Download Biochemistry - Problem Drill 22: DNA Question No. 1 of 10

Biochemistry - Problem Drill 22: DNA
Question No. 1 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
1. Which of the following are not DNA bases?
Question
(A) Adenine
(B) Guanine
(C) Cytosine
(D) Uracil
(E) Thymine
A. Incorrect!
Adenine is typically part of the DNA molecule so this is not the correct answer.
B. Correct!
Yes, Uracil is found in RNA.
C. Incorrect!
Guanine is typically part of the DNA molecule so this is not the correct answer.
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D. Incorrect!
Cytosine is typically part of the DNA molecule so this is not the correct answer.
E. Incorrect!
No, one of the answers is not correct look again.
Uracil is found in mRNA it is not a typical part of the DNA molecule.
There are four different nucleotide bases that occur in DNA: adenine (A), cytosine
(C), guanine (G) and thymine (T).
The correct answer is (B).
Solution
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Question No. 2 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
2. Which of the following are the components of deoxyribonucleic acid?
Question
(A) Bases (A, T, G and C)
(B) Amino acid
(C) Phosphate
(D) Fructose
(E) All of the above
A. Correct!
Yes, this is the best answers to the question.
B. Incorrect
No, amino acids are part of proteins.
C. Incorrect!
While phosphates can be found on the DNA chain it is not the best response to the
question.
Feedback
D. Incorrect!
Analytical chemistry is a well established branch of chemistry. So this selection is
not correct.
E. Incorrect!
No, there is a best answer to the question.
Bases such as A, T, G, and C are part of DNA.
DNA is a polymer. The monomer units of DNA are nucleotides, and the polymer is
known as a "polynucleotide." Each nucleotide consists of a 5-carbon sugar
(Deoxyribose), a nitrogen containing base attached to the sugar, and a phosphate
group.
The correct answer is (A).
Solution
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Question No. 3 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
3. Which of the following is not a Watson-Crick Rule?
Question
(A) Two helical polynucleotide chains are coiled around a common axis. The
chains run in parallel direction.
(B) The polymerase and helicase are on the inside of the helix, whereas the
primase and topoisomerase units are on the outside.
(C) The diameter of the helix is 20 Å. Adjacent bases are separated by 3.4 Å
along the helix axis and related by a rotation of 36 degrees. Hence, the
helical structure repeats after 10 residues on each chain, that is, at interval
of 34 Å.
(D) The two chains are held together by phosphate bonds between pairs of
bases. Adenine is always paired with thymine; guanine is always paired with
cytosine.
(E) The sequence of bases along a polynucleotide chain is not restricted in the
direction of 3’ to 5’.
A. Incorrect!
No, the chains run in antiparallel direction.
B. Incorrect!
No, Polymerase, helicase, primase, and topoisomerase are involved in DNA
replication but not described in Watson-Crick Rules.
C. Correct!
Transcription is the process of going from DNA to mRNA.
Feedback
D. Incorrect!
DNA polymerase is involved with DNA replication, repair or copying.
E. Incorrect!
No, this is not a correct response.
Solution
Watson-Crick rules:
Two helical polynucleotide chains are coiled around a common axis. The chains run
in opposite direction.
The purine and pyrimidine bases are on the inside of the helix, whereas the
phosphate and deoxyribose units are on the outside.
The diameter of the helix is 20 Å. Adjacent bases are separated by 3.4 Å along the
helix axis and related by a rotation of 36 degrees. Hence, the helical structure
repeats after 10 residues on each chain, that is, at interval of 34 Å.
The two chains are held together by hydrogen bonds between pairs of bases.
Adenine is always paired with thymine; guanine is always paired with cytosine
The sequence of bases along a polynucleotide chain is not restricted in any way.
The correct answer is (C).
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Question No. 4 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
4. Which of the following is a correct description of hydrogen bonds and bonding
in a DNA molecule?
Question
(A) Hydrogen bonds are attractive forces between two hydrogen
atoms.
(B) DNA phosphates are involved in hydrogen bonding.
(C) Hydrogen on the NH groups is attracted and bond to oxygen on
the phosphate groups.
(D) Hydrogen bonds are attractive forces between an electronegative
atom and a hydrogen atom bonded to another electronegative
atom.
(E) None of the above
A. Incorrect!
No, think about the charges on the hydrogen atom.
B. Incorrect!
No, visualize the hydrogen bonding between two strands of DNA. Where are the
phosphate groups?
C. Incorrect!
No, visualize the hydrogen bonding between two strands of DNA. Where are the
phosphate groups?
Feedback
D. Correct!
Yes, this is the correct description of hydrogen bonding in the DNA molecule.
E. Incorrect!
No, one of the answers is correct. First review in your mind what a hydrogen bond
is and does in a DNA molecule.
Hydrogen bonds are attractive forces between an electronegative atom and a
hydrogen atom bonded to another electronegative atom.
The correct answer is (D).
Solution
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Question No. 5 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
5. Which of the following is a valid reason for why topoisomerase is needed for
DNA replication?
Question
(A) Two DNA strain must be separated completely to allow the
binding of DNA polymerase.
(B) DNA duplex is bound by protein histones that need be removed
by topoisomerase.
(C) Topoisomerase can help reform of DNA duplex after DNA
replication.
(D) Topoisomerases relax supercoiled DNA structures to enable the
binding of helicase, primase, and DNA polymerase.
(E) None of the above
A. Incorrect!
No, The two DNA strain do not need be separated completely.
B. Incorrect!
No, the topoisomerase does not remove histones.
C. Incorrect!
No, the topoisomerase is not part of the reanealing process of DNA replication.
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D. Correct!
Yes, on binding to DNA the topoisomerase which is an enzyme functions as
described.
E. Incorrect!
No, one of the answers is correct. First review in your mind what a hydrogen bond
is and does in a DNA molecule.
On binding to DNA, topoisomerase I cleaves one strand of the DNA through a
tyrosine (Y) residue attacking a phosphate. This process results in partial or
complete relaxation of a supercoiled DNA. Type II Topoisomerases Can Introduce
Negative Supercoils Through Coupling To ATP Hydrolysis. Both enzymes relax
supercoiled DNA structures to enable the binding of helicase, primase, and DNA
polymerase.
Solution
The correct answer is (D).
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Question No. 6 of 10
Instructtions: (1) Read
R
the pro
oblem and answer choic
ces carefully
y (2) Work the
t
problems on paper as
needed (3) Pick the answer (4) Go back to review the core concep
pt tutorial as
s needed.
agram of the
e process off DNA replic
cation at a replication fo
ork, the
6. In this dia
strrand labeled
d B is the __
________.
Questtion
(A) Primer
(B) Templa
ate
(C) Leading
g strand
(D) Lagging strand
ki fragment
(E) Okazak
A. Incorrect!
D and
a
E are primers.
B. Incorrect!
A is a templatte.
C. Correct!
The leading sttrand synthe
esize in the same as the direction of the moving fork.
Feedb
back
D. Incorrect!
C is
i the laggin
ng strand he
ere.
E. Incorrect!
C is
i the Okaza
aki fragment.
The key to sollve this prob
blem is to understand the
t
mechaniism of DNA replication.
y
got this
s question wrong
w
please
e review the
e basics of DNA
D
replicattion.
If you
he correct answer
a
is (C).
(
Th
Solution
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ningCenter.com
m
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arning Inc. All Rights Reserve
ed
Question No. 7 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
7. For the DNA strand 5'-TACGATCATAT-3' the correct complementary DNA strand
is _____.
Question
(A) 3'-TACGATCATAT-5'
(B) 3'-ATGCTAGTATA-5'
(C) 3’-AUGCUAGUAUA-5’
(D) 3’-GCATATACGCG-5’
(E) 3’-ATATACTAGCAT-5’
A. Incorrect!
This is the same sequence but reverse direction, not complementary.
B. Correct!
The complementary strand to a DNA is anti-parallel and follows the base-pairing
principle. Therefore the following two strands are complementary:
5'-TACGATCATAT-3'
3’-ATGCTAGTATA-5'
C. Incorrect!
This is the RNA strand, also complementary to the original DNA strand.
Feedback
D. Incorrect!
This sequence comes out from nowhere.
E. Incorrect!
The direction is reversed.
The complementary strand to a DNA molecule is anti parallel and follows the base
pairing principles.
The correct answer is (B).
Solution
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Question No. 8 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
8. Which of the flowing enzyme is not involved in DNA replication?
Question
(A) DNA ligase
(B) DNA polymerase
(C) RNA primase
(D) RNA polymerase
(E) Topoisomerase
A. Incorrect!
DNA ligase is required to ligate the Okazaki fragments together.
B. Incorrect!
DNA polymerase is required for DNA strand elongation.
C. Incorrect!
RNA primase is required for synthesis of RNA primers which are required for
initiating DNA synthesis.
Feedback
D. Correct!
RNA polymerase is only required for RNA synthesis, not required for DNA synthesis.
E. Incorrect!
Telomerase is also involved in DNA replication, only it is required for replicating the
ends.
It is important to understand how DNA is replicated and what enzymes are
involved.
The correct answer is (D).
Solution
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Question No. 9 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
9. Which of the following statements is correct with respect to primase structure
and function in replication?
Question
(A) The DNA primase is a form of RNA polymerase.
(B) The primase binds to the DNA helicase making a complex called a
primosome.
(C) The RNA primer made is about 11 base pairs long.
(D) Nucleotides can be added by DNA polymerase to the RNA primer.
(E) All of the statements are correct.
A. Incorrect!
No, while this answer is correct it is not the best answer.
B. Incorrect!
No, while this answer is correct it is not the best answer.
C. Incorrect!
No, while this answer is correct it is not the best answer.
Feedback
D. Incorrect!
No, while this answer is correct it is not the best answer.
E. Correct!
Yes, all of the answers are correct, so this is the best answer choice.
The characteristics of the DNA primase are listed below. It is important to
memorize these and understand what each statement means.
The DNA primase is a form of RNA polymerase.
The primase binds to the DNA helicase making a complex called a primosome.
The RNA primer made is about 11 base pairs long.
Nucleotides can be added by DNA polymerase to the RNA primer.
DNA polymerases cannot initiate DNA synthesis without a RNA primer.
The primer is complementary to a DNA segment.
The correct answer is (E).
Solution
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Question No. 10 of 10
Instructions: (1) Read the problem and answer choices carefully (2) Work the problems on paper as
needed (3) Pick the answer (4) Go back to review the core concept tutorial as needed.
10. Which of the following statements is the best with respect to the structure and
function of DNA Polymerase III?
Question
(A) DNA polymerase III holoenzyme catalyzes the polymerization of
ribonucleotides complementary to a DNA template strand.
(B) The enzyme has very limited percussiveness but is very accurate.
(C) It proofreads the sequence it has added and enlists another
polymerase to correct replication mistakes.
(D) DNA Pol II is part of the replisome that is at the replication fork.
(E) DNA polymerase is a holoenzyme and requires Fe (iron) as a
cofactor.
A. Incorrect!
No, DNA polymerase III holoenzyme catalyzes the polymerization of
deoxyribonucleotides complementary to a DNA template strand.
B. Incorrect!
No, the enzyme is highly processive (catalyzed many nucleotides before falling off)
and accurate.
C. Incorrect!
No, it proofreads the sequence it has added and can correct replication mistakes by
use of it exonuclease activity.
Feedback
D. Correct!
Yes, DNA Pol II is part of the replisome that is at the replication fork.
E. Incorrect!
No, DNA polymerase is a holoenzyme and requires magnesium as a cofactor.
The following are characteristics of DNA Polymerase III:
• DNA polymerase III holoenzyme catalyzes the polymerization of
deoxyribonucleotides complementary to a DNA template strand.
• The enzyme is highly processive (catalyzed many nucleotides before falling
off) and accurate.
• It proofreads the sequence it has added and can correct replication mistakes
by use of it exonuclease activity.
• DNA Pol II is part of the replisome that is at the replication fork.
• DNA polymerase is a holoenzyme and requires magnesium as a cofactor.
The correct answer is (D).
Solution
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