Microbiology Chapter 8 - Bacterial Genetics

Chemical mutagens can cause two types of mutations:

Base substitutions Frameshift mutations

Two methods used to identify mutants in a culture are ___ and ____ selection.

Direct Indirect

Which mutations result in the production of a shortened and non-functional protein?

Frameshift Nonsense

What term refers to an organism that has a mutation?

Mutant

Spontaneous mutations are important because

They allow bacteria to adapt to a changing environment

What types of radiation are mutagenic?

X-rays Ultraviolet Rays ( not IR rays)

____ mutations are generally the most harmful to cells because they change all of the codons downstream of the mutation.

Frameshift

What term describes a sequence of nucleotides or genetic makeup of an organism or a cell?

Genotype

Occur in many copies in a cell

High copy number

In bacterial conjugation, F+ donor cells are high frequency recombinant (Hfr) cells when the F _____ is integrated into the chromosome.

Plasmid

Many DNA polymerases have the ability to detect and repair their own errors in nucleotide incorporation. This ability is called

Proofreading

A bacteriophage consists of a _____ coat that surrounds a nucleic acid _____.

Protein coat Nucleic acid genome

A bacteriophage consists of a _____ coat that surrounds the nucleic acid _____.

Protein coat Nucleic acid genome

Encode resistance traits

R genes

Encodes properties needed for conjugation

RTF (resistance transfer factor)

Bacteria routinely adjust to new circumstances by

Regulating gene expression Genetic change

Mutation rates are low because proofreading and ____ mechanisms fix altered or damaged DNA before it can be passed to progeny.

Repair

Plasmids and chromosomes:

- Contains an origin of replication - Made of double stranded DNA

_____ sometimes incorporates the incorrect nucleotide when generating a new strand of DNA during DNA ______; this leads to a detectable distortion in the DNA helix.

- DNA polymerase - Replication

"Jumping genes" or _____, can lead to changes in genotype within a cell or between cells.

Transposons

Mutations that are DNA segments that insert themselves into genes and inactivate them are called

Transposons

_____ are segments of DNA that can move from one location to another in a cell's genome.

Transposons

In _____ gene transfer, DNA or DNA changes are passed from a parent cell to its progeny.

Vertical

Transfer of DNA from parent organisms during reproduction

Vertical gene transfer

If a scientist is working with a bacterium that has the typical phenotype of strains isolated from nature, that bacterium is called a _____ type.

Wild type

Can replicate in many different species

Broad host range

In _____ gene transfer, DNA moves from one organism to another.

Horizontal

Transfer of DNA from a source other than the parent organism

Horizontal gene transfer

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

Induced mutations

Bacteriophages can consist of

- Protein coat (capsid) - RNA genome - DNA genome (Bacteriophages do not have an envelope (membrane)

Which are sources of "naked" DNA?

- Secreted into the environment by bacteria - Lysed (burst) bacterial cells

The two types of transduction are:

- Specialized - Generalized

Plasmids:

- Typically do not encode genes essential to the life of the cell - Often the location of antibiotic resistance genes in bacteria

Two types of transduction are

Specialized Generalized

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

Spontaneous mutations

The most common type of mutation is the base _____, where an incorrect nucleotide is incorporated during DNA replication.

Substitution

Chemical mutagens can cause

- Base substitutions - Frameshift mutations

____ refers to DNA transfer requiring cell to cell contact

Conjugation

Occur in one or a few copies per cell

Low copy number

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

Place the steps of F plasmid transfer in the correct order

1. F pilus makes contact with recipient 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

The consequences of not repairing damaged DNA in cells include

Cancer (in animals) Cell death

Cells that have the ability to take up DNA from the environment area called _____ cells.

Competent

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

Core genome

In bacterial conjugation, which term refers to a recipient cell that has no F plasmid?

F -

T or F: A point mutation always leads to a shift of the reading frame from the point of mutation downstream.

False

New virus particles that have assembled in the bacterial host cell are released from that cell, usually as a result of host cell ____.

Lysis

Can replicate in only one species

Narrow host range

The process in which better adapted organisms reproduce at higher rates in a given environment is called

Natural selection

A base substitution that changes an amino acid-encoding codon to a stop coding is called a _____ mutation.

Nonsense

Which of the following mutations results in the production of a shortened and non-functional protein?

Nonsense Frameshift

The transfer of bacterial DNA from a donor to recipient via a bacteriophage is called

Transduction

DNA-mediated _____ involved the uptake of "naked" DNA by competent bacterial recipient cells

Transformation

What can be transferred from one cell to another by conjugation?

- Plasmid DNA - Chromosomal DNA

Which of the following are possible outcomes of a base substitution?

- Nonsense mutation - Missense mutation - Silent mutation

It is important for people interested in human health to have a basica understanding of bacterial genetics because it can help explain how

- Bacteria acquire resistance traits - Multi-drug resistant bacteria like MRSA arise

Chromosomes:

- Cells cannot survive their loss - Found in all eukaryotes and prokaryotes

Errors by DNA polymerase that incorporate the wrong nucleotide into replicating DNA can be repaired quickly by which two mechanisms?

- Mismatch repair - Proofreading by DNA polymerase

Genetic change in bacteria occurs through which two mechanisms?

- Mutation - Horizontal gene transfer

Place the steps of F plasmid transfer in order.

1. F plus makes contact with recipient 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

____ are circular pieces of bacterial DNA that do not usually encode information essential to the life of a cell.

Plasmids

Bacteria are a great experimental system for genetic studies because when they can accumulate to very high numbers in small volumes:

Rare genetic changes that happen can be easily studied.

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

Within that cell before being released

The return of a gene from a mutated state to its original, non-mutated state is called a

Reversion