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Explain what transposable means:
DNA with the ability to be moved and integrated into different sites in the chromosomes.
Characterize the following types of transposable elements: Insertion sequences
- "IS" elementsm a short sequence, that only contains the gene for the enzyme transposase and is bounded at both ends by inverted repeats.
- Transposase is required for transposition and recognizes the IS ends.
Characterize the following types of transposable elements: Composite transposons
Transposable elements that also contain genes in addition to those needed for transposition.
Characterize the following types of transposable elements: Replicative transposons
When the O.G. transposon remains at the parental site on the chromosome and a replicate is inserted at the target DNA site.
Identify the characteristics of plasmids:
- Small & double stranded
- Can exist independently of chromosomes
- Contains its own oriC
- Autonomously replicate and are inherited
Characterize the following type of plasmid:Episome
can integrate reversibly with the host chromosome
Characterize the following type of plasmid:Conjugative plasmid
transfer copies of themselves to other bacteria during conjugation
Characterize the following type of plasmid:F factor
A specific type of conjugative plasmid. It bears genes for cell attachment and plasmid transfer
Identify what is required for conjugation to occur:
- Direct cell to cell contact mediated by F-pilus
- Type IV secretion system
- Rolling circle replication of plasmid
Characterize the following types of cells:F+,F-,HFR, and F'
- F+ has an F factor
- F- lacks an F factor
- HFR has F factor integrated into the bacterial chromosome
- F' has F factor + cell gene(s)
Describe the results of the following matings: F+ x F-
Cellular genes are transferred to second host by cell conjugation. A plasmid from F+ moves through sex pilus into F-. The F factor is transferred between the cells, F- becomes F+.
Describe the results of the following matings: Hfr x F-
Hfr makes a sex pilus, then has a break where the Ffactor is, a piece of DNA breaks off with it and goes into recipient cell. It transfers part of the chromosome and part of the F factor. F- remains F-.
Describe the results of the following matings: F' x F-
F' has an Ffactor that comes out of the chromosome with chromosome attached. All of it goes to the recipient and turns the F- into F', it gives the Ffactor and genetic information
Conjugation in Gram + bacteria
- Cell to cell contact through sex pilus.
- Fewer transfer genes are required.
Explain what transformation is:
- Uptake of naked DNA by a competent cell.
- DNA is incorporated into the recipient cell's genome.
Describe the mechanism of transformation in S. pneumoniae:
- DNA fragment binds to a cell surface receptor.
- Extracellular endonuclease cuts the DNA into smaller fragments.
- One strand is degraded, another enters.
- DNA strand aligns itself with a homologous region on chromosome.
- DNA strand is incorporated (YAY).
- Makes the thingey lac+.
Characterize transformation in Gram - cells:
does not produce protein factor to stimulate competence. takes up DNA only from closely related species. Double strand DNA taken in by vesicles.
Discuss the requirements for transformation:
- DNA must be in the surrounding environment.
- DNA must encounter a competent cell.
- Bacteria have to be in a certain stage of growth.
Explain what transduction is:
horizontal gene transfer mediated by viruses
Distinguish between generalized transduction and specialized transduction:
- Generalized:Mispackaging of DNA. LYTIC CYCLE, some viruses only get cellular DNA and inject it into another bacteria
- Specialized:LYSOGENIC CYCLE, viruses get part prophage part cellular DNA. This is transfered into future cells.