Bacterial genetics

• bacteriophage

  Virus that infects bacteria
• plasmid

  Small circular DNA molecule found in bacteria
• transformation

  Uptake of naked DNA by a bacterial cell
• transduction

  Transfer of bacterial genes from one bacteria to another by a bacteriophage
• conjugation

  DNA transfer through a mating bridge between bacterial cells
• F factor

  Plasmid that codes for sex pili and enables conjugation
• F+ cell

  Bacterial cell containing the F factor
• F- cell

  Bacterial cell lacking the F factor
• Hfr cell

  Bacterial cell where the F factor has integrated into the chromosome
• trp operon

  Genes involved in tryptophan synthesis
• lac operon

  Genes involved in lactose metabolism
• gene repression

  Blocking of gene expression
• constitutive genes

  Genes expressed all the time
• structural gene

  Gene that codes for a protein
• regulatory gene

  Gene that controls expression of other genes
• polycistronic mRNA

  mRNA that encodes multiple proteins
• operator

  DNA sequence where a repressor binds to control gene expression
• repressor

  Protein that binds to an operator to repress gene expression
• Why are bacteria used in genetic technologies

  They are easily cultured because they have a short generation time.
• Which type of escherichia coli is not used in genetics

  0157 because this is the strain that causes food poisoning.
• What shape are bacterial chromosomes

  Circular
• Lytic bacteriophage

  Divide and lyse the bacterial cell to release progeny
• Temperate bacteriophage

  Can integrate into the bacterial chromosome and remain dormant
• What are the types of bacteriophage

  
  

  1. Lytic

  2. Lysogenic
• Processes of gene transfer and recombination in bacteria

  • Transformation
  • Transduction
  • Conjugation
• Generalized transduction

  Occurs only with virulent phage
• Specialized transduction

  Occurs only with temperate phage
• Describe conjugation

  1. F+ cell contains F plasmid
  2. Sex pili form a mating bridge to the F- cell
  3. F plasmid replicates and travels into the F- cell.
  4. F- cell is now called an exconjugant
• Describe conjugation between an Hfr and an F- bacterium

  1. Hfr cell contains an F plasmid integrated in the chromosome
  2. F plasmid codes for sex pili
  3. Sex pili form mating bridge to F- cell
  4. Hfr DNA is replicated and transferred along the mating bridge to F- cell
  5. Recombination of genes within the F- cell
• Define constitutive genes

  Genes which code for proteins required all the time by the bacterial cell
• Define regulated genes

  Genes that are only active when required
• What is the structure of the E.coli genome

  Single double stranded circular DNA molecule.
• What are the two types of transduction in bacteria

  Generalised and specialised.
• Define sex pili

  They form a mating bridge to the F- cell during conjugation.
• What is this cycle and describe it

  This is the lytic cycle.

  1. Tail fibres allow attachment
  2. DNA is inserted into bacteria
  3. DNA is hydrolysed and broken down
  4. Phage DNA controls the metabolic activity of the cell
  5. Cell's broken DNA is used to make phage DNA
  6. Phage is assembled
  7. Lysozymes are produced and digest the cell wall

  A) Attachment

  B) Insertion

  C) DNA broken

  D) Replication

  E) Assembly

  F) Lysis and release

  
• Describe the temperate life cycle

  The lytic cycle can be initiated when the prophage exits the bacterial chromosome

  1. Tail fibres allow for attachment and entry
  2. Phage DNA circularises
  3. Phage DNA is integrated [Prophage]
  4. Binary fission

  A) Lytic cycle

  B) Lysogenic cycle

  C) Attchment and Entry

  D) DNA circulisation

  E) DNA integrates

  F) Binary fission

  
• Describe general transduction

  1. Attachment and Entry
  2. Host DNA hydrolyzed
  3. Replication
  4. Host DNA packaged in phage capsid
  5. Transducing phage infects new host
  6. Crossing over and recombination
• Describe specialized transduction

  1. Attachment and entry
  2. DNA integrates to form a prophage
  3. Prophage exists with bacterial DNA
  4. Transducing phage infects new host
  5. Crossing over and recombination
• How is bacterial gene expression contrlled

  When transcription is initiated
• What intiates transcription

  When RNA polymerase binds to a promoter