Question 1

Direct selection involves inoculating cells onto growth media on/in which

Accepted Answer

A)  the mutant but not the parental cell type will grow. 
B)  the mutation will be reversed. 
C)  the nutrients necessary for mutation to occur are present. 
D)  the mutagen is present. 
E)  histidine has been added.

Question 2

The characteristics displayed by an organism in any given environment is its

Accepted Answer

A)  archaetype. 
B)  phenotype. 
C)  genotype. 
D)  mutatotype. 
E)  phenogene.

Question 3

A quick microbiological test for potential carcinogens was developed by

Accepted Answer

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

Question 4

F plasmids and oftentimes R plasmids are both able to code for production of a pilus.

Accepted Answer

A) True 
 B)False

Question 5

A patient comes to see you complaining of a spider bite. He shows you a sore on his wrist—the area around it is red and swollen, and the lesion is leaking pus. The patient tells you he found a spider in his car, which is why he thinks this is a bite. He also tells you that he has been taking penicillin tablets that his wife had left over after being prescribed the drug a few months previously for pneumonia. Even though he has taken the tablets for four days, the lesion is not healing and that he is really feeling terrible, with pain, fever, and chills. You suspect that your patient has a wound infection, so you sample the pus and send it to the lab for analysis.
-You explain to your patient that there has been an increase in the number of strains of S. aureus that are now resistant to methicillin. The gene conferring resistance has moved from one strain to another via mobile gene elements, an example of which is a(n) ________.

Accepted Answer

A)  bacteriovirus 
B)  insertional divider 
C)  histone 
D)  transposon 
E)  chromosome

Question 6

The clustered, regularly interspaced short palindromic repeats (CRISPR) system in bacterial cells has been called the "immune" system of bacteria. CRISPR protect bacteria from a repeat infection from the same phage because bacterial cells

Accepted Answer

A)  recognize proteins on the surface of the phage and secrete enzymes that digest the phage. 
B)  recognize proteins on the surface of the phage and secrete proteins that block the binding of the phage. 
C)  integrate fragments from the phage DNA in their own chromosomes and target for destruction any DNA that contains the same fragments in the future. 
D)  modify the attachment sites for the phages so that new infections cannot take place. 
E)  integrate fragments from the phage RNA in their own chromosomes and target for destruction any RNA that contains the same fragments in the future.

Question 7

Which is NOT True about mismatch repair?

Accepted Answer

A)  It uses an endonuclease. 
B)  It requires DNA polymerase and DNA ligase. 
C)  It uses methylation of the DNA to differentiate between strands. 
D)  It removes both strands in the mismatch area. 
E)  It fixes errors missed by the proofreading of DNA polymerase.

Question 8

Colonies of the bacterium Serratia marcescens are red when incubated at 22°C but white when incubated at 37°C. This is an example of

Accepted Answer

A)  antigenic variation. 
B)  genotypic change. 
C)  phenotypic change. 
D)  mutation. 
E)  selective media.

Question 9

Thymine dimers are removed by

Accepted Answer

A)  no repair mechanisms. 
B)  SOS repair AND photoreactivation repair. 
C)  SOS repair AND excision repair. 
D)  photoreactivation repair AND excision repair. 
E)  SOS repair, photoreactivation repair AND excision repair.

Question 10

Planar molecules used as chemical mutagens are called

Accepted Answer

A)  intercalating agents. 
B)  nitrous oxide. 
C)  base analogs. 
D)  alkylating agents. 
E)  acids.

Question 11

Which of the following about transposons is NOT True?

Accepted Answer

A)  They are informally known as jumping genes. 
B)  They may cause insertion mutations. 
C)  They may cause knockout mutations. 
D)  They were first recognized in fungi. 
E)  All of the statements are True.

Question 12

Gene transfer that requires cell-to-cell contact is

Accepted Answer

A)  transformation. 
B)  competency. 
C)  conjugation. 
D)  functional genomics. 
E)  transduction.

Question 13

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.

Question 14

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.

Question 15

The restriction-modification system always has two genes involved, the cutting enzyme and the methylating enzyme.

Accepted Answer

A) True 
 B)False

Question 16

X-rays

Accepted Answer

A)  have no effect on DNA. 
B)  cause thymine trimers. 
C)  cause breaks in DNA molecules. 
D)  make the DNA radioactive. 
E)  destroy lipopolysaccharide.

Question 17

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 18

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 19

The properties of a cell that are determined by its DNA composition are its

Accepted Answer

A)  phenotype. 
B)  genotype. 
C)  metabolism. 
D)  nucleoid. 
E)  plasmids.

Question 20

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)  that contains histidine and penicillin. The other is a glucose salts agar (plate 
C)  The prototrophs are resistant to penicillin but the auxotrophs are sensitive to this antibiotic. 
D)  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? 
E)  Prototrophs and auxotrophs in this experiment are resistant to penicillin.

Exam 8: Bacterial Genetics