Lecture 12 - Chapter 8. Bacterial Genetics

How many strands of donor DNA integrate into a recipient chromsome during transformation?

One

Which of the following are sources of "naked DNA"?

Secreted in the environment by bacteria Lysed (burst) bacterial cells p. 206

In E. coli, about 75% of the genes are found in all strains. These conserved genes are called the ___ genome.

core

The genes that are present in all strains of a given species are called the ____.

core genome

A transducting particle carries ____.

donor cell DNA (NOT phage or recipient DNA!)

True or false? Plasmids are insertion sequences that can lead to changes in genotype within a cell or between cells.

false

A large segement of a cell's genome that originated in other species is called a(n) ___.

genomic islands (206)

What is the term for the plasmid property statement: occur in many copies in a cell

high copy number

Donor and recipient bacterial cells are connected by a sex ___ during conjugation.

pilus

The easiest way to detect if DNA transformation occurred in the laboratory is if _____ grow under selective conditions.

transformed

Which of the following are components of the simplest transposon, an insertion sequence?

transposase gene, inverted repeats (206)

Examples of conditions where bacteria can become naturally competent in the environment include _____.

when there is a high density of bacteria OR when certain nutrients are scarce

When bacteriophages replicate, phage components are synthesized in the host cell and assemble into new viruses _____.

within that cell before being released.

What is true about BOTH plasmids and chromosomes?

- circular double-stranded DNA molecules - contains an origin of replication

Although mobilizable plasmids encode an origin of transfer, they lack other genetic information required for transfer. Under what circumstances can a mobilizable plasmid transfer to another bacterial cell?

When a conjugative plasmid is present in the same cell.

What is the term for the plasmid property statement: can replicate in many different species

broad host range

A bacterial cell described as ___ can take up DNA from the surrounding environment

competent

In insertion sequences, the ___ gene (the only gene) is flanked by ____ repeats.

transposase, inverted

CRISPR systems were discovered _____.

"... when scientists recognized that certain bacterial genomes include very small pieces of phage DNA." (233)

What do you know about nucleic acid molecules known as "chromosomes"?

- cells cannot survive their loss - they're found in all eukaryotes and prokaryotes - are made of double-stranded DNA - contain an origin of replication

How does a modification enzyme protect a bacterial cell from its own restriction enzyme?

By adding methyl groups to the nucleobases of the cell's DNA that are recognized by the restriction enzyme. "...adding methyl groups to the nucleobases recognized by the restriction enzyme. Because restriction enzymes cannot degrade methylated DNA, a restriction enzyme will destroy incoming foreign DNA but not the host DNA." (233)

A bacteriophage consists of what two major components?

DNA or RNA genome Protein coat

Dnase is added to a mixture of donor DNA and recipient. If the donor DNA is naked, what will happen?

The recipient will be unable to acquire DNA via transformation. (Explanation: The enzyme can destroy DNA that is free in the medium but cannot access/degrade DNA within a cell or phage. Thus, if DNAse prevents the recipient cell from acquiring DNA, the donor's DNA must have been naked. p. 206)

When DNA is transferred from an Hfr cell to a recipient cell, the recipient becomes ___.

an F- cell

What is the term for the plasmid property statement: occur in one or few copies per cell

low copy number

Plasmids, transposons, and phage DNA are all examples of _____.

mobile genetic elements.

What is the term for the plasmid property statement: can replicate in only one species

narrow host range

The integration of a region of DNA into a segment that does not have extensive similarity in nucleotide sequence is called ___.

non-homologous recombination

Genomic islands that encode disease-causing factors such as exotoxins, capsules, and adherence factors are called ___ islands.

pathogenicity (206)

After new virus particles have assembled in the bacterial host cell, they are usually _____.

released as a result of host cell lysis.

Protection against the toxic effects of antimicrobial compouds or heavy metals is often found to be encoded on ___ plasmids.

resistance

In an experiment, donor DNA, recipient cells, and DNase are added to a mixture. The recipient cells are not transformed. This tells us what about the donor DNA?

It is naked

Which of the following are systems bacteria can use to protect against invading DNA?

Restriction-modification systems CRISPR systems

What do you know about nucleic acid molecules known as "plasmids"?

- typically do not encode genes essential to the life of the cell. - circular double-stranded DNA molecules - contains an origin of replication

CRISPR system "chronology" (according to book)

1) cut fragments inserted nito chromosomal region called CRISPR array 2) cell transcribes array and processes trasncript to generate crRNA's. Each binds to a Cas nuclease to form a complex. 3) bacterial cell or its descendants will be recognized and destroyed by Cas nuclease-crRNA

CRISPR system chronological order (Smartbook assignment)

1. Cas protein complex cuts initial invading DNA into short fragments. 2. Short DNA fragments are inserted into chromosomal region called CRISPR array. 3. The cell transcribes the CRISPR array to produce small RNAs called crRNAs. 4. Each crRNA binds to a Cas nuclease. 5. If crRNA base-pairs to invading DNA, Cas nuclease cuts the DNA.

In bacteria ___ refers to DNA transfer requiring cell-to-cell contact.

conjugation

This image is showing a step required for bacterial ___.

conjugation (there was a squiggly pilus between an F+ and F-)

During transduction, donor DNA is injected into a recipient cell by a phage. This DNA integrates into the recipient's chromosome by ___ ___.

homologous recombination.

When some species of bacteria reach a certain density or when nutrients are in short supply, they _____.

turn on genes required for competence.

When an excision errors produces a plasmid containing both chromosomal and F plasmid DNA, the resulting plasmid is called a(n) ___ plasmid.

F'

True or false: in bacterial conjugation, all F+ donor cells are high frequency recombinant (Hfr) cells.

False

True or false? When an Hfr cell transfers chromosomal DNA to a recipient cell, it does not need to produce an F pilus.

False

The type of transduction that can transfer any genes of a host cell is called ___ transduction.

Generalized

A ___ is a virus that infects bacteria, and can transfer bacterial genes from a donor cell to a recipient cell.

bacteriophage