Deck 9: DNA Replication and Recombination

Question 1

In the diagram below, which letter indicates the 5' end of the leading strand?

A)A
B)B
C)C
D)D
E)C and D

Answer 1

C

Question 2

Suppose that some cells are grown in culture in the presence of radioactive nucleotides for many generations so that both strands of every DNA molecule include radioactive nucleotides.The cells are then harvested and placed in new medium with nucleotides that are not radioactive so that newly synthesized DNA will not be radioactive.What proportion of DNA molecules will contain radioactivity after two rounds of replication?

A)0
B)1/8
C)1/4
D)1/3
E)1/2

Answer 2

E

Question 3

Which of the following typically only has one origin of replication?

A)Prokaryotes
B)Eukaryotes
C)Linear model of replication
D)Humans
E)Plants

Answer 3

A

Question 4

What is the function of DNA gyrase?

A)Connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone
B)Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork
C)Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding
D)Binds to oriC and causes a short
E)Prevents the formation of secondary structures within single-stranded DNA

Question 5

Which of the following enzymes do NOT aid in unwinding of DNA for replication?

A)Helicase
B)Single-stranded binding proteins
C)Primase
D)Gyrase
E)Topoisomerase

Question 6

Suppose Meselson and Stahl had obtained the following results in their experiment.Which model of replication are these results consistent with?

A)Conservative replication only
B)Semiconservative and conservative replication
C)Semiconservative replication only
D)Dispersive replication only
E)Semiconservative and dispersive replication

Question 7

DNA polymerase I and DNA polymerase III both have _____ activity, but only DNA polymerase I has _____ activity.

A)5' $\rightarrow$ 3' exonuclease; 3' $\rightarrow$ 5' exonuclease
B)5' $\rightarrow$ 3' polymerase; 3' $\rightarrow$ 5' polymerase
C)3' $\rightarrow$ 5' polymerase; 5' $\rightarrow$ 3' polymerase
D)3' $\rightarrow$ 5' exonuclease; 5' $\rightarrow$ 3' exonuclease
E)5' $\rightarrow$ 3'polymerase; 3' $\rightarrow$ 5' exonuclease

Question 8

The nuclear genome of a single human cell (i.e., the entire diploid complement)contains about 6.6 billion (6.6 × 10⁹)base pairs of DNA.If synthesis at each replication fork occurs at an average rate of 50 nucleotides per second, all the DNA is replicated in 5 minutes.Assume that replication is initiated simultaneously at all origins.Assuming that the origins are approximately equally distributed across the chromosomes, what is the average number of origins per human chromosome?

A)4783
B)19, 130
C)4)6 × 10⁶
D)1)21 × 10⁹
E)2)9 × 10¹⁰

Question 9

You are studying a new virus with a DNA genome of 12 kb.It can synthesize DNA at a rate of 400 nucleotides per second.If the virus uses theta replication, how long will it take to replicate its genome?

A)7)5 seconds
B)15 seconds
C)30 seconds
D)1 minute
E)2 minutes

Question 10

The diagram below represents a replication fork.The leading strand is the _____ strand.

A)lower
B)upper

Question 11

The nuclear genome of a single human cell (i.e., the entire diploid complement)contains about 6.6 billion (6.6 × 10⁹)base pairs of DNA.If synthesis at each replication fork occurs at an average rate of 50 nucleotides per second, all the DNA is replicated in 5 minutes.Assume that replication is initiated simultaneously at all origins.How many origins of replication exist in a human diploid genome?

A)220, 000
B)440, 000
C)880, 000
D)2)64 × 10⁷
E)1)32 × 10⁸

Question 12

Topoisomerases help DNA replication by:

A)unwinding the DNA.
B)creating RNA primers.
C)breaking hydrogen bonds between the two DNA strands.
D)proofreading DNA.
E)joining phosphodiester bonds.

Question 13

What is the function of single-strand-binding proteins?

A)Connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone
B)Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork
C)Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding
D)Binds to oriC and causes a short
E)Prevents the formation of secondary structures within single-stranded DNA

Question 14

You learn that a Mars lander has retrieved a bacterial sample from the polar ice caps.To determine how the Mars bacteria replicate their DNA, you obtain a sample of these bacteria and perform the same kind of experiment that Meselson and Stahl did.Based on the following equilibrium density gradient centrifugation results, what type of replication would you propose for these new bacteria?

A)Conservative
B)Semiconservative
C)Dispersive
D)Semiconservative or dispersive
E)Conservative or dispersive

Question 15

Okazaki fragments are found in all of the following EXCEPT:

A)the leading strand.
B)the lagging strand.
C)eukaryotic DNA.
D)bacterial DNA.
E)linear replication models.

Question 16

What type of synthesis occurs on the leading strand?

