Plasmids + Transformation Flashcards
Describe how bacterial chromosomes are organised, how they evolve, how they differ between species and how they are compressed to fit within the bacterial cell. Also understand the role of accessory elements, horizontal gene transfer and gene depletion in chromosome evolution Explain the general features of plasmids Understand plasmid nomenclature Describe a range of biological functions that plasmids provide Understand how plasmids are structured Understand the modes of plasmid replication Disp
What is meant by a wildtype?
The natural appearance of a species within the wild
What is meant by a phenotype?
An observable property of a strain
What is meant by a genotype?
The genetic composition of an organism
What is transformation?
Introduction of naked DNA into a strain (From the environment)
What is transposition?
Movement of genes from one place inside the cell to another
What is conjugation?
Transfer of DNA from one strain into another
What is Transduction?
Use of bacteriophages to move mutations from strain to strain
What is the function of the methyl base?
To protect the DNA against endonucleases
What % of the bacterial chromosome is coding regions?
90%
What is the purpose of the non coding regions within the bacteria?
Promoter/operator regions
Why might a bacteria have multiple chromosomes?
Allows for faster replication
Specilisation of chromosome
What was the minimal genome project?
Create the smallest genome possible for an organism
What is meant by Synteny?
Related bacteria have common backbones, with a majority of the genes having the same order
What is the nomenclature for genetic phenotypes?
First letter capitalised
+ Shows it’s ability to synthesize
- Shows it cannot
What is the nomenclature for genetic genotypes?
All letters italicised/underlined
^R if resistant to AB
^S is sensitive to AB
What do plasmids usually confer?
Genes required for growth under specific environmental conditions
What are replicons?
DNA molecules which can replicate autonomously
Where does the replication of a plasmid begin?
The oirigin of replication site
What items does the plasmid create for replication?
Protein required for initiation at ori site
What does a plasmid need from the host in order to replicate?
DNA polymerase
Ligases
Helicases
How does theta replication work?
Initiation: OriV site
Proceeds either bidirectionally (until the two forks meet)
Or unidirectionally (until it reaches origin site)
How does rolling circle replication work?
RepA binds to origin and nicks 5’ end
3’ end attracts dna polymerase 3 which replicates the strand
The 5 prime falls off and is replicated too
What is a host range?
Types of bacteria which a plasmid can replicate in
Give an example of a bacteria with a narrow host range
E.coli
Why would a plasmid have a narrow host range?
Requirement of host-specific regulatory elements or machinery
Give an example of a bacteria which has high host ranges
RK2
What usage is there for a bacteria with a high host range
Can be used in cloning
What is copy number?
The number of plasmids per cell
Why would a cell not want a high copy number?
Would cause overcrowding
What controls the copy number?
the plasmid-encoded components (E.g high initiation replication will increase copy number)
What is curing?
When a bacteria loses it’s plasmids
What is the multimer-resolution system?
Ensures that the plasmid multimers are converters to monomers (aka 2 -> 1)
What is plasmid partitioning?
Ensures that both daughter cells will contain a copy of the plasmid
When is plasmid partitioning typically used?
In a low copy-number cell
What is plasmid addiction?
A plasmid which encodes a protein which will kill the cell if it becomes cured
How does plasmid addiction kill a cell?
Addition plasmids encode an antidote protein constantly, which prevents the toxin from building up
What is plasmid incompatability?
Where a cell cannot have two of the same plasmids from an incompatability group
