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