Question 1

Further tests indicate that your patient has a methicillin-resistant Staphylococcus aureus (MRSA)  infection. You explain to the patient that these bacteria are not impacted by penicillin or the related drug methicillin. This resistance is thought to have arisen originally by a random change in the cell's chromosome through a process called

Accepted Answer

A)   spontaneous mutation.
B)   antigenic variation.
C)   quorum sensing.
D)   vertical gene transfer.
E)   indirect selection.

Question 2

The source of variation among microorganisms that were once identical is

Accepted Answer

A)   antibiotic resistance.
B)   virulence factors.
C)   mutation.
D)   sigma factors.
E)   mutant.

Question 3

Your patient asks why the penicillin he has been taking hasn't helped his infection. Which of the following is a possible explanation for your patient?

Accepted Answer

A)   The patient has become resistant to penicillin and he needs to take a different medication.
B)   The bacteria causing the infection are resistant to penicillin; a different antibiotic is needed.
C)   Bacteria are never killed by a single type of antibiotic; combinations of drugs are needed.
D)   Penicillin has been overused by people and it no longer works against any bacteria; it can be used against viruses.
E)   The patient's body is neutralizing the antibiotic; he needs to take a probiotic to help the penicillin work.

Question 4

You make two agar plates: one is a nutrient agar plate (plate A)  that contains histidine and penicillin. The other is a glucose salts agar (plate B)  that also contains penicillin. You inoculate a sample onto both plates using replica plating technique, incubate the plates, and compare the growth after 48 hours. There are 12 colonies on the nutrient agar plate and 11 colonies on the glucose salts medium. Which of the following statements is INCORRECT?

Accepted Answer

A)   The colony that is missing from plate B is an auxotroph that cannot synthesize histidine.
B)   The prototrophs are resistant to penicillin but the auxotrophs are sensitive to this antibiotic.
C)   Prototrophs and auxotrophs in this experiment are resistant to penicillin.

Question 5

In conjugation the donor cell is recognized by the presence of

Accepted Answer

A)   an F plasmid.
B)   a Y chromosome.
C)   diploid chromosomes.
D)   an SOS response.
E)   an F plasmid AND diploid chromosomes.

Question 6

On further reading, you learn that strains of H. influenzae vary genotypically. Many of them have silent mutations. Select the TRUE statement regarding this type of mutation.

Accepted Answer

A)   It is a point mutation-a single base pair is altered, causing the change of one amino acid in the protein that changes the function of that protein.
B)   It is a point mutation-a single base pair is altered, causing the change of one amino acid in the protein that stops the correct formation of a protein.
C)   It is a point mutation-a single base pair is altered, causing the change of one amino acid in the protein that does not affect the function of that protein.
D)   It is a frameshift mutation-base pairs are added or deleted, causing the change of one or more amino acids in the protein but does not affect the function of that protein.
E)   It is a point mutation-several base pairs are altered, causing the change of many amino acids in the protein that completely changes the function of that protein.

Question 7

Your patient asks whether there is any way for him to get rid of this infection. You tell him that he will be given a different antibiotic such as doxycycline. This antibiotic works by binding to a cell structure called the 30S ribosomal subunit, which stops the bacterial cells from growing by

Accepted Answer

A)   preventing DNA replication.
B)   inhibiting transcription.
C)   stopping capsule formation.
D)   inhibiting protein synthesis.
E)   preventing protein packaging.

Question 8

The transfer of vancomycin resistance from Enterococcus faecalis to Staphylococcus aureus is thought to have involved

Accepted Answer

A)   conjugation AND transformation.
B)   conjugation AND transposons.
C)   transformation AND transduction.
D)   transduction AND transposons.
E)   transformation AND transposons.

Question 9

Irradiation of cells with ultraviolet light may cause

Accepted Answer

A)   four nucleotides to covalently bind together.
B)   thymine dimers.
C)   adenine complementary base pairing with cytosine.
D)   the addition of uracil.
E)   cytosine trimers.

Question 10

A clever technique that streamlines the identification of auxotrophic mutants is

Accepted Answer

A)   gas chromatography.
B)   replica plating.
C)   direct selection.
D)   reversion.
E)   intercalation.

Question 11

Segments of DNA capable of moving from one area in the DNA to another are called

Accepted Answer

A)   base analogs.
B)   intercalating agents.
C)   transposons.
D)   inverted repeats.
E)   mutagens.

