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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