Genetic Transfer Flashcards
Genetic Transfer is?
the mechanism by which DNA is transferred from a donor to a recipient
Genetic Transfer is always _____ and ______
Unidirectional & Partial
Once donor DNA is inside the recipient _____ ____- can occur
crossing over
3 forms of genetic transfer
Conjugation
Transduction
Transformation
Conjugation?
Movement of DNA through a pilus, by action of the F’ fertility factor.
Transduction
Usage of a virus vector to deliver the DNA into the target cell
Transformation
Direct uptake of naked DNA by the cell. Naturally, this doesn’t happen very readily (you don’t know where that DNA’s been!), so there are some tricks to help the DNA in
In bacterial conjugation donor strains contain an additional genetic element, called the?
fertility factor or (F)
F(+ or -) strain mate with F(+ or -) strains.
F+ , F-
DNA transfer occurs unidirectionally from?
F+ to the F-
The F’ fertility factor can replicate both through _____ & _____ _____ _____ replication
rolling-circle and normal double-stranded (theta-structure) replication
Key areas on the F’ site include (4)
oriT
Tra genes
Inception sequences
oriV
F+ cells do not attach to other?
F+ cells, due to the presence of two proteins in F+ cells:
An Hfr (high frequency of recombination) strain occurs when?
the F’ factor becomes integrated into the E. coli host chromosome, due to the presence of the insertion sequences.
Transformation direct uptake of DNA ‘tricks’ to allow entry? (2)
Electro-competence
Calcium competence
Transduction (also known as transfection): Usage of a?
Usage of a virus vector to deliver the DNA into the target cell
A bacteriophage or phage is a?
virus that infects bacteria.
General Steps Of The Lytic Cycle? (5)
1) Attachment of T4 to receptors on E. coli cell wall.
2) Penetration of the cell wall by tail core. Inject DNA into host.
3) E. coli DNA is hydrolyzed. Phage DNA directs biosynthesis of viral parts using the host cell’s machinery.
4) The phages mature as the parts are assembled.
5) Lyses of E. coli and release of the new phages.
Regulatory genes products are responsible for?
regulation the transcription (turn on or off the transcription of other genes)
Regulatory cascade, is?
the regulation performed by regulatory genes
Prophage
state of the phage in a lysogen in which the phage DNA is integrated into the chromosomal DNA of the bacterium or replicates as plasmid
Lysogen
a strain of bacteria that harbors a prophage
Lysogenic cycle series of?
series of events that follow infection by a bacteriophage and culminate in the formation of stable prophage
Lysogenic phage
is a phage which is capable of entering a prophage state
General Steps of The Lysogenic Cycle
1) Phage attaches to E. coli and injects DNA.
2) Phage circularizes and can enter either the lytic or the lysogenic cycle.
3) In the lysogenic cycle the circular phage DNA recombines with E. coli DNA and the phage DNA is now called prophage.
4) E. coli undergoes cell division, copying prophage and passing to daughter.
With more divisions there are more cells with the prophage.
5) The prophage may exit the chromosome and start a lytic cycle at any time.
6) The lytic cycle would occur as previously described.
Phage Transduction?
A genetic exchange in which bacteriophages carry bacterial genes from one host cell to another.
Two classes of transduction: (2)
Generalized transduction
Specialized transduction
The Steps Of General Transduction
1) A phage attaches to cell wall of bacterium and injects DNA.
2) The bacterial chromosome is broken down and biosynthesis of phage DNA and protein occurs.
3) Sometimes bacterial DNA can be packaged into the virus instead of phage DNA.
This phage is defective (can’t destroy another host cell) because it does not carry its own genetic material.
4) The cell lyses, releasing viruses.
5) The phage carrying bacterial DNA infects another cell.
6) Crossing over between donor and recipient DNA can occur producing a recombinant cell.
Specialized Transduction
1) Remember that in the lysogenic cycle, phage DNA only exist as a prophage integrated in the bacterial chromosome)
2) Occasionally when the prophage exits it can take adjacent bacterial genes with it.
3) The phage DNA directs synthesis of new phages.
The phage particles carry phage DNA and bacterial DNA.
4) The cell lyses, releasing the phages.
5) A phage carrying bacterial DNA infects another cell.
6) The joined phage and bacterial DNA circularize.
7) Along with the prophage, bacterial DNA integrates with the recipient chromosome by a cross over event.
This forms a recombinant cell.
