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Prokaryotic Molecular Genetics > Exam 1 review > Flashcards

Exam 1 review Flashcards

1
Q

A repeating DNA sequence at the end of chromosomes that prevents them from losing base pair sequences at their ends and from fusing together is called?

A

Telomere

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2
Q

The enzyme responsible for initiating the unwinding of double-stranded DNA (eliminating supercoiling) by nicking a single strand of the DNA molecule is?

A

Topoisomerase

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3
Q

The enzyme that accomplishes the unwinding of the original double stranded DNA molecule, once supercoiling has been eliminated, by breaking the hydrogen bonds that hold the two strands together are?

A

Helicase

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4
Q

The enzyme that stitches Okazaki fragments together (along the lagging strand) is called?

A

DNA ligase

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5
Q

The enzyme “x” removes RNA primers attached by primase and this gap is then filled in by DNA polymerase I. The enzyme “x” is?

A

RNase H

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6
Q

The enzyme that (during replication) proceeds along one of the strands of a DNA molecule adding deoxynucleotide-triphosphates to hydrogen bond with their appropriate complementary dNTP on the other single strand and to form a covalent phosphodiester bond with the previous nucleotide of the same strand is called?

A

DNA Polymerase III

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7
Q

DNA Polymerase III is actually an aggregate of several different protein subunits. So it is often called a?

A

Holoenzyme

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8
Q

A major difference between DNA replication in prokaryotes and eukaryotes is?

A

There is only one replication origin in prokaryotes

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9
Q

The enzyme that creates a short RNA oligonucleotide at initiation sites where replication is to be carried out is called?

A

Primase

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10
Q

DNA is a polymer of?

A

deoxinucleotides

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11
Q

What are pyrimidines?

A

Cytosine and Thymine

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12
Q

What are purines?

A

Adenine and Guanine

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13
Q

A nucleic acid was analyzed and found to contain 32% A, 18% G, 17% C, and 33% T. The nucleic acid must be?

A

double-stranded DNA

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14
Q

A nucleic acid was analyzed and found to contain 37% A, 16% G, 22% C, and 25% T. The nucleic acid must be?

A

single-stranded DNA

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15
Q 
For double-stranded DNA, consider the following base ratios:
1. A/G
2. C/T
3. C/G
4. (A+C)/(G+T)
5. (A+G)/(C+T)
6. (A+T)/(G+C)
Which of those ratios always equals 1?
A

Answer:

  1. C/G
  2. (A+C)/(G+T)
  3. (A+G)/(C+T)
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16
Q

The two polynucleotide chains in DNA are?

A

Antiparallel

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17
Q

In the Meselson-Stahl experiment, which model of DNA was eliminated by the analysis of DNA isolated from bacteria one replication cycle after shifting from 15N to 14N medium?

A

Conservative

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18
Q

In the semiconservative replication of DNA, progeny DNA molecules consist of?

A

All molecules with one parental and one new strand

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19
Q

In the conservative model for replication of DNA, progeny DNA molecules consist of?

A

One-half of the molecules with two parental strands and one-half of the molecules with two new strands

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20
Q

What are the complementary base-pairing rules?

A

The specific pairing of bases on the two polynucleotide chains of a double helix, that is, A with T and G with C

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21
Q

What is the base sequence of the DNA strand that would be complementary to the following single-stranded DNA molecule?

5’-GGATCTGATCCAGTCA-3’

A

3’-CCTAGACTAGGTCAGT-5’

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22
Q

The percent of cytosine in a double-stranded DNA is 21. What is the percent of thymine in that DNA?

A

T=29%.

If C=21 then G=21 and G+C=42. Therefore A+T=100-42=58, T=58/2=29%

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23
Q

The percent of adenine in a double-stranded DNA is 38. What is the percent of cytosine in the DNA?

A

C=12%.

If A=38 then T=38 and A+T=76. Therefore G+C=100-76=24, C=24/2=12%

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24
Q

The percent of guanine in a double-stranded DNA is 14. What is the percent of adenine in the DNA?

A

A=36%.

If G=14 then C=14 and G+C=28. Therefore A+T=100-28=72, A=72/2=36%

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25
Q

Explain how the bacterial chromosome replication stops.

A

The bacterial chromosome replication stops when DNA Pol III reaches a termination sequence in which case DNA Pol III is removed and the process of ligation is initiated.

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26
Q

What direction is 5’ to 3’?

A

Sense

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27
Q

What direction is 3’ to 5’?

A

Anti-sense

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28
Q

What base is found on RNA and not on DNA?

A

Uricil

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29
Q

How many bases are in a codon? In an anti-codon?

A

Codon = 3 and Anticodon = 3

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30
Q

How many amino acids are attached to a single transfer RNA?

A

1 amino acid

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31
Q

Transcription occurs in the __________ direction.