A)Conservative
B)Dispersive
C)Continuous
D)Discontinuous
E)Recombination

Question 17

All DNA polymerases synthesize new DNA by adding nucleotides to the _____ of the growing DNA chain.

A)3' OH
B)5' OH
C)3' phosphate
D)5' phosphate
E)nitrogenous base

Question 18

Meselson and Stahl showed that DNA is replicated by a _____ system.

A)conservative
B)semiconservative
C)dispersive
D)semidispersive
E)conservative in prokaryotes and dispersive in eukaryotes

Question 19

The leading and the lagging strands differ in that the:

A)leading strand is synthesized toward the replication fork and the lagging strand is synthesized in the opposite direction.
B)leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.
C)lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately attached to each other.
D)leading strand is synthesized at twice the rate of the lagging strand.

Question 20

Which of the following does NOT utilize bidirectional replication?

A)Theta model
B)Archaebacteria
C)Linear model
D)Eukaryotes
E)Bacteria

Question 21

DNA polymerases require all of the following for DNA replication EXCEPT:

A)DNA template.
B)primer.
C)free 3' OH.
D)3' to 5'polymerase activity.
E)dNTPs.

Question 22

What type of bonds does DNA ligase create between adjacent nucleotides?

A)Hydrogen
B)Phosphodiester
C)Ionic
D)Metallic
E)Ribonucleotide

Question 23

You have a bacterial cell in which a mutation occurred.You observe that Okazaki fragments are created but RNA primers are not removed.Which gene is mutated?

A)DNS ligase
B)DNA polymerase I
C)DNA polymerase III
D)DNA helicase
E)SS binding proteins

Question 24

For which of the following is the "end-replication problem" relevant?

A)Circular DNA
B)Linear chromosomes
C)The centromere region of a chromosome
D)Bacterial chromosome
E)Theta model of replication

Question 25

DNA synthesis during replication is initiated from:

A)a free 5' OH.
B)DNA primers.
C)RNA primers.
D)telomerase.
E)DNA polymerase I.

Question 26

The proofreading function of DNA polymerases involves _____ activity.

A)5' $\rightarrow$ 3'exonuclease
B)3' $\rightarrow$ 5' exonuclease
C)5' $\rightarrow$ 3' telomerase
D)3' $\rightarrow$ 5'telomerase
E)5' $\rightarrow$ 3'gyrase

Question 27

Which of the following BEST describes heteroduplex DNA?

A)A single-stranded DNA molecule of one chromosome pairs with a single-stranded DNA molecule of another chromosome.
B)A single-stranded DNA molecule of one chromosome pairs with a single-stranded RNA molecule of another chromosome.
C)DNA that consists of sequences from two different species brought together through homologous recombination
D)DNA that consists of an RNA primer and newly synthesized DNA on the lagging strand
E)Newly synthesized DNA that has yet to be reassembled into nucleosomes

Question 28

_____ are tandemly repeated DNA sequences located at the ends of eukaryotic chromosomes.

A)Replication bubbles
B)Telomeres
C)Nucleosomes
D)Licensing factors
E)Holliday junctions

Question 29

What is the function of DNA ligase?

A)Connects Okazaki fragments by sealing nicks in the sugar-phosphate backbone
B)Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork
C)Reduces the torsional strain that builds up ahead of the replication fork as a result of unwinding
D)Binds to oriC and causes a short
E)Prevents the formation of secondary structures within single-stranded DNA

Question 30

Which activity is NOT associated with DNA polymerases?

A)Ability to attach a DNA nucleotide to the 3'end of previously incorporated DNA nucleotide
B)Ability to excise a newly incorporated nucleotide that does not match the template strand
C)Ability to "read" a template strand 3' to 5'and synthesize a complementary strand
D)Ability to synthesize a DNA from scratch without a primer
E)Ability to synthesize new DNA in a 5'to 3'direction

Question 31

What would be a likely result of expressing telomerase in somatic cells?

A)Premature aging
B)Cancer
C)Lower rates of replication
D)Immortality of gametes
E)Early termination of replication

Question 32

Replication in archaebacteria is similar to:

A)eukaryotic replication in the proteins involved.
B)eubacteria replication in proteins involved.
C)eubacteria in that they mostly have one origin of replication.
D)eukaryotes that mostly have one origin of replication.
E)both eukaryotic replication in the proteins involved and eubacteria in that they mostly have one origin of replication.

Question 33

Which of the following is TRUE of DNA polymerases of eukaryotic cells?

A)The same DNA polymerase replicates mitochondrial, chloroplast, and nuclear DNA.
B)There are only two different DNA polymerases that function in the process of replication.
C)Some DNA polymerases have the ability to function in DNA repair mechanisms.
D)All eukaryotic DNA polymerases have 3' $\rightarrow$ 5' exonuclease activity.
E)Leading and lagging strand synthesis are performed by the same type of DNA polymerase.

