Deck 8: Microbial Genetics

Question 1

Which of the following statements about bacteriocins is FALSE?

A) They can be used to identify certain bacteria.
B) The genes coding for them are on plasmids.
C) They cause food-poisoning symptoms.
D) Nisin is a bacteriocin used as a food preservative.
E) Bacteriocins kill bacteria.

Answer 1

C

Question 2

Transformation is the transfer of DNA from a donor to a recipient cell

A) by a bacteriophage.
B) by cell-to-cell contact.
C) as naked DNA in solution.
D) by sexual reproduction.
E) by crossing over.

Answer 2

C

Question 3

DNA is constructed of

A) a single strand of nucleotides with internal hydrogen bonding.
B) two strands of identical nucleotides in a parallel configuration with hydrogen bonds between them.
C) two complementary strands of nucleotides bonded A-C and G-T.
D) two strands of nucleotides running in an antiparallel configuration.
E) None of the answers is correct.

Answer 3

D

Question 4

Which of the following statements is FALSE?

A) DNA replication proceeds in only one direction around the bacterial chromosome.
B) The leading strand of DNA is made continuously.
C) The lagging strand of DNA is started by an RNA primer.
D) Multiple replication forks are possible on a bacterial chromosome.
E) DNA polymerase joins nucleotides in one direction (5ʹ to 3ʹ) only.

Question 5

A gene is best defined as

A) a sequence of nucleotides in DNA that codes for a functional product.
B) a sequence of nucleotides in RNA that codes for a functional product.
C) any random segment of DNA.
D) the RNA product of a transcribed section of DNA.
E) three nucleotides that code for an amino acid.

Question 6

Genetic change in bacteria can be brought about by

A) transformation.
B) conjugation.
C) transduction.
D) mutation.
E) All of the answers are correct.

Question 7

Table 8.2
Codon on mRNA and corresponding amino acid
$$\begin{array} { | l | l | l | l | } \hline \text { UUA } & \text { leucine } & \text { UAA } & \text { nonsense } \\\hline \text { GCA } & \text { alanine } & \text { AAU } & \text { asparagine } \\\hline \text { AAG } & \text { lysine } & \mathrm { UGC } & \text { cysteine } \\\hline \text { GUU } & \text { valine } & \mathrm { UCG } , \mathrm { UCU }& \text { serine } \\\hline\end{array}$$

-Refer to Table 8.2. What is the sequence of amino acids encoded by the following sequence of bases in a strand of DNA (pay attention to the polarity of the DNA here)? 3? ATTACGCTTTGC

A) Translation would stop at the first codon.
B) asparagine-arginine-lysine-alanine
C) asparagine-cysteine-valine-serine
D) leucine-arginine-lysine-alanine
E) The answer cannot be determined based on the information provided.

Question 8

Table 8.2
Codon on mRNA and corresponding amino acid
$$\begin{array} { | l | l | l | l | } \hline \text { UUA } & \text { leucine } & \text { UAA } & \text { nonsense } \\\hline \text { GCA } & \text { alanine } & \text { AAU } & \text { asparagine } \\\hline \text { AAG } & \text { lysine } & \mathrm { UGC } & \text { cysteine } \\\hline \text { GUU } & \text { valine } & \mathrm { UCG } , \mathrm { UCU }& \text { serine } \\\hline\end{array}$$

-Refer to Table 8.2. If an indeterminate frameshift mutation occurred in the sequence of bases shown below, what would be the sequence of amino acids coded for? 3? ATTACGCTTTGC

A) Translation would stop at the first codon.
B) leucine-arginine-lysine-alanine
C) asparagine-cysteine-valine-serine
D) asparagine-arginine-lysine-alanine
E) The answer cannot be determined based on the information provided.

Question 9

The initial effect of ionizing radiation on a cell is that it causes

A) DNA to break.
B) base substitutions.
C) the formation of highly reactive ions.
D) bonding between adjacent thymines.
E) the cells to get hot.

Question 10

Synthesis of a repressible enzyme is stopped by the

A) substrate binding to the repressor.
B) corepressor-repressor complex binding to the operator.
C) corepressor binding to the operator.
D) allosteric transition.
E) end product binding to the promoter.

Question 11

Which of the following is NOT a product of transcription?

A) rRNA
B) a new strand of DNA
C) tRNA
D) mRNA
E) None of the answers are correct; all of these are products of transcription.

Question 12

Figure 8.2

In Figure 8.2, if base 4 is thymine, what is base 4ʹ?

A) guanine
B) adenine
C) cytosine
D) thymine
E) uracil

Question 13

Table 8.2
Codon on mRNA and corresponding amino acid
$$\begin{array} { | l | l | l | l | } \hline \text { UUA } & \text { leucine } & \text { UAA } & \text { nonsense } \\\hline \text { GCA } & \text { alanine } & \text { AAU } & \text { asparagine } \\\hline \text { AAG } & \text { lysine } & \mathrm { UGC } & \text { cysteine } \\\hline \text { GUU } & \text { valine } & \mathrm { UCG } , \mathrm { UCU }& \text { serine } \\\hline\end{array}$$

-Refer to Table 8.2 The anticodon for valine is

A) CUU.
B) GUU.
C) GTA.
D) CTT.
E) CAA.