A

5’ to 3’

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32
Q

Translation occurs in the __________ direction.

A

3’ to 5’

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33
Q

The process of making RNA from DNA is called what? In which direction does it occur?

A

Transcription and it occurs in 3’ to 5’ direction

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34
Q

The process of assembling a protein from RNA is called what? In which direction does it occur?

A

Translation and it occurs in the 5’ to 3’ direction

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35
Q

The end of a strand of nucleic acid that has a OH group on the number 3 carbon of the deoxyribose or ribose and is not linked to another nucleotide is?

A

3’ end

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36
Q

The covalent bond that links ribonucleotides together to form RNA is?

A

phosphodiester bond

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37
Q

The portion of DNA that contains the actual message for protein synthesis is?

A

coding sequence

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38
Q

A molecule synthesized by complementary base pairing of ribonucleotides with deoxyribonucleotides to match a portion of one strand of DNA coding for a polypeptide or protein is?

A

mRNA

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39
Q

A series of three consecutive mRNA bases coding for one specific amino acid is?

A

codon

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40
Q

A segment of DNA that determines what region of the DNA and which strand of DNA will be transcribed into RNA is?

A

promoter

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41
Q

The enzyme that initiates transcription, joins the RNA nucleotides together, and terminates transcription is?

A

RNA polymerase

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42
Q

A “stop” signal at the end of a gene that causes the completed mRNA to drop off the gene is?

A

transcription terminator

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43
Q

If a DNA strand reads TACGGCATG (where the names of the bases are abbreviated), then the RNA molecule created by transcription would read?

44
Q

A promoter is best described as a what?

A

A sequence of bases at which RNA polymerase begins transcription

45
Q

Which of these statements about the mRNA code is false?

A

Most amino acids are coded for by only one sequence of bases

46
Q

RNA is synthesized under the direction of DNA by what enzyme?

A

RNA polymerase

47
Q

Which component of RNA polymerase facilitates the recognition of promoter sequences?

A

Sigma subunit

48
Q

What is the role of molecular chaperones?

A

To aid a newly synthesized polypeptide in folding to its proper shape

49
Q

Which part of translation involves the addition of amino acids to an existing polypeptide chain?

A

Elongation

50
Q

What molecule catalyzes the transpeptidation reaction?

A

Peptidyl transferase

51
Q

Aminoacytl-tRNA binds to which site of the ribosome during elongation?

52
Q

Most prokaryotic proteins begin with this modified amino acid?

A

N-formylmethionine

53
Q

Which of the following components is found in all prokaryotic transcription terminators?

A

a hairpin structure

54
Q

Identify which of the following is more likely to be a Rho factor independent transcription termination site:

a) 3’-ACTAGCCTAAGCATCTTGAGGCACAGTTTAACAAATGC-5’
b) 3’-ACGTAAGGGTTTAAACGTACCCAAAAAAAAAAATCG-5’
c) 3’-AATGTGTGGCCGGGCGCTTTCGAACACAGGCGCCCGGCCAAAAAAAAAAAAA

A

C)3’-AATGTGTGGCCGGGCGCTTTCGAACACAGGCGCCCGGCCAAAAAAAAAAAAA

55
Q

Changing the codon AGC to AGA represents a ______mutation

56
Q

A spontaneous mutation usually originates as an error in

A

DNA replication

57
Q

The codon for leucine is CUC. How many different amino acids could possibly result from single-base substitutions?

58
Q

Which characteristic of the genetic code lowers the likelihood of mutation

A

degeneracy

59
Q

A frameshift mutation (what it does DNA)

A

introduces a section of amino acids not normally found

60
Q

A _________ mutation is intentionally caused.

A

site-directed

61
Q

A point mutation that changes a codon specifying an amino acid into a stop codon is called a ?

A

nonsense mutation

62
Q

What type of mutation does not change the sequence of the gene product?

63
Q

What is the consequence of a nonsense mutation?

A

Introduces a stop codon

64
Q

Gene A contains a frameshift mutation. To revert that mutation (change it back to normal or wild type) you would use a mutagen causing?

A

Frameshifts

65
Q

To revert a transition mutation you would use a mutagen causing?

A

transitions

66
Q

To revert a transversion mutation you would use a mutagen causing?

A

Transversions

67
Q

Protein Z contains the amino acid sequence: AlaArgAlaAlaArgArgGlu. What type of mutation with the sequence they might this be?

AlaArgAlaGluArgArgGlu

A

Missense mutation

68
Q

Protein Z contains the amino acid sequence: AlaArgAlaAlaArgArgGlu. What type of mutation with the sequence they might this be?

AlaArgAlaAlaArgArgGlu

A

Silent mutation

69
Q

Protein Z contains the amino acid sequence: AlaArgAlaAlaArgArgGlu. What type of mutation with the sequence they might this be?

