Brock Biology of Microorganisms Michael T.- Madigan 13th Edition Test Bank

Brock Biology of Microorganisms Michael  T.- Madigan  13th Edition  Test Bank
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Exam
Name___________________________________

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1)

The functional unit of genetic information is called the

1)

_______

A)

protein.

B)

nucleotide.

C)

gene.

D)

chromosome.

2)

The process whereby RNA specifies a DNA sequence is known as

2)

_______

A)

RNA translation.

B)

the central dogma of molecular biology.

C)

reverse transcription.

D)

RNA transcription.

3)

Proteins interact predominantly within which portion of a double-stranded DNA helix?

3)

_______

A)

supercoil

B)

telomere

C)

major groove

D)

minor groove

4)

AT-rich DNA will denature/melt

4)

_______

A)

at a lower temperature than GC-rich DNA.

B)

in accordance with the animal or plant from which it was taken.

C)

at a higher temperature than GC-rich DNA.

D)

usually at the same temperature as GC-rich DNA, with some minor variations.

5)

In Bacteria and most Archaea, the enzyme that introduces negative supercoils into DNA is known as

5)

_______

A)

prokaryotic gyrase.

B)

prokaryotic supercoilase.

C)

DNA gyrase.

D)

supercoiling gyrase.

6)

Ciprofloxacin, nalidixic acid, and novobiocin are effective antibiotics because they inhibit the activity of

6)

_______

A)

prokaryotic supercoilase.

B)

DNA gyrase.

C)

reverse gyrase.

D)

RNA topoisomerase.

7)

Most plasmids are

7)

_______

A)

linear, though a few are circular.

B)

replicated in conjunction with the chromosome.

C)

found in eukaryotic cells, though a few are found in prokaryotic cells.

D)

double-stranded DNA, though a few are not.

8)

Housekeeping genes are present in

8)

_______

A)

plasmids.

B)

neither chromosomes nor plasmids.

C)

chromosomes.

D)

chromosomes and plasmids.

9)

The precursor of each new nucleotide in a strand of DNA is a

9)

_______

A)

deoxynucleoside 3-triphosphate.

B)

deoxynucleoside 5-triphosphate.

C)

deoxynucleoside 3-diphosphate.

D)

deoxynucleoside 5-diphosphate.

10)

DNA replication always proceeds from the ________ of the incoming nucleotide to the ________ of the previously added nucleotide.

10)

______

A)

3-hydroxyl /5-phosphate

B)

3-phosphate / 5-hydroxyl

C)

5-phosphate / 3-hydroxyl

D)

5-hydroxyl / 3-phosphate

11)

During DNA synthesis, the RNA primer is removed by a(n)

11)

______

A)

Pol I exonuclease.

B)

replisome.

C)

Okazaki fragment.

D)

DNA ligase.

12)

The template for RNA polymerase is ________, and the RNA chain growth is ________ the chain growth of DNA.

12)

______

A)

DNA / identical to

B)

DNA / the opposite of

C)

an independent RNA segment / the opposite of

D)

an independent RNA segment / identical to

13)

Promoters are specific sequences of ________ that are recognized by ________.

13)

______

A)

DNA / RNA polymerase

B)

RNA / DNA polymerase

C)

RNA / RNA polymerase

D)

DNA / sigma factor

14)

An example of nucleotide pairing is

14)

______

A)

G and U.

B)

T and U.

C)

C and U.

D)

A and T.

15)

Stop codons are also called ________ codons.

15)

______

A)

nonsense

B)

conversion

C)

release factor

D)

degeneracy

16)

There are about ________ different tRNAs in bacterial cells and about ________ in mammalian cells.

16)

______

A)

100-110 / 140

B)

60 / 100-110

C)

40 / 70

D)

200 / 200

17)

tRNA is released from the ribosome at the ________ site.

