8 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 8...

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PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 8 Overview of the Bacteria and Archaea II
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Highly resolved Tree Of Life based on completely sequenced genomes The phylogenetic tree is based on 31 universal protein families and covers 191 species whose genomes have been fully sequenced. Ciccarelli et al. (2006) Science, 311:1283-1287
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Many of the molecular themes that are shared between Archaea and Eukarya appear to involve the Central Dogma—the flow of information from DNA to RNA to protein serc.carleton.edu/15909
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Differences in information transfer between prokaryotes and eukaryotes The genes of Archaea and Bacteria are organized into operons and are transcribed into one polycistronic mRNA, which encodes for more than one gene product. In Eukarya , a protein-encoding gene is split into two or more coding regions (exons), with noncoding regions (introns) separating the coding regions. The chromosomes are located inside the nucleus, while ribosomes are in the cytoplasm. So in contrast to prokaryotes, transcription and translation are spatially separated processes.
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Eukarya have linear chromosomes Shown at left is human chromosome 1 (1 of 46). If stretched out, it would be ~2 cm long. 240,000,000 base pairs, 3,148 genes http://www.cbs.dtu.dk/staff/dave/roanoke/genetics980218.html; www.gsbs.utmb.edu/microbook/ch005.htm Prokaryotes typically have a single circular chromosome The circular chromosome of E. coli K12 undergoing replication. 4,639,221 base pairs, 4,377 genes Human genome 3,300,000,000 base pairs ~20,500 genes
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DNA replication is fundamentally conserved in the three domains of life, but the archaeal system is closer to that of eukarya than bacteria Models of the initiation of DNA replication in the three domains of life. In bacteria, DnaA recognizes and binds the origin, causing localized melting of the DNA strands. Six molecules of ATP-bound DnaC interact with a hexamer of DnaB, and this complex associates with the DnaA-origin complex. ATP hydrolysis by DnaC causes a conformational change, releasing the helicase. In eukarya, ORC binds the origin and local melting of the origin occurs either by ORC alone or in
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This note was uploaded on 08/04/2009 for the course BIOL 4125 taught by Professor Christner during the Spring '08 term at LSU.

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8 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 8...

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