Question 1

As helicase unwinds the DNA molecule, what keeps the strands apart?
A) Replication fork
B) Okazaki fragments
C) DNA polymerase
D) Reverse transcriptase
E) Single-strand binding proteins

Accepted Answer

Single-strand binding proteins stabilize the unwound DNA strands and prevent them from re-annealing during replication.

Question 2

Which enzyme activity is associated with DNA polymerase I?
A) 5' to 3' polymerase
B) 3' to 5' exonuclease
C) 5' to 3' exonuclease
D) Both A and B
E) All of the above

Accepted Answer

DNA polymerase I has 5' to 3' polymerase activity, 3' to 5' exonuclease activity for proofreading, and 5' to 3' exonuclease activity for removing RNA primers.

Question 3

In eukaryotes, chromosomes are duplicated during which stage of the cell cycle?
A) M
B) G1
C) C1
D) S
E) G2

Accepted Answer

Chromosomes are duplicated during the S (synthesis) phase of the cell cycle in eukaryotes.

Question 4

Where does the initiator protein bind DNA at the start of replication?
A) At a replication fork
B) At an origin of replication
C) At a promoter region
D) At a start codon
E) At any AT-rich region

Accepted Answer

The initiator protein binds at the origin of replication, which is the specific sequence where DNA replication begins.

Question 5

The two most basic steps of DNA replication are
A) the new strand is denatured and a template is synthesized.
B) helicase unwinds template and DNA polymerase binds.
C) primase causes primer to bind template and ligase copies the template.
D) the template is denatured and a new strand is synthesized.
E) leading strand is copied first and lagging strand second.

Accepted Answer

The answer of The two most basic steps of DNA...

Question 6

In both prokaryotes and eukaryotes, DNA replication is
A) bidirectional and semiconservative.
B) bidirectional and dispersive.
C) unidirectional and dispersive.
D) dispersive and semiconservative.
E) unidirectional and semiconservative.

Accepted Answer

DNA replication in both prokaryotes and eukaryotes is bidirectional, meaning it proceeds in two directions from the origin of replication, and semiconservative, meaning each new DNA molecule consists of one old strand and one new strand.

Question 7

What allows for the base-pairing error rate to be kept very low during replication?
A) UV light radiation corrects any base mispairs.
B) DNA repair mechanisms can fix the mispaired bases.
C) Mispaired bases cause the cell to die.
D) Bases that are mispaired can excise themselves.
E) There are no errors.

Accepted Answer

DNA repair mechanisms, such as mismatch repair, can identify and correct errors that occur during DNA replication, keeping the error rate low.

Question 8

During replication, the direction of synthesis of new DNA from the leading and lagging strands is
A) 3' to 5' only.
B) both 5' to 3' and 3' to 5'.
C) from left to right only.
D) 5' to 3' only.
E) different, depending on whether the cell is prokaryotic or eukaryotic.

Accepted Answer

DNA synthesis occurs in the 5' to 3' direction for both the leading and lagging strands. The leading strand is synthesized continuously, while the lagging strand is synthesized in short segments called Okazaki fragments, but both are in the 5' to 3' direction.

Question 9

Which enzyme replaces RNA primers with DNA after elongation?
A) RNA primase
B) DNA polymerase I
C) RNA polymerase
D) DNA ligase
E) DNA polymerase III

Accepted Answer

DNA polymerase I is responsible for removing RNA primers and replacing them with DNA nucleotides during DNA replication.

Question 10

In E. coli, replication begins at which chromosome site?
A) ter
B) oriC
C) The replication fork
D) TBP
E) Any of the above

Accepted Answer

Replication in E. coli begins at a specific chromosome site called the origin of replication (oriC).

Question 11

Which kind of enzyme prevents DNA from tangling up by introducing negative supercoils as the replication fork migrates during replication?
A) Helicase
B) DNA polymerase I
C) Topoisomerase
D) DNA polymerase III
E) Ligase

Accepted Answer

Topoisomerase prevents DNA from tangling by introducing negative supercoils, which helps in relieving the tension created during the unwinding of DNA strands at the replication fork.

Question 12

Replication of nuclear DNA in eukaryotes requires
A) Pol alpha only.
B) Pol beta only.
C) Pol alpha and delta.
D) Pol epsilon only.
E) Pol alpha, delta, and epsilon.

Accepted Answer

Replication of nuclear DNA in eukaryotes involves multiple DNA polymerases. Pol alpha initiates DNA synthesis by laying down an RNA-DNA primer. Pol delta and Pol epsilon are responsible for the elongation of the lagging and leading strands, respectively.

