a.
Is
unidirectional & semiconservative
b.
Contain
one intact parental strand of each daughter DNA molecule
c.
Occurs
at sites of origin of both strands which have specific base sequences
d.
Occurs
only at one point of origin in each strands
2)
Steps in
DNA replication include
a.
Helicases
which unwind the double helix without using energy
b.
Unwinding
and separating the 2 strands & form a ‘V’ where active synthesis occur
c.
Replication
of unidirectional double-stranded DNA
d.
Maintaining
the double helix by SSB proteins
3)
Topoisomerases
enzyme
a.
Type I
appear to store energy from the phosphodiester bond they sealed
b.
Irreversibly
cut one strand of the double helix
c.
Create
a transient ‘nick’ in one DNA strand, relieve
the accumulated supercoils and resealed it
d.
In
eukaryotes, DNA gyrase can be inhibited by antibiotics of quinolone family
4)
Single
stranded DNA binding proteins
a.
Provides
single-stranded template required by polymerases
b.
Protect
DNA from nucleases that cleave single stranded DNA
c.
Serve to
shift the equilibrium between double strand DNA and single strand DNA in the
direction of single strand DNA forms
d.
Prevent
reannealing of the double helix
5)
The
nucleotide sequences in 3’- 5’ direction
a.
Is used
as the template strand
b.
Is read
in that way to be copied by DNA polymerases
c.
Act as
template for synthesizing the new strands of DNA in parallel direction
d.
Serves
as parental strand for leading strand
6)
The
synthesizing new DNA
a.
Is
initiated by DNA polymerase in both strands
b.
Requires
DNA polymerase to add deoyribonucleotides to the 3’-hydroxyls of the RNA
primers
c.
Involve
discontinuously adding nucleotides in both strands
d.
Involve
reaction of 5’triphosphate with the 3’end of the growing DNA strand forming a
covalent bond
7)
Okazaki
fragments are
a.
Formed
in 5’- 3’direction of the leading strand
b.
Synthesized
continuously in the lagging strands from 3’- 5’direction
c.
Then
sealed by DNA ligase after the removal of primer & replacement of
nucleotides.
d.
Formed
by the DNA polymerase III after the unwinding of the double helix
Enzyme Action
|
Prokaryotics
|
|
a.
|
Leading strand synthesis
|
DNAP III
|
b.
|
Leading strand synthesis (RNA
primer formation)
|
Primase
|
c.
|
Lagging strand synthesis
(replacement of RNA primer with DNA)
|
DNAP III
|
d.
|
Joining of Okazaki fragments
to lagging strands
|
DNA ligase
|
8)
9)
DNA
chain elongation is
a.
Adding
deoxyribonucleotides randomly
b.
Done
by using the 5’-hydroxyl group of the RNA primer as the acceptor of the first
deoxyribonucleotide
c.
The
action of DNA polymerase III adding nucleotides along the single-stranded
template
d.
Result
in the newly synthesized strand in the antiparallel direction to the parental
strand.
10)
Proofreading
of newly synthesized DNA
a.
Is done
by DNA polymerase I and III
b.
Is
highly important for the survival of an organism
c.
Involved
activation of 5’-
3’exonuclease activity if there is any irregularity in the helix
d.
Must be
done in the direction along with the newly synthesized nucleotides.
11)
Lagging
strand
a.
Synthesized
continuously
b.
Being
copied in the direction towards replication fork
c.
Involving
small fragments of DNA being copied near replication fork
d.
Involve
the joining of fragments becoming single, continuous strand
12)
RNA
primer
a.
Is
formed by DNA-dependent RNA primase
b.
Consist of free hydroxyl group on the 5’end of the RNA
strand
c.
Is
formed for the start of synthesizing new strands
d.
Has
hydroxyl group that serves as first receptor of a nucleotide
13)
DNA
polymerase III
a.
Includes
5’-deoxyribonucleoside triphosphates as precursors
b.
Mechanism
involves releasing of pyrophosphate when each new nucleoside monophosphate is
added
c.
Involves
in proofreading mechanism using 5’to 3’exonuclease activity
d.
Has
3’ to 5’polymerase to replace the mistaken nucleotide with the new one
14)
According
to Francis Crick,
a.
Information
flow from DNA to proteins
b.
Central
dogma is well followed for most of the time
c.
Central
dogma is represented by 3 main stages
15)
Suppose
a mutation occurs in a cell such that abnormal Okazaki fragments were created
during DNA replication and were not linked together into a continuous
strand. The gene for which enzymes would
you predict was altered by this mutation?
a.
Helicase
b.
Ligase
c.
