Lecture 32 Flashcards
bacteria participate in both _______ gene transfer (between same generation), and ______ gene transfer (pass genes to offspring)
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Transformation
genetic transfer process by which free (naked) DNA is taken up by a cell, and incorporated into their chromosome by recombination. this free and naked DNA often comes from dead bacteria after they have been lysed
Some prokaryotes are _________ transformable meaning they readily take up free DNA on their own. While others must be ______ meaning they must be manipulated in the laboratory in order to take up free DNA.
naturally induced
A cell that is able to take up DNA and incorporate it into their chromosome (undergo transformation) is said to be what?
competent
Cells can be induced to be competent using what? ex.
calcium chloride or by electroporation E. coli works better if their cell walls are altered so that DNA can pass through more easily
In the lab, cells can be made _______ by a process that uses _______ and heat shock treatments. This process is thought to induce temporary __________ that allow molecules to pass. Competence results from these alterations in the cell wall that make it permeable to large DNA molecules.
-competent -calcium chloride -holes in the cell wall and membrane
Transformation can involve both ________ and ________.
linear DNA fragments or plasmids Plasmids are more stable, so not usually degraded, although linear DNA fragments can often become degraded if DNA is not incorporated into chromosome.
Successfully transformed plasmid will replicate on its own if it has…
has its own oriC, such as a plasmid or phage genome
Plasmids – what are the classifications by function?
virulence plasmids: encode proteins that enhance the pathogenicity of a microbe
resistance factors: r factors cause problems with treating infectious diseases bc of increased antibiotic resistance
dissimilation plasmids: encode for enzymes that aid in breaking down unusual compounds such as unusual sugars and hydrocarbons
The F-plasmid is an ________ , which means what? What does it carry?
episome (a plasmid that can integrate itself into the bacterial chromosome by homologous recombination)
It carries its own origin of vegetative replication (oriV), and an origin of transfer, or oriT.
There can only be _______ copy of the F-plasmid in a given bacterium, either ________, and bacteria that possess a copy are called ________. Cells that lack F plasmids are called __________and as such can function as recipient cells. The tra or Transfer region contains the ____________.
- one
- integrated or free
- F+ (F positive or F plus)
- F- (F negative or F minus)
- sex pilus genes and transfer genes
Plasmids can contain a number of _______and _________that allow the plasmid to integrate into the host chromosome. What do these two things do?
transposable elements (Tn) and insertion sequences (IS)
The Tn and IS provide regions of sequence homology between chromosomal and F plasmid DNA. Consequently, homologous recombination between an IS or Tn on the F plasmid and a corresponding IS or Tn on the chromosome results in integration of the F plasmid into the host chromosome.
Conjugation
This type of DNA transfer involves cell-to-cell contact and a conjugative plasmid (such as the F plasmid) in the donor cell. The F plasmid governs its own ability to transfer from one cell to another and encodes genes necessary for the transfer of the plasmid from one microbe to another.
Donor cells for conjugation have what type of plasmid, and what are they termed? Acceptor/recepient cells are termed what?
F+ plasmid (males)
F- recipient cells have no F plasmid (female)
Sex pilus on F+ draws F- closer inducing the formatin of a ________. This allows DNA transfer via a _______ . Typically, the DNA transferred consists of the genes needed to make and transfer pili, but other pieces of DNA are transferred as well like antibiotic resistance genes. Not all bacteria can make conjugative pili, but conjugation can occur between ________ .
- mating bridge
- pore
- between bacteria of different species
Hfr Conjugation in E. coli
Replication of the Hfr chromosome begins in the middle of the integrated F factor, and a small piece of the F factor leads the transfer, usually the chromosome breaks before it is completely transferred.
Temporate phages: what are the two cycles, and describe them. What is this form of receiving DNA called in bacteria? In its integrated form, the viral genome is called what?
lytic and lysogenic
transduction
lysogenic - viral DNA is integrated, replication is quite along with bacterial DNA for many generations. In its integrated form the viral genome is called a provirus or prophage. under optimal conditions for the virus, the integrated viral DNA frees itself from the bacterial DNA, and moves into the lytic cycle.
The two types of transduction? And define each. What is a phage with host bacterial DNA called?
generalized and specialized
generalized is when random fragments of bacterial DNA are packaged by mistake into the virus
This DNA can be either degraded (by restriction enzymes), or can be integrated into the chromosome by homologous recombination, or it can exist as stable material.
Specialized transduction
When a prophage or provirus is excised from the host chromosome, adjacent genes from either side may remain attached to the phage DNA.
mobile genetic elements vs. transposable elements? is there a difference. what enzyme does insertion sequences and transposons code for?
insertion sequence able to pop itself out of the genome, and move to another place on the same chromosome
-transporase enzyme
