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Functions of DNA
DNA, which carries the blueprint of life, is the key
performer of the central dogma. In addition to
transmitting hereditary information from one
generation to the next by means of replication, the
genes of DNA code for protein sequences in all
organisms.
Deepa John
Harini Chandra
Affiliations
Master Layout (Part 1)
1
This animation consists of 3 parts:
Part 1 – Proposed models for DNA replication
Part 2 – Replication of DNA
Part 3 – Transcription of DNA
Parent DNA molecule
2
Replication
3
Conservative
model
Dispersive
model
4
5
Daughter DNA molecules
Semi-conservative
model
1
2
3
4
5
Definitions of the components:
Part 1 – Proposed models for DNA replication
1. Parent DNA molecule: The DNA molecule that is being replicated to
produce new daughter DNA molecules.
2. Replication: It is a fundamental process that occurs in all living
organisms to transmit their genetic material from one generation to the
next. Two copies of nucleic acid are synthesized from one parent molecule
during the process of cell division such that each daughter cell obtains one
copy of the genetic material. The process can be inhibited by novobiocin,
nalidixic acid and coumeomycin in prokaryotes and by aphidicolin, Nethylmaliamide and camptothucin in eukaryotes.
3. Daughter DNA molecules: The new DNA molecules that are
synthesized from the parental DNA molecules and are complementary to
parental DNA molecules.
4. Conservative model: One of the three proposed models for DNA
replication. According to the conservative model, the two parental strands
of DNA as a whole serve as a template for the synthesis of progeny DNA
molecules. Thus, one of the daughter DNA molecules is actually the
parental DNA while the other daughter DNA consists of two newly
synthesized strands from fresh nucleotides.
1
Definitions of the components:
Part 1 – Proposed models for DNA replication
2
5. Dispersive model: One of the three proposed models for DNA
replication. The dispersive model of DNA replication hypothesizes that the
parental DNA molecule is cleaved into smaller double stranded DNA
segments which serve as the template for synthesis of new DNA strands.
The segments then reassemble into complete DNA double helices, with
parental and daughter DNA segments interspersed.
3
6. Semi-conservative model: One of the three proposed models for DNA
replication. According to the semi-conservative model of replication, each
parental strand acts as a template for the synthesis of a new strand of DNA
which is complementary to the parental strand. Each daughter DNA
molecule always has one parental DNA strand and one newly synthesized
daughter strand. This model was ultimately proved by an experiment
conducted by Meselson & Stahl.
4
5
1
Part 1, Step 1:
Conservative model:
Original parent
DNA molecule
Round 1 replication
2
First generation
daughter molecules
3
New nucleotides
Round 2 replication
Second generation
daughter molecules
4
Action Description of the action
5
As shown
in
animation
(Please use black background)
First show the green strands on top with its
label. Next show the two arrows below it
and the red & green figures below. Next
show the down arrows and the figures
below this with text as depicted in the
animation.
Audio Narration
Several models have been postulated to explain the
process of DNA replication. According to the conservative
model, the two parental strands of DNA as a whole serve
as a template for the synthesis of progeny DNA molecules.
Thus, one of the daughter DNA molecules is actually the
parental DNA while the other daughter DNA consists of two
newly synthesized strands from fresh nucleotides.
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Part 1, Step 2:
Dispersive model:
Original parent
DNA molecule
Round 1
replication
2
First generation
daughter molecules
3
Round 2 replication
Second generation
daughter molecules
4
Action Description of the action
5
As shown
in
animation
(Please use black background)
First show the green strands on top with its
label. Next show the two arrows below it
and the red & green figures below where
the green and red strands must be
interspersed. Next show the down arrows
and the figures below this with text as
depicted in the animation.
Audio Narration
The dispersive model of DNA replication hypothesizes that
the parental DNA molecule is cleaved into smaller double
stranded DNA segments which serve as the template for
synthesis of new DNA strands. The segments then
reassemble into complete DNA double helices, with
parental and daughter DNA segments interspersed. The
content of parental DNA in the double helix goes on
decreasing with each generation.
1
Part 1, Step 3:
Semi-conservative model:
Original parent
DNA molecule
Round 1 replication
2
First generation
daughter molecules
3
Parent DNA
strand
Newly synthesized
DNA strand
Round 2 replication
Second generation
daughter molecules
4
Action Description of the action
5
(Please use black background)
As shown First show the green strands on top with its label.