17)

______

A)

P

B)

R

C)

A

D)

E

18)

Which statement is generally TRUE regarding protein synthesis?

18)

______

A)

The 23S rRNA plays a role in termination; the 16S rRNA plays a role in elongation.

B)

The 23S rRNA plays a role in translocation; the 16S rRNA plays a role in elongation.

C)

The 23S rRNA plays a role in elongation; the 16S rRNA plays a role in translocation.

D)

The 23S rRNA plays a role in translocation; the 16S rRNA plays a role in initiation.

19)

Streptomycin inhibits ________ of protein synthesis, whereas tetracycline inhibits ________ of protein synthesis.

19)

______

A)

initiation / maturation

B)

maturation / protein folding

C)

elongation / protein folding

D)

initiation / elongation

20)

In all cells, genes are composed of

20)

______

A)

mRNA.

B)

proteins.

C)

nucleic acids.

D)

chaperones.

21)

Which of the following is an example of one codon?

21)

______

A)

CCGUAA

B)

CATT

C)

GCCATT

D)

CAG

22)

In all cells a gene encodes for

22)

______

A)

an rRNA.

B)

a tRNA.

C)

a protein (via mRNA).

D)

all of the above.

23)

Which of the following is NOT correct regarding DNA and RNA synthesis?

23)

______

A)

DNA is the template for both DNA and RNA synthesis.

B)

The overall direction of chain growth is from the 5 to 3 end.

C)

Both processes require an RNA primer to begin.

D)

The template strand is antiparallel to the newly synthesized strand.

24)

Termination of RNA synthesis is ultimately determined by

24)

______

A)

specific nucleotide sequences on the template strand.

B)

special protein factors.

C)

exhaustion of RNA polymerase activity.

D)

CG-rich sequences followed by AT-rich sequences.

25)

GTP provides energy for

25)

______

A)

protein folding.

B)

DNA replication.

C)

transcription.

D)

translation.

26)

Transcription of chaperonins is greatly accelerated when a cell is stressed by

26)

______

A)

lack of oxygen.

B)

excessive osmotic pressure.

C)

excessive heat.

D)

extremes in pH value.

27)

The flow of biological information begins with

27)

______

A)

RNA transcription.

B)

mRNA translation.

C)

transcriptional regulation.

D)

DNA replication.

TRUE/FALSE. Write T if the statement is true and F if the statement is false.

28)

Most prokaryotic genomes are double-stranded circular DNA.

28)

______

29)

Inverted repeats can lead to stem-loop structures in the DNA molecule.

29)

______

30)

In nature, the predominant form of DNA is supercoiled in a negative direction.

30)

______

31)

A polymerase chain reaction (PCR) amplifies a specific DNA sequence up to a billion-fold.

31)

______

32)

The genetic material in a virus is technically called a plasmid.

32)

______

33)

DNA replication is bidirectional in prokaryotes with circular chromosomes.

33)

______

34)

RNA acts at both the genetic and the functional levels.

34)

______

35)

Sometimes it appears that bases in tRNA loops are actually paired with bases in other tRNA loops, which is not the case because pairing occurs exclusively within a given loop.

35)

______

36)

Aminoacyl-tRNA synthetase catalyzes the reaction between the appropriate amino acid and ATP to form an activated amino acid: amino acid + ATP aminoacyl-AMP + P-P

36)

______

37)

One high-energy phosphate bond is required for the activation of an aminoacyl-tRNA.

37)

______

38)

rRNA has a functional role in all stages of protein synthesis.

38)

______

39)

Proteins known as chaperones are found only in Bacteria, and their sequences vary from organism to organism.

39)

______

40)

Throughout the living world, the genetic code is generally universal; however, there are some slight variations.

40)

______

41)

DNA replication involves the synthesis of an RNA primer on one strand of the DNA.

41)

______

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.

42)

DNA participates in protein synthesis through a(n) ________.

42)

_____________

43)

A DNA double helix occurs when ________.