AlaArgAlaAla-C terminus

A

Nonsense mutation

70
Q

Protein Z contains the amino acid sequence: AlaArgAlaAlaArgArgGlu. What type of mutation with the sequence they might this be?

AlaArgGlyGly-Cterminus

A

Frameshift mutation

71
Q

A replicon is?

A

a DNA molecule that is able to replicate and be maintained

72
Q

Plasmids can best be described as?

A

Small, circular DNA molecules that can exist independently of chromosomes commonly found in bacteria

73
Q

In insertional inactivation if foreign DNA is inserted, what happens?

A

The beta galactosidase marker is activated, and the colonies remain white.

74
Q

If host cells are ampicillin sensitive and are plated on a medium containing ampicillin, what happens?

A

Only cells that have taken up the ampicillin resistant vector can grow

75
Q

When foreign DNA and plasmid are both cut with the same restriction enzyme and mixed together, all molecules will form recombinants ( True or False)

76
Q

True or False: Theta replication is both unidirectional and bidirectional.

77
Q

True or False: ColE1 plasmid do not require a plasmid-encode protein to initiate replication at their oriV, only an RNA primer synthesized from the plasmid

78
Q

In a molecular biology laboratory, a student obtained competent E.coli cells and used a common transformation procedure to induce the uptake of plasmid DNA with a gene for resistance to the antibiotic kanamycin. The results below were obtained.

Plate 1: LB agar +kan plasmid
Plate 2: LB agar with kanamycin   
              \+kan plasmid
Plate 3: LB agar no plasmid added
Plate 4: LB agar with kanamycin 
              no plasmid added

Which petri dish do only transformed cells grow?

79
Q

The F plasmid does what?

A

Codes for making the F pilus

80
Q

The F pilus is a what?

A

Protein appendage on the F+ donor that attaches to specific receptors on the cell wall of the recipient

81
Q

When an F+ donor gives an F plasmid to an F- recipient, what happens?

A

both become F+

82
Q

Contact is required between an F+ and an F- cell for conjugation to occur. ( True or False)

83
Q

When F+ cells are mixed with F- cells, eventually all the cells will become F+. (True or False)

84
Q

DNA transformation involves the transfer of DNA via what?

A

Naked DNA in solution

85
Q

The mismatch repair system will repair what? (DNA)

A

Either the donor or the recipient strand

86
Q

When DNA from an ampicillin resistant organism is brought into an ampicillin sensitive organism by transformation and the product is grown on agar containing ampicillin, what happens?

A

Only the transformed cells will grow

87
Q

The relationship between a virus and host where no new viral particles are produced and the viral genome is replicated along with the host chromosome, what is that called?

88
Q

In which type of transduction does the transducing particle carry only specific portions of the bacterial genome?

A

Specialized transduction

89
Q

What happens when F+ x F- mate?

A

DNA is transferred from F+ to F- cells

90
Q

This type of plasmid can exist with or without being integrated into the host’s chromosome

91
Q

In the lytic cycle the bacterial cell is ruptured by the action of what?

92
Q

_________ is the recombination of DNA sequences having nearly the same nucleotide sequence and involving Rec A proteins.

A

Homologous recombination

93
Q

It is a movement of the Holliday junction up and down the DNA by breaking and reforming the hydrogen bonds between the bases is?

A

Branch migration

94
Q

True or False: In the Holliday double strand invasion model if the same strands are cleaved a second time then non recombinant DNA molecules are generated, but they each contain a region of heteroduplex DNA that spans the region of branch migration

95
Q

The rearrangement between the strands after the formation of the Holliday junction called what?

A

Isomerisation

96
Q

Recombination depends of the Holliday junction configuration when they are resolved, if both junctions with the same configuration- either one or II, then it is not crossover and no recombination happens. What type of model?

A

Double strand break repair model

97
Q

The major pathway of recombination in E. coli is?

A

RecBCD pathway

98
Q

________ is required for recombination (prepare the single strand end of DNA to invade the other double-strand DNA- first step in recombination), degradation of foreign linear DNA and in restart the replication when the replication fork stalls at single or double-strand-breaks in the template DNA.

99
Q

True or False: The chi sequence is recognizing in both strands of DNA.

100
Q

True or False: Chi site active RecD subunit and stimulate 5’ to 3’ activity.

101
Q

_____ Is formed when two DNA molecules are joined through the formation of the D-loop.

102
Q

______ bind to ssDNA and form nucleoprotein filaments.

103
Q

_______ force the ssDNA into the helical conformation.

104
Q

It has ATP and DNA binding activities and weak ATPase activity

105
Q

_______ passes over the site only on the other strand making the orientation of the chi sequence important.

106
Q

It is used to prepare single stranded DNA for D-loop formation in E.coli.

A

Pathway RecF

107
Q

Following diagram represents what?

A

Holliday single strand invasion model

Prokaryotic Molecular Genetics (13 decks)

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