Next show the two arrows below followed by the
in
animation figures below with the green and red strands
intertwined. Next, the arrows below must be shown
followed by figures below.
Audio Narration
According to the semi-conservative model of
replication, each parental strand acts as a template
for the synthesis of a new strand of DNA which is
complementary to the parental strand. Each daughter
DNA molecule always has one parental DNA strand
and one newly synthesized daughter strand.
1
Part 1, Step 4:
Meselson & Stahl Experiment - proof for the semi-conservative model of repllication
2
E.Coli
grown in 15N
containing
medium
Cells transferred and
grown in normal 14N
medium
Round 1 replication
3
Heavy 15N labeled parent DNA
Round 2 replication
First generation
daughter molecules
15N-14N labeled hybrid DNA
Second generation
daughter molecules
15N-14N
hybrid DNA
+ 14N light DNA
4
Centrifugation pattern in CsCl density gradient
Action
Description of the action
Audio Narration
First show the figure on top left with the light pink cylindrical
Of the three replication models suggested, Meselson and Stahl proved that the
transferred into the light blue solution in the flask. The number
of pink shapes must increase by a few numbers after which
one of the shapes must be zoomed into and the red & green
strands shown followed by the figure below that. Next, the
number of pink cylindrical shapes must again increase by 4-5
and then one must be zoomed into and the last figure strands
must be shown followed by the figure on the bottom.
an N-containing medium. Throughout the period of growth, samples were taken,
cells lysed and the DNA analyzed by centrifugation in CsCl gradient. The parent
DNA showed 1 band in CsCl gradient corresponding to 15N DNA, the 1st
generation daughter molecules also showed 1 band which was not at the same
position as parent DNA. This corresponded to 14N-15N DNA while the 2nd
generation showed 2 bands, one of 14N-15N and the other of 14N light DNA. These
results exactly matched the semiconservative replication model .
As shown shapes. This must be zoomed into and the green strands
semiconservative model was correct. For this they grew E.coli cultures for several
below must be shown. After zooming out, the figure below that generations in 15N-containing medium so that the bases in DNA contained 15N
in
instead of 14N. Next they transferred & grew the cultures for several generation in
animation must be shown. Next, the pink cylindrical shapes must be
14
5
Master Layout (Part 2)
1
This animation consists of 3 parts:
Part 1 – Proposed models for DNA replication
Part 2 – Replication of DNA
Part 3 – Transcription of DNA
2
Replication fork
Single strand binding protein
Helicase
3
RNA primer
Primase
Template DNA
DNA pol III
4
DNA pol I
DNA ligase
Lagging strand
5
Definitions of the components:
1
2
Part 2 – Replication of DNA
1. Template: A polynucleotide DNA strand that serves as the guide for making
a complementary polynucleotide.
2. Origin of replication: Unique sequences in the genome where replication
is initiated.
3. Replication fork: The point where the two parental DNA strands separate
to allow replication.
3
4. Helicase: An enzyme that unwinds a polynucleotide double helix using
energy derived form ATP hydrolysis.
5. Single strand binding protein (SSB): Binds to single stranded DNA
during replication and keeps it from base pairing with a complementary strand.
6. Primer: A small RNA fragment that provides the free 3’ OH end needed for
DNA replication to begin.
4
5
7. Primase: The enzyme that catalyzes the synthesis of a small piece of RNA
complementary to the single stranded DNA that provides the free 3’ OH end
needed for DNA replication to begin. It is a key component because DNA
polymerases cannot initiate the synthesis of DNA without an RNA primer.
1
2
3
4
5
Definitions of the components:
Part 2 – Replication of DNA
8. Supercoil: A form of circular double stranded DNA in which the double
helix coils around itself like twisted rubber band, leading to a lot of torsional
strain.
9. DNA polymerase: An enzyme that synthesizes DNA by linking together
deoxyribonucleoside monophosphates in the order directed by the
complementary sequences of nucleotides in a template strand. DNA
polymerases can synthesize DNA only in 5’ to 3’ direction and can add
nucleotides only on to a pre-existing 3'-OH group. Prokaryotes have three
types of DNA Polymerase while eukaryotes have five.
10. Leading and lagging strands: DNA polymerase can synthesize DNA
only in 5’to 3’ direction. Therefore, it synthesizes one strand (leading strand)
continuously and the other strand(lagging strand) discontinuously. Each new
piece synthesized on the lagging strand template is called Okazaki fragment.
