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Modern Biology Study Guide
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Section 10-1 Review
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SEC T I O N 10 - 2 R E VIEW
DNA S TRUCTURE
VOCABULARY REVIEW Define the following terms and provide one example for each.
1. purine
2. pyrimidine
3. complementary base pair
4. nitrogenous base
MULTIPLE CHOICE Write the correct letter in the blank.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
1. The primary function of DNA in cells is to
a.
b.
c.
d.
serve as a storage form for unused nucleotides.
occupy space in the nucleus to keep the nucleus from collapsing.
store information that tells the cells which proteins to make.
serve as a template for making long, spiral carbohydrates.
2. The two strands of a DNA molecule are held together by
a. ionic bonds.
b. covalent bonds.
c. peptide bonds.
d. hydrogen bonds.
3. According to the base-pairing rules, guanine binds with
a. cytosine.
b. adenine.
c. thymine.
d. guanine.
4. Which of the following is NOT a correct structure of a nucleotide?
a. adenine—deoxyribose—phosphate
c. cytosine—deoxyribose—phosphate
b. adenine—ribose—phosphate
d. guanine—deoxyribose—phosphate
5. The percentage of adenine in DNA is
a. equal to the percentage of cytosine.
b. equal to the percentage of thymine.
c. not related to the percentage of thymine.
d. equal to the percentage of guanine.
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SHORT ANSWER Answer the questions in the space provided.
1. What are the three parts of a DNA nucleotide, and how are they connected to each other?
2. If 15% of the nucleotides in a DNA molecule contain guanine, what percentage of the nucleotides
contain each of the other three bases? Explain your reasoning.
3. Why is complementary base pairing important in DNA structure?
4. Critical Thinking How did X-ray diffraction photographs help Watson and Crick determine the
structure of DNA?
STRUCTURES AND FUNCTIONS Label each part of the figure in the spaces provided.
c
a
C
T
b
d
52
Section 10-2 Review
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The diagram below shows two nucleotide base pairs in a segment of a DNA molecule.
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SEC T I O N 10 - 4 R E VIEW
DNA R EPLICATION
VOCABULARY REVIEW Define the following terms.
1. replication fork
2. helicase
3. semi-conservative replication
MULTIPLE CHOICE Write the correct letter in the blank.
1. Before replication can take place,
Copyright © by Holt, Rinehart and Winston. All rights reserved.
a.
b.
c.
d.
DNA polymerases must add complementary nucleotides to the DNA.
the two strands of DNA must separate.
the covalent bonds in DNA must break.
helicases must break the bonds in the nucleotides.
2. Replication of the two DNA strands takes place
a.
b.
c.
d.
in two different directions.
in the same direction of the replication fork.
in a direction opposite to that of the replication fork.
at right angles to the direction of the replication fork.
3. In replication in prokaryotes,
a.
b.
c.
d.
there are two origins.
two replication forks move in opposite directions.
replication proceeds in one direction.
there are no replication forks.
4. A mutation is a
a. change in the direction of a replication fork.
b. form of cancer.
c. kind of DNA replication.
d. change in the nucleotide sequence of DNA.
5. Which of the following enzymes is involved with breaking hydrogen bonds?
a. DNA polymerase
b. DNA ligase
c. DNA helicase
d. Both a and b
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SHORT ANSWER Answer the questions in the space provided.
1. How does replication occur so quickly in eukaryotes?
2. Why is it important that exact copies of DNA are produced during replication?
3. How is DNA replication related to cancer?
4. Critical Thinking Why is it advantageous to have weak hydrogen bonds between complementary
bases and strong covalent bonds between phosphate and deoxyribose groups in a DNA molecule?
STRUCTURES AND FUNCTIONS The figure below shows DNA replicating. In the space
provided, describe what is occurring at each lettered section of the figure.
Part a.
Part b.
Part c.
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Part a.
Part b.
Part c.
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Section 10-3 Review
SEC T I O N 10 - 4 R E VIEW
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SEC T I O N 10 - 3 R E VIEW
P ROTEIN S YNTHESIS
VOCABULARY REVIEW Define the following terms.
1. codon
2. translation
3. anticodon
MULTIPLE CHOICE Write the correct letter in the blank.
1. A protein is a polymer consisting of a specific sequence of
a. amino acids.
b. fatty acids.
c. RNA nucleotides.
d. DNA nucleotides.
2. The genetic code specifies the correlation between
a.
b.
c.
d.
a DNA-nucleotide sequence and an RNA-nucleotide sequence.
an mRNA-nucleotide sequence and a tRNA-nucleotide sequence.
an mRNA-nucleotide sequence and an rRNA-nucleotide sequence.
an RNA-nucleotide sequence and an amino-acid sequence.
3. During translation, one end of a tRNA molecule pairs with a complementary
a. nucleotide sequence in DNA.
b. mRNA codon.
c. tRNA molecule.
d. protein molecule.
4. In eukaryotic cells, RNA is copied from DNA in the
a. ribosomes.
b. nucleus.
c. nuclear membrane.
d. cytosol.
