Question 1
What is the genetic material of all living organisms?
A.
DNA in animals and RNA in plants
B.
RNA only
C.
DNA only
D.
Protein in prokaryotes and DNA in eukaryotes
Question 2
In the conventional symbolic diagram of a nucleotide, the phosphate is shown as a circle, the pentose sugar as a pentagon and the nitrogenous base as a rectangle. What is the correct relative arrangement of these components?
A.
pentose sugar--phosphate--base
B.
base--phosphate--pentose sugar
C.
phosphate--base--pentose sugar
D.
phosphate--pentose sugar--base
Question 3
What forms the strong backbone in each strand of DNA or RNA?
A.
A sequence of hydrogen-bonded complementary base pairs
B.
A folded chain of ribose sugars held by peptide bonds
C.
A chain of nitrogenous bases joined directly to each other
D.
A continuous chain of covalently bonded sugars and phosphates
Question 4
What happens when RNA nucleotide monomers are polymerized to form an RNA strand?
A.
Amino acids are joined by peptide bonds along the strand.
B.
Bases are removed so that only the sugar-phosphate chain remains.
C.
Water is released as covalent bonds form between nucleotides.
D.
Water is added as hydrogen bonds form between nucleotides.
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Question 5
One strand of a DNA molecule has the base sequence AGTCCG. What is the complementary base sequence on the other DNA strand?
A.
TCAGGC
B.
GACGGT
C.
UCAGGC
D.
AGTCCG
Question 6
A nucleic acid strand is being extended during replication. At which end of the growing strand are new nucleotides added?
A.
The end of the growing strand
B.
The end of the growing strand
C.
Either end, depending only on the base sequence
D.
The middle of the strand, between paired bases
Question 7
What is the structure of a nucleosome?
A.
Protein wrapped around two DNA strands, with no linker DNA between units
B.
DNA wrapped around eight histone proteins, with an additional histone attached to linker DNA
C.
DNA enclosed inside a phospholipid membrane and joined to a centromere
D.
RNA wrapped around eight ribosomal proteins, with an additional protein attached to mRNA
Question 8
Some viruses contain RNA as their genetic material. All living organisms use DNA as their genetic material.
State why the presence of RNA viruses does not contradict the statement that DNA is the genetic material of all living organisms.
[2]
State the function of genetic material.
[1]
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Question 9
Nucleotides are the monomers from which nucleic acids are built.
Draw and label a simple diagram of a nucleotide using the conventional symbols for its three components.
[3]
Question 10
DNA and RNA are both nucleic acids found in cells.
Compare DNA and RNA with respect to the number of strands normally present.
[1]
Compare DNA and RNA with respect to the pentose sugar present.
[1]
Compare DNA and RNA with respect to one nitrogenous base that differs between them.
[1]
Question 11
A short DNA strand contains six base positions. Each position can contain A, T, G or C. How many different base sequences are possible for this strand?
A.
24
B.
64
C.
4096
D.
46656
Question 12
Why does purine-to-pyrimidine bonding contribute to the stability of the DNA helix?
A.
Pyrimidines pair with pyrimidines to reduce the number of hydrogen bonds.
B.
Each base pair contains two identical ring structures, increasing symmetry.
C.
Purines pair with purines to make the helix wider at every base pair.
D.
Each base pair has equal length, keeping the backbones a constant distance apart.
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Question 13
In a Hershey--Chase experiment, T2 bacteriophages with radioactive phosphorus in their DNA infect bacteria. After agitation and centrifugation, where should most radioactivity be detected if DNA enters the bacterial cells?
A.
In the supernatant containing detached phage coats
B.
In the pellet containing bacterial cells
C.
Equally in the pellet and supernatant
D.
Only in newly formed protein coats
Question 14
Chargaff measured the percentage of bases in double-stranded DNA from a species and found A , T , G and C . What conclusion is best supported by these data?
A.
The tetranucleotide hypothesis is not supported because all four bases are not present in equal amounts.
B.
The molecule is RNA because adenine is more common than guanine.
C.
The DNA cannot form complementary base pairs between its two strands.
D.
The DNA must contain equal numbers of all four bases in every species.
