Deck 7: Microbial Genetics

Question 1

A wild-type organism and a genetic variant both have a gene encoding a receptor producing a chemotactic response to metabolite A. The genetic variant has a mutation in a regulatory gene for expression of the receptor. Which of the following statements with respect to the receptor is CORRECT?

A) The organisms have the same receptor genotype but different phenotypes.
B) The organisms have different genetic sequences for the receptor.
C) The phenotypes of both organisms are the same, but the genotypes differ.
D) The genotypes and phenotypes of both organisms are the same.
E) The answer cannot be determined from the information provided.

Answer 1

A

Question 2

Typical eukaryotic genomes are composed of DNA molecule(s).

A) a single circular
B) a single linear
C) multiple circular
D) multiple linear
E) both linear and circular

Answer 2

D

Question 3

Which of the following is found at the 5ʹ end of a DNA strand?

A) a phosphate group
B) a hydroxyl group
C) histones
D) a hydrogen bond
E) a methyl group

Answer 3

A

Question 4

During elongation a charged tRNA first enters the ribosomal site and then moves into the site.

A) A; P
B) P; A
C) P; E
D) A; E
E) E; A

Question 5

Which of the following processes is involved in the ʺcentral dogmaʺ of genetics?

A) transcription only
B) DNA replication and translation
C) translation only
D) transcription and translation
E) DNA replication only

Question 6

Which of the following is involved in translation?

A) tRNA only
B) mRNA only
C) rRNA only
D) both mRNA and tRNA
E) mRNA, rRNA, and tRNA are all involved.

Question 7

A codon is a particular combination of three nucleotides. Therefore, there are possible combinations of the nucleotides A, C, G, and T.

A) 16
B) 32
C) 12
D) 4
E) 64

Question 8

Which of the following types of plasmids facilitates the transfer of genetic material among bacteria?

A) bacteriocin plasmids
B) resistance plasmids
C) fertility plasmids
D) cryptic plasmids
E) virulence plasmids

Question 9

Semiconservative DNA replication means that

A) the cell can proofread its newly synthesized DNA only part of the time.
B) each daughter DNA molecule is composed of one original strand and one new strand.
C) nucleotides are constantly being recycled as cells make DNA.
D) each strand of a double-stranded DNA molecule is replicated differently.
E) the sequence of a DNA molecule is preserved as it is being replicated.

Question 10

The bacterial chromosome is

A) found in a nucleus.
B) usually circular.
C) found in a nucleoid.
D) both circular and found in a nucleoid.
E) both circular and found in a nucleus.

Question 11

DNA replication and RNA transcription have many features in common. Which of the following does NOT occur in both processes?

A) base-pairing of complementary nucleotides
B) a requirement for a primer
C) separation of the DNA strands (ʺunzippingʺ)
D) directionality of synthesis
E) energy to drive the process is provided by triphosphate nucleotides

Question 12

Which of the following occurs in DNA but not RNA?

A) deoxyribose
B) uracil
C) thymine
D) ribose
E) both deoxyribose and thymine

Question 13

The AUG codon functions in coding for the amino acid methionine and as a

A) marker for introns.
B) recognition site for RNA polymerase.
C) start signal.
D) termination signal.
E) ʺwobbleʺ codon.

Question 14

Which of the following regulatory RNAs alter translation in response to environmental conditions?

A) microRNAs
B) transfer RNAs
C) riboswitches
D) miRNA-induced silencing complexes (miRISCs)
E) small interfering RNAs

Question 15

Which of the following is a characteristic shared by DNA and RNA polymerases?

A) type of nucleotides used
B) direction of polymerization
C) speed
D) efficiency of proofreading
E) dependence on helicase

Question 16

Which of the following statements is TRUE of bacterial plasmids?

A) They are always found in the nucleoid.
B) They carry genes for essential metabolic functions.
C) They are small circular DNA molecules.
D) They can replicate autonomously.
E) They are small circular DNA molecules that can replicate autonomously.

Question 17

The process indicated by the arrow in Figure 7-1 represents

A) transcription.
B) homologous recombination.
C) translation.
D) leading strand synthesis.
E) lagging strand synthesis.

Question 18

Which of the following contributes to the packaging of bacterial chromosome?

A) Okazaki fragments
B) gyrase
C) histone proteins
D) helicase
E) nucleosomes

Question 19

Which of the following is NOT a characteristic of Okazaki fragments?

A) They are checked for accuracy by DNA polymerase III.
B) They are longer in eukaryotic cells.
C) They make up the lagging strand of replicated DNA.
D) They begin with an RNA primer.
E) They are joined together by DNA ligase.