Question 14

Figure 8.2

In Figure 8.2, base 2 (and ONLY the base) is covalently bound/attached to

A) deoxyribose.
B) phosphate.
C) thymine.
D) ribose.
E) The answer cannot be determined based on the information provided.

Question 15

Figure 8.2

In Figure 8.2, if base 4 is thymine, what is base 11ʹ (remember the complimentary configuration of bases in DNA)?

A) guanine
B) thymine
C) adenine
D) uracil
E) cytosine

Question 16

Table 8.2
Codon on mRNA and corresponding amino acid
$$\begin{array} { | l | l | l | l | } \hline \text { UUA } & \text { leucine } & \text { UAA } & \text { nonsense } \\\hline \text { GCA } & \text { alanine } & \text { AAU } & \text { asparagine } \\\hline \text { AAG } & \text { lysine } & \mathrm { UGC } & \text { cysteine } \\\hline \text { GUU } & \text { valine } & \mathrm { UCG } , \mathrm { UCU }& \text { serine } \\\hline\end{array}$$

-Refer to Table 8.2. If the sequence of amino acids encoded by a strand of DNA is serine-alanine-lysine-leucine, what is the order of bases in the sense strand of DNA?

A) 3? AGACGTTTCAAT
B) 5? AGAGCTTTGAAT
C) 5? TGTGCTTTCTTA
D) 3? UGUGCAAAGUUA
E) 3? TCTCGTTTGTTA

Question 17

Which of the following statements regarding a bacterium that is R+ is FALSE?

A) It possesses a plasmid.
B) It is resistant to certain drugs and heavy metals.
C) R+ can be transferred to a cell of the same species.
D) R+ can be transferred to a different species.
E) It is F+.

Question 18

According to the operon model, for the synthesis of an inducible enzyme to occur, the

A) repressor must bind to the operator.
B) end-product must not be in excess.
C) substrate must bind to the enzyme.
D) repressor must not be synthesized.
E) substrate must bind to the repressor.

Question 19

Which of the following pairs is mismatched?

A) DNA gyrase - coils and twists DNA
B) transposase - insertion of DNA segments into DNA
C) DNA polymerase - makes a molecule of DNA from a DNA template
D) DNA ligase - joins segments of DNA
E) RNA polymerase - makes a molecule of RNA from an RNA template

Question 20

Figure 8.2

The damage caused by ultraviolet radiation is

A) never repaired.
B) repaired by DNA replication.
C) repaired during translation.
D) cut out and replaced.
E) repaired during transcription.

Question 21

Conjugation differs from reproduction because conjugation

A) transcribes DNA to RNA.
B) replicates DNA.
C) transfers DNA vertically, to new cells.
D) copies RNA to make DNA.
E) transfers DNA horizontally, to nearby cells without those cells undergoing replication.

Question 22

The necessary ingredients for DNA synthesis can be mixed together in a test tube. The DNA polymerase is from Thermus aquaticus, and the template is from a human cell. The DNA synthesized would be most similar to

A) human DNA.
B) human RNA.
C) T. aquaticus RNA.
D) T. aquaticus DNA.
E) a mixture of human and T. aquaticus DNA.

Question 23

Assume the two E.coli strains shown below are allowed to conjugate. Hfr: pro+, arg+, his+, lys+, met+, ampicillin-sensitive F-: pro-, arg-, his-, lys-, met-, ampicillin-resistant
What supplements would you add to glucose minimal salts agar to select for a recombinant cell that is lys+, arg+, amp-resistant?

A) ampicillin, proline, histidine, lysine
B) lysine, arginine
C) ampicillin, proline, histidine, methionine
D) proline, histidine, methionine
E) ampicillin, lysine, arginine

Question 24

The mechanism by which the presence of glucose inhibits the lac operon is

A) DNA polymerase.
B) repression.
C) catabolite repression.
D) translation.
E) induction.

Question 25

Figure 8.4 In Figure 8.4, the antibiotic chloramphenicol binds the 50S large subunit of a ribosome as shown (the light gray area is the large subunit, while the black shape is the drug). From this information you can conclude that chloramphenicol

A) prevents translation in eukaryotes.
B) prevents translation in prokaryotes.
C) prevents transcription in eukaryotes.
D) prevents mRNA-ribosome binding.
E) prevents transcription in prokaryotes.

Question 26

The cancer gene ras produces mRNA containing an extra exon that includes a number of UAA codons. Cancer cells produce ras mRNA missing this exon. This mistake most likely is due to a mistake by

A) photolyases.
B) a chemical mutagen.
C) DNA polymerase.
D) UV radiation.
E) snRNPs.