5. Two amino acids are linked by a peptide bond when
a.
b.
c.
d.
two ribosomes attach simultaneously to the same mRNA transcript.
two tRNAs pair with neighboring codons on an mRNA transcript.
two codons on an mRNA transcript bind to each other.
a ribosome attaches to two codons on an mRNA transcript.
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SHORT ANSWER Answer the questions in the space provided.
1. List, in order, the tRNA anticodons that are complementary to the mRNA sequence
AUGCAUGCAAGUUAG.
How many amino acids will be in the polypeptide that is initially formed when this mRNA
sequence is translated?
2. Explain why methionine is the first amino acid in every growing polypeptide.
3. Describe three ways that RNA differs from DNA.
4. Critical Thinking How would a deletion of one nucleotide in the middle of an mRNA transcript
affect the polypeptide specified by that transcript?
STRUCTURES AND FUNCTIONS Label each part of the figure in the spaces provided.
The diagram below summarizes the events that occur during translation.
b
c
d
e
a
f
g
h
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Section 10-3
VOCABULARY REVIEW
1. A replication fork is a Y-shaped region that results
when the two strands of DNA separate during
replication.
2. A helicase is an enzyme that separates the strands
of DNA during replication.
3. Semi-conservative replication produces a new
DNA molecule with one original strand and one
new strand.
MULTIPLE CHOICE
1. b
2. a
3. b
4. d
5. c
SHORT ANSWER
1. Replication occurs simultaneously at many origins
along the DNA.
2. Producing exact copies ensures that when a cell
divides, the offspring cells will receive the same
genetic information as the parent cell.
3. Cancer can result when errors occur in the replication of DNA in genes that control how a cell
divides. A mass of cancerous cells called a tumor
can result.
4. The hydrogen bonds break easily, making it easier
for the two strands in the molecule to separate
during replication. The strong covalent bonds
ensure that the sequence of nucleotides remains
fixed in each strand.
Section 10-2
MULTIPLE CHOICE
1. c
2. d
3. a
4. b
5. b
SHORT ANSWER
1. The three parts are a deoxyribose sugar, a phosphate group, and a nitrogenous base. The phosphate
group and the base are connected to different parts
of the sugar.
2. Since guanine and cytosine are complementary,
another 15% of the nucleotides must contain
cytosine. The remaining 70% of the nucleotides
(100%–30%) must contain adenine and thymine in
equal proportions (35% each), since they are complementary to each other.
3. Complementary base pairing is important because
the hydrogen bonds between the bases hold the
two strands of DNA together and because it serves
as a way for DNA to replicate.
4. The X-ray diffraction photographs showed that the
shape of the DNA molecule was a double helix.
STRUCTURES AND FUNCTIONS
a, deoxyribose; b, guanine; c, adenine;
d, phosphate group
8
Modern Biology Study Guide Answer Key
Section 10-4
VOCABULARY REVIEW
1. A codon is a sequence of three mRNA nucleotides
that codes for a specific amino acid or a start or
stop signal.
2. Translation is the process of assembling polypeptides from information encoded in mRNA.
3. An anticodon is a sequence of three tRNA
nucleotides that pairs with a specific codon.
MULTIPLE CHOICE
1. a
2. d
3. b
4. b
5. b
SHORT ANSWER
1. The anticodons are UAC, GUA, CGU, and UCA.
(The last three nucleotides in the mRNA sequence
are a stop codon, which has no anticodon.) The
polypeptide will initially contain four amino acids.
2. The tRNA that pairs with the start codon on
mRNA carries methionine.
3. RNA contains ribose; DNA contains deoxyribose.
RNA usually contains uracil in place of thymine.
RNA is single stranded; DNA is double stranded.
4. All of the codons from the deletion point to the
end of the transcript would be shifted by one
nucleotide, so the sequence of amino acids specified from that point on would be different.
Translation would terminate prematurely if the
shift resulted in a new stop codon before the end
of the transcript.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
VOCABULARY REVIEW
1. A purine is a nitrogenous base with two rings of
carbon and nitrogen atoms. Examples may include
adenine or guanine.
2. A pyrimidine is a nitrogenous base with one ring
of carbon and nitrogen atoms. Examples may
include cytosine or thymine.
3. A complementary base-pair is a pair of nitrogenous
bases connected to each other by hydrogen
bonds. Examples may include adenine-thymine
and cytosine-guanine.
4. A nitrogenous base is a base in DNA containing
nitrogen and carbon.
STRUCTURES AND FUNCTIONS
Part a: helicase enzymes separate DNA strands;
Part b: DNA polymerase enzymes add complementary
nucleotides to each original strand of DNA and covalent bonds form between adjacent nucleotides;
Part c: DNA polymerases finish replicating DNA and
fall off, two DNA molecules identical to original DNA
molecule have formed.
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STRUCTURES AND FUNCTIONS
a, polypeptide or protein; b, peptide bond;
c, amino acid; d, tRNA; e, anticodon; f, codon; g, mRNA
or transcript; h, ribosome