Genetics Chapter 7
A bacterial strain that can synthesize a nutrient (e.g., methionine) and does not require that nutrient in its growth medium is called a(n)
Phototroph
What is required in order for genetic material to be transferred between two bacterial cells by conjugation?
Physical contact between two cells.
During conjugation, the initial contact between the donor and recipient cell involves structures called sex _______ that are made by F+ strains.
Pili
A DNA molecule that can exist independently of the bacterial chromosome is called a(n) ______.
Plasmid
How is conjugation stopped during an interrupted mating experiment?
By using a blender to separate the bacterial cells
Which type of strain does a bacterial cell become when an F factor integrates into its chromosome?
Her
During transformation, homologous recombination may create a region of DNA containing one or more base mismatches that must be repaired. This region is called the ______.
Heteroduplex
Which type of E. coli strain frequently transfers chromosomal genes to recipient bacterial cells?
Hfr
DNA from the bacterial chromosome may be transferred from one cell to another if a(n) ________ cell conjugates with an F— cell.
Hfr of F'
During transformation, a functional gene may be replaced with a nonfunctional gene within the bacterial chromosome if the two copies of the gene align and exchange pieces through a process called ____ _______
Homologous recombination
What event is required for genes on an Hfr chromosome to be transferred onto the recipient cell's chromosome?
Homologous recombination -While replication occurs to restore double-stranded DNA structure, recombination is required to integrate genes into the chromosome of the recipient cell.
In order for a segment of transformed DNA that carries a lys+ gene to be incorporated into a lys— cell ______.
Homologous recombination must occur
Relaxosome
Protein complex that recognizes the origin of transfer.
After conjugation, a recipient cell may have a new combination of alleles if homologous ___________occurred between the transferred Hfr chromosome and the original chromosome of the bacterial cell.
Recombination
During conjugation, the protein complex that recognizes the origin of transfer in the F factor, cuts one of the strands, and then separates the two DNA strands is called the
Relaxosome
The length of the Hfr chromosome that is transferred to a recipient cell during conjugation is directly related to the ______.
Length of time allowed for conjugation to occur.
Infection of a bacterial cell with bacteriophage can lead to the production and assembly of new phages, which eventually cause the host cell to burst open. This is referred to as the ________ cycle.
Lytic
During conjugation, the chromosome in the Hfr strain is first _______, then transferred into the F— cell, where it may ________ with the homologous region of the recipient cell's chromosome.
Nicked & recombine
What two types of molecules are found in a nucleoprotein?
Nucleic Acid & Protein
A complex of DNA and protein is called a(n) ______.
Nucleoprotein
How do F+ and F- strains of E. coli differ from one another?
Only F+ strains contain an F factor
If the two cells undergo conjugation, but only for a short period of time, what is the likely outcome?
Only a short segment of the chromosome is transferred. -About 1.5 to 2 hours is required for the entire Hfr chromosome to pass into the F- cell. Because most conjugations do not proceed for that long, usually only a portion of the Hfr chromosome is transmitted to the F- cell.
During conjugation, the starting point and direction of DNA transfer are determined by a DNA sequence within the F factor called the ______.
Origin of transfer
Conjugation Bridge
Passageway for DNA transfer between the donor and recipient cell.
A conjugation bridge is a ______.
Passageway for DNA transfer.
A bacterium is typically _______ for a particular gene, meaning that it only has one copy of the gene
haploid
The transfer of genetic material to an organism that is not the offspring of the donor organism is referred to as _______ gene transfer.
horizontal
The incorporation of a transformed DNA fragment into the bacterial chromosome at a random site is called ______ recombination.
nonhomologous
Based on the time it takes for different genes to be transferred from an Hfr strain to an F—strain, one can deduce the ________ of genes along the bacterial chromosome.
order
In order to be replicated independently of the bacterial chromosome, a plasmid must have its own ________ of _________
origin of replication
To initiate conjugation, the F factor must be cut at a site called the _____ of _____
origin of transfer
Bacteriophages are composed of genetic material that is surrounded by a coat made of
protein
The competence-stimulating peptide of Streptococcus pneumoniae ______.
stimulates nearby cells to express competence proteins
The competence of a bacterial cell can be affected by environmental factors such as ionic conditions________, , and the availability of _________.
temperature & nutrients
During conjugation, the time that it takes for different genes to be transferred to a donor cell depends on ______.
their order on the bacterial chromosome.
