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MICROBIAL GENETICS

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MICROBIAL GENETICS

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  1. MICROBIAL GENETICS CHAPTER 7

  2. Microbial Genetics • Heredity • transmission of biological traits from parent to offspring • expression & variation of those traits • structure & function of genetic material • how this material changes • Chromosomes • length of DNA containing genes • gene- fundamental unit of heredity responsible for a given trait site on the chromosome that provides information for a certain cell function • segment of DNA that contains the necessary code to make a protein or RNA molecule Locus: location of the gene. Alleles: genes with different information at the same locus are called alleles. • Mutations: a permanent alteration in DNA.

  3. Genome Size • smallest virus – 4-5 genes • E. coli – single chromosome containing 4,288 genes; 1 mm; 1,000X longer than cell • Human cell – 46 chromosomes containing 31,000 genes; 6 feet; 180,000X longer than cell

  4. DNA Structure:Double helix, Antiparallel

  5. 2 strands twisted into a helix • sugar -phosphate backbone • nitrogenous bases form steps in ladder • constancy of base pairing • A binds to T with 2 hydrogen bonds • G binds to C with 3 hydrogen bonds • antiparallel strands 3’to 5’ and 5’to 3’ • each strand provides a template for the exact copying of a new strand • order of bases constitutes the DNA

  6. Microbial Genetics • Genes • Alleles • Mutations

  7. Genetic Information Storage • DNA/Base sequences • Genetic information transfer

  8. Infomation transfer (Vertical transfer) • Replication: DNA make new DNA • Transcription: DNA makes RNA • Translation: RNA links amino acid together • to form proteins. • Template

  9. DNA Replication • Strand unwinding • Replication fork • DNA polymerase • strand orientation • leading strand • lagging strand • Okzaki fragments • RNA primer • Ligase • Semiconservative model

  10. DNA Replication

  11. DNA Polymerase • Leading strand synthesis • Lagging strand synthesis • Need for DNA Ligase

  12. Protein Synthesis: Transcription (RNA Synthesis) • RNA Polymerase • The transcription of RNA from DNA plate • 3 RNA types • rRNA • mRNA • tRNA

  13. Gene Complexity Compared • Eukaryotic • Exons • Introns • Gene splicing • Prokaryotic

  14. Genetic Code • mRNA codons (triplet, sequence of three bases) • Start codon, terminator • (stop codon) • sense condon • Nonsense codon

  15. Protein Synthesis: Translation • tRNA : to transfer amino acids from the cytoplasm to the ribosome • anticodons • Amino acid links • t-RNA: anticodon • Role of ribosomes • Polyribosome

  16. Protein Synthesis” Translation

  17. Protein Synthesis

  18. Coupling of Transcription/Translation • Prokaryotic streamlining

  19. Regulation of Metabolism • Feedback Inhibition (Enzymatic)

  20. Genetic Regulation of Metabolism • Enzyme Induction • Enzyme Repression

  21. Genetic Regulation of Metabolism

  22. Mutations • Genotype • Phenotype

  23. Mutation Types • Point mutations • Silent • Missense • Nonsense

  24. Mutation Types • Frameshift • Rearrangements

  25. Causes of Mutation • Spontaneous • Chemical mutagens

  26. Causes of Mutation • Radiation

  27. DNA Repair • Light Repair • Dark Repair

  28. Mutation Studies: Xeromderma pigementosum

  29. Ames Test