Lecture 9 - David's Lecture Flashcards
HD
What are the three major forms of horizontal gene transfer in bacteria?
Transformation, conjugation, transduction
Generalised and specialised transduction both occur during what type of transduction?
bacteriophage mediated transduction
In generalised transduction and specialised transduction bacterial DNA is transferred. How are they transferred in each?
Generalised - transfer of random sections
Specialised transfer adjacent to a prophage
An extrachromosomal DNA molecule that replicates independently of the chromosome
plasmid
Transformation involves the uptake of _____ ________by bacterial cells.
naked DNA
Transformation alters what two things of a cell.
Genotype and phenotype
Competency can be either ______ or _______
natural or artificial
Artificially competent bacteria are prepared by incubation in ice-cold _______ _________.
calcium chloride.
In the environment, transformation probably plays an important role in transferring ______ between organisms, even if they are different species.
genes
Transformation is used as a common method to place __________ DNA into bacterial cells.
recombinant
Basis of biotechnology
Transformation
Unidirectional transfer of DNA between a donor and recipient through a conjugal bridge
Conjugation
Can transfer themselves from a donor cell to a recipient cell
Self transmissible plasmids
Require the help of self transmissible plasmids for transfer
Mobilisable plasmids
Self transmissible plasmid genes are involved in what 2 things?
formation of conjugal bridge, involved in preparing and transferring DNA (eg relaxase)
What makes a nick in one strand at the nicsite within OriT?
Relaxase
What end of the DNA is attached to the relaxase?
5’
Relaxase and a what is transferred to the recipient?
single strand of DNA
Relaxase ________ the plasmid in the recipient
recyclizes. Then a complementary Strand is synthesised
In the donor cell, DNA polymerase makes a complementary ______ at what site?
DNA, 3’
Conjugation is the transfer of bacterial (plasmid) DNA by what to what contact
cell to cell
Do all self transmissible plasmids possess all genes necessary for their own transfer ?
Yes (egF plasmid)
What initiates DNA transfer
A single stranded nick in OriT by relaxase
F plasmids can integrate into the chromosome, forming an what
Hfr strain
In an Hfr strain, oriT is located on the what?
chromosome
Mobilisableplasmids can not transfer themselves, but can be transferred by what?
other plasmids
Mobilisable plasmids contain what type of genes involved in DNA transfer?
mob
The transfer of DNA from one bacteria to another by bacteriophage
Transduction
How many phages are there on the planet?
10 to the 31
How many bacterial per ml of sea water
10 to the 7
Lysogenic phages and lysogeny - phage DNA integrates into the bacterial ________, or exists as a __________
chromosome, a plasmid
Temperate phages when integrated into chromosome do not place any burden on the _______
host
Prophage state can continue for how long?
almost indefinitely
Damage to DNA or infection with another phage results in phage induction and the start of a ______ ______
lytic cycle
lysogenic phage often encode genes that contribute to ___________
virulence
Transfer of bacterial DNA by bacteriophage
transduction
Is the transduction of bacterial DNA an accidental process or a purposeful process?
accidental
Are transducing particles transferred the same way as ordinary phage particles?
yes
Lytic and lysogenic phages - How is general transduction and specialised transduction arisen?
General - from lytic cycle
Specialised - after lysogenic infection
Is this general transduction or specialised? - Randon bacterial DNA fragments are transferred.
General Transduction
Is this general transduction or specialised? Only genes close to the attachement site are transferred
specialised transduction
DNA sequesnces that can ‘jump’ from one place to another in a genome.
Transposable elements (eg. different coloured corn)
What are 3 classes of transposable elements in bacteria?
insertion sequences
composite transposons
non-composite transposons
Transposable elements all contain ________ DNA repeat sequences at their _________
inverted, ends
Where are transposable elements often found?
Plasmids or bacteriophages
Insertion sequences only encode genes necessary for ____________
transposition
Transposable elements that carry one or more genes in addition to those needed for transposition
Bacterial transposons
DNA flanked by two IS elements of the same type
composite transposons
Can composite transposons bracket additional genes?
Yes
Transposable elements that carry one or more genes in addition to those needed for transposition
Bacterial transposons
What is this describing: Do not contain IS elements at their ends. Do contain inverted repeats. May contain additional genes within the IR.
Non-composite transposons
Often contain multiple antibiotic resistance genes
Transposons
Transposons are often found on _________
plasmids
What are the 2 types of gene transfer?
Vertical (binary fission) and Horizontal
Uptake of naked DNA (ie. plasmid) from surroundings. Plays a role in biotechnology
Transformation
Unidirectional transfer of DNA between a donor and recipient through a conjugal bridge. Self transmissible vs mobilizable plasmids.
Conjugation
The transfer of DNA via a bacteriophage. Lytic vs Lysogenic. Generalised vs Specific.
Transduction
DNA elements that move from one place in DNA to another in a genome
Transposable
What type of gene transfer plays a role in virulence and multi-antibiotic resistance?
Horizontal