Question 12

A quick microbiological test for potential carcinogens was developed by

Accepted Answer

A)   Fleming.
B)   Lederberg.
C)   Ames.
D)   Crick.
E)   McClintock. C

Question 13

The designation his- refers to

Accepted Answer

A)   the genotype of bacteria that lack a functional gene for histidine synthesis AND bacteria that are auxotrophic for histidine.
B)   the genotype of bacteria that have a functional gene for histidine synthesis AND bacteria that require addition of histidine to the growth medium.
C)   the genotype of bacteria that have a functional gene for histidine synthesis AND bacteria that are auxotrophic for histidine.
D)   the genotype of bacteria that lack a functional gene for histidine synthesis AND bacteria that have a hers gene.
E)   the genotype of bacteria that lack a functional gene for histidine synthesis AND bacteria that do not require addition of histidine to the growth medium.

Question 14

Is it as effective to take two antibiotics sequentially for an infection as it is to take them simultaneously, as long as the total length of time of the treatment is the same?

Accepted Answer

A)   No. There's always one specific antibiotic that will be the most effective, and that is the only antibiotic that should be used to treat a particular infection.
B)   Yes. As long as the length of time is the same, the two treatments should be essentially the same in terms of effectively eliminating the infection.
C)   No. Taken sequentially, the first antibiotic will select for the small portion of the population that will spontaneously mutate toward resistance. Then, the second antibiotic will do the exact same thing-selecting for resistance to the second drug from the few bacterial cells that remained from the first drug treatment.
D)   It depends. Provided that the majority of the infectious agent is killed off by the first drug, the likelihood that the few that are left would not also be killed by the second drug is low. However, simultaneous treatment should be more effective at eliminating all the microbes in the shortest time possible, and with the least probability of selection for multiple drug resistance mutations.
E)   Yes. Each antibiotic will kill all the cells that are sensitive to it, no matter if the drugs are taken simultaneously or sequentially. The important thing is to take the medication for as few days as possible. D

Question 15

H. influenzae has genes that it needs to make pili for attachment to host cells. These pili genes are not always expressed; sometimes the bacterium turns them off and does not produce pili. This is an example of

Accepted Answer

A)   phase variation.
B)   antigenic sensing.
C)   two-component control.
D)   transduction.
E)   gene splicing.

Question 16

Plasmids often carry the information for antibiotic resistance.

Accepted Answer

A) True 
 B)False

Question 17

You mix two bacterial stains in a tube of glucose-salts agar. One strain is His−, Val−, while the other strain is Trp−, Leu−. You previously showed that neither strain grows on glucose-salts agar. After incubating the tube, you plate a sample onto a new glucose-salts agar plate. Several colonies grow. What do you know is TRUE about these colonies?

Accepted Answer

A)   The bacteria in the colonies are His−, Val−, Trp+, Leu+.
B)   The bacteria in the colonies are His−, Val+, Trp+, Leu+.
C)   The bacteria in the colonies are His−, Val−, Trp−, Leu−.
D)   The bacteria in the colonies are His+, Val+, Trp+, Leu+.
E)   The bacteria in the colonies are His+, Val+, Trp+, Leu+, PenR.

Question 18

The F plasmid carries the information for

Accepted Answer

A)   the sex pilus.
B)   recipient cell DNA replication.
C)   antibiotic resistance.
D)   the Y chromosome.
E)   bacterial flagella. A

Question 19

Double-stranded DNA enters the recipient cell during transformation.

Accepted Answer

A) True 
 B)False

Question 20

Some bacteria have a higher incidence rate of thymine dimer mutations following exposure to UV light than others. What might be going on here to lead to this outcome?

Accepted Answer

A)   They may simply have a higher proportion of T nucleotides next to each other in their DNA sequences than other bacteria, leading to more possible dimers being formed.
B)   They may simply have a higher proportion of T nucleotides next to each other in their DNA sequences than other bacteria, leading to more possible dimers being formed AND they may have a stronger expression of photoreactivation enzymes, leading to formation of more thymine dimers.
C)   They may simply have a higher proportion of T nucleotides next to each other in their DNA than other bacteria, leading to more possible dimers being formed AND they may have a weaker expression of photoreactivation enzymes, leading to formation of more thymine dimers.
D)   They may have a stronger expression of photoreactivation enzymes, leading to more thymine dimers being formed and retained.
E)   They may have a weaker expression of photoreactivation enzymes, leading to more thymine dimers being formed and retained.