11. DNA ligase: This enzyme catalyze the formation of a phosphodiester
bond between the 5' phosphate of one strand of DNA and the 3' hydroxyl of
the another thereby covalently linking DNA fragments together during DNA
replication and repair.
Part
2,
Step
1:
1
Unwinding the DNA double helix
Single Stranded Binding
(SSB) proteins
3’
2
3’
Direction of fork
movement
5’
5’
DNA helicase
DNA gyrase
SSBs stabilize
the ssDNA
3
5’
3’
5’
3’
DNA gyrase
4
Action Description of the action
5
The
transparent
blue oval
must move
across the
intertwined
strands &
separate
them
(Please use black background)
First show the green & red strands on top. Next show
the blue transparent oval and the yellow circles. The
blue oval must then move in the direction indicated.
As it moves the two strands must be separated as
shown below and the yellow circles must coat the red
strand on either side. Simultaneously, the purple ‘pie
shape’ must move in the same direction along the
two strands.
Audio Narration
DNA undergoes semi-conservative, bi-directional replication
which begins with the unwinding of the DNA double helix. This is
done by the enzyme DNA helicase which binds to the replication
fork and unwinds the DNA using the energy of ATP hydrolysis.
As this occurs, the enzyme DNA gyrase relieves the trosional
strain that builds up during the process in the unwound part of
the double helix. The single-stranded binding proteins bind to
and stabilize the unwound single stranded regions of the DNA
helix to allow replication to occur.
1
Part 2, Step 2:
Initiation
2
Lagging strand
5’
3’
5’
RNA primers
3
5’
3’
5’
Leading strand
Primase
4
Action Description of the action
5
As shown in (Please use black background)
animation.
First show the figure from the previous step as such
followed by the pink circles. These must move in the
directions shown in the animation and as they move
on the top strand, the yellow circles must be
displaced. Once they move a small distance, the
small blue fragment must appear.
Audio Narration
Initiation of DNA replication is carried out by a primase enzyme
which synthesizes short RNA primer fragments since DNA
Polymerase is not capable of carrying out this process. The
SSBs are displaced as the short fragments get synthesized.
Synthesis takes place in the 5’ to 3’ direction such that
nucleotides can be added to the free 3’ OH group with
concomitant cleavage of the high energy phosphate bond of the
incoming nucleotide. .
1
Part 2, Step 3:
Elongation
Lagging strand
5’
3’
5’
Okazaki fragment
2
5’
5’
3’
Newly synthesized
complementary DNA
Leading strand
DNA Polymerase III
5’
3
Next Okazaki fragment
3’
5’
4
3’
Action Description of the action
5
As
shown
in
animati
on.
(Please use black background) First show the figure on top upto the stage
depicted in previous slide. Next show the green ovals which move in the
direction indicated with the yellow circles on top getting displaced as the oval on
top moves towards it. Once it moves the distance indicated, the red and green
fragments must appear. Next the blue oval and violet pie shaped object must
move as in step 1 with unwinding of the green & red strands as shown below.
Again yellow circles must coat the red strand. Then the pink circle must appear
and move as shown with appearance of the small blue fragment. This is followed
by the green ovals moving with appearance of the green & red fragments as
shown in animation.
Audio Narration
Elongation takes place continuously in the 5’-3’
direction on one strand, known as the leading
strand. On the other strand, replication is
discontinuous with short primers being added
as the helicase unwinds the double helix.
Elongation is carried out by DNA Pol III, a
highly processive enzyme. The short fragments
synthesized on the lagging strand are known
as Okazaki fragments.
1
Part 2, Step 4:
Removal of primers & sealing gaps
3’
Lagging strand 5’
2
Okazaki fragments
3’
Leading strand
5’
3’
5’ 3’
3’
5’
3’
5’
3
3’
DNA Polymerase I
5’ 3’
5’ 3’
5’ 3’
DNA ligase
Fully replicated
DNA strands
5’
3’
3’
5’
4
Action Description of the action
As shown
in
animation
.
5
(Please use black background)
First show the red and green strands with their small
blue fragments. Next show the grey pie-shaped objects
moving across these blue fragments as shown in
animation, after which they must be removed and filled
with green and red fragments of the same size. The
gaps remaining in the top green strand must then be
filled in by the violet oval shaped objects which must be
move across the gaps after which they must be filled.
Audio Narration
The entire DNA is unwound in this manner by DNA helicase
with DNA Pol III synthesizing the new complementary strands.
