microbial genetics
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Microbial Genetics. Chapter 8. Structure and Function of Genetic Material. DNA & RNA DNA deoxyribonucleic acid RNA ribonucleic acid Nucleotides Phosphate group Pentose sugar Nitrogenous base. Structure of DNA. Double stranded (double helix) polymers of nucleotides

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structure and function of genetic material
Structure and Function of Genetic Material
  • DNA & RNA
  • DNA
    • deoxyribonucleic acid
  • RNA
    • ribonucleic acid
  • Nucleotides
    • Phosphate group
    • Pentose sugar
    • Nitrogenous base
structure of dna
Structure of DNA
  • Double stranded (double helix)
  • polymers of nucleotides
  • 5’ to 3’ (strands are anti-parallel)
  • Complimentary Base Pairing
    • A - T
    • G - C
dna replication
DNA Replication
  • Bacteria have only 1 chromosome (ccDNA)
  • E. coli
    • about 4 million base pairs
    • 1 mm long (1000 times longer than the cell)
    • DNA takes up only about 10 % of cells volume
slide7

E. coli DNA

1u 1,360u

1ft. 1,360 ft.

dna replication occurs at the replication fork 5 to 3
DNA Replication occurs at the Replication Fork (5’ to 3’)
  • DNA Helicase
  • 1. Leading Strand ( 5’ to 3’ )
    • DNA Polymerase
  • 2. Lagging Strand ( 5’ to 3’)
    • RNA Polymerase (RNA Primer)
    • DNA Polymerase (extends primer and digests RNA)
    • DNA Ligase
      • Okazaki Fragments
bidirectional replication
Bidirectional replication
  • Origin of replication
  • Termination site
protein synthesis
Protein Synthesis
  • DNA mRNA Protein
  • Transcription Translation
  • Central Dogma of Molecular Genetics
transcription
Transcription
  • One strand of DNA is used as a template to form a complimentary strand of mRNA
  • mRNA ----> messenger RNA
transcription1
Transcription
  • 3 ways RNA differs from DNA
  • Promoter
  • RNA Polymerase
  • Termination Site
  • 5’ to 3’
3 types of rna
3 Types of RNA
  • 1. mRNA
    • Contains the codons
  • 2. rRNA
    • Ribosomes (70S)
  • 3. tRNA
    • Transfer amino acids to the ribosomes for protein synthesis
    • Anti-codon
genetic code
DNA

mRNA

tRNA

Triplet code

codons

anticodons

Genetic Code
genetic code1
Genetic Code
  • Codons code for a specific amino acid
  • 20 amino acids
  • 3 base code - 4 bases ( A,U,G,C )
  • 64 possible combinations ( 43)
  • Amino acids are coded for by more than one codon
  • Genetic Code is Degenerative
  • Genetic Code is Universal
translation
Translation
  • rRNA
    • ribosomal RNA (forms the ribosomes) (70S)
  • tRNA
    • transfer RNA (transfers amino acids to the ribosomes for protein synthesis)
    • anticodon
      • 3 base sequence that is complimentary to the codon on mRNA
regulation of gene expression
Regulation of Gene Expression
  • All Genes are not always being expressed
  • Genes turned on all the time - Constitutive
  • Other genes can be regulated:
    • Turned On
    • Turned Off
lac operon
lac operon
  • Lac - Lactose (dissacharide)
    • Glucose and Galactose
  • operon - series of structural genes all under the control of a Regulatory Gene
  • lac operon is normally turned off
  • lac operon is an Inducible operon
tryptophan operon
Tryptophan operon
  • Tryptophan - amino acid
  • operon - series of structural genes all under the control of a Regulatory Gene
  • Tryptophan operon is normally turned on
  • Tryptophan operon is a repressible operon
mutations a change in the base sequence of dna
Mutations - a change in the base sequence of DNA
  • Mutations can be:
  • 1. Harmful
  • 2. Lethal
  • 3. Beneficial
  • 4. Silent (neutral)
    • UUU - Phe
    • UUC - Phe
slide29

Base Substitution Mutation

C

Missense Mutation

slide30

Base Substitution Mutation

T

Nonsense Mutation

frame shift mutation
Frame Shift Mutation
  • ATG CAT GCA TGC ATT TCC TGC TTA AAA
  • 1. Addition Mutation
  • AAT GCA TGC ATG CAT TTT CCT GCT TAA
  • Reading Frame is Shifted
  • 2. Deletion Mutation
  • TGC ATG CAT GCA TTT CCT GCT TAA
  • Reading Frame is Shifted
genetic transfer in bacteria
Genetic Transfer in Bacteria
  • Genetic Transfer - results in Genetic Variation
  • Genetic Variation - is needed for Evolution
  • 3 Ways Genetic Transfer can occur in Bacteria
    • 1. Transformation
    • 2. Cunjugation
    • 3. Transduction
transformation
Transformation
  • Genes are transferred from one bacterium to another as “naked” DNA
  • Frederick Griffith (1928)
griffith s experiment
Griffith’s Experiment
  • 2 Strains of Streptococcus pneumoniae
    • 1. Virulent strain with a capsule - Pneumonia
    • 2. Avirulent strain without a capsule - no disease
slide40

Conjugation

One bacterium passes some DNA (in a plasmid) to another bacterium

transduction
Transduction
  • DNA is transferred from one bacterium to another by a virus
  • Bacteriophage
    • virus that only infects bacteria
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