Exam 8: Bacterial Genetics

Correct Answer
verified

The source of variation among microorganisms that were once identical is

Correct Answer
verified

Your patient asks why the penicillin he has been taking hasn't helped his infection. Which of the following is a possible explanation for your patient?

Correct Answer
verified

Correct Answer
verified

In conjugation the donor cell is recognized by the presence of

Correct Answer
verified

On further reading, you learn that strains of H. influenzae vary genotypically. Many of them have silent mutations. Select the TRUE statement regarding this type of mutation.

Correct Answer
verified

Your patient asks whether there is any way for him to get rid of this infection. You tell him that he will be given a different antibiotic such as doxycycline. This antibiotic works by binding to a cell structure called the 30S ribosomal subunit, which stops the bacterial cells from growing by

Correct Answer
verified

The transfer of vancomycin resistance from Enterococcus faecalis to Staphylococcus aureus is thought to have involved

Correct Answer
verified

Irradiation of cells with ultraviolet light may cause

Correct Answer
verified

A clever technique that streamlines the identification of auxotrophic mutants is

Correct Answer
verified

Segments of DNA capable of moving from one area in the DNA to another are called

Correct Answer
verified

A quick microbiological test for potential carcinogens was developed by

Correct Answer
verified
C

The designation his- refers to

Correct Answer
verified

Is it as effective to take two antibiotics sequentially for an infection as it is to take them simultaneously, as long as the total length of time of the treatment is the same?

Correct Answer
verified
D

H. influenzae has genes that it needs to make pili for attachment to host cells. These pili genes are not always expressed; sometimes the bacterium turns them off and does not produce pili. This is an example of

Correct Answer
verified

Plasmids often carry the information for antibiotic resistance.

Correct Answer
verified

Correct Answer
verified

The F plasmid carries the information for

Correct Answer
verified
A

Double-stranded DNA enters the recipient cell during transformation.

Correct Answer
verified

Some bacteria have a higher incidence rate of thymine dimer mutations following exposure to UV light than others. What might be going on here to lead to this outcome?

Correct Answer
verified

Exam 8: Bacterial Genetics

Correct AnswerverifiedShow Answer

The source of variation among microorganisms that were once identical is

Correct AnswerverifiedShow Answer

Your patient asks why the penicillin he has been taking hasn't helped his infection. Which of the following is a possible explanation for your patient?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

In conjugation the donor cell is recognized by the presence of

Correct AnswerverifiedShow Answer

On further reading, you learn that strains of H. influenzae vary genotypically. Many of them have silent mutations. Select the TRUE statement regarding this type of mutation.

Correct AnswerverifiedShow Answer

Your patient asks whether there is any way for him to get rid of this infection. You tell him that he will be given a different antibiotic such as doxycycline. This antibiotic works by binding to a cell structure called the 30S ribosomal subunit, which stops the bacterial cells from growing by

Correct AnswerverifiedShow Answer

The transfer of vancomycin resistance from Enterococcus faecalis to Staphylococcus aureus is thought to have involved

Correct AnswerverifiedShow Answer

Irradiation of cells with ultraviolet light may cause

Correct AnswerverifiedShow Answer

A clever technique that streamlines the identification of auxotrophic mutants is

Correct AnswerverifiedShow Answer

Segments of DNA capable of moving from one area in the DNA to another are called

Correct AnswerverifiedShow Answer

A quick microbiological test for potential carcinogens was developed by

Correct AnswerverifiedC

The designation his- refers to

Correct AnswerverifiedShow Answer

Is it as effective to take two antibiotics sequentially for an infection as it is to take them simultaneously, as long as the total length of time of the treatment is the same?

Correct AnswerverifiedD

H. influenzae has genes that it needs to make pili for attachment to host cells. These pili genes are not always expressed; sometimes the bacterium turns them off and does not produce pili. This is an example of

Correct AnswerverifiedShow Answer

Plasmids often carry the information for antibiotic resistance.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

The F plasmid carries the information for

Correct AnswerverifiedA

Double-stranded DNA enters the recipient cell during transformation.

Correct AnswerverifiedShow Answer

Some bacteria have a higher incidence rate of thymine dimer mutations following exposure to UV light than others. What might be going on here to lead to this outcome?

Correct AnswerverifiedShow Answer

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C

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D

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A

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