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The DNA World

DNA topoisomerases are the magicians of the DNA world. By allowing DNA strands or double helices to pass through each other, they can solve all of the topological problems of DNA in replication, transcription and other cellular transactions. [Pg.923]

Although the data on the archaebacterial DNA world are far from exhaustive, it is nevertheless already possible to draw tentative phylogenetic considerations. In their transcription and translation machineries, archaebacteria exhibit several eukaryotic-like features, compared to those in eubacteria, such as an RNA polymerase and elongation factors of the eukaryotic type (see ref. [151], and other chapters of this volume). Several features of the DNA world have been frequently considered to be eukaryotic the presence of histone-like proteins, first HTa[152], more recently HMf[23], the sensitivity of halobacteria to drugs otherwise specific of the eukaryotic DNA topoisomerasell [103], and the existence of an aphidicolin-sensitive DNA polymerase [124]. However, it appears that HTa is a close relative of eubacterial HU proteins (see Fig. 2), that Haloferax Type II DNA topoisomerase is very similar to eubacterial DNA gyrases (see Fig. 9) and that aphidicolin also inhibits an eubacterial DNA polymerase. HMf is clearly homologous to eukaryotic histones, but HMf nucleosomes are drastically different from eukaryotic ones furthermore, one cannot exclude the existence of HMf-related proteins in eubacteria. [Pg.358]

The many millions of DNA molecules in the cells of your body are identical to each other. That is, the base sequence in all of these molecules is the same. In contrast, the base sequence of the DNA molecules in every other person in the world differs at least slightly from yours. In that sense, your "DNA fingerprint" is unique. [Pg.628]

The hypothesis that our biological world built on the DNA-RNA-protein central dogma was preceded by an RNA world in which RNA molecules carried both the genetic information and executed the gene functions (through ribozyme activity) is now widely accepted [130]. However, it is also well recognized that RNA due to its vulnerability to hydrolysis - especially as a result of catalysis by divalent metal ions - would not have been able to evolve in a harsh pre-biotic environment Also the formation of RNA under presumed pre-biotic conditions is extremely inefficient It is not so far-fetched to propose that a peptide nucleic acid-like molecule may have been able to function as a form of pre-biotic genetic material since it... [Pg.168]

Natural polymers are far more complex materials, being exclusively "organic", that is, products of life (cellulose, proteins, DNA,...). Nevertheless, as nature seems to have formed (size, weight, hardness, etc.) several natural polymers (wood, bones, ivory, etc.) in such a way as to be almost immediately usable by our ancestors, they were most probably the bases of the first human tools. The commonly widespread conception that polymers are the youngest "materials" in the historical world is not true, but, strictly speaking, only applies to synthetic polymers, which were discovered about 100 years ago, early in the XXth century. [Pg.14]

Brown, P. O. and Botstein, D. (1999), Exploring the new world of the genome with DNA microarrays , Nature (Genetics Supplement), 21, 33-37. [Pg.186]

Essentially all biological catalysts in the modern world are themselves proteins, enzymes. However, in 1989 Sidney Altman and Thomas Cech received the Nobel prize in chemistry for showing that RNA itself could act as a catalyst for some biological reactions. This led to the idea that in an earlier time, as life was evolving, RNA may have been both the information molecule (a role usually played by the more stable DNA now) and the catalyst (the role that protein enzymes now play.) Since this idea indicates that in early times the synthesis of proteins was catalyzed by RNA, not by protein enzymes, the intriguing question is whether this is still true today. [Pg.112]

Conspicuously missing from this mixture is thymine, which led to the suggestion that RNA preceded DNA in what has become known as the RNA World hypothesis. [Pg.241]

HUMPHERY-SMITH, I., CORDWELL, S.J., BLACKSTOCK, W.P., Proteome research complementarity and limitations with respect to the RNA and DNA worlds, Electrophoresis, 1997,18,1217-1242. [Pg.12]

ESR resonation of the DNA. That s it. If you have followed it this far, the rest is easy. DNA is what you are. The physical form is just a lot of juicy macro-physical crystals caused by gene expression, you know, the result of enzymes set in motion and coded by DNA. Neural DNA is known to be non-metabolizing. It does not go away. The meat on your body comes and goes every few years. Your skeleton is not the same one you had five years ago, but neural DNA is an exception. It is there for all time. You come into the world with it. It records and it is an antenna for memory. Not only our personal memory, but any entity or organism which has DNA in it there is a way to find a connection to it. This is how we open a passage to the Divine Imagination, this is how William Blake understood Redemption. This is now within reach. [Pg.75]


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