Bacterial Genetics & Gene Regulation Flashcards
Describe the genetics of bacteria
haploid due to single bacteria chromosome
What are the advantages of using bacteria for genetic analysis
easy to maintain in labs, gene transfer, mutant bacteria possible
TRUE or FALSE - Bacteria can produce gametes
FALSE
What do E.Coli grow on
simple liquid broth and solid agar petri dishes
What do wild type bacteria grow well on
minimal media
What is in minimal media
salt water and sugar
What do wild type bacteria synthesise
amino acids and nucleotides themselves
What do mutations in bacteria that block bio-synthetic pathways prevent
growth on minimal media
Describe complete media
contains amino acids, vitamins, etc
How can you identify mutations in bacteria
observe which bacteria grow on complete medium but NOT minimal medium
What is an auxotroph
mutants that X synthesise essential nutrients
What does changing composition identify
which pathways are affected
What are prototrophs
wild types for a specific biosynthetic process - can synthesise
What does gene transfer between bacteria require?
cell-cell contact
How do we know gene transfer requires cell-cell contact?
block physical contact between bacteria
Describe the direction of genetic exchange between bacteria
unidirectional
How is DNA transferred between bacteria
Across a physical bridge from donor to recipient
What enables bacteria to transfer genetic material
Fertility factor - F plasmid
What is the function of the fertility factor?
enables carriers to conjugate with other cells without the F factor
What is oriT
DNA sequence where transfer begins
What do tra genes encode
components of transfer machinery
What is F pilus
cytoplasmic bridge between two bacteria
What creates the F pilus
transfer machinery
Describe the fertility factor
Circular DNA
What happens when bacteria with and without the F factor mate
F factor pulls across entire donor chromosome or fuses with chromosome
Describe integration of the F plasmid with host chromosome
high frequency recombination event
When do Hfr strains arise
when F plasmid recombines with host chromosomal DNA
What causes the emergence of phototrophic colonies
formation of Hfr donor chromosomes
Describe feedback inhibition
turns down genes
How is transcription regulated
controlling DNA sequence next to the promoter
What do repressors block the passage of in transcription
RNA polymerase
What is the controlling site in transcription
operator
How is transcription induced
dissociation of repressor from the operator
What are lac genes required for in E.Coli
metabolism of lactose
What is the lac operon
cluster of adjacent genes with closely related biochemical functions
When is the lac operon activated
presence of lactose
When is the lac operon inhibited/blocked?
presence of glucose
What does the lac repressor block?
RNA synthesis of downstream genes
What binds to the lac operon
lac repressor
What can bind to the lac repressor
lactose
What happens when lactose binds to the lac repressor
dissociation of repressor from operator
What drives synthesis when bound to promoter
RNA polymerase and CAP protein
What makes up the Trp operon
5 enzymes
TRUE or FALSE - Trp operon is an activator
FALSE
What suppresses transcription of the Trp operon
biosynthetic product of trp operon encoded enzymes - tryptophan