Question 20

Which of the following statements is CORRECT about bacterial transcription?

A) A single RNA polymerase produces all RNA transcripts.
B) It occurs in the periplasm.
C) Various sigma factors recognize different promoter sequences.
D) Rho protein is required for termination of transcription.
E) The mRNA is extensively modified before transcription.

Question 21

Which of the following are considered to be frameshift mutations?

A) insertions only
B) deletions only
C) inversions only
D) both inversion and insertions
E) both deletions and insertions

Question 22

DNA damage caused by ethidium bromide results in mutations.

A) deletion
B) insertion
C) substitution
D) both inversion and insertion
E) both insertion and deletion

Question 23

Which of the following causes mutations by creating thymine dimers?

A) nitrous acid
B) nucleotide analogs
C) benzopyrene
D) ultraviolet light
E) gamma rays

Question 24

Which of the following is NOT involved in the regulation of the lac operon?

A) an inducer
B) glucose
C) an iRNA
D) a repressor protein
E) cyclic AMP

Question 25

What repair mechanism is most likely involved in repairing DNA damage caused by ionizing radiation?

A) mismatch repair
B) dark repair response
C) DNA photolyase
D) SOS response
E) either DNA photolyase or dark repair

Question 26

In conjugation, F+ cells

A) contain an F plasmid.
B) serve as recipient cells.
C) can transfer DNA only to other F+ cells.
D) do not have conjugation pili.
E) contain ʺjumping genes.ʺ

Question 27

The Ames test demonstrates that a chemical is

A) mutagenic in Salmonella.
B) carcinogenic in humans.
C) carcinogenic in Salmonella.
D) carcinogenic.
E) mutagenic in humans.

Question 28

The procedure known as ʺreplica platingʺ is used in

A) negative selection only.
B) both positive and negative selection.
C) the Ames test.
D) positive selection only.
E) mutagenesis.

Question 29

Which of the following is characteristic of prokaryotic genomes but NOT eukaryotic genomes?

A) histones
B) enclosed in a nuclear membrane
C) circular chromosomes
D) typically consist of a few to several chromosomes
E) linear chromosomes

Question 30

Which of the following statements is CORRECT about BOTH bacterial and eukaryotic DNA replication?

A) The lagging strand is synthesized in fragments of about 1000 or so bases.
B) A single DNA polymerase is responsible for both leading strand and lagging strand synthesis.
C) Replication proceeds bidirectionally from the origin of replication.
D) An RNA primase is required for initiation of synthesis.
E) Each chromosome has multiple origins of replication.

Question 31

The DNA sequence of a portion of gene in a wild-type organism is TTACCATATTCACCC, and the corresponding peptide sequence is Leu-Pro-Tyr-Ser-Pro. The corresponding gene fragment in a phenotypic variant of the organism is TTACCATATTCACCC and the peptide sequence is Leu-Pro-Cys-Ser-Pro. This is an example of a(n) mutation (type) resulting in a
Mutation (effect).

A) base substitution; silent
B) base substitution; missense
C) deletion; missense
D) insertion; nonsense
E) base substitution; nonsense

Question 32

Inducible operons

A) usually require an activator to be transcribed.
B) are active in the presence of a repressor.
C) are generally anabolic pathways.
D) are normally active.
E) usually require a repressor to be transcribed.

Question 33

Which of the following occurs in eukaryotes but NOT in prokaryotes?

A) transcription
B) translation
C) DNA replication
D) transformation
E) polyadenylation

Question 34

Bacteria acquire new DNA from the environment in the process of

A) transformation.
B) the SOS response.
C) transposition.
D) recombination.
E) conjugation.

Question 35

Sigma factors are involved in the regulation of bacterial

A) transcription.
B) mutation repair.
C) DNA replication.
D) translation.
E) transformation.

Question 36

DNA sequences known as transposons contain

A) origins.
B) promoters.
C) F+ plasmids.
D) sigma factor sequences.
E) palindromes.

Question 37

Codons are recognized by

A) siRNAs.
B) sigma factors.
C) rRNAs.
D) tRNAs.
E) mRNAs.

Question 38

The events of are initiated at sequences called origins.

A) DNA replication
B) splicing
C) translation
D) transposition
E) transcription

Question 39

The process of requires the activity of DNA ligase.

A) translation
B) transcription
C) DNA replication
D) capping
E) transduction

Question 40

The horizontal transfer process known as transduction

A) involves a virus.
B) requires a cell to be ʺcompetent.ʺ
C) involves a mutagen.
D) requires a plasmid.
E) requires a pilus.

