Chapter 8. Bacterial Genetics

An auxotroph can be isolated from a prototrophic parent strain by ______ selection

indirect

____ mutations are genetic changes caused by factors from outside of the cell such as radiation or chemicals

induced

In this image, the base substitution leading to a stop codon is called a(n) ________ mutation

nonsense

Chemical mutagens that modify _____ increase the odds of incorrect nucleotide incorporation during DNA replication

nucleobases

Repair of nucleotide incorporation errors during the process of DNA replication is accomplished by ________ by DNA polymerase and by _______ repair.

proofreading; mismatch

Mutation rates are low because proofreading and _______ mechanism fix altered or damaged DNA before it can be passed to progeny

repair

Match each statement with the correct nucleic acid molecule

- Plasmid and Chromosomes - Made of double stranded DNA - Contains an origin of replication - Plasmid - Typically do not encode genes essentials to the life of the cell - Chromosomes - Found in all eukaryotes and prokaryotes - Cells cannot survive their loss

Which of the following are characteristics of recombinants?

- They result from horizontal gene transfer - The have properties of both donor and recipient cells

In generalized transduction, a(n) ______ transfers DNA from one bacterial cell to another

- bacteriophage

Place the descriptions of how CRISPR systems work in chronological order

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

True or False: A point mutation always leads to a shift of the reading frame from the point of mutation downstream

False

True or False: In bacterial conjugation all F+ donor cells are high frequency recombinant (Hfr) cells.

False

True or false: Plasmid are insertion sequences that can lead to changes in genotype within a cell or between cells

False, Transposons are the "Jumping Genes"

A(n) ______ ______ is a large segment of a cell's genome that has clearly originated in a different species

Genomic island

True or false: A point mutation involves any substitution of a single nucleotide

True

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

bacteriophage

Modified nucleobases can result in ____ if they are not required before DNA replication occurs.

base substitutions

Chemicals that cause cancer are called ______

carcinogens

Cells that have the ability to take up DNA from the environment are called ____ cells

competent

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

core genome

Which type of mutation alters the reading frame of a gene?

frameshift

_______ transduction results from a packaging error during virus replication, when a piece of bacterial DNA is included in the new virus particle

generalized

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 2 bacterial strains that are His-/Trp- (require his and trp for growth) and Leu-/Thr- (require leu and thr for growth) are mixed together and plated on minimal media, any colonies that form are likely due to one strain acquiring genes from another strain. This is called _____ gene transfer

horizontal

______ is the change of a mutated genetic sequence back to its original, non-mutated form.

reversion

Chromosomal DNA is transferred with F plasmid DNA in an Hfr cell because _______.

the plasmid DNA is integrated into the chromosome in these cells

Mutagens that are DNA segments that insert themselves into genes and inactive them are called ______

transposons

Sequences of DNA that can move to new positions within the genome of a single cell are called

transposons

A bacteriophage consists of what major components?

- DNA or RNA genome - Protein coat

X-rays can cause which types of damage to a DNA molecule

-Nucleobase alterations -Single stranded breaks -Double stranded breaks

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

CRISPR Restriction-modification

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

released as a result of host cell lysis

Restriction-modification systems of bacteria include what two components?

- A restriction enzyme that recognizes and cuts at a short nucleotide sequence - A modification enzyme that adds protective methyl groups to the cell's own DNA

The illustrated base sustitution mutation leading to trytophan is an example of a _____ mutation

missense

The _____ is the observed characteristics of an organism

phenotype

When horizontal gene transfer occurs between a donor and recipient cells, the resulting cells are called ________

recombinants

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

- when certain nutrients are scarce - when there is high density of bacteria

Which of the following are methods of gene transfer in bacteria?

- Transformation - Conjugation - Transduction

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

- Transposase gene - inverted repeats

Some types of bacteria become competent _____.

- When nitrogen or carbon sources are scarce - When there is a high concentration of bacterial cells

The consequences of not repairing damaged DNA in cells include ______

- cell death - cancer (in animals)

Chemical mutagens can cause which of the following?

- frameshift mutations - base substitutions

What are some of the disadvantages of the SOS DNA polymerase?

- it can result in a lot of mutations in the DNA - it has no proofreading ability

Which of the following are examples of mobile genetic elements?

- phage DNA - genomic islands - transposons - plasmids

Which of the following are replicons?

- plasmid - chromosome

Which of the following types of radiation are mutagenic?

- x - rays - ultraviolet rays

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

within that cell before being released

Place the steps of DNA-mediated transformation into the correct order

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

Place the steps of F plasmid transfer in the correct order

1. F pilus makes contact with donor cell 2. One strand of F plasmid is cut in origin of transfer 3. Single strand of F plasmid is transferred to the recipient cell 4. Complement of transferred strand is synthesized

Which term refers to an organism that has mutation?

Mutant

Which of the following describes an organism's observable characteristics?

Phenotype

Which process requires visible light to repair DNA damage caused by ultraviolet light?

Photoreactivation

Protection against the toxic effects of antimicrobial compounds or heavy metals is often found to be encoded on ______ plasmids

R

the distortion of DNA by thymine dimers directly blocks which of the following cellular processes?

Replication and transcription.

Extensively damaged DNA activates the _____ repair mechanism, which cannot always determine the correct nucleotide sequence, thus introducing mutations resulting from the repair process itself.

SOS

Which mechanism of gene transfer involves the uptake of "naked" DNA by competent bacterial recipient cells?

Transformation

When treating tuberculosis, two or more antimicrobial medications are often prescribed because _______.

a sensitive cell is unlikely to become resistant to two medications simultaneously through separate spontaneous mutations

Base _____ structurally resemble nucleobases and can be mistakenly incorporated into nucleotides and then into DNA

analogs

Mutants that can grow under conditions in which the parent (wild type) cells cannot are easily isolated by ________ selection

direct selection

Mutant cells in bacterial cultures can be isolated by ______ and ______ selection methods

direct, indirect

Proteins that remove thymine dimers without light are termed _____ repair enzymes

excision

Chemical mutagens that squeeze between base pairs and induce frameshift mutations are called ________

intercalating agents

During DNA replication, the template strand can be distinguished from the newly synthesized strand by the presence of ______ groups on certain nucleobases. This is very important for mismatch repair.

methyl

Random genetic changes that result from normal cellular processes are _____.

spontaneous mutations

Genetic change in bacteria occurs through which two mechanism

- Mutation - Horizontal gene transfer

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

F prime

If a scientist is working with bacteria that have the typical phenotype of those isolated from nature, the bacteria are considered to be _______ type

wild

the native or ______ _____ strain describes cells that carry non-mutated DNA

wild type

Please match the statements about plasmid properties with the correct definition

- Low copy number: Occur in one or a few copies per cell -High copy number: Occur in many copies in a cell -Narrow host range: Can replicate in only one species -Broad host range: Can replicate in many different species

A(n) _____ mutation results from an insertion or deletion of nucleotides, leading to a shift of the reading frame from the point of mutation downstream?

frameshift

Consider a population of bacteria susceptible to an antimicrobial. If a bacterium acquires a spontaneous mutation that gives resistance to the antimicrobial, the bacterium will ____ if the pollution is expose to the antimicrobial

grow without competition

True or false: Incorporation of an incorrect of an incorrect nucleotide in a molecule of DNA results in a distortion of the DNA helix that can be detected by repair enzyme

True

recognition and repair of errors in nucleotide incorporation by DNA polymerase is called _______.

proofreading

In bacterial conjugation, the terms ______ designates a donor cell with an F plasmid.

F+