genetics ch.9

A strain of E. coli that frequently transfers chromosomal genes to recipient bacterial cells is designated a(n) Hfr strain. F+ strain. (An HFR strain is formed when a plasmid recombines with the cells chromosome.) virulent strain. F- strain.

Hfr strain.

What event is required for genes on an Hfr chromosome to be transferred onto the recipient cell's chromosome? Infection with a bacteriophage Homologous recombination DNA replication (While replication occurs to restore double-stranded DNA structure, recombination is required to integrate genes into the chromosome of the recipient cell.) Lysis of the recipient cell

Homologous recombination

A scientist mapping two genes isolated 25 colonies that survived the selection conditions for the first gene. After these 25 colonies were restreaked and exposed to the second selection condition, there were 10 colonies remaining. What is the cotransduction frequency for these two genes? 0.10 0.25 (What is the percentage of 10 colonies that meet both conditions out of 25 colonies that only meet the first selection condition?) 0.40 0.025

0.40

If two genes are cotransduced with a frequency of 0.20 and the total length of DNA carried by the P1 phage is 2 minutes, then the distance between the two genes is equal to 10 minutes. 0.08 minutes. 0.84 minutes. 0.4 minutes. (Cotransduction frequency = (1 - d/L)3 where d = distance between 2 genes in minutes; L =size of chromosomal pieces (in min.) that the phage carries during transduction.)

0.84 minutes.

How long does it take for an entire Hfr chromosome to be transferred from an Hfr strain to an F- cell? 10 to 12 hours 10 to 15 minutes 1.5 to 2 hours 4 to 6 hours

1.5 to 2 hours

A scientist conducts an interrupted conjugation experiment and finds that the argR gene transfers at 10 minutes, and the thrA gene transfers at 40 minutes. What is the distance between these two genes? 30 minutes 10 minutes 40 minutes 15 minutes 50 minutes

30 minutes

*Figure 9.9 Time course of an interrupted E. coli conjugation experiment.* Based on the data in the graph, what is the distance between the lacZ and galE genes on the bacterial chromosome? 9 minutes 50 minutes 25 minutes 16 minutes

9 minutes

Arrange the events that occur during transduction in the correct order. A phage infects a bacterial cell New phages are assembled; some of them carry a fragment of the host cell's chromosome The transduced DNA is recombined into the chromosome of the new recipient cell The transducing phage injects its DNA into a new recipient cell The host cell's DNA is digestd into fragments

A phage infects a bacterial cell The host cell's DNA is digestd into fragments New phages are assembled; some of them carry a fragment of the host cell's chromosome The transducing phage injects its DNA into a new recipient cell The transduced DNA is recombined into the chromosome of the new recipient cell

What is a bacteriophage? Multiple choice question. A type of growth medium for bacterial cells A virus that infects bacteria A bacterial cell that can take up foreign DNA from its environment A dead bacterial cell

A virus that infects bacteria

What is an F' factor? An F factor that contains genes conferring resistance to antibiotics An F factor that contains genes encoding proteins that kill other bacteria An F factor that carries portions of a bacterial chromosome

An F factor that carries portions of a bacterial chromosome

What happens during the lytic cycle? An infected bacterial cell synthesizes new bacteriophages and then bursts, releasing the phages. The genetic material of a bacteriophage becomes integrated into the chromosome of an infected bacterial cell. The F factor is excised from a bacterial chromosome and transferred to a recipient cell, along with some bacterial genes.

An infected bacterial cell synthesizes new bacteriophages and then bursts, releasing the phages.