Question 13

The enzymatic activity of a telomerase is best described as a
A) polymerase.
B) reverse transcriptase.
C) exonuclease.
D) ligase.
E) topoisomerase.

Accepted Answer

Telomerase is an enzyme that adds DNA sequence repeats to the 3' end of DNA strands in the telomere regions. It acts as a reverse transcriptase, using an RNA template to synthesize DNA.

Question 14

What is a replication bubble?
A) A localized site in the nucleus where chromosomes are replicating
B) A DNA sequence that initiates replication
C) A complex of replication enzymes on the DNA template strand
D) A locally denatured segment of DNA where replication originates
E) A tangle of denatured DNA strands near the replication fork

Accepted Answer

A replication bubble is a locally denatured segment of DNA where replication originates, allowing the replication machinery to access the DNA strands for synthesis.

Question 15

Which enzyme elongates the new DNA strand starting at an RNA primer?
A) DNA polymerase III
B) DNA ligase
C) RNA primase
D) RNA polymerase
E) DNA polymerase I

Accepted Answer

DNA polymerase III is responsible for adding nucleotides to the new DNA strand, starting at the RNA primer, during DNA replication.

Question 16

Which of the following are necessary for DNA replication in vitro?
A) DNA can't replicate in vitro
B) Okazaki fragments, helicase, DNA polymerase
C) RNA, helicase, DNA polymerase
D) Template DNA, DNA polymerase, four dNTPs, magnesium ions
E) Template DNA, four dNTPs, and magnesium ions

Accepted Answer

For DNA replication in vitro, a template DNA, DNA polymerase, four deoxynucleotide triphosphates (dNTPs), and magnesium ions are necessary to facilitate the synthesis of new DNA strands.

Question 17

After removal of the RNA primers and replacement with DNA nucleotides, the single-stranded nick adjacent to Okazaki fragments is filled in through a reaction that involves which enzyme?
A) DNA ligase
B) SSB protein
C) DNA primase
D) RNA polymerase
E) DNA helicase

Accepted Answer

DNA ligase is the enzyme responsible for sealing the nicks between Okazaki fragments on the lagging strand during DNA replication, completing the formation of a continuous DNA strand.

Question 18

After a region of DNA has been replicated, ______ removes the RNA primers.
A) DNA helicase
B) DNA polymerase III
C) DNA ligase
D) DNA polymerase I
E) RNA primase

Accepted Answer

DNA polymerase I removes the RNA primers and replaces them with DNA nucleotides during DNA replication.

Question 19

How many replication forks are produced when DNA denatures at an origin?
A) 1
B) 2
C) 0
D) 3
E) The number varies

Accepted Answer

When DNA denatures at an origin, it produces two replication forks, one on each strand of the DNA.

Question 20

What did Meselson and Stahl's experiment demonstrate?
A) DNA replication is sometimes conservative and sometimes semiconservative.
B) DNA replication is semiconservative.
C) DNA replication is conservative.
D) DNA replication is dispersive.
E) DNA replication is discontinuous.

Accepted Answer

Meselson and Stahl's experiment demonstrated that DNA replication is semiconservative, meaning each new DNA molecule consists of one old strand and one newly synthesized strand.

Quiz 10: Non-Mendelian Inheritance

As helicase unwinds the DNA molecule, what keeps the strands apart?

Which enzyme activity is associated with DNA polymerase I?

In eukaryotes, chromosomes are duplicated during which stage of the cell cycle?

Where does the initiator protein bind DNA at the start of replication?

The two most basic steps of DNA replication are

In both prokaryotes and eukaryotes, DNA replication is

What allows for the base-pairing error rate to be kept very low during replication?

During replication, the direction of synthesis of new DNA from the leading and lagging strands is

Which enzyme replaces RNA primers with DNA after elongation?

In E. coli, replication begins at which chromosome site?

Which kind of enzyme prevents DNA from tangling up by introducing negative supercoils as the replication fork migrates during replication?

Replication of nuclear DNA in eukaryotes requires

The enzymatic activity of a telomerase is best described as a

What is a replication bubble?

Which enzyme elongates the new DNA strand starting at an RNA primer?

Which of the following are necessary for DNA replication in vitro?

After removal of the RNA primers and replacement with DNA nucleotides, the single-stranded nick adjacent to Okazaki fragments is filled in through a reaction that involves which enzyme?

After a region of DNA has been replicated, ______ removes the RNA primers.

How many replication forks are produced when DNA denatures at an origin?

What did Meselson and Stahl's experiment demonstrate?