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