43)

_____________

44)

The artificial construction of a double-stranded nucleic acid by complementary base pairing of two single-stranded nucleic acids is known as ________.

44)

_____________

45)

In Bacteria, a chromosome can be distinguished from a plasmid, because by definition a chromosome is a genetic element whose genes encode for ________.

45)

_____________

46)

A transposable element is the general term for ________.

46)

_____________

47)

In complementary base pairing of DNA, adenine pairs with ________ (or ________ in RNA) and cytosine always pairs with ________.

47)

_____________

48)

The function of the DNA polymerase is to ________.

48)

_____________

49)

DNA replication is started with a(n) ________, which, in most cases, in vivo is a short stretch of ________.

49)

_____________

50)

The function of RNA polymerase is to ________.

50)

_____________

51)

If a transcription unit contains two or more genes, these genes are then ________, giving a single RNA molecule.

51)

_____________

52)

A group of genes that are transcribed together is called a(n) ________, which synthesizes a(n) ________.

52)

_____________

53)

Bacterial proteins that kill closely related strains or species are collectively called ________, and the genes that encode for them are usually present on ________.

53)

_____________

54)

The genetic code is conventionally written as ________ rather than ________, because that is the molecule with which the translation process occurs.

54)

_____________

55)

The universal start codon is ________, and it codes for ________ in Bacteria.

55)

_____________

56)

The structure and function of a protein are determined by its ________ sequence.

56)

_____________

57)

The sequence of three to nine nucleotides upstream of the start codon that helps bind the mRNA to the ribosome is known as the ________.

57)

_____________

58)

When several ribosomes are simultaneously translating a single mRNA molecule, the complex is called a(n) ________.

58)

_____________

59)

To fold properly or to assemble into larger complexes, many proteins require assistance from other proteins called ________.

59)

_____________

60)

The twenty-first and twenty-second genetically encoded amino acids are ________ and ________.

60)

_____________

61)

________ is an enzyme that adds phosphodiester bonds between nicked regions of DNA.

61)

_____________

62)

A triplet of bases on an mRNA molecule is known as a(n) ________.

62)

_____________

63)

Each adenine-thymine base pair has ________ hydrogen bonds, while each guanine-cytosine base pair has ________ hydrogen bonds.

63)

_____________

64)

DNA synthesis occurs continuously on the ________ strand, while on the ________ strand DNA synthesis occurs discontinuously.

64)

_____________

ESSAY. Write your answer in the space provided or on a separate sheet of paper.

65)

Name and give one characteristic feature of each of the three major types of transposable elements.

66)

Define genome in terms of the various DNA components of the cell or virus.

67)

Explain why DNA, RNA, and proteins are often called informational macromolecules.

68)

Explain the difference between transcription and translation.

69)

Explain the concept of semiconservative replication.

70)

Discuss the initiation of DNA synthesis in Bacteria using the terms origin of replication, replication fork, and theta structures.

71)

Explain the function of the helicases.

72)

In DNA replication, relate the leading strand to the lagging strand.

73)

Explain the role of sigma factors in RNA synthesis.

74)

Explain the process of RNA transcription using the terms upstream, Pribnow box, and consensus sequence.

75)

Explain the difference between an intrinsic terminator and a Rho-dependent termination site.

76)

How can an open reading frame (ORF) be used to determine the location of a protein-encoding gene?

77)

Describe protein synthesis in terms of initiation, elongation, and termination/release.

78)

Explain the A site, the P site, and the E site in terms of the ribosomal subunits.

79)

Explain the role of the signal recognition particle (SRP) in protein secretion compared to SecA.

80)

Explain how Escherichia coli can grow with a doubling time of 20 minutes when chromosome replication takes 40 minutes.

81)

Speculate on why the half-life of mRNA is short, while the half-lives of rRNA and tRNA are long.