How are F' factors produced? By excision of an F factor from a bacterial chromosome By integration of an F factor into the bacterial chromosome (An Hfr strain is formed when a plasmid recombines with the cells chromosome. The imprecise excision of the F factor from a bacterial chromosome results in production of an F' factor.) By the transfer of viral DNA into a bacterial cell By conjugation with a strain carrying the F factor

By excision of an F factor from a bacterial chromosome

How is conjugation stopped during an interrupted mating experiment? By exposing the bacterial cells to chemicals that damage DNA By using a blender to separate the bacterial cells By suddenly changing the temperature at which the cells are growing By exposing the bacterial cells to bacteriophages

By using a blender to separate the bacterial cells

If a scientist wishes to determine the order and distance of genes that are far away from one another on the bacterial chromosome, what method should be used? Transduction (Conjugation is used to determine the relative order and distance of genes, particularly those that are far apart. Transduction experiments can provide fairly accurate mapping data for genes that are relatively close together.) Conjugation Transformation

Conjugation

In an interrupted mating experiment, what genes will be transferred to the recipient cell first? Genes that are essential for survival Genes that are small Genes that are close to the origin of transfer Genes that have homologs in the recipient cell

Genes that are close to the origin of transfer

DNA from the bacterial chromosome may be transferred from one cell to another if a(n) ____cell conjugates with an F— cell.

Hfr

It takes about 90-120 minutes for the entire ___ chromosome to pass into the F- cell.

Hfr

When an F factor integrates into a bacterial chromosome, the bacterial cell becomes a(n) bacteriophage. Hfr strain. F- strain. virulent strain.

Hfr strain.

What is the procedure followed in a cotransduction experiment? Infect donor and recipient cells separately with the same type of phage. Mix donor and recipient cells together, then infect them with phage at the same time. Infect donor cells first, then collect phage lysate to infect recipient cells.

Infect donor cells first, then collect phage lysate to infect recipient cells.

What event leads to the formation of an Hfr strain? Exposure to high temperatures Infection of a bacterial cell with a bacteriophage Integration of an F factor into a bacterial chromosome Uptake of foreign DNA from dead bacterial cells

Integration of an F factor into a bacterial chromosome

What is released at the end of the lytic cycle, when a bacterial lyses? New plasmid DNA The ribosomes from the bacterial cell New phages New bacterial cells

New phages

Arrange the steps involved in conjugation between an Hfr strain and an F— strain in the correct order starting at the top. The Hfr chromosome is nicked at the origin of transfer One strand of DNA from the Hfr chromosome begns to enter the F- cell DNA from the Hfr chromosome recombines with the homologous region of the recipient cell's chromosome

The Hfr chromosome is nicked at the origin of transfer One strand of DNA from the Hfr chromosome begns to enter the F- cell DNA from the Hfr chromosome recombines with the homologous region of the recipient cell's chromosome

What determines the starting point and direction of DNA transfer during conjugation involving an Hfr strain? The origin of replication of an excised F' factor The origin of transfer of the integrated F factor The origin of replication of the bacterial chromosome (these are determined by properties of the F factor.)

The origin of transfer of the integrated F factor

*Figure 9.5 Integration of an F factor to form an Hfr cell and its subsequent excision to form an F′ factor.* If these two cells undergo conjugation, but only for a short period of time, what is the likely outcome? The recipient cell will be able to metabolize lactose. The recipient cell will be able to synthesize proline. The entire genome is transferred. The entire plasmid is transferred.

The recipient cell will be able to metabolize lactose.

What is cotransduction? The packaging of bacterial DNA and phage DNA into the same bacteriophage Homologous recombination between the bacterial chromosome and the genetic material of a bacteriophage The transfer of two genes that are close to one another to a new cell via a bacteriophage

The transfer of two genes that are close to one another to a new cell via a bacteriophage

Both conjugation and transduction experiments can be used to map bacterial genes. Which method is more useful for mapping genes that are relatively close together on the bacterial chromosome? Transduction Conjugation (Conjugation is used to determine the relative order and distance of genes, particularly those that are far apart. Transduction experiments can provide fairly accurate mapping data for genes that are relatively close together.)