Question 15
The diagram shows two RNA nucleotides positioned before they are joined into an RNA polymer.
State the monomer from which RNA is formed.
[1]
Outline how the two monomers become part of one RNA polymer.
[2]
State the name given to the repeating sugar and phosphate chain in RNA.
[1]
Question 16
The diagram shows a short, untwisted representation of a DNA molecule. One strand has the base sequence 5'-A G T C-3'. The complementary strand is not labelled.
State the base sequence of the complementary strand from left to right as shown in the diagram.
[1]
State the type of bond that links complementary bases in DNA.
[1]
Explain what is meant by antiparallel strands in DNA.
[2]
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Question 17
The diagram shows part of a nucleic acid strand with its terminal groups labelled.
Identify which labelled end is the 5' terminal.
[1]
State the chemical feature of a 3' terminal.
[1]
Explain the significance of 5' to 3' directionality during replication or transcription.
[2]
Question 18
The diagram shows a nucleosome from a eukaryotic chromosome.
State the composition of the histone core in a nucleosome.
[1]
State the role of the additional histone protein shown near the linker DNA.
[1]
Explain how the association between DNA and histones assists DNA packaging.
[2]
Question 19
A student made symbolic diagrams of three nucleotides. Circles represent phosphate groups, pentagons represent pentose sugars and rectangles represent nitrogenous bases.
Identify the diagram that shows the correct relative positions of the three nucleotide components.
[1]
State the component represented by each of the three symbols used in the diagrams.
[1]
Explain why the nitrogenous base is the component that varies between nucleotides in a DNA sequence.
[2]
Question 20
Samples of two nucleic acids were analysed. The table summarizes structural features detected in each sample.
Structural feature | Sample P | Sample Q |
|---|---|---|
Thymine | present | absent |
Uracil | absent | present |
Sugar | deoxyribose | ribose |
Strands | double-stranded | single-stranded |
Identify the sample that is DNA.
[1]
Using the data, distinguish between the two samples in terms of their bases.
[1]
Using the data, distinguish between the two samples in terms of sugar and number of strands.
[2]
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Question 21
During translation, in which direction is an mRNA molecule read by a ribosome?
A.
From the end towards the end
B.
From the end towards the end
C.
In either direction if codons are complementary
D.
From both ends at the same time
Question 22
A short section of DNA has eight base positions. At each position, one of four bases can occur.
Calculate the number of possible base sequences for this section of DNA.
[2]
Outline why DNA has an enormous capacity for storing information.
[1]
State why conservation of the genetic code across life supports universal common ancestry.
[1]
Question 23
The diagram represents possible base pairing in DNA. Some bases have a two-ring structure and some have a one-ring structure.
State which DNA bases are purines and which are pyrimidines.
[2]
Explain how purine-to-pyrimidine bonding contributes to DNA helix stability.
[2]
Question 24
Hershey and Chase used T2 bacteriophages with radioactively labelled DNA or radioactively labelled protein. After infection of bacteria, the mixtures were agitated and centrifuged.
State why different radioisotopes could be used to distinguish DNA from protein in this experiment.
[2]
State the result expected for phages with labelled DNA after centrifugation.
[1]
Explain how this result supports DNA as the genetic material.
[1]
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Question 25
The diagram shows transcription of an RNA strand from a DNA template strand.
State the direction in which the new RNA strand is synthesized.
[1]
Explain why the DNA template and the RNA product are antiparallel during transcription.
[2]
State the direction in which a ribosome reads an RNA molecule during translation.
[1]
Question 26
The diagram shows part of a DNA molecule before replication and two possible products after one round of replication.
State the base that would be added opposite adenine during DNA replication.
[1]
Identify the product that shows semi-conservative replication.
[1]
Explain how complementary base pairing allows accurate replication of DNA.
[2]
Question 27
The graph shows how the number of possible DNA base sequences changes with the length of a DNA strand.
State the number of possible bases at one position in a DNA sequence.
[1]
Calculate the number of possible sequences in a DNA strand of 6 bases.
[1]
Suggest why DNA has a vast capacity for storing information despite having only four different bases.