The traits of bacteriophages are governed by ______.
their own genetic material
What is the function of the sex pili during conjugation?
They make contact with recipient cells.
When does conjugation result in the transfer of part of the bacterial chromosome to recipient cells?
When an Hfr strain conjugates with an F- strain
Acquired antibiotic resistance is a phenomenon in which a(n) ______.
bacterial strain that was previously susceptible to an antibiotic becomes resistant to it
A virus that infects bacteria is called a(n)
bacteriophage, phage, bacteriophages, or phages
What is the F factor that is found in F+ donor strains of E. coli?
A small circular segment of DNA that is separate from the circular chromosome.
Arrange the steps that occur during transformation in the correct order, putting the first step at the top.
1) A DNA fragment binds to a cell surface receptor on a competent bacterium. 2) An extracellular endonuclease cuts the DNA into smaller fragments. 3) One strand of DNA is degraded, and a single strand is transported into the cell. 4) The DNA strand aligns itself with a homologous region of the bacterial chromosome. 5) The DNA strand is incorporated into the bacterial chromosome via homologous recombination. 6) The heteroduplex DNA is repaired, changing the genotype of the recipient cell.
The functions of competence factors include ______.
1) Allowing DNA fragments to bind to the surface of a bacterial cell. 2) Aiding the uptake of DNA into the cytoplasm of a bacterial cell. 3) Incorporating DNA into the bacterial chromosome.
Place the events that occur during conjugation in the correct order.
1) Pili from F+ cell make contact with an F- cell. 2) A conjugation bridge forms between the two cells. 3) The F factor DNA is cut. 4) Single-stranded DNA and the relaxes protein form a nucleoprotein. 5) The nucleoprotein passes through the exporter complex. 6) Relaxase joins the ends of the donated DNA together to form a circular molecule.
Arrange the steps involved in conjugation between an Hfr strain and an F— strain in the correct order starting at the top.
1) The Hfr chromosome is nicked at the origin of transfer. 2) One strand of DNA from the Hfr chromosome begins to enter the F- cell. 3) DNA from the Hfr chromosome recombines with the homologous region of the recipient cell's chromosome.
How long does it take for an entire Hfr chromosome to be transferred from an Hfr strain to an F- cell?
1.5 to 2 hours
What is a plasmid?
A DNA molecule that can exist independently of the bacterial chromosome.
What is a competent cell?
A bacterial cell that can take up foreign DNA
What is an episome?
A plasmid that can integrate into a chromosome.
What is a heteroduplex?
A region of DNA containing one or more mismatches that must be repaired
Fertility Plasmid
Allows conjugation
What happens during the lytic cycle?
An infected bacterial cell synthesizes new bacteriophages and then bursts, releasing the phages.
A bacterial strain that cannot synthesize a particular nutrient and therefore requires that nutrient to be included in its growth medium is called a(n)
Auxotroph
Virulence Plasmid
Carries genes that turn a bacterium into a pathogenic strain
What is the shape of the majority of plasmids?
Circular
Bacteria that can take up DNA from the environment carry genes encoding proteins that aid DNA binding to the cell surface, uptake of DNA into the cytoplasm, and incorporation of foreign DNA into the bacterial chromosome. These proteins are called _____ factors.
Comepetence
A bacterial cell that is able to take up foreign DNA from its environment is called a(n) ________ cell.
Competent Cell
Exporter
Complex of proteins that spans the membranes of the donor cell.
Resistance Plasmid
Confers resistance against antibiotics and other toxins
F factors carry genes that are necessary for the process of_____
Conjugation
The genes that are carried on F factors are required for ______.
Conjugation
Which type of genetic transfer requires direct physical contact between two living bacterial cells?
Conjugation
The passageway for DNA transfer between a donor cell and a recipient cell is called a conjugation
Conjugation Bridge.
Pilus
Contacts the recipient cell and draws the donor and recipient cell together.
Col-Plasmid
Contains genes encoding proteins that kill other bacterial cells
Degradative Plasmid
Enables bacteria to digest unusal substance
Relaxase
Enzyme that rejoins the ends of the transferred DNA to form a circular molecule.
A plasmid that can integrate into a chromosome is called a(n)
Episome
What is contained in a minimal medium?