Transduction

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 When an F+ strain conjugates with an F- strain (An Hfr strain is formed when a plasmid recombines with the cells chromosome.) When two Hfr strains conjugate with one another When two F- strains conjugate with one another

When an Hfr strain conjugates with an F- strain

A virus that infects bacteria is called a(n) ___

bacteriophage

The lytic cycle results in the production and release of new ____

bacteriophage

In different Hfr strains, the origin of transfer is always at the same location on the chromosome and in the same orientation. can be at different locations on the chromosome and in different orientations. can be at different locations on the chromosome but is always in the same orientation. is always at the same location on the chromosome, but can be in different orientations. (In any particular HFR strain, the origin of transfer has a specific orientation that promotes either a counterclockwise or clockwise transfer of genes. However, among different HFR strains, the origin of transfer may be located in different regions of the chromosome.)

can be at different locations on the chromosome and in different orientations.

During transduction, new bacteriophages that include portions of the host cell's ____ are assembled and then infect new cells, resulting in gene transfer.

chromosome

The length of the Hfr chromosome that is transferred to a recipient cell during conjugation is directly related to the number of copies of the Hfr chromosome in the donor cell. size of the two bacterial cells involved in the conjugation. length of time allowed for conjugation to occur.

length of time allowed for conjugation to occur.

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 and recombine

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

During conjugation, the starting point and direction of DNA transfer are determined by a DNA sequence within the F factor called the ______. origin of replication (The origin of replication is where DNA replication, not the transfer of DNA, begins.) insertion sequence origin of transfer high frequency recombinant

origin of transfer

An Hfr bacterial strain is very efficient at producing new bacteriophages and releasing them into the environment. transferring genes from its chromosome to F— strains. taking up foreign DNA from the environment.

transferring genes from its chromosome to F— strains.

In a P1 cotransduction experiment, a researcher determines that two genes are cotransduced at a frequency of 0.90. If the phage being used in the experiment can hold 2 minutes of DNA, then what is the distance between the two genes? 2.2 minutes (Cotransduction frequency = (1 - d/L)3 where d = distance between 2 genes in minutes; L =size of chromosomal pieces (in min.) that the phage carries during transduction.) 0.45 minutes 0.07 minutes 1.8 minutes

0.07 minutes

In a cotransduction experiment, a scientist finds that of the 50 colonies that were selected for transduction of one gene, 15 of the colonies also carried the second gene. What is the cotransduction frequency of these two genes? 0.15 0.60 0.75 (Calculate the percentage of colonies carrying both genes.) 0.30

0.30

What is the formula that relates the cotransduction frequency of two genes to the distance between them? L represents the size of the chromosomal pieces carried by the phage, and d represents the distance between genes in minutes. Cotransduction frequency = (1 - d/L)3 Cotransduction frequency = (d X L)3 Cotransduction frequency = 1 - (L/d) Cotransduction frequency = (d/L)2

Cotransduction frequency = (1 - d/L)3

An F factor that has been excised from the bacterial chromosome and carries portions of the bacterial chromosome is called a(n) ___ factor.

F'

The imprecise excision of the F factor from a bacterial chromosome results in production of a(n) Hfr strain. episome. F' factor. F- strain. (An Hfr strain is formed when a plasmid recombines with the cell's chromosome. The imprecise excision of the F factor from a bacterial chromosome results in production of an F' factor.)

F' factor.

What pair of scientists carried out the first genetic mapping experiments in bacteria in the 1950s? Wollman and Jacob Watson and Crick Morgan and Bridges Beadle and Tatum

Wollman and Jacob

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. increasing the number of Hfr cells in the experiment. eliminating bacteriophages from the experiment.

allowing conjugation to proceed for a longer period of time.

Two genes are expected to have a high cotransduction frequency if they are present in multiple copies on the bacterial chromosome. (Two genes are expected to have a high cotransduction frequency if they are very close together. If they are far apart have a cotransduction frequency that is very low or close to zero.) close together on the bacterial chromosome. far away from one another on the bacterial chromosome.

close together on the bacterial chromosome.

