Lecture 12
Sources of "naked" DNA
(DNA not contained) Lysed (burst) bacterial cells secreted into the environment by bacteria
in bacterial conjugation, the term ____ designates a donor cell with an F plasmid
F+
True or false: in bacterial conjugation all F+ donor cells are high frequency recombinant (Hfr) cells
Fals
True or false; bacterial conjugation does not require contact
False
What can be transferred from one cell to another by conjugation?
Plasmid DNA Chromosomal DNA
Steps of CRISPR
1. Cas protein complex cuts into initial invading DNA into short fragments 2. short DNA fragments are inserted into chromosomal reguion called CRISPR array 3. the cell transcribes the CRISPR array to produce small FNAs called crRNAs 4. each crRNA bidns to a Cas nuclease 5. If crRNA base-pairs to invading DNA, Cas nucelase cuts the DNA
When an excision errors produces a plasmid containing both chromosomal and F plasmid DNA, the resulting plasmid is called a(n) ______ plasmid
F`
in generalized transduction, donor DNA is mistakenly packaged into a phage coat, forming a _____ particle
transducting
in insertion sequences, the ____ gene (the only gene) is flanked by ____ repeats
transposase inverted
"jumping genes" or ____ can lead to changes in genotype within a cell or bewteen cells
transposons
plasmids
typically do not encode genes essential to the life of the cell
Restriction-modification systems of bacteria include what two components?
A resitriction enyyme that recognizes and cuts at a short nucleotide sequence a modification enzyme that adds protective methy groups to the cell's own DNA
When DNA is transferred from an Hfr cell to a recipient cell, the recipient becomes _____
an F` cell
A ___ is a virus that infect bactera, and can transfer bacterial genes from a donor cell to a recipient cell
bacteriophage
chromosomes
cells cannot survivie their loss found in all eukaryotes and prokaryotes
a bacterial cell described as ____ can take up DNA from the surrounding environment
competent
Plasmids and chromosomes
contains an origin of replication made of double stranded DNA
Bacteriophages can consist of ____-
either DNA or RNA, protein coat (capsid)
A(n) ____ ____ is a large segment of a cell's genome that has clearly originated in a different speices
genomic island
During transduction, donor DNA is injected into a recipient cell by a phage. This DNA integrates into the recipients chromosome by ____ _____
homologous recombination
protection against the toxic effects of antimicrobial compounds or heaby metnals is often found endoded on ____ plasmids
resistance
Chromosomal DNA is transferred with F plasmid DNA in an Hfr cell beause _____
the plasmid DNA is integrated into the chromosome in these cells
Chromosomal DNA that is transferred from an Hfr cell but does not integrate into the recipient's chromosome _______
is degraded
In bacterial conjugation, F+ donor cells are high frequency recombinant (hfr) cells when the F plasmid ____
is integrated into the chromosome
plasmids, transpondons and phage DNA are all examples of _____
mobil genetic elements
genes that vary considerably among strains of a species are caleld the ____
mobile gene pool
in transformation only one daughter cell inherits donor DNA, this is because ____
only a single strand of donor DNA integrates into the recipient chromosome
genomic islands that contain genes that increase the disease-causing abilities of the bacterium are called ____ islands
pathogenicity
in bacterial conjugation, a donor cell with an F _____ is considered F+
plasmid
____ are circuluar pieces of bacterial DNA that do not usually encode informatin essential to thelife of a cell
plasmids
range vs number?
range is species and number is copies?
after new virus partices have assembled in the bacterial host cell, they are usually _____
released as a result of host cell lysis
Steps of DNA-mediated transformation
1. Double stranded DNA molecule binds to surface receptor 2. Nucleases degrade one strand of double-stranded DNA at the cell surface 3. single-stranded DNA enters cell after one strand has been degraded 4. single-stranded DNA integrates into genome after entering the cell 5. strand being replaced by donor DNA is degraded
what are systems bacteria can use to protect against invading DNA?
Restriction-modification CRISPR
although mobilizable plasmids encode an origin of transfer, they lack other genetic information required to transfer. Under what circumstances can a mobilizable plasmid transfer to anther bacterial cell?
when a conjugative plasmid is present in the same cell