Essential nutrients - A minimal medium is a growth medium that contains the essential nutrients for a wild-type (non-mutant) bacterial species to grow.
In addition to their circular chromosome, strains of E. coli that can act as donors during conjugation contain a small circular segment of DNA called a(n) factor.
F factor or fertlity factor
A strain of E. coli that contains an F factor and can act as a conjugation donor is designated ____________, and a strain that lacks the F factor may be a recipient and is designated ______
F+ & F-
True or false: An entire Hfr chromosome may be transferred to a recipient cell if conjugation is allowed to proceed for at least 30 minutes.
False
True or false: Transformation, the uptake of foreign DNA by bacterial cells, does not occur in nature, but it is possible in genetically engineered bacterial strains.
False -Transformation is a natural process that has evolved in some species of bacteria.
True or false: Most plasmids are linear.
False. -There are very fresh plasmids which are linear, most are circular.
F factor
Found in a bacterial strain capable of conjugation.
Degradative Plasmids
Found in a bacterial strain that can digest organic solvents such as toluene.
Virulenece Plasmid
Found in a bacterial strain that causes disease.
R factor
Found in a bacterial strain that is resistant to an antibiotic.
Col-plasmid
Found in bacterial strain that kills other types of bacteria.
In an interrupted mating experiment, what genes will be transferred to the recipient cell first?
Genes that are close to the origin of transfer
Any process in which one bacterium transfers genetic material to another bacterium is called ______.
Genetic Transfer
What is the structure of a bacteriophage?
Genetic material surrounded by a protein coat
What is nonhomologous recombination?
Incorporation of a DNA fragment at a random chromosomal location
What event leads to the formation of an Hfr strain?
Integration of an F factor into a bacterial chromosome
What is the significance of a plasmid's origin of replication?
It allows the plasmid to be copied separately from the bacterial chromosome.
What are the functions of the relaxosome in conjugation?
It recognizes the origin of transfer in the F factor & It separates the two strands of the F factor.
What determines the starting point and direction of DNA transfer during conjugation involving an Hfr strain?
The origin of transfer of the integrated F factor
What DNA sequence in the F factor is recognized and cut to begin the process of conjugation?
The origin of transfer. -This is the place where DNA replication begins, rather than the site that is cut for DNA transfer.
What is horizontal gene transfer?
Transfer of DNA to a recipient that is not the offspring of the donor organism
An Hfr bacterial strain is very efficient at ______.
Transferring genes from is chromosome to F- strains.
Which of the following statements about transformation is correct?
Transformation is a natural process that has evolved in some species of bacteria.
True or false: Bacteriophages contain their own genetic material, which governs the traits of the phage.
True
The phenomenon in which a bacterial strain that is susceptible to a specific antibiotic becomes resistant to that antibiotic is called ______ antibiotic resistance
acquired
A scientist conducting an interrupted mating experiment can increase the amount of the Hfr chromosome that is transferred by ______.
allowing conjugation to proceed for a longer period of time
A Streptococcus pneumoniae cell may begin to express competence proteins if a nearby cell secretes the _________ - _________ peptide.
competence -stumulating
Which of the following mechanisms of genetic transfer utilizes a physical connection between two bacteria?
conjugation
A bacterial strain that is a leucine prototroph is a strain that ______.
does not require leucine in its growth medium.
During transformation, a DNA fragment that has bound to a cell surface receptor is cut into smaller fragments by an extracellular _______. After the DNA has been taken up by the cell, it is incorporated into the bacterial chromosome by homologous
endonuclease & recombination
Wollman and Jacob used a blender to separate bacterial cells in the act of conjugation without killing the cells. Their technique is called _______ mating
interrupted mating
In a conjugation experiment between between the two cells shown here, transfer of both the leu+ and thr+ genes could be monitored by growing the recipient cells on media ______.
lacking both leucine and threonine -Because the recipient cells lacked genes to make leucine and threonine, they would have to be grown on media that lacked these amino acids to demonstrate the gene transfer occurred.
In a bacterial conjugation experiment, the unit used for genetic mapping is the ______.
minute
The linear order of genes on a bacterial chromosome can be deduced based on the _____ it takes for different genes to be transferred to a recipient strain by conjugation.
time
If conjugation occurs between these two cells, transfer of the strs and azis genes from the Hfr to the F- cell would be confirmed if the cells were ______.
unable to grow in the presence of either streptomycin or azide
