lecture 9 - Microbial Genomics The Entire genetic...

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Microbial Genomics • The Entire genetic complement of DNA in a cell = genome • Genomes of bacteria are usually made up of chromosome(s) and plasmids • One circular chromosome – Can be linear • Many bacteria contain plasmids • Bacterial genome = 0.6–9.4 x 10 6 bp • About 1000 bases in a typical bacterial gene • Human genome = 4 x 10 9 bp • 1000x as large as E. coli • But 6x genes: 25,000 (us) vs. 4,000 ( E. coli ) • Bacterial genomes have less non-coding sequences – more compact
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Bacteria 0.58-9.4Mb 500-8000 Human 4038Mb 25000 Rice 430Mb 29262 Genome size Number of genes
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Welch , et al . 2002, PNAS, 99:17020
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DNA (deoxyribonucleic acid) • Double helix • Complementary base pairing through hydrogen bonds – can be denatured (melted) • 5’ and 3’ ends • Two antiparallel chains – contain the same amount of information
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DNA is compacted by supercoiling • A nucleoid appears as ~ 50 tightly wound loops – domains • Histone-like anchoring proteins keep these loops relatively independent • Topoisomerases (DNA gyrase) change DNA supercoiling • Type I nick the DNA and relieve supercoils • Type II cleave both strands and introduce supercoils • target of the quinolone antibiotics
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This note was uploaded on 01/31/2011 for the course BIO 121 taught by Professor Ma during the Winter '10 term at UC Riverside.

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lecture 9 - Microbial Genomics The Entire genetic...

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