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Chapter 8 Microbial Genetics. Biology 1009 Microbiology Johnson-Summer 2003. Structure and Function of Genetic Material. DNA & RNA DNA=deoxyribonucleic acid RNA=ribonucleic acid Basic building blocks: Nucleotides Phosphate group Pentose sugar Nitrogenous base. Structure of DNA.

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chapter 8 microbial genetics

Chapter 8Microbial Genetics

Biology 1009

Microbiology

Johnson-Summer 2003

structure and function of genetic material
Structure and Function of Genetic Material
  • DNA & RNA
    • DNA=deoxyribonucleic acid
    • RNA=ribonucleic acid
    • Basic building blocks:
      • Nucleotides
        • Phosphate group
        • Pentose sugar
        • Nitrogenous base
structure of dna
Structure of DNA
  • Double stranded (double helix)
  • Chains of nucleotides
  • 5’ to 3’ (strands are anti-parallel)
  • Complimentary base pairing
    • A-T
    • G-C
dna structure
DNA Structure

Phosphate-P

Sugar-blue

Bases-ATGC

dna replication
DNA Replication
  • Bacteria have closed, circular DNA
  • Genome: genetic material in an organism
  • E. coli
    • 4 million base pairs
    • 1 mm long (over 1000 times larger that actual bacterial cell)
    • DNA takes up around 10% of cell volume
dna replication occurs at the replication fork
DNA Replication-occurs at the replication fork
  • 5’ to 3 ‘
  • DNA helicase-unzips + parental DNA strand that is used as a template
    • Leading stand (5’ to 3’-continuous)

*DNA polymerase-joins growing DNA strand after nucleotides are aligned (complimentary)

    • Lagging strand (5’ to 3’-not continuous)

*RNA polymerase (makes short RNA primer)

*DNA polymerase (extends RNA primer then digests RNA primer and replaces it with DNA)

*DNA ligase (seals Okazaki fragments-the newly formed DNA fragments)

protein synthesis
Protein Synthesis
  • DNA------- mRNA------ protein

transcription translation

Central Dogma

of Molecular Genetics

transcription
Transcription
  • One strand of DNA used as a template to make a complimentary strand of mRNA
  • Promoter/RNA polymerase/termination site/5’ to 3’
  • Ways in which RNA & DNA differ:
    • RNA is ss
    • RNA sugar is ribose
    • Base pairing-A-U
types of rna
Types of RNA
  • Three types:
    • mRNA: messenger RNA
      • Contains 3 bases ( codon)
    • rRNA: ribosomal RNA
      • Comprises the 70 S ribosome
    • tRNA: transfer RNA
      • Transfers amino acids to ribosomes for protein synthesis
      • Contains the anticodon (3 base sequence that is complimentary to codon on mRNA)
genetic code
Genetic Code
  • DNA: triplet code
  • mRNA: codon (complimentary to triplet code of DNA)
  • tRNA: anticodon (complimentary to codon)
genetic code1
Genetic Code
  • Codons: code for the production of a specific amino acid
  • 20 amino acids
  • 3 base code
  • Degenerative: more than 1 codon codes for an amino acid
  • Universal: in all living organisms
translation
Translation
  • Three parts:
    • Initiation-start codon (AUG)
    • Elongation-ribosome moves along mRNA
    • Termination: stop codon reached/polypeptide released and new protein forms
  • rRNA=subunits that form the 70 S ribosomes (protein synthesis occurs here)
  • tRNA=transfers amino acids to ribosomes for protein synthesis)
mutations
Mutations
  • Changes in base sequence of DNA/lethal and inheritable
  • Can be:
    • Harmful
    • Lethal
    • Helpful
    • Silent
genetic transfer in bacteria
Genetic Transfer in Bacteria
  • Genetic transfer-results in genetic variation
  • Genetic variation-needed for evolution
  • Three ways:
    • Transformation: genes transferred from one bacterium to another as “naked” DNA
    • Conjugation: plasmids transferred 1 bacteria to another via a pilus
    • Transduction: DNA transferred from 1 bacteria to another by a virus
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