DNA
polymerase III
d.
DNA
polymerase I
16)
What
happens after the RNA primer laying down a new primer on the new strands?
a.
The RNA
primer is removed and is replaced by DNA.
b.
DNA
polymerase I add deoxyribonucleotides
c.
Elongation
from the primer producing lagging strand
d.
The
3’hydroxyls of RNA primer are being added with deoxyribonucleotides
17)
A
mutation to DNA polymerase that
eliminated the 3-to-5 exonuclease activity would prevent:
a.
ligation
of the okazaki fragments.
b.
removal
of the RNA primer.
c.
removal
of base mismatches.
d.
repair of deaminated bases.
18)
The best
explanation for why DNA synthesis is discontinuous would be that:
a.
DNA
polymerase can only move along the DNA strand in one orientation.
b.
This
allows for efficient error checking of newly synthesized DNA.
c.
DNA polymerase must stop periodically to
reload more nucleotides.
d.
It
happens in lagging strand
19)
Match
each of the following DNA replication mechanisms with the correct description
Mechanism Description
a.
DNA
Polymerase proofreading might
repair a base mismatches
b.
Homologous recombination fix a mismatch that evades DNA
polymerase
c.
DNA
polymerase I replacement of RNA primer
d.
DNA
dependent RNA primer initiate
synthesis of new strands
20)
A
mutation to DNA polymerase that eliminated the 3-to-5 exonuclease activity would prevent:
a.
ligation
of the okazaki fragments.
b.
removal of the RNA primer.
c.
removal
of base mismatches.
d.
repair
of deaminated bases.
21)
DNA
replication is said to be semiconservative because:
a.
both RNA and DNA synthesis are involved in the
process.
b.
part of the telomere is lost during each round
of replication.
c.
a new
double helix contains one old and one new strand.
d.
each new
strand is complementary, not identical, to its template.
22)
Why is
an RNA primer necessary for DNA replication?
a.
The RNA
primer is necessary for the activity of DNA ligase.
b.
The RNA
primer creates the 5’ and 3’ ends of the
strand.
c.
DNA
polymerase can only add nucleotides to RNA molecules.
d.
Acts as
initiator to synthesize new strands
23)
Choose
the correct statements.
a.
Single-stranded
binding proteins attach after DNA helicase separates the double helix.
b.
Formation of a leading strand but not a
lagging strand does not require a primer.
c.
DNA
Ligase is the enzyme that links together DNA strands.
d.
RNA
primers are removed and replaced with DNA before DNA ligase links together the
new DNA strands.
24)
A
replication fork:
a.
is only seen
in prokaryotic chromosomes.
b.
is a
Y-shaped structure where both DNA strands are replicated simultaneously.
c.
is a
site where one DNA strand serves as a template, and the other strand is not
replicated.
d.
is
created by the action of the enzyme RNA polymerase.
25)
Why does
DNA synthesis only proceed in the 5´ to 3´ direction?
a.
Because
DNA polymerases can only add nucleotides to the 3´ end of a
polynucleotide strand.
b.
Because
that is the direction in which the two strands of DNA unzip.
c.
Because
that is the only direction that the polymerase can be oriented.
d.
Because
the chromosomes are always aligned in the 5´ to 3´
direction in the nucleus.
Answers:
ANSWERS
A
|
B
|
C
|
D
|
|
1)
|
F
|
T
|
T
|
F
|
2)
|
F
|
T
|
F
|
F
|
3)
|
F
|
F
|
T
|
F
|
4)
|
T
|
T
|
T
|
F
|
5)
|
T
|
T
|
F
|
T
|
6)
|
F
|
T
|
F
|
F
|
7)
|
F
|
F
|
T
|
F
|
8)
|
T
|
F
|
F
|
T
|
9)
|
F
|
F
|
T
|
T
|
10)
|
T
|
T
|
F
|
F
|
11)
|
F
|
F
|
T
|
T
|
12)
|
T
|
F
|
T
|
T
|
13)
|
T
|
T
|
F
|
F
|
14)
|
T
|
F
|
T
|
|
15)
|
F
|
T
|
T
|
F
|
16)
|
F
|
F
|
T
|
T
|
17)
|
F
|
F
|
T
|
F
|
18)
|
T
|
F
|
F
|
T
|
19)
|
T
|
F
|
T
|
F
|
20)
|
F
|
F
|
T
|
F
|
21)
|
F
|
F
|
F
|
T
|
22)
|
F
|
F
|
T
|
T
|
23)
|
T
|
F
|
F
|
T
|
24)
|
F
|
T
|
F
|
F
|
25)
|
T
|
F
|
F
|
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