11 Genetics 2-16-11_NEW SECTION

11 Genetics 2-16-11_NEW SECTION - Microbial Genetics...

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Microbial Genetics Chapter Sections 7.1; 7.2; 7.4; 7.5; 9.2; 10.8; 10.9
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All the genetic information of the cell Chromosome(s) Plasmid(s) Virus(es) Transposable element(s) The Bacterial Genome The Bacterial Genome Figure 7.22 Figure 7.5 DNA
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Figure 3.27 Figure 3.28 Bacterial Chromosome or Nucleoid Bacterial Chromosome or Nucleoid Usually single, circular dsDNA, but there are some bacteria that have multiple types and linear dsDNA ~4x10 6 bp in many bacteria; extended length = 1,000 X cell length Compacted by supercoiling and binding to DNA binding proteins Replicates once for each cell division Attached to cell membrane (a segregation mechanism)
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Genome Sizes Genome Sizes Bacteria: range from 580-9,400 kbp Smallest ones are from parasitic bacteria (e.g., Mycoplasma genitalium 580 kbp and encodes 480 proteins) that have lost certain metabolic capabilities (e.g., ability to make certain amino acids or cell walls) Largest ones are free living bacteria from the soil E. coli genome is ~4,600 kbp (4,000 genes) Archaea: range from 935-6,500 kbp Like bacteria, usually single, circular dsDNA Eukarya: range from 2,900-670,000,000 kbp Linear dsDNA Human genome is ~3,000,000 kbp (25,000 genes)
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Table 7.1 Genomes of Representative Bacteria and Archaea Table 7.1 Genomes of Representative Bacteria and Archaea
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Bacterial Nucleoid Up Close Bacterial Nucleoid Up Close 30-100 loops (domains) of dsDNA Loops held by histone-like anchoring proteins Domains are supercoiled that compacts the DNA (maintained by topoisomerases – e.g., DNA gyrase makes negative supercoils) Figure 7.8
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Negative and Positive Supercoiling Negative and Positive Supercoiling Bacteria, eukaryotes and most archaea have negative supercoils Underwound DNA Makes it easier to separate the two strands of dsDNA Archaea that live in high temperature environments have positive supercoils Overwound DNA Makes it harder to separate the two strands of dsDNA
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Plasmids Plasmids Extrachromosomal pieces of DNA Usually circular (some linear), dsDNA, negatively supercoiled Found in bacteria, archaea and eukaryotic microbes Figure 7.22
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Replicates separately from chromosome Contains its own origin of replication ( ori ) Bidirectional replication and/or rolling circle replication Figure 7.23 Plasmids Plasmids
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Special topic 7.2; Figure 1 Plasmids Plasmids Copy number (number of copies per cell)
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This note was uploaded on 01/29/2012 for the course MCB 300 taught by Professor Salyers during the Spring '08 term at University of Illinois, Urbana Champaign.

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11 Genetics 2-16-11_NEW SECTION - Microbial Genetics...

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