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Flashcards in Exam 1 review Deck (107):
1

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?

Telomere

2

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

Topoisomerase

3

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?

Helicase

4

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

DNA ligase

5

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

RNase H

6

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?

DNA Polymerase III

7

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

Holoenzyme

8

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

There is only one replication origin in prokaryotes

9

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

Primase

10

DNA is a polymer of?

deoxinucleotides

11

What are pyrimidines?

Cytosine and Thymine

12

What are purines?

Adenine and Guanine

13

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

double-stranded DNA

14

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

single-stranded DNA

15

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?

Answer:
3. C/G
4. (A+C)/(G+T)
5. (A+G)/(C+T)

16

The two polynucleotide chains in DNA are?

Antiparallel

17

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?

Conservative

18

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

All molecules with one parental and one new strand

19

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

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

20

What are the complementary base-pairing rules?

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

21

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

5'-GGATCTGATCCAGTCA-3'

3'-CCTAGACTAGGTCAGT-5'

22

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

T=29%.

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

23

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

C=12%.

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

24

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

A=36%.

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

25

Explain how the bacterial chromosome replication stops.

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.

26

What direction is 5' to 3'?

Sense

27

What direction is 3' to 5'?

Anti-sense

28

What base is found on RNA and not on DNA?

Uricil

29

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

Codon = 3 and Anticodon = 3

30

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

1 amino acid

31

Transcription occurs in the __________ direction.

5' to 3'

32

Translation occurs in the __________ direction.

3' to 5'

33

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

Transcription and it occurs in 3' to 5' direction

34

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

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

35

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?

3' end

36

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

phosphodiester bond

37

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

coding sequence

38

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?

mRNA

39

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

codon

40

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

promoter

41

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

RNA polymerase

42

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

transcription terminator

43

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

AUGCCGUAC

44

A promoter is best described as a what?

A sequence of bases at which RNA polymerase begins transcription

45

Which of these statements about the mRNA code is false?

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

46

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

RNA polymerase

47

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

Sigma subunit

48

What is the role of molecular chaperones?

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

49

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

Elongation

50

What molecule catalyzes the transpeptidation reaction?

Peptidyl transferase

51

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

A site

52

Most prokaryotic proteins begin with this modified amino acid?

N-formylmethionine

53

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

a hairpin structure

54

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

C)3'-AATGTGTGGCCGGGCGCTTTCGAACACAGGCGCCCGGCCAAAAAAAAAAAAA

55

Changing the codon AGC to AGA represents a ______mutation

missense

56

A spontaneous mutation usually originates as an error in

DNA replication

57

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

7

58

Which characteristic of the genetic code lowers the likelihood of mutation

degeneracy

59

A frameshift mutation (what it does DNA)

introduces a section of amino acids not normally found

60

A _________ mutation is intentionally caused.

site-directed

61

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

nonsense mutation

62

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

Silent

63

What is the consequence of a nonsense mutation?

Introduces a stop codon

64

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

Frameshifts

65

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

transitions

66

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

Transversions

67

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

AlaArgAlaGluArgArgGlu

Missense mutation

68

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

AlaArgAlaAlaArgArgGlu

Silent mutation

69

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

AlaArgAlaAla-C terminus

Nonsense mutation

70

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

AlaArgGlyGly-Cterminus

Frameshift mutation

71

A replicon is?

a DNA molecule that is able to replicate and be maintained

72

Plasmids can best be described as?

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

73

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

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

74

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

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

75

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

False

76

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

True

77

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

False

78

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?

Plate 2

79

The F plasmid does what?

Codes for making the F pilus

80

The F pilus is a what?

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

81

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

both become F+

82

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

True

83

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

True

84

DNA transformation involves the transfer of DNA via what?

Naked DNA in solution

85

The mismatch repair system will repair what? (DNA)

Either the donor or the recipient strand

86

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?

Only the transformed cells will grow

87

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?

lysogeny

88

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

Specialized transduction

89

What happens when F+ x F- mate?

DNA is transferred from F+ to F- cells

90

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

Episome

91

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

Lysozyme

92

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

Homologous recombination

93

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

Branch migration

94

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

True

95

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

Isomerisation

96

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?

Double strand break repair model

97

The major pathway of recombination in E. coli is?

RecBCD pathway

98

________ 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.

RecBCD

99

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

False

100

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

False

101

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

Synapse

102

______ bind to ssDNA and form nucleoprotein filaments.

RecA

103

_______ force the ssDNA into the helical conformation.

RecA

104

It has ATP and DNA binding activities and weak ATPase activity

RecF

105

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

RecBCD

106

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

Pathway RecF

107

Following diagram represents what?

Holliday single strand invasion model