Genetics of Bacteria and Archaea Flashcards
Lecture 17
Small circular DNA autonomously replicating. Can be transferred between cells
Plasmids
The transforming principle comes from experiments of
Griffith
In Griffith experiments, infections of mice with strains of Steptococus, ___ and ___ colony types. The phenotype due to _____ production
Rough and smooth. Capsule
What is the significant things of Griffith’s 1928 experiment?
He mixed dead S with live R, and the mice were infected with S, and S came back alive.
Avery, MacLeod, McCarty 1944 experiment found
DNA is the transforming material
Competence is the ability to…
take up exogenous (naked) DNA
Naked DNA taken up, incorporated, and expressed
Genetic Transformation
Conjucation requires a
plasmid
Plasmid-directed transfer requires cell contact
Conjucation
What is needed for conjucation direct contact?
Pilus
T/F: Transfomration requires a cell to die
True
T/F: Conjucation requires a cell to die
False
Integrated F factor, Hfr strains
A type of conjucation wehre rather than a plasmid, Hfr strain needs direct contact and the replicating gene is biased based on what genes are closest to replicate.
Generalized transduction involved a ____ ____
lytic phage
Specialized trnasduction has ___ ____
lysogenic phage
Generalized transduction
begins when a virulent phage attatches to a donor and infectis it.
The infected cell lyses, poducing some reare phages that contain bacterial DNA instead of phage DNA.
When infect another cell, the bacterial DNA enters the cell
The bacterial DNA becomes incorporated by the recombination into the recipient cell’s chromosome
Transfer of the dollar gene!
Specialized transduction
- inserts as prophage
- aberrant excision
- pick up adjacnt gene
- defective phage
- one in a million odds (do it enough times then!)
To protect against transferred DNA, bacteria cut entering DNA into piences, cirring at specific ___ ____.
restriction sites
To protect against transferred DNA, bacteria add ____ groups to DNA to know what to cut and what not to.
methyl groups
____ will inhibit transformation
DNase
… will disrupt conjucation
0.2 microm membranes
Needs naked DNA
Transformation
Needs cell contact
Conjugation
Involves bacteriophage
Transduction
The most common mutation is ___ mutation, where wrong bases are incorporated
point mutation
Ato G, or C to T
big to big, little to little
Transition
A to C, T to G
Big to little, or little to big
Transversion
TAT to TAC»_space; Tyr to Tyr
silent mutation
No phenotype (usually)
TAt to TTT»_space; Tyr to Phe
Missense mutation
TAT to TAA»_space; Tyr to stop
Nonsense mutation
Indel
Insertion, deletion, or insertion and deletion of nucleotides in genomic DNA
Indel examples
- mutations
- mutants
- mutagens
5-Bromouracil Mutagenesisq
- Shifting from Keto to enol,
- In keto, bond with A. In enol, bond with G.
- Keto form strongly preferred.
- Need T, 5BU looks like T, so stick to A. Later, it looks like U, so it is paired with G, so a C is stuck on.
- takes 3 rounds to fix
-TRANSITION mutation
Ames test
Salmonella used to test mutagns (no ability to make His, so are His-). Wild types grow, mutants can’t.
In exposure to product, look for reversions to His+
Rather than measuring the breaking, we are measuring the fixing to see if this product is a mutagen and therefore cause cancer.
In example picture, the product is so potent that is is killing the cells near it and then farther we see His+.
Adding or deleting 1 to 2 bases knocks the system out of frame
Frame shift mutations
Potential reading frames
Since we read triplet codons there are three reading frames in the forward direction, and three possible frames in the reverse direction
Which technique can be used to study transcriptomics?
Gene chip
How are proteins modified in a two-component signal cascade?
Phosphorylated
Which of these regulatory proteins favors the lytic cycle in lambda phage?
cro
RpoH (sigma 32) is involved in what process?
Heat shock response
What is the default setting for flagella rotation in E. coli?
Counter-clockwise
Which of these techniques can be used to study proteomics?
2D gels
What sigma factor strategy is used to coordinate gene expression in a developing endospore?
anti-sigma factors
What happens when MCP proteins have methyls groups added to them?
They become less sensitive
How do E. coli flagella spin when conditions become more favorable (increasing resources)?
counter-clockwise