Question 34

Telomerase activity is MOST likely to be found in which cells in humans?

A)Red blood cells
B)Muscle cells
C)Neurons
D)Germ line
E)Any type of somatic cell

Question 35

Which one of the following statements is NOT true for all E.coli DNA polymerases?

A)They require a primer to initiate synthesis.
B)They use dNTPs to synthesize new DNA.
C)They produce newly synthesized strands that are complementary and antiparallel to the template strands.
D)They possess 5' $\rightarrow$ 3'exonuclease activity.
E)They synthesize in the 5' $\rightarrow$ 3'direction by adding nucleotides to a 3' -OH group.

Question 36

If a deletion occurs in a gene that encodes DNA polymerase I and no functional DNA polymerase I is produced, what will be the MOST likely consequence of this mutation?

A)The DNA strands would contain pieces of RNA.
B)The DNA would not exist in a supercoiled state.
C)There would be no DNA replication on the leading or lagging strands.
D)There would be no RNA primers laid down.
E)The DNA will not be able to unwind to initiate replication.

Question 37

DNA primase requires a _____ template and _____ nucleotides to initiate primer synthesis.

A)DNA; DNA
B)RNA; RNA
C)DNA; RNA
D)RNA; DNA
E)leading strand; DNA

Question 38

Which of the following is a protein that facilitates the termination of replication in E.coli?

A)Telomerase
B)DNA gyrase
C)Tus
D)Primase
E)Topoisomerase

Question 39

You have a bacterial cell in which a mutation occurred.You observe that Okazaki fragments are created but not linked as one continuous strand.Which gene is mutated?

A)DNS ligase
B)DNA polymerase I
C)DNA polymerase III
D)DNA helicase
E)SS binding proteins

Question 40

Telomerase uses _____ to synthesize new DNA.

A)exonuclease activity
B)a licensing factor
C)strand invasion
D)a DNA template
E)an RNA template

Question 41

In the diagram below, the arrow indicates the direction of movement of a replication fork. a.Which strand, top or bottom, is the leading strand? Explain.
b.On which strand, top or bottom, would you expect to find Okazaki fragments? Explain.

Question 42

The following is a depiction of a Holliday junction with the option of cutting on the horizontal plane or the vertical plane.

A)The horizontal plane will result in no recombination, and the vertical plane will result in crossover recombination.
B)The horizontal plane will result in crossover recombination, and the vertical plane will result in no recombination.
C)Both will result in no recombination.
D)Both will result in crossover with crossover recombination.
E)Which plane is cut is not important.

Question 43

Both gyrase and helicase help to open up the DNA for replication.How do they differ?

Question 44

There is a misconception that telomerase prevents the shortening of telomeres by just filling in the piece of RNA primer lost.What does telomerase actually do?

Question 45

Why did the Meselson and Stahl experiment require two rounds of replication?

Question 46

The Holliday model describes which process?

A)Semiconservative replication
B)Homologous recombination
C)End replication
D)RNA primer synthesis
E)None of the answers is correct.

Question 47

Explain the effect on DNA replication of mutations that destroy each of the following activities in DNA polymerase.Also, for each kind of mutation, how might you detect the effect in an in vitro replication reaction?
a.5' to 3' polymerase
b.5'to 3'exonuclease
c.3' to 5'exonuclease

Question 48

Are Okazaki fragments formed on the leading strand during DNA replication? Explain your answer.

Question 49

List and describe the key events of DNA replication in their relative order for E.coli.

Question 50

(a)Explain the significance of telomerase in cells of the germ line.(b)Explain the significance of telomerase in cancer cells.

Question 51

Explain the need for and mechanism of licensing of DNA replication.

Question 52

What does the term "noncrossover recombinant" mean with respect to homologous recombination?

Question 53

What would be the phenotype of a differentiated cell that is a telomerase mutant? Would it be viable?

Question 54

Why do eukaryotic chromosomes have multiple origins of replication, whereas prokaryotic chromosomes typically have only one origin?

Question 55

Which different DNA polymerases are found in eukaryotic cells? What are their functions?

Question 56

What does "proofreading" refer to with regard to DNA replication?

Question 57

You discovered a special dye that reveals the position of recombination sites on meiotic chromosomes.You use this dye to count the number of recombination sites and then compare this to the number of genetic exchanges that you can detect by looking at the segregation of markers across the genome.You find many more recombination sites as compared to genetic exchanges.Explain this result.

Question 58

What is a heteroduplex region, and how is it created?

Question 59

Which of the following is a necessary step in the Holliday model of recombination?

A)DNA primase generates an RNA primer.
B)The RNA template of telomerase binds to the telomere.
C)Topoisomerases aid in supercoiling.
D)DNA polymerase $\alpha$ initiates DNA synthesis.
E)A single-strand break occurs in the DNA molecule.