Chpt 3: Dna Replication

Front 1

At the conclusion of DNA replication, the two resulting DNA double helices each contain:
A. one parental and one progeny strand.
B. two parental or two progeny strands.
C. stretches of progeny DNA interspersed with parental DNA along both strands.
D. two newly synthesized strands.

Back 1

A. Each polynucleotide strand in DNA serves as a template for the synthesis of a second strand. Therefore, each progeny double helix contains one parental and one progeny strand.

Front 2

DNA polymerase catalyzes the formation of a phosphodiester bond between a:
A. 5′ phosphate and a 5′ hydroxyl group.
B. 3′ phosphate and a 5′ hydroxyl group.
Student Response
C. 5′ phosphate and a 3′ hydroxyl group.
D. 3′ phosphate and a 3′ hydroxyl group.

Back 2

C - DNA polymerase catalyzes the formation of a phosphodiester bond between the 5′ phosphate of one nucleotide and the 3′ hydroxyl on the incoming nucleotide; therefore, chain growth is said to occur in the 5′ arrow 3′ direction.

Front 3

DNA polymerases are enzymes that copy:
A. DNA into DNA.
B. DNA into RNA.
C. RNA into DNA.
D. RNA into RNA.

Back 3

A - DNA polymerase catalyzes the chemical reactions necessary for replication of the genome.

Front 4

During synthesis, all DNA polymerases add nucleotides in which direction?
A. from left to right
B. from 3′ to 5′
C. from 5′ to 3′
D. in more than one direction at a time

Back 4

C - DNA polymerase catalyzes the formation of a phosphodiester bond between the 5′ phosphate of one nucleotide and the 3′ hydroxyl on the incoming nucleotide; therefore, chain growth is said to occur in the 5′ arrow 3′ direction.

Front 5

In bacteria such as E. coli, replication of the chromosome is:
A. semidiscontinuous and bi-directional.
B. discontinuous and unidirectional.
C. continuous and bi-directional.
D. semidiscontinuous and unidirectional.

Back 5

A -DNA synthesis is continuous on one strand and discontinuous on the other and is therefore considered semidiscontinuous. The reaction proceeds in opposite directions from the origin of replication on the bacterial chromosome.

Front 6

In eukaryotes, DNA replication occurs during which phase of the cell cycle?
A. S
B. G1
C. G2
D. M

Back 6

A - DNA replication must occur before the cell divides to ensure that the progeny cells each receive a complete copy of the genetic information.

Front 7

Many types of mammalian cancer cells are notable for their:
A. telomerase activity.
B. lack of telomerase activity.
C. lack of telomeres.
D. increased number of telomeres.

Back 7

B - Telomerase is the enzyme that maintains the telomeres (end regions) of eukaryotic chromosomes. It has been noted that the telomeres of cancer cells become progressively shorter due to inactivity of the telomerase enzyme.

Front 8

On the E. coli chromosome, oriC :
A. encodes DNA polymerase I.
B. is a binding site for histone proteins.
C. is the start site for replication.
D. encodes an RNA primer.

Back 8

C - The oriC region is the origin of replication in E. coli.

Front 9

Why, exactly, is a primer necessary to initiate lagging-strand DNA synthesis?
A. The new DNA strand will be composed of linked primers.
B. The primer binds DNA polymerase to the site of new synthesis.
C. The primers are converted into Okazaki fragments, which are then joined to form the new strand.
D. A free 3′-OH group is necessary for DNA polymerase.

Back 9

D - DNA polymerase can only catalyze phosphodiester bonds between a free 3′ hydroxyl group and the 5′ phosphate group of a free nucleotide.

Front 10

The 3′ arrow 5′ exonuclease activity associated with DNA polymerase reduces the frequency of replication errors to:
A. 1/10.
B. 1/1,000.
C. 1/1,000,000.
D. 1/1,000,000,000.

Back 10

D - With proofreading, the frequency of replication errors by DNA polymerase I or III is reduced to lower than 10-9.

Front 11

The enzyme that unwinds the double helix to facilitate replication is:
A. 3′ arrow 5′ exonuclease.
B. DNA helicase.
C. DNA polymerase.
D. topoisomerase.

Back 11

B - Before replication can begin, DNA helicase provides a single-stranded template for DNA polymerase.

Front 12

The proofreading activity of DNA polymerase removes errant nucleotides from the ___ of a strand DNA.
A. 3' end
B. 5' end
C. 3' and 5' end
D. middle

Back 12

A - DNA polymerases I, II, and III have all been shown to have the ability to remove erroneous bases from the 3′ end of newly synthesized polynucleotide chains.

Front 13

Under a hypothesis of semi-conservative DNA replication, Meselson and Stahl expected to see _____ DNA band(s) in the cesium chloride gradient after one round of replication, and _____ band(s) after two rounds of replication.
A. 2;2
B. 1;2
C. 1;1
D. 2;4

Back 13

B - After one round of replication, both new DNA molecules consist of one strand of original DNA and one strand of new DNA (a hybrid double helix), making a single band in the cesium chloride gradient. The second round produces two new hybrid molecules and two molecules consisting of wholly new DNA; thus there should be two bands in evidence in a 1:1 ratio.

Front 14

Identify the order in which the following enzymes play a role in DNA replication:
topoisomerase
ligase
primase
helicase
polymerase

Back 14

helicase, polymerase, ligase :

Helicase locally unwinds the double helix

polymerase synthesizes a new DNA strand

ligase ultimately catalyzes the final phosphodiester bond (on the discontinuous strand)

Front 15

When the DNA double helix is replicated, the newly synthesized 5′ arrow 3′ strand is considered the ___ strand:
A. leading
B. lagging
C. template
D. discontinuous

Back 15

A - The 5' >> 3' strand is called the leading strand because synthesis of this strand is continuous

Front 16

Which E. coli DNA polymerase has the ability to "proofread" newly synthesized DNA and remove erroneous bases?
A. DNA polymerase I only
B. DNA polymerase III only
C. DNA polymerase I and III
D. all three DNA polymerases have proofreading ability

Back 16

D - DNA polymerases I, II, and III have all been shown to have the ability to remove erroneous bases from the 3′ end of newly synthesized polynucleotide chains.

Front 17

What do the following genes encodes for?
A. polA
B. polB
C. dnaA
D. holE

Back 17

A - polA = DNA polI

B - polB = DNA polII

C - dnaA = initiator protein (binds to oriC)

D - holE = theta polypeptide w/in polIII

*pg50

Front 18

Which of the following is not required for DNA synthesis reactions?

dCTPs / template DNA / DNA poly / Ca+

Back 18

Ca+: Mg+ is needed

Front 19

What type of DNA is duplicated by rolling circle replication?

Back 19

bacteriophages (ex: X174 & lambda) & plasmid DNA