence record such that it is difficult to reconstruct the phylogenetic tree of life. HGT among prokaryotes is not random, however. Some genes (informational genes) are more difficult to transfer than others (operational genes). Furthermore, environmental, metabolic, and genetic differences among organisms restrict HGT, so that prokaryotes preferentially share genes with other prokaryotes having properties in common, including genome size, genome G+C composition, carbon utilization, oxygen utilization/sensitivity, and temperature optima, further complicating attempts to reconstruct the tree of life. A new method of phylogenetic reconstruction based on gene presence and absence, called conditioned reconstruction, has improved our prospects for reconstructing prokaryotic evolution. It is also able to detect past genome fusions, such as the fusion that appears to have created the first eukaryote. This genome fusion between a deep branching eubacterium, possibly an ancestor of the cyanobacterium and a proteobacterium, with an archaeal eocyte (crenarchaea), appears to be the result of an early symbiosis. Given new tools and new genes from relevant organisms, it should soon be possible to test current and future fusion theories for the origin of eukaryotes and to discover the general outlines of the prokaryotic tree of life.

Newer findings are in favour of a "ring of life" due to the high amount of horizontal gene transfer.

 

[valich]

Dr. James Lake, who I keep referring to about the Eocyte Tree, says that this tree is a ring of life: the genomes of the ring of life are from two yeasts, a proteobacterium, a hallobacterium, an eocyte, and a bacilli. He says that "an endosymbiosis between two prokaryotes is probably the mechanism responsible for the genome fusion." He also says something earlier in the paper that "the yeast lineage is the fusion product of prokaryotes."

This is a very recent theory and everything written on it always only refers back to him and no one else, except him and his coworkers. I know what lateral gene transfer is but I do not yet have a firm grasp on HGT, genome fusion, or what bootstrap analyses is. Either way they always refer back to an ancient proteobacteria.