The RNA primers are then removed and the gaps filled by the
enzyme DNA Pol I. The Okazaki fragments on the lagging
strand, which still have a nick between two consecutive
fragments, are then joined together by means of the enzyme
DNA ligase. Sealing of the nicks completes the process of
replication after which all the machinery dissociates from the
DNA strands.
Master Layout (Part 3)
1
This animation consists of 3 parts:
Part 1 – Proposed models for DNA replication
Part 2 – Replication of DNA
Part 3 – Transcription of DNA
RNA polymerase
2
Rewinding
Unwinding
3
5'
Movement of polymerase
4
5
Source : Biochemistry by Stryer, 6th edition (ebook):
1
Definitions of the components:
Part 3 – Transcription of DNA
2
1.Transcription: Transcription is a process by which information from a double stranded DNA
molecule is converted to a single stranded RNA molecule by making use of one strand as the
template. The process differs slightly between prokaryotes and eukaryotes and is inhibited by
rifampicin in prokaryotes, by a-aminitin in eukaryotes and by acridine and actinomycin D in
both.
3
2. RNA polymerase: An enzyme that catalyzes the synthesis of RNA molecules from a DNA
template. In prokaryotes, the RNA polymerase holoenzyme consists of the core enzyme form
which has four polypeptides(two α,β,β‘) bound to another factor called sigma factor. In
eukaryotes, three RNA polymerases exist called RNA pol I, RNA pol II and RNA pol III. RNA
pol II is involved in the transcription process. RNA Pol IV, found in plants, is involved in the
synthesis of small interfering RNA (siRNA) which is responsible for degradation of
homologous mRNA for gene silencing.
3. Nascent RNA - The RNA molecule that is being synthesized from DNA and in the process
of development in order to produce the final mature RNA.
4
4. Coding strand – The DNA strand that has same base sequence as that of the RNA
transcript being produced. In other words, it is the complementary sequence of the template
strand.
5. Template strand – The DNA strand of a gene that serves as a template for the synthesis
of RNA strand during transcription. It is complementary to that of the RNA transcript that is
produced.
5
6. Promoter: A specific recognition nucleotide sequence in DNA to which the RNA
polymerase binds for initiation of transcription.
1
2
Definitions of the components:
Part 3 – Transcription of DNA
7. Closed promoter complex: The complex formed by relatively loose binding between RNA
polymerase and the promoter region. It is said to be closed because the DNA duplex remains
intact and there is no melting of DNA base pairs.
8. Open promoter complex: The complex formed by tight binding of RNA polymerase with
the promoter element. It is said to be open because approximately 17 base pairs of DNA open
up.
9. Sigma factor: A prokaryotic transcription initiation factor which is essential for promoter
recognition. If the sigma factor is not present, the core enzyme binds to DNA in various places
but does not initiate transcription efficiently from any one of them.
3
10. Transcription factors: Specific proteins that are required for the initiation of transcription
by RNA polymerases. In prokaryotes it is the sigma factor. In eukaryotes they are TFIID,
TFIIB, TFIIH, TFIIE and TFIIF.
11. Terminator sequence: A transcription regulatory sequence located at the distal end of a
gene that signals the termination of transcription.
4
12. Rho factor: Rho factor is a protein essential for prokaryotic transcription termination. It
has two domains, one that binds to ATP and the other that binds to the newly synthesized
RNA transcript.
13. rut elements: Rho utilization elements. These are the sequences to which rho protein
binds and are essential for its terminator function.
5
1
Part 3,Step 1:
Prokaryotic transcription initiation
s factor
Closed promoter complex
3'
5'
2
5'
3'
RNA polymerase
Promoter
Open promoter complex
3
5'
3'
3'
5'
4
5
Action
Description of the action
As shown
in
the
animation
(Please use black background & redraw all figures)
First show the text box with prokaryotic transcription
initiation. Then show the two strands on top. Next
show the blue shape with brown C shape inside it
coming in from left and occupying the red area.
Then show the blue & brown shapes moving across
the red region. When this happens, the two strands
must separate in the red region to give rise to the
figure below.
Audio Narration
Transcription is the process by which information from a
double stranded DNA molecule is converted to a single
stranded RNA molecule. For prokaryotic transcription to begin, the
RNA polymerase holoenzyme consisting of the core enzyme bound to
the σ factor must bind to the promoter region. The s factor is
responsible for recognition of the promoter sequence. Binding results
in a local unwinding of around 17 base pairs centered around the
promoter. At this point RNA polymerase is correctly oriented to begin
transcription from the +1 nucleotide.