82)

Speculate on why it may be problematic to clone a gene from a prokaryote into a eukaryote.

83)

Explain why GC-rich DNA requires a higher temperature to denture or melt than AT-rich DNA.

84)

Explain why a cell needs both type I and type II topoisomerases.

85)

Explain the differences between viruses and plasmids.

1)

C

2)

C

3)

C

4)

A

5)

C

6)

B

7)

D

8)

C

9)

B

10)

C

11)

A

12)

A

13)

D

14)

A

15)

A

16)

B

17)

D

18)

D

19)

D

20)

C

21)

D

22)

D

23)

C

24)

A

25)

D

26)

C

27)

D

28)

TRUE

29)

TRUE

30)

TRUE

31)

TRUE

32)

FALSE

33)

TRUE

34)

TRUE

35)

FALSE

36)

TRUE

37)

FALSE

38)

TRUE

39)

FALSE

40)

TRUE

41)

TRUE

42)

RNA intermediate

43)

two long antiparallel polynucleotide chains whose purine and pyrimidine bases are held together by hydrogen bonds

44)

hybridization

45)

products necessary for essential cellular functions

46)

a molecule of DNA that can move from one site on a DNA molecule to another site on the same molecule or on a different DNA molecule

47)

thymine / uracil / guanine

48)

catalyze the addition of deoxynucleotides

49)

primer / RNA

50)

catalyze the formation of phosphodiester bonds between ribonucleotides

51)

cotranscribed

52)

operon / polycistronic mRNA

53)

bacteriocins / plasmids

54)

mRNA / DNA

55)

AUG / N-formylmethionine

56)

amino acid

57)

Shine-Dalgarno sequence

58)

polysome

59)

chaperones (or chaperonins)

60)

selenocysteine / pyrrolysine

61)

DNA ligase

62)

codon

63)

two / three

64)

leading / lagging

65)

Insertion sequences are the smallest, and no additional genetic information is carried other than what is required to move about the chromosome. Transposons are larger with additional genes being potentially transposable. Certain viruses such as Mu are also bacteriophages.

66)

Answers will vary but should include a statement that the genome includes the entire complement of genes in a cell or virus, and that it includes the chromosome as well as other genetic elements.

67)

Answers will vary but should focus on the central dogma of molecular biology and how each of these three macromolecules holds discrete information in its amino acid (protein) or nucleotide (DNA and RNA) sequences.

68)

Transcription is the process in which mRNA (transcripts) is synthesized from DNA, whereas translation uses RNA as a template to synthesize peptides (or proteins).

69)

During replication, only one of the two strands is used as a template (called the parental strand) to form a complementary strand called the progeny (or daughter) strand. Therefore, because only one of the two parental strands is needed for replication, it is considered partially (or semi-) conservative.

70)

The initiation protein DnaA binds to the origin of replication (oriC gene) where DnaB and DnaC proteins help unwind the DNA. This unwound and accessible region of DNA, called the replication fork, is where DNA synthesis occurs. Theta structures are used to describe the appearance of the DNA replication during bidirectional circular DNA replication.

71)

Helicase enzymes require energy from ATP to unwind double-stranded DNA into single-stranded (ss) DNA. Its function is necessary during the initiation of DNA synthesis, because the polymerase can operate only on ssDNA as the template.

72)

Figure 6.16 in the textbook illustrates these two strands during DNA replication. The leading strand always has a 3-hydroxyl group nearest to the replication fork, where a new nucleotide can be added continuously. The other strand lags during replication because the 3-hydroxy group is at the opposite end of the replication fork, and therefore primase must make new RNA primers to add on new nucleotides to the growing strand of DNA.

73)

A sigma factor is one of five subunits within an RNA polymerase involved exclusively in transcription of DNA to RNA. It identifies and binds to a promoter (initiation) site, notably the highly conservative -10 and -35 sites, which creates an RNA polymerase-DNA template complex that facilitates transcription initiation. A sigma factor then dissociates from the template after a short stretch of RNA is synthesized. They are also subject to regulation by anti-sigma factor proteins that temporarily inactivate a sigma factor and thus halt RNA synthesis.