Question 41

Cells must be naturally or artificially ʺcompetentʺ for which of the following events to occur?

A) transformation
B) conjugation
C) specialized transduction
D) transposition
E) generalized transduction

Question 42

Loosely packed, transcriptionally active regions of a eukaryotic chromosome are called (euchromatin/heterochromatin/nucleosomes).

Question 43

During , a new peptide bond is formed with the amino acid located in the A site.

A) translation elongation
B) transcription elongation
C) polyadenylation
D) mismatch repair
E) DNA replication elongation

Question 44

DNA polymerase III participates in the dark repair mechanism of DNA mutation repair.

Question 45

The phenotype of an organism reflects only part of its genotype.

Question 46

Not all genetic material of eukaryotic cells is contained in the nucleus.

Question 47

Prokaryotic cells are diploid.

Question 48

Pyrimidine dimers are severe mutations because cells have few mechanisms for repairing them.

Question 49

The structure of DNA explains both its ability to encode genetic information and the way in which it is copied during cell reproduction.

Question 50

Initiation of messenger RNA (mRNA) transcription requires a primer, which is provided by a promoter.

Question 51

The phenotype of an organism is its set of (genes/traits/chromosomes).

Question 52

The enzyme responsible for separating the DNA strands during DNA replication is (topoisomerase/gyrase/helicase).

Question 53

The process known as is initiated with the incorporation of fMet.

A) transcription
B) capping
C) DNA replication
D) translation
E) light repair

Question 54

Ribozymes are required for

A) RNA splicing.
B) capping.
C) translation.
D) both translation and RNA splicing.
E) capping, RNA splicing and translation.

Question 55

Most bacteria have a natural ability to take up DNA from their environment.)

Question 56

Transfer of DNA between bacterial cells by viruses is called (transformation/transduction/conjugation).

Question 57

A chemical is reported to inhibit bacterial replication. Bacterial cells are placed in medium with all nutrients necessary for replication. The chemical is added to the culture, and after a half hour an extract of the DNA is prepared. A significant percentage of the DNA is in pieces about 1000 to 2000 bases in length. The results are consistent with the chemical blocking the function of DNA ligase.

Question 58

A(n) (operon/codon/gene) is a specific sequence of nucleotides that codes for a protein or an RNA molecule.

Question 59

When incorporated into a growing DNA strand, these base analogs prevent further elongation of the strand.

Question 60

The process of is described as semiconservative.

A) mismatch repair
B) transcription
C) transformation
D) translation
E) DNA replication

Question 61

The (phenotype/genome/genotype) is the set of genes in the genome of an organism.

Question 62

A mutation in the (acceptor/anticodon/loop) region of a transfer RNA may result in altered amino acid sequences in proteins.

Question 63

Hepatitis C and other viruses with RNA genomes have higher mutation rates than viruses with DNA genomes. Based on information up to this point in the text suggest some possible explanations for the higher mutation rates. (You may also want to consider information in chapter 2, chemistry.)

Question 64

A protein has altered function as a result of a single amino acid substitution in the polypeptide. This change resulted from a (missense/nonsense/silent) mutation.

Question 65

A point mutation can be completely harmless, or it can result in the death of a cell or organism. Explain why these types of mutations can have such varying effects.

Question 66

While studying a bacterial strain a scientist notes a short DNA sequence between inverted repeats is present in both the chromosome and a plasmid within the cell. This sequence is most likely a (phage/transposon/transformation).

Question 67

Describe the basic similarities and differences between DNA replication and transcription.

Question 68

The chemical 5-bromouracil mimics the chemical structure of thymine, making it a(n) (analog/nucleotide/precursor) of thymine.

Question 69

A(n) (genome/codon/operon) is a set of prokaryotic genes that are regulated and transcribed as a unit.

Question 70

The (leading/lagging/replicating) strand is the DNA strand that is synthesized continuously during DNA replication.

Question 71

Acridine dyes distort the structure of DNA causing (frameshift/missense/nonsense) mutations in gene sequences. (Answer in terms of the effect on gene function.)

Question 72

Except during initiation of translation, transfer RNA molecules carrying amino acids initially bind to the ribosome at the (P/A/E) site.

Question 73

RNA polymerase initiates transcription by recognizing specific DNA sequences called (promoters/origins/operons).

Question 74

Bacterial strain A contains a plasmid. Bacterial strain B does not. After the bacteria are incubated together in a broth culture strain B cells containing the plasmid can be isolated. Devise an experiment to determine what type of gene transfer process is involved.

Question 75

Compare and contrast the lactose operon with the tryptophan operon.