Source: Molecular Biology of the Cell 5/e Garland Science, 2008
1
Part 3,Step 2:
Eukaryotic transcription initiation
Promoter
Closed promoter complex
3'
5'
2
TFIIH TFIID
TFIIF
TFIIE
TFIIB
3'
RNA polymerase II
5'
Transcription factors
Open promoter complex
3
5'
3'
3'
5'
TFIIH
TFIID
TFIIE TFIIB TFIIF
4
Action
As shown
in
the
animation
5
Description of the action
(Please use black background & redraw all figures)
First show the text box with eukaryotic transcription
initiation. Then show the two strands on top. Next
show the yellow oval with orange circles inside it
coming in from left and occupying the red area.
Then show the circle moving across the red region.
As it moves, the two strands must separate out and
give rise to the figure shown below.
Source: Molecular Biology of the Cell 5/e Garland Science, 2008
Audio Narration
In case of eukaryotic transcription initiation, RNA
polymerase binds to the promoter region along with
several transcription factors (TF), which recognize the
promoter site. The first step is the binding of TFIID.
This complex acts as a binding site for TFIIB which
then recruits RNA polymerase II and TFIIF. Finally
TFIIE and TFIIH also bind to produce the complete
transcription initiation complex.
Part 3,Step 3:
1
Elongation
5'
3'
3'
2
Newly synthesized RNA
3
5'
Direction of movement
Helix re-winding
5'
Template DNA strand
Promoter clearance - s factor
dissociates
Helix unwinding
3'
5'
3'
Terminator sequence
4
RNA transcript
Action
5
As
shown
in
the
animati
on
Description of the action
Audio Narration
(Please use black background & redraw all figures) First show the strands on top In prokaryotes, the sigma factor dissociates from the
core enzyme, a process known as promoter
with the red region separated and the yellow oval & violet triangle bound to it.
This complex must then move across the red region in the direction shown. As it clearance, once it has synthesized around 9-10
moves, the blue strand above it must appear. Once it crosses the red region, the nucleotides. RNA polymerase continues elongation of
violet triangle must dissociate. The yellow oval must continue to move in the
new RNA chain in the 5’-3’ direction by unwinding the
same direction. As it moves, the black strands in front must open up in a manner DNA ahead of it as it moves and re-winding the DNA
similar to the red & the strands that the yellow oval crosses must rejoin again. As helix that has already been transcribed. Eukaryotic
it moves, more blue strand must be formed and must come out in a manner
elongation is similar except that the polymerase
shown in the figure below. This continues until it reaches the green region of the involved is RNA polymerase II.
strands.
Source: Molecular Biology of the Cell 5/e Garland Science, 2008
1
Part 3, Step 4:
Termination: Rho dependent
2
5'
3'
3'
5'
Stalled transcription
complex
Release of RNA transcript
ATP+ H2O
3
ADP + Pi AC rich rut element
RNA transcript
Rho protein
RNA polymerase dissociates
4
Action
5
As shown
in
the
animation
Description of the action
Audio Narration
Termination of transcription is signaled by controlling elements
(Please use black background & redraw all figures)
called terminators that have specific distinguishing features.
First show the strands which are unwound at the green
marked region with the yellow oval and blue strand bound to it Prokaryotic termination can be rho-dependent or rho-independent. In
but not moving. Then show the violet ovals binding to the blue rho-dependent termination, one subunit of the rho protein gets
strand as shown and moving to the yellow oval. Next show
activated by binding to ATP after which the other subunit binds to the
the equation given, following which the yellow circle, blue
RNA transcript and moves to the stalled transcription complex.
strand as well as the purple ovals must all dissociate from the
Hydrolysis of ATP leads to release of the RNA transcript as well as
black strands. The purple ovals must be last to dissociate.
RNA Polymerase, thereby terminating the transcription process.
Source: Molecular Biology of the Cell 5/e Garland Science, 2008
1
Part 3, Step 5:
Termination: Rho independent
2
5'
3'
3'
5'
Stalled transcription
complex
3
Self complementary region
forming hair pin loop
Conserved AAA residues in
template
Release of RNA transcript
RNA polymerase dissociates
4
Action Description of the action
5
(Please use black background & redraw
As shown all figures) The blue strand which is
in
comes out as the yellow oval moves
the
towards the right, must be made to
animation assume this shape once the yellow oval
reaches the green region of the figure.