74)

RNA polymerase holoenzyme initiates transcription without the need for a primer. The sigma factor component of RNA polymerase easily dissociates from the holoenzyme to first recognize the promoter region by specifically binding to the Pribnow box and consensus sequence, which are both upstream of the transcriptional start site.

75)

Intrinsic terminators occur at the nucleotide (DNA) level and require no additional protein involvement. They can develop into secondary structures such as loops, which freely form through base pairing with itself to ultimately halt transcription of RNA. Rho-dependent termination also stops RNA transcription but requires the protein Rho, which interacts with the DNA template-RNA polymerase complex to dissociate the complex at specific nucleotide sequences.

76)

Answers will vary, but an ORF is often predicted by identifying a start codon, followed by a nucleotide sequence, and a terminating nonsense codon in the same reading frame. Once an ORF is predicted using computational (i.e., bioinformatics) methods, it then is possible for a geneticist to identify the mRNA transcript to confirm the ORF is a gene. From the ORF sequence, the amino acid sequence can be predicted, which aids in the biochemical characterization of the translated protein.

77)

Answers should describe Figure 6.35b in the textbook where initiation involves a complex formation of the ribosome, initiation proteins, formylmethionine-tRNA, GTP, and mRNA. Elongation uses elongation factors, GTP, and tRNAs to extend a peptide, and termination occurs when release factors are recruited to a nonsense codon that breaks apart the tRNA and polypeptide to release the newly synthesized protein.

78)

A theme to this answer should be how a ribosome can interact with and translocate several molecules (e.g., tRNAs) all at once by having structurally distinct subunits (A, P, and E). During translation, an incoming tRNA attaches to the A site of the ribosome in the presence of elongation factor (EF)-Tu. The P site of the ribosome binds the previous tRNA used with the growing polypeptide chain, and the E site serves as an exit/release point for the previously used tRNA.

79)

SecA and SRP both carry proteins to the membrane secretion system. A protein to be transported contains a signal sequence, which allows for the binding of either SecA or SRF depending on the sequence. SRP carries proteins to remain in the cell membrane, and SecA binds proteins that are to be secreted out of the membrane.

80)

Answers will vary, but the principle idea is that essential genes are made earlier during the replication of its chromosome. When E. coli is placed in a nutrient rich medium, many pathways, such as amino acid biosynthesis, are not evoked.

81)

An important feature present in rRNA and tRNA yet lacking in mRNA is the secondary structures that make them more difficult to degrade by ribonucleases. These additional bonds also require more energy input to degrade them.

82)

Answers will vary, but one issue is that the universal genetic code does have exceptions. This means some mRNA could be translated into different proteins in different cells or not terminated at the correct location. Codon bias is another problem that can influence translational efficiency. The machinery and methods of post-translational modification are also very different and can therefore make interdomain cloning difficult.

83)

The overall increase in stability of G-C pairing should be emphasized over A-T binding. A DNA strand with high GC content (low AT) has more triple H bonds compared to an AT rich (low GC) strand of the same length contains mostly double H bonds. More energy is therefore required to break more H bonds, and thus GC rich DNA is more heat resistant to denaturation.

84)

Prokaryotes use topoisomerase II (DNA gyrase) to negatively supercoil DNA, which is critical for packaging large quantities of DNA into a small volume. DNA gyrase also can work in the opposite way to unwind a supercoil by breaking both strands for DNA replication. Topoisomerase I instead makes only a break on one of the two DNA strands, and this nicking process unwinds a coiled region of DNA.

85)

A major difference between a plasmid and a virus is that viruses infect other cells to propagate, and plasmids do not. Viruses also can lyse and kill its host, and plasmids cannot.

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