Question 27

Figure 8.3 - Metabolic Pathway
$$\begin{array} { c c } &\text { Gene } a & \text { Gene } b \\&\downarrow & \downarrow \\&\text { Enzyme A } & \text { Enzyme B } \\&\downarrow & \downarrow \\\text { Compound A } & \rightarrow &\text { Compound B } \rightarrow \text { Compound C }\end{array}$$

-In Figure 8.3, if compound C reacts with the allosteric site of enzyme A, this would exemplify

A) competitive inhibition.
B) transcription.
C) feedback inhibition.
D) a mutation.
E) repression.

Question 28

Figure 8.3 - Metabolic Pathway
$$\begin{array} { c c } &\text { Gene } a & \text { Gene } b \\&\downarrow & \downarrow \\&\text { Enzyme A } & \text { Enzyme B } \\&\downarrow & \downarrow \\\text { Compound A } & \rightarrow &\text { Compound B } \rightarrow \text { Compound C }\end{array}$$

-In Figure 8.3, if enzyme A is an inducible enzyme,

A) compound B would bind to enzyme A directly.
B) compound C would react with gene a directly.
C) compound C would bind to the repressor for Gene a.
D) compound A would react with enzyme B directly.
E) compound A would bind to the repressor for Gene a.

Question 29

The miRNAs in a cell

A) are responsible for inducing operons.
B) are a part of the eukaryotic ribosome.
C) allow different cells to produce different proteins.
D) are a part of the prokaryotic ribosome.
E) are found in prokaryotic cells.

Question 30

Figure 8.3 - Metabolic Pathway
$$\begin{array} { c c } &\text { Gene } a & \text { Gene } b \\&\downarrow & \downarrow \\&\text { Enzyme A } & \text { Enzyme B } \\&\downarrow & \downarrow \\\text { Compound A } & \rightarrow &\text { Compound B } \rightarrow \text { Compound C }\end{array}$$

-In Figure 8.3, if enzyme A is a repressible enzyme, compound C would

A) bind directly to gene a.
B) bind to the corepressor for Gene a.
C) bind to RNA polymerase.
D) bind to Enzyme A.
E) always be in excess.

Question 31

Open-reading frames are segments of DNA in which both start and stop codons are found.

Question 32

Figure 8.5 In Figure 8.5, which model of the lac operon correctly shows RNA polymerase, lactose, and repressor protein when the structural genes are being transcribed?

A) a
B) b
C) c
D) d
E) e

Question 33

Table 8.3 Amino Acids Encoded by the Human p53 Gene
Based on the information in Table 8.3, prostate cancer is probably the result of which kind of mutation?

A) frameshift
B) nonsense
C) analog
D) missense
E) None of the answers is correct.

Question 34

Repair of damaged DNA, in some instances and mechanisms, might be viewed as a race between an endonuclease and

A) methylase.
B) primase.
C) DNA ligase.
D) DNA polymerase.
E) helicase.

Question 35

Recombination will always alter a cellʹs genotype.

Question 36

An enzyme that catalyzes the cutting and resealing of DNA, and is translated from insertion sequences, is

A) RNA polymerase.
B) DNA ligase.
C) DNA helicase.
D) transposase.
E) DNA polymerase.

Question 37

An enzyme that copies DNA to make a molecule of RNA is

A) RNA polymerase.
B) DNA ligase.
C) DNA helicase.
D) transposase.
E) DNA polymerase.

Question 38

If you knew the sequence of nucleotides within a gene, which one of the following could you determine with the most accuracy?

A) the tertiary structure of the protein
B) the primary structure of the protein
C) the quaternary structure of the protein
D) the secondary structure of the protein
E) The answer cannot be determined based on the information provided.

Question 39

An enzyme that makes covalent bonds between the sugar of one nucleotide and the phosphate groups in another nucleotide in DNA is

A) RNA polymerase.
B) DNA ligase
C) DNA helicase.
D) transposase.
E) DNA polymerase.

Question 40

Protein synthesis in eukaryotes is similar to the process in prokaryotes in that both eukaryotes and prokaryotes

A) use methionine as the ʺstartʺ amino acid.
B) require snRNPS.
C) have introns.
D) use codons to determine polypeptide sequences.
E) have exons.

Question 41

Bacteria typically contain multiple chromosomes.

Question 42

Transposition (insertion of a transposon into a DNA sequence) results in the formation of base substitution mutations in a cellʹs DNA.

Question 43

Cell-to-cell contact is required for transduction to occur.

Question 44

In the Ames test, any colonies that form on the control should be the result of spontaneous mutations.

Question 45

Some cells may contain multiple genomes.

Question 46

Mutations that are harmful to cells occur more frequently than those that benefit cells.

Question 47

Both base substitution and frameshift mutations can result in the formation of premature stop codons.

Question 48

The miRNAs in a cell inhibit protein synthesis by forming complementary bonds with rRNA.