If d represents the distance between two genes in minutes and L represents the size of chromosomal pieces carried by phage, then the formula (1 - d/L)3 is equal to the ____ frequency of the two genes.

cotransduction

The phenomenon in which a bacteriophage packages a single piece of the bacterial chromosome that carries two genes and then transfers those genes to another bacterium is called ____

cotransduction

When Hfr strains are compared to one another, the order in which genes are transferred to recipient strains is always the same, regardless of the location and orientation of the origin of transfer. depends on both the location and orientation of the origin of transfer. depends on the location of the origin of transfer, but not its orientation.

depends on both the location and orientation of the origin of transfer.

After conjugation, a recipient cell may have a new combination of alleles if ___ ____occurred between the transferred Hfr chromosome and the original chromosome of the bacterial cell.

homologous 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

*Figure 9.7 The use of conjugation to map the order of genes along the E. coli chromosome.* 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 lacking leucine, but containing threonine containing 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.) containing leucine, but lacking threonine

lacking both leucine and threonine

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

Elie Wollman and Francois Jacob are well known for discovering the molecular mechanism of recombination. discovering horizontal gene transfer among different strains of bacteria. mapping genes in bacteria. mapping the distance between two mutations in the same gene in bacteriophages. (The first genetic mapping experiments in bacteria were carried out by Elie Wollman and Francois Jacob.)

mapping genes in bacteria.

In a bacterial conjugation experiment, the unit used for genetic mapping is the base pair. kilodalton. nanometer. minute.

minute.

The unit of measure that is used for the distance between two genes on a bacterial chromosome is the ___

minutes

Cotransduction experiments can be used only to map genes that are relatively close together because phages can only package a portion of the bacterial chromosome. cotransduction requires homologous recombination. (The size of the transferred DNA is the limiting factor.) the interaction between a bacteriophage and its host cell usually lasts for only short period of time. (Recall that a bacteriophage can inject all of the DNA it carries in its short interaction with a host cell.)

phages can only package a portion of the bacterial chromosome.

Because bacteriophages can only package a small portion of the bacterial chromosome, cotransduction experiments can be used to map genes that are very far apart on the bacterial chromosome. on plasmids instead of on the bacterial chromosome. relatively close together on the bacterial chromosome.

relatively close together on the bacterial chromosome.

*Figure 9.5 Integration of an F factor to form an Hfr cell and its subsequent excision to form an F′ factor.* If conjugation occurs between the two cells shown in this figure, ______. both genes will be transferred at exactly the same time the pro+ gene will be transferred first the lac+ gene will be transferred first neither of the two genes will be transferred because they are chromosomal, and not plasmid, genes

the lac+ gene will be transferred first

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. their size relative to one another. whether they are advantageous for the recipient cell.

their order on the bacterial chromosome.

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 two genes are far apart on the bacterial chromosome, their cotransduction frequency is likely to be very low. unpredictable. very high. (Two genes are expected to have a high cotransduction frequency if they are very close together. If they are far apart have a cotransduction frequency that is very low or close to zero.)

very low.

A scientist infects a bacterial strain that is his+ trp+ with bacteriophage P1, then uses the P1 lysate to infect a strain that is his— trp—. To determine the cotransduction frequency of these two genes, the scientist should plate the recipient cells on growth medium that. lacks both histidine and tryptophan, then on complete medium. contains both histidine and tryptophan. lacks histidine first, then on medium that lacks tryptophan.

lacks histidine first, then on medium that lacks tryptophan.

*Figure 9.7 The use of conjugation to map the order of genes along the E. coli chromosome.* 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 ______. able to grow in the presence of streptomycin and azide (Because the recipient cells lacked resistance genes to azide or streptomycin, they would have to be grown on media that lacked these antibiotics to demonstrate the gene transfer occurred) able to grow in the presence of streptomycin, but not in the presence of azide unable to grow in the presence of either streptomycin or azide able to grow in the presence of azide, but not in the presence of streptomycin

unable to grow in the presence of either streptomycin or azide