Deck 25: Dna Replication

Question 1

In a type I topoisomerase,the active site amino acid _________ is covalently bound to the free _______ end of the cut in the DNA.

A)serine;3'
B)serine;5'
C)tyrosine;3'
D)tyrosine;5'
E)none of the above

Answer 1

tyrosine;5'

Question 2

Which of the following is required for DNA polymerase I activity?

A)3' hydroxyl group
B)ATP,GTP,TTP and CTP
C)Zn²⁺
D)an RNA template
E)all of the above

Answer 2

3' hydroxyl group

Question 3

What is an Okazaki fragment?

A)a small section of DNA bound to the leading strand
B)a small section of DNA bound to the lagging strand
C)a small section of RNA and DNA bound to the leading strand
D)a small section of RNA and DNA bound to the lagging strand
E)none of the above

Answer 3

D

Question 4

Replication of DNA in E.coli occurs in what type of fashion?

A)unidirectional
B)bidirectional
C)multidirectional
D)directionality can change depending upon specific conditions in the cell
E)none of the above

Question 5

Which of the subunits of DNA polymerase III is responsible for the high processivity of the enzyme?

A) $\beta$
B) $\gamma$
C) $\delta$
D) $\delta$ '
E) $\varepsilon$

Question 6

Which of the following exonuclease activities is present in DNA polymerase I?

A)3' exonuclease that degrades double stranded DNA
B)3' exonuclease that degrades hairpin DNA
C)5' exonuclease that degrades single stranded DNA
D)5' exonuclease that removes RNA from a DNA-RNA duplex
E)none of the above

Question 7

Which of the following explains the result of type I topoisomerase activity on underwound DNA,considering that no energy (ATP)is used in the reaction?

A)the linking number is decreased by 1
B)the linking number is increased by 1
C)the linking number remains the same but the twist decreases by 1
D)the linking number remains the same but the twist increases by 1
E)none of the above

Question 8

Type I topoisomerases break _____ strand(s)of DNA;type II topoisomerases break _____strand(s)of DNA.DNA gyrase is a type ___ topoisomerase.

A)both;1;I
B)both;1;I
C)both;1;III
D)1;both;I
E)1;both;II

Question 9

In eukaryotic replication,which polymerase is analogous to E.coli primase?

A)pol $\alpha$
B)pol $\beta$
C)pol $\gamma$
D)pol $\delta$
E)pol $\varepsilon$

Question 10

How does the gp32 protein facilitate both stabilization of single-stranded DNA as well as its renaturation to double-stranded DNA?

A)gp32 is an enzyme and thus its reaction of separating DNA strands is freely reversible
B)gp32 binds only to regions of high A and T content so hydrogen bonding is reversible
C)gp32 displays cooperativity in binding to single stranded DNA
D)the gp32 C-terminal domain acts as a switch between weak and strong single stranded DNA binding
E)none of the above

Question 11

Which of the following DNA polymerases is correctly defined?

A)polymerase I: DNA repair
B)polymerase I: RNA primer excision
C)polymerase II: DNA repair
D)polymerase III: nucleotide incorporation during replication
E)all of the above

Question 12

What protein complexes with ATP and cardiolipin to initiate E.coli DNA replication by creating negative superhelical tension in the double stranded DNA?

A)DnaA
B)DnaB
C)DnaC
D)DnaJ
E)DnaK

Question 13

Which of the following describes the correct sequence of enzyme activity upon the lagging strand?

A)primase,DNA ligase,DNA polymerase I,DNA polymerase III
B)primase,DNA polymerase I,DNA polymerase III,DNA ligase
C)DNA polymerase III,primase,DNA polymerase I,DNA ligase
D)primase,DNA ligase,DNA polymerase III,DNA polymerase I
E)primase,DNA polymerase III,DNA polymerase I,DNA ligase

Question 14

What enzyme that is part of the primosome is responsible for unwinding of the DNA ahead of the replication fork?

A)topoisomerase
B)helicase
C)primase
D)clamp loading complex
E)single-stranded binding protein

Question 15

A mutation in a gene results in a mutant phenotype.What occurs if the wild-type phenotype is restored by a mutation at another site in the gene?

A)reversion
B)silent mutation
C)conjugation
D)silent conjugation
E)suppression

Question 16

Which of the following is the best description for primase?

A)a DNA-dependent DNA polymerase
B)an RNA-dependent DNA polymerase
C)a DNA-dependent RNA polymerase
D)an RNA-dependent RNA polymerase
E)none of the above

Question 17

In the Klenow fragment of many DNA polymerases,the Mg²⁺ ions that are required for activity are coordinated to which amino acid R-groups?

A)histidine and aspartate
B)two aspartates
C)aspartate and asparagine
D)aspartate and glutamate
E)glutamate and glutamine

Question 18

Which of the following is an 11-base consensus sequence that makes up the autonomously replicating sequence present in yeast DNA that is a requirement for the start of replication?

A)5'-GTGCGTGCGTG-3'
B)5'-CCTCCTGGTGG-3'
C)5'-AAGCGCGCGCC-3'
D)5'-GGTGGACCTCC-3'
E)5'-TTTTATATTTT-3'

Question 19

Which of the following was evidence that DNA polymerase I was not responsible for the bulk of DNA synthesis in vivo?

A)the requirement for an RNA primer
B)the presence of both polymerase and exonuclease activity in the same enzyme
C)the number of enzyme copies in each cell far exceeded the number of replication forks
D)the requirement for Mg²⁺
E)none of the above

Question 20

In DNA synthesis,the _____________ strand is synthesized in a __________ fashion.

A)template;discontinuous
B)template;continuous
C)leading;discontinuous
D)lagging;discontinuous
E)none of the above

Question 21

If a segment of a eukaryotic chromosome contained three origins of replication (at the sites indicated with arrows),how would the segment appear when replication was about half completed?

Question 22

What feature of the telomerase enzyme allows it to synthesize DNA without the use of a DNA or RNA primer?

A)it synthesizes new DNA in a 3'to 5' direction
B)it contains an RNA oligonucleotide complementary to the telomeric sequence
C)since the telomeric sequence is a 15 base repeat,it is synthesized separately from the replication process and merely sealed in place by the ligase action of telomerase
D)telomeric DNA forms a hairpin that is used to create its own complimentary primer
E)none of the above

Question 23

For the following sequence,indicate the RNA primer that would be needed to start synthesis of the Okazaki fragment.
5'-A-A-C-T-A-G-A-C-C-A-G-A-3'

Question 24

Show the reaction (with arrow pushing)for addition of the next nucleotide: