Download Organic Chemistry - Problem Drill 24: Nucleic Acids Question No. 1

Organic Chemistry - Problem Drill 24: Nucleic Acids
Question No. 1 of 10
Instructions: (1) Read the problem statement 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.
Question 1. What are the components of a nucleotide?
(A)
(B)
(C)
(D)
(E)
A
A
A
A
A
sugar residue
sugar residue + a nitrogenous base
sugar residue + a nitrogenous base + phosphate group(s)
sugar residue + phosphate group(s)
nitrogenous base + phosphate group(s)
Question
A. Incorrect!
A sugar residue is only part of a nucleotide. Go back and review the structure of nucleotides.
B. Incorrect!
A sugar residue bonded to a nitrogenous base is called a nucleoside. Go back and review the structure
of nucleotides.
C. Correct!
A nucleotide is composed of three parts: a sugar, a nitrogen base and at least one phosphate group.
Feedback
D. Incorrect!
A sugar residue and phosphate groups are only part of a nucleotide. Go back and review the structure
of nucleotides.
E. Incorrect!
A nitrogenous base and phosphate groups are only part of a nucleotide. Go back and review the
structure of nucleotides.
(1) Recall the structure of nucleotides.
There are several components used to construct the nucleotides in chains of DNA and RNA. A sugar is
bonded to a nitrogenous base first to form a nucleoside. The nucleoside is then phosphorylated one to
three times to form various nucleotides.
Once phosphorylated, the nucleotides are ready to place in a nucleic acid chain.
Therefore, the correct answer is (C).
Solution
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Question No. 2 of 10
Instructions: (1) Read the problem statement 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.
Question 2. The sugar residue below will be found in which nucleic acid?
HO
OH
H O H
H
H
OH H
Question
(A)
(B)
(C)
(D)
(E)
DNA
t-RNA
m-RNA
r-RNA
All RNAs
A. Correct!
The sugar shown is 2’-deoxyribose and is the sugar found in DNA only.
B. Incorrect!
t-RNA contains 2’-ribose as a sugar where the 2’ carbon has a hydroxyl group on it. Go back and review
the structure of the different nucleic acids.
C. Incorrect!
m-RNA contains 2’-ribose as a sugar where the 2’ carbon has a hydroxyl group on it. Go back and
review the structure of the different nucleic acids.
Feedback
D. Incorrect!
r-RNA contains 2’-ribose as a sugar where the 2’ carbon has a hydroxyl group on it. Go back and review
the structure of the different nucleic acids.
E. Incorrect!
All RNAs contain 2’-ribose as a sugar where the 2’ carbon has a hydroxyl group on it. Go back and
review the structure of the different nucleic acids.
(1) Recall the structure of the two nucleic acids DNA and RNA.
The nucleotides used to construct DNA and RNA consist of a sugar, nitrogenous base and phosphorus
groups. The sugar used will differ depending on which nucleic acid it will be used in. DNA uses 2deoxyribose and RNA uses ribose.
These sugars only differ by one hydroxyl group. In ribose, there is a hydroxyl group on carbon 2 of the
ring. In 2-deoxyribose, this hydroxyl group has been replaced by a hydrogen.
(2) Study the structure above and determine if it is ribose or deoxyribose.
In the above structure, there are two hydrogens on carbon 2 of the ring instead of a hydrogen and a
hydroxyl group. Thus, it must be 2-deoxyribose.
Therefore, the correct answer is (A).
Solution
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Question No. 3 of 10
Instructions: (1) Read the problem statement 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.
Question 3. What is the name of the nitrogenous base below?
NH2
N
N
N
H
Question
N
(A)
(B)
(C)
(D)
(E)
Adenine
Thymine
Guanine
Cytosine
Uracil
A. Correct!
Adenine is a purine base found in both DNA and RNA.
B. Incorrect!
Thymine is a pyrimidine base not a purine base. Go back and review the structural difference between
the two types of bases. Be able to identify all five bases by structure.
C. Incorrect!
While guanine is a purine base, this is not its structures. Go back and review the structural difference
between the two types of bases. Be able to identify all five bases by structure.
Feedback
D. Incorrect!
Cytosine is a pyrimidine base not a purine base. Go back and review the structural difference between
the two types of bases. Be able to identify all five bases by structure.
E. Incorrect!
Uracil is a pyrimidine base not a purine base. Go back and review the structural difference between the
two types of bases. Be able to identify all five bases by structure.
(1) Recall the different types of nitrogenous bases used in nucleic acids.
There are two types of nitrogenous bases used in nucleic acids: purines and pyrimidines.
Purines are bicyclic compounds consisting of a five membered ring fused to a six membered ring. Both
rings contain at least two nitrogen atoms. Pyrimidines are monocyclic compounds consisting of a six
membered ring containing at least 2 nitrogens.
There are two types of purines: adenine and guanine.
There are three types of pyrimidines: thymine, uracil, and cytosine.
(2) Look at the above structure and determine first whether it is a purine or pyrimidine.
It is bicyclic so it must be one of the purines.
(3) Determine whether the molecule is adenine or guanine.
Solution
Here, it becomes important to have the ability to discern the differences between all the bases so that
one can identify them on a test. The rings’ cyclic cores do not differ in adenine and guanine. The only
differences in the two bases come from the groups attached to the bicyclic core. In adenine, there is an
amino group attached to carbon 6. In guanine, there is a carbonyl at carbon 6 and an amino group
attached to carbon 2.
The compound above has an amino group at carbon 6 so it must be adenine.
Therefore, the correct answer is (A).
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Question No. 4 of 10
Instructions: (1) Read the problem statement 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.
Question 4. How many hydrogen bonds can occur between the nitrogenous bases of guanine and
cytosine?
Question
(A)
(B)
(C)
(D)
(E)
0
1
2
3
4
A. Incorrect!
All of the sets of complimentary nitrogen bases can form some hydrogen bonds between their
structures. Go back and review the complimentary nitrogen bases.
B. Incorrect!
All of the sets of complimentary nitrogen bases can form more than one hydrogen bond between their
structures. Go back and review the complimentary nitrogen bases.
C. Incorrect!
Adenine and thymine can only form two hydrogen bonds between their structures. Go back and review
the complimentary nitrogen bases.
Feedback
D. Correct!
Guanine and cytosine can form three hydrogen bonds between them. Adenine and thymine can only
form two.
E. Incorrect!
None of the sets of complementary nitrogen bases can form four hydrogen bonds between themselves.
Go back and review the complimentary nitrogen bases.
(1) Recall the structure of the nitrogenous bases and their complementarity.
Adenine always pairs with thymine in DNA or uracil in RNA.
Guanine always pairs with cytosine.
The number of hydrogen bonds that can occur between each base pairing depends on the structure of
the bases involved in the pairing.
In the adenine-thymine (or uracil) pairing, only two hydrogen bonds can be formed:
H
N
N
Hydrogen bond
H
O
N
N
N
Sugar
Solution
N
O
N
Sugar
In the guanine-cytosine pairing, three hydrogen bonds can be formed:
H
O
N
N
N
N
Sugar
N
Hydrogen bond
H
N
N
H
H
O
N
Sugar
Therefore, the correct answer is (D).
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Question No. 5 of 10
Instructions: (1) Read the problem statement 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.
Question 5. Which statement below regarding the structure of DNA is incorrect?
Question
(A) DNA is a long polymer made up of nucleotides and has a backbone made of sugars and
phosphate groups joined by phosphodiester bonds.
(B) The nitrogenous bases found in DNA include guanine and adenine, both purines, and thymine
and cytosine, both pyrimidines.
(C) A double helix structure is formed when two strands are joined together by hydrogen bonds.
(D) The two strands of DNA have direction with one end known as the 5’ end, which is capped by a
hydroxyl group, and the other end known as the 3’ end, which is capped by a phosphate group.
(E) The two strands in a double helix of DNA are antiparallel meaning they run in opposite
directions.
A. Incorrect!
The backbone of the strands of DNA is comprised of sugars and phosphate groups joined by
phosphodiester bonds. DNA is essentially a long polymer of nucleotides that encodes genetic
information. . Go back and review the structure of DNA.
B. Incorrect!
DNA is comprised of four nitrogenous bases: adenine, thymine, guanine, and cytosine. Adenine and
guanine are purines and thymine and cytosine are pyrimidines. . Go back and review the structure of
DNA.
C. Incorrect!
The strands in a double helix of DNA are held together by hydrogen bonds. . Go back and review the
structure of DNA.
Feedback
D. Correct!
While the two strands of DNA do have direction, the 5’ end is capped with a phosphate group and the 3’
end is capped with a hydroxyl group.
E. Incorrect!
DNA strands in a double helix are antiparallel which means they run in opposite directions. The 5’ end of
one strand lines up with the 3’ end of the other. Go back and review the structure of DNA.
(1) Recall what you learned about the structure of DNA in this tutorial.
DNA is a long polymer made up of a backbone made of sugars and phosphate atoms joined by
phosphodiester bonds. Each sugar has one of four nitrogenous bases attached to it: adenine, thymine,
guanine, and cytosine. Adenine and guanine are purines which contain a bicyclic core while thymine and
cytosine are pyrimidines which contain a monocyclic core.
DNA is double stranded and it has been determined that the bases in DNA are complementary meaning
the bases on one strand will pair up with those on the second strand. Adenine always pairs with
thymine and guanine with cytosine. The two strands of DNA are held together by hydrogen bonds
between base pairs. The adenine-thymine base pairing can form two hydrogen bonds while the
guanine-cytosine base pairing can form three hydrogen bonds per pairing.
Solution
It has been determined that the two strands of DNA form a helical structure with the two strands
running in opposite directions (antiparallel). The 5’ end of one strand pairs up with the 3’ end of the
other strand. All 5’ ends of DNA strands are capped by a phosphate group while all 3’ ends of DNA
strands are capped by a hydroxyl group.
(2) Read each statement carefully and determine which one is incorrect.
Therefore, the correct answer is (D).
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Question No. 6 of 10
Instructions: (1) Read the problem statement 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.
Question 6. What is the complementary base sequence for 5’ ATCGGTGTCC 3’?
(A)
(B)
(C)
(D)
(E)
5’
5’
3’
3’
5’
TAGCCACAGG 3’
CGTAGGCACC 3’
TAGCCACAGG 5’
CGTAGGCACC 5’
TAGCCTGTGG 3’
Question
A. Incorrect!
If the given sequence runs from 5’ to 3’, what direction does the complementary strand have to run? Go
back and study base pairing and directionality of DNA strands.
B. Incorrect!
If the given sequence runs from 5’ to 3’, what direction does the complementary strand have to run?
Also, recall that A pairs with T and C pairs with G. Are the bases in this sequence paired correctly? Go
back and study base pairing and directionality of DNA strands.
C. Correct!
The given sequence runs 5’ to 3’ so the complementary strand must run 3’ to 5’. Also, the bases are
correctly paired in this answer.
Feedback
D. Incorrect!
Recall that A pairs with T and C pairs with G. Are the bases in this sequence paired correctly? Go back
and study base pairing and directionality of DNA strands.
E. Incorrect!
If the given sequence runs from 5’ to 3’, what direction does the complementary strand have to run?
Also, recall that A pairs with T and C pairs with G. Are the bases in this sequence paired correctly? Go
back and study base pairing and directionality of DNA strands.
(1) Recall the directionality of the two strands of DNA.
DNA is composed of two complementary strands of nucleotides. The two strands are antiparallel which
means the 5’ end of one strand pairs up with the 3’ end of the other strand. This fact means that the
correct answer will be written in the 3’ to 5’ direction. Knowing this allows us to eliminate three of the
five possible choices.
(2) Recall how the nitrogenous bases pair up in DNA.
Adenine (A) pairs with thymine (T).
Guanine (G) pairs with cytosine (C).
(3) Write out the correct complementary base sequence for the one given:
5’ ATCGGTGTCC 3’
3’ TAGCCACAGG 5’
Solution
Therefore, the correct answer is (C).
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Question No. 7 of 10
Instructions: (1) Read the problem statement 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.
Question 7. Which nucleotide does not appear in RNA?
(A)
(B)
(C)
(D)
(E)
AMP
CMP
GMP
UMP
TMP
Question
A. Incorrect!
AMP is found in both DNA and RNA. Go back and review the structure of RNA.
B. Incorrect!
CMP is found in both DNA and RNA. Go back and review the structure of RNA.
C. Incorrect!
GMP is found in both DNA and RNA. Go back and review the structure of RNA.
Feedback
D. Incorrect!
UMP is found only in RNA. It replaces one of the other nucleotides. Go back and review the structure of
RNA.
E. Correct!
TMP is replaced with UMP in RNA.
(1) Recall the nucleotides used in nucleic acids.
AMP = adenosine 5’-monophosphate
CMP = cytidine 5’-monophosphate
GMP = guanosine 5’-monophosphate
UMP = uridine 5’-monophosphate
TMP = thymidine 5’-monophosphate
We have seen that DNA uses AMP, GMP, CMP, and TMP.
But RNA substitutes uracil for thymine so it uses UMP instead.
Therefore, the correct answer is (E).
Solution
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Question No. 8 of 10
Instructions: (1) Read the problem statement 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.
Question 8. Which statement about RNA structure is incorrect?
(A)
(B)
(C)
(D)
Question
RNA is a linear polymer made up of nucleotide monomers linked by phosphodiester bonds.
RNA is single stranded and therefore does not form a double helix.
The secondary structure of RNA molecules typically consists of stem and loop domains.
There are three kinds of RNA: transfer RNA (t-RNA), messenger RNA (m-RNA), and ribosomal
RNA (r-RNA). All three RNAs are involved in the process of protein synthesis.
(E) Loop regions in RNA structure arise from base pairing between complementary stretches of
bases within the same strand.
A. Incorrect!
The nucleotide monomers of ATP, CTP, GTP, and UTP combine to form a linear polymer of RNA and these
monomers are linked by phosphodiester bonds. Go back and study the structure of RNA to help
determine the correct answer.
B. Incorrect!
RNA is single stranded and will not form a double-stranded double helix like DNA does. Go back and
study the structure of RNA to help determine the correct answer.
C. Incorrect!
Stems and loops comprise the secondary structure of RNA. Go back and study the structure of RNA to
help determine the correct answer.
Feedback
D. Incorrect!
The three types of RNA, m-RNA, t-RNA and r-RNA, are involved in protein synthesis. Go back and study
the structure of RNA to help determine the correct answer.
E. Correct!
Loop regions in RNA molecules occur where a lack of complementary bases prevents base pairing.
Double helical regions arise from base pairing between complementary stretches of bases within the
same strand.
(1) Recall the information regarding RNA structure that was covered in this tutorial.
RNA and DNA do share some similarities but they also have several differences. RNA is a linear polymer
made up of nucleotide monomers linked by phosphodiester bonds. Unlike DNA, adenine, guanine,
cytosine and uracil are the four nitrogenous bases used in RNA; thymine is not used at all. Another
difference between RNA and DNA is that RNA does not form a double helix because it is single stranded.
The secondary structure of RNA includes areas called loops and stem domains. Loop regions occur
where the lack of complementary bases prevent base pairing. Stem regions are double helical regions
that arise from base pairing between complementary stretches of bases within the same strand.
There are three types of RNA: messenger RNA (m-RNA), transfer RNA (t-RNA), and ribosomal RNA (rRNA). All three types have some sort of function in protein synthesis. t-RNA transfer a specific amino
acid to a growing polypeptide chain at the ribosomal site of protein synthesis. m-RNA carries
information from DNA to the ribosome. r-RNA binds m-RNA during protein synthesis.
Solution
(2) Read each statement carefully and determine which one contains inaccurate information.
Therefore, the correct answer is (E).
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Question No. 9 of 10
Instructions: (1) Read the problem statement 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.
Question 9. Which statement best completes this sentence:
Transfer RNA (t-RNA):
Question
(A) Transfers a specific amino acid to a growing peptide chain at the ribosome during protein
synthesis.
(B) Has an “anticodon” region used for codon recognition that binds to specific sequences of mRNA.
(C) Binds to mRNA by hydrogen bonding.
(D) Has a CCA tail sequence at the 3’ end that is required for recognition of tRNA by enzymes used
in protein translation.
(E) All of the above.
A. Incorrect!
t-RNA is used for transferring amino acids during protein synthesis at the ribosome, however, is this
choice the only one that best completes the sentence?
B. Incorrect!
t-RNA strands have an anticodon region that binds to specific sequences of mRNA, however, is this
choice the only one that best completes the sentence?
C. Incorrect!
t-RNA does bind to mRNA by hydrogen bonding, however, is this choice the only one that best completes
the sentence?
Feedback
D. Incorrect!
t-RNA does have a CCA 3’ tail sequence that is used by enzymes to recognize the molecule during
translation, however, is this choice the only one that best completes the sentence?
E. Correct!
All statements correctly describe t-RNA’s structure and uses.
(1) Recall what you learned about transfer RNA in the tutorial.
t-RNA is one of the three types of RNA found in the body. It consists of a small RNA chain of about 7495 nucleotides. It has many interesting structural features including an anticodon region for codon
recognition that binds to specific sequences of mRNA using hydrogen bonding to determine what amino
acid should be placed in the amino acid sequence of the growing peptide. It then transfers that specific
amino acid to the growing peptide chain at the ribosome during protein synthesis using a CCA tail
sequence at the 3’ end of the strand. The CCA tail also aids in enzymes recognizing the t-RNA during
protein translation.
(2) Read each statement carefully and determine which best completes the sentence.
All answers given are correct and could be used to complete the sentence.
Therefore, the correct answer is (E).
Solution
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Question No. 10 of 10
Instructions: (1) Read the problem statement 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.
Question 10. Which below is the process of producing RNA from DNA?
(A)
(B)
(C)
(D)
(E)
Replication
Transcription
Splicing
Translation
Condensation
Question
A. Incorrect!
Replication is the process of making copies of DNA from DNA during cell division. Go back and review
the process of going from DNA to a complete protein.
B. Correct!
Transcription is the process of producing RNA molecules from DNA.
C. Incorrect!
Splicing is the process used to remove non-coding regions of DNA. Go back and review the process of
going from DNA to a complete protein.
Feedback
D. Incorrect!
Translation is the process of producing proteins from RNA. Go back and review the process of going
from DNA to a complete protein.
E. Incorrect!
Condensation is the type of reaction that occurs during the process of nucleotide formation. Go back
and review the process of going from DNA to a complete protein.
(1) Recall all the processes used to turn the genetic information coded in DNA into proteins.
Replication is a process where copies of DNA are made from the DNA found in the nucleus of the cell
during cell division.
Transcription is the process of producing RNA from DNA.
Splicing is a process to remove non-coding regions from the copies of DNA prior to RNA synthesis.
Translation is the process of producing proteins from RNA.
(2) Determine which process is used to make RNA from DNA.
Transcription is used to make RNA from DNA.
Therefore, the correct answer is (B).
Solution
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