Once the blue strand assumes this shape,
both the yellow oval and blue strand must
dissociate from the black strands above.
Audio Narration
Rho-independent termination takes place due to the formation of a hairpin loop
structure by the newly synthesized RNA transcript. The terminators for this
mechanism have two specific features – the first is a region on the template that
will produce a self-complementary sequence on the RNA transcript located
around 15-20 nucleotides before the expected end of the RNA. The next feature
is a conserved sequence of 3 adenine residues on the template near the 3’ end
of the hairpin. Formation of the hairpin disrupts the weak AU interactions,
thereby allowing dissociation of the newly synthesized RNA transcript and the
RNA polymerase.
Source: Molecular Biology of the Cell 5/e Garland Science, 2008
Interactivity
option
1:Step
No:1
1
Nitrous acid deaminates cytosine to produce uracil, a base that pairs with adenine.
After this conversion, which base pair occupies this position in each of the
daughter strands resulting from one round of replication and two rounds of
replication?
2
A) After one round of replication, two GC and after two rounds, two GC and two AT
B) After one round of replication, one GC, one AT and after two rounds, two AT
3
C) After one round of replication, one GC, one AU and after two rounds, two GC and one
AU, one AT.
D) After one round of replication, two GC and after two rounds, two GC and one
AU, one AT.
4
Interacativity Type
Choose the
correct option
5
Options
User has to choose
one of the four options.
If A or B or D chosen,
then they must turn
red. User can however
continue till he gets
the right answer(C)
which must turn green.
User is then directed to
step 2.
Boundary/limits
Results
User has to choose one of
the four options. If A or B or D
chosen, then they must turn
red. User can however
continue till he gets
the right answer(C)
which must turn green.
User is then directed to step
2.
Interactivity option 1:Step No:2(a)
C
U
Nitrous acid
G
Original Base pair
Modified Base pair
Replication round 1
U
C
A
G
Replication round 2
C
C
U
T
G
G
A
A
Interactivity
option
2:Step
No:1
1
2
FRET (Fluorescence Resonance Energy Transfer) is a technique for measuring
interactions between two proteins in vivo. In this technique, two different
fluorescent molecules (fluorophores) are genetically fused to the two proteins of interest. In
FRET, light energy is added at the excitation frequency for the donor fluorophore, which
transfers some of this energy to the acceptor, which then re-emits the light at its own
emission wavelength. The efficiency of FRET is dependent on the inverse sixth power of
the intermolecular separation. Using this technique it is possible to show that sigma factor
dissociates from RNA polymerase during elongation of prokaryotic transcription process.
Click on the button below to view the process.
3
4
Interacativity Type
Choose the
action button
5
Options
User has to click on
the action button below
and the user is then
directed to step 2.
Boundary/limits
Results
User has to click on
the action button below
and the user is then
directed to step 2.
Interactivity option 2:Step No:2
Open promoter complex – ready for elongation
5'
3'
3'
Fluorescent
5' acceptor
s
RNA polymerase
s factor
Bright fluorescence
due to proximity of
donor & acceptor
fluorophores
Fluorescent donor
5'
3'
3'
Newly synthesized RNA
5'
Direction of movement
s
Template DNA strand
Promoter clearance - s factor
dissociates
Decrease in
fluorescence intensity
as donor moves away
from acceptor
1
Questionnaire
1. The unwinding of DNA is done by _____.
Answers: a) DNA polymerase b) DNA repair enzymes c) DNA helicase d) DNA ligase
2
2. Replication forks are characteristic of the DNA replication of _____.
Answers: a) Viruses b) Prokaryotes c) Eukaryotes d) Both viruses and eukaryotes
3
3. Rifampicin is an inhibitor of transcription of bacteria. It binds to the following subunit of RNA
polymerase.
Answers: a) β
b)
β'
c) α
d) σ
4. Okazaki fragments are characteristic of the DNA replication of the _____ strand.
4
Answers: a) Leading strand b) Lagging strand c) Both a and b d) Non of the above
5. α- amanitin at very low concentrations inhibit
Answers: a) RNA pol II only b) RNA pol I only c) RNA pol III only
d) Both RNA pol I and RNA pol II
5
Links for further reading
Books:
Molecular biology by Robert F. Weaver, 4th edition
Genetics by Peter J. Russel, 5th edition
Biochemistry by Stryer, 6th edition