Exam 1 review

Question 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?

Answer 1

Telomere

Question 2

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

Answer 2

Topoisomerase

Question 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?

Answer 3

Helicase

Question 4

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

Answer 4

DNA ligase

Question 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?

Answer 5

RNase H

Question 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?

Answer 6

DNA Polymerase III

Question 7

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

Answer 7

Holoenzyme

Question 8

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

Answer 8

There is only one replication origin in prokaryotes

Question 9

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

Answer 9

Primase

Question 10

DNA is a polymer of?

Answer 10

deoxinucleotides

Question 11

What are pyrimidines?

Answer 11

Cytosine and Thymine

Question 12

What are purines?

Answer 12

Adenine and Guanine

Question 13

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

Answer 13

double-stranded DNA

Question 14

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

Answer 14

single-stranded DNA

Question 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 15

Answer:

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

Question 16

The two polynucleotide chains in DNA are?

Answer 16

Antiparallel

Question 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?

Answer 17

Conservative

Question 18

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

Answer 18

All molecules with one parental and one new strand

Question 19

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

Answer 19

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

Question 20

What are the complementary base-pairing rules?

Answer 20

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

Question 21

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

5’-GGATCTGATCCAGTCA-3’

Answer 21

3’-CCTAGACTAGGTCAGT-5’

Question 22

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

Answer 22

T=29%.

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

Question 23

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

Answer 23

C=12%.

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

Question 24

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

Answer 24

A=36%.

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

Question 25

Explain how the bacterial chromosome replication stops.

Answer 25

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.

Question 26

What direction is 5' to 3'?

Answer 26

Sense

Question 27

What direction is 3' to 5'?

Answer 27

Anti-sense

Question 28

What base is found on RNA and not on DNA?

Answer 28

Uricil

Question 29

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

Answer 29

Codon = 3 and Anticodon = 3

Question 30

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

Answer 30

1 amino acid

Question 31

Transcription occurs in the __________ direction.

Answer 31

5' to 3'

Question 32

Translation occurs in the __________ direction.

Answer 32

3' to 5'

Question 33

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

Answer 33

Transcription and it occurs in 3' to 5' direction

Question 34

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

Answer 34

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

Question 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?

Answer 35

3' end

Question 36

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

Answer 36

phosphodiester bond

Question 37

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

Answer 37

coding sequence

Question 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?

Answer 38

mRNA

Question 39

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

Answer 39

codon

Question 40

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

Answer 40

promoter

Question 41

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

Answer 41

RNA polymerase

Question 42

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

Answer 42

transcription terminator

Question 43

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

Answer 43

AUGCCGUAC

Question 44

A promoter is best described as a what?

Answer 44

A sequence of bases at which RNA polymerase begins transcription

Question 45

Which of these statements about the mRNA code is false?

Answer 45

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

Question 46

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

Answer 46

RNA polymerase

Question 47

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

Answer 47

Sigma subunit

Question 48

What is the role of molecular chaperones?

Answer 48

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

Question 49

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

Answer 49

Elongation

Question 50

What molecule catalyzes the transpeptidation reaction?

Answer 50

Peptidyl transferase

Question 51

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

Answer 51

A site

Question 52

Most prokaryotic proteins begin with this modified amino acid?

Answer 52

N-formylmethionine

Question 53

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

Answer 53

a hairpin structure

Question 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

Answer 54

C)3'-AATGTGTGGCCGGGCGCTTTCGAACACAGGCGCCCGGCCAAAAAAAAAAAAA

Question 55

Changing the codon AGC to AGA represents a ______mutation

Answer 55

missense

Question 56

A spontaneous mutation usually originates as an error in

Answer 56

DNA replication

Question 57

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

Answer 57

7

Question 58

Which characteristic of the genetic code lowers the likelihood of mutation

Answer 58

degeneracy

Question 59

A frameshift mutation (what it does DNA)

Answer 59

introduces a section of amino acids not normally found

Question 60

A _________ mutation is intentionally caused.

Answer 60

site-directed

Question 61

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

Answer 61

nonsense mutation

Question 62

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

Answer 62

Silent

Question 63

What is the consequence of a nonsense mutation?

Answer 63

Introduces a stop codon

Question 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?

Answer 64

Frameshifts

Question 65

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

Answer 65

transitions

Question 66

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

Answer 66

Transversions

Question 67

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

Answer 67

Missense mutation

Question 68

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

Answer 68

Silent mutation

Question 69

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

Answer 69

Nonsense mutation

Question 70

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

Answer 70

Frameshift mutation

Question 71

A replicon is?

Answer 71

a DNA molecule that is able to replicate and be maintained

Question 72

Plasmids can best be described as?

Answer 72

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

Question 73

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

Answer 73

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

Question 74

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

Answer 74

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

Question 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)

Answer 75

False

Question 76

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

Answer 76

True

Question 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

Answer 77

False

Question 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?

Answer 78

Plate 2

Question 79

The F plasmid does what?

Answer 79

Codes for making the F pilus

Question 80

The F pilus is a what?

Answer 80

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

Question 81

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

Answer 81

both become F+

Question 82

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

Answer 82

True

Question 83

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

Answer 83

True

Question 84

DNA transformation involves the transfer of DNA via what?

Answer 84

Naked DNA in solution

Question 85

The mismatch repair system will repair what? (DNA)

Answer 85

Either the donor or the recipient strand

Question 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?

Answer 86

Only the transformed cells will grow

Question 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?

Answer 87

lysogeny

Question 88

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

Answer 88

Specialized transduction

Question 89

What happens when F+ x F- mate?

Answer 89

DNA is transferred from F+ to F- cells

Question 90

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

Answer 90

Episome

Question 91

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

Answer 91

Lysozyme

Question 92

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

Answer 92

Homologous recombination

Question 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?

Answer 93

Branch migration

Question 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

Answer 94

True

Question 95

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

Answer 95

Isomerisation

Question 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?

Answer 96

Double strand break repair model

Question 97

The major pathway of recombination in E. coli is?

Answer 97

RecBCD pathway

Question 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.

Answer 98

RecBCD

Question 99

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

Answer 99

False

Question 100

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

Answer 100

False

Question 101

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

Answer 101

Synapse

Question 102

______ bind to ssDNA and form nucleoprotein filaments.

Answer 102

RecA

Question 103

_______ force the ssDNA into the helical conformation.

Answer 103

RecA

Question 104

It has ATP and DNA binding activities and weak ATPase activity

Answer 104

RecF

Question 105

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

Answer 105

RecBCD

Question 106

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

Answer 106

Pathway RecF

Question 107

Following diagram represents what?

Answer 107

Holliday single strand invasion model