[2]
Question 28
The table shows genetic material and cellular characteristics of four biological entities.
Entity | Genetic material | Cellular characteristic |
|---|---|---|
Bacterium | DNA | cellular |
Yeast | DNA | cellular |
Maize plant | DNA | cellular |
RNA virus | RNA | acellular |
Identify the entity in the table that is acellular.
[1]
State the genetic material used by the living organisms shown in the table.
[1]
Evaluate whether the RNA virus in the table contradicts the statement that DNA is the genetic material of all living organisms.
[2]
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Question 29
The diagram shows synthesis of a short nucleic acid strand by an enzyme. The ends of the template and growing strand are labelled.
Identify the end of the growing strand to which the incoming nucleotide is added.
[1]
State the direction in which the new strand is synthesized.
[1]
Explain why directionality is significant in replication and transcription.
[2]
Question 30
A molecular visualization of a nucleosome is shown with selected regions labelled.
Identify the labelled molecule wrapped around the histone core.
[1]
State the number of histone proteins in the core of one nucleosome.
[1]
Explain how the association between DNA and histones helps form the nucleosome structure.
[2]
Question 31
The table shows the relative percentages of bases in DNA extracted from several organisms. The data are similar to those collected by Chargaff.
Organism | Adenine / % | Thymine / % | Guanine / % | Cytosine / % |
|---|---|---|---|---|
Human | 29 | 29 | 21 | 21 |
Wheat | 27 | 27 | 23 | 23 |
Yeast | 31 | 31 | 19 | 19 |
Bacterium | 24 | 24 | 26 | 26 |
Frog | 33 | 33 | 17 | 17 |
Describe two patterns in the base composition data for double-stranded DNA.
[2]
Explain how Chargaff's data falsified the tetranucleotide hypothesis.
[1]
State how falsification gives greater certainty than induction in this example.
[1]
Question 32
The table compares how selected codons are interpreted during protein synthesis in organisms from different kingdoms.
Codon | Bacterium | Plant | Animal |
|---|---|---|---|
AUG | Methionine | Methionine | Methionine |
UUU | Phenylalanine | Phenylalanine | Phenylalanine |
GGC | Glycine | Glycine | Glycine |
UGG | Tryptophan | Tryptophan | Tryptophan |
UAA | Stop | Stop | Stop |
CCA | Proline | Proline | Proline |
Describe the pattern shown by the codon meanings in the three organisms.
[1]
State the number of possible codons formed from three base positions.
[1]
Explain why conservation of the genetic code is evidence for universal common ancestry.
[2]
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Question 33
A model was used to compare the distance between the two sugar-phosphate backbones in DNA for different possible base-pair combinations.
Base-pair combination | Distance between backbones / nm |
|---|---|
A–T | 2.0 |
G–C | 2.0 |
A–G | 2.2 |
C–T | 1.8 |
Identify the class of base to which adenine and guanine belong.
[1]
Describe the effect of purine-pyrimidine pairing on the distance between the sugar-phosphate backbones.
[1]
Suggest why purine-purine or pyrimidine-pyrimidine pairing would reduce DNA helix stability.
[2]
Question 34
The Hershey-Chase experiment used bacteriophages with either radioactively labelled DNA or radioactively labelled protein. After infection of bacteria, agitation and centrifugation, radioactivity was measured in the pellet and supernatant.
Phage labelling treatment | Pellet radioactivity / % | Supernatant radioactivity / % |
|---|---|---|
DNA-labelled phage | 85 | 15 |
Protein-labelled phage | 10 | 90 |
Identify the labelled molecule that was found mainly in the bacterial pellet.
[1]
State why different radioisotopes could be used to distinguish DNA from protein in this experiment.
[1]
Explain the purpose of agitation and centrifugation in the experiment.
[2]
Evaluate how the results support the conclusion that DNA is the genetic material.
[1]
Question 35
An RNA molecule was analysed during translation. The positions of ribosomes on the same RNA at three successive times are shown.
State the direction in which the ribosomes are moving along the RNA.
[1]
Identify the type of nucleic acid shown, using one feature from the diagram.
[1]
Explain the significance of nucleic acid directionality for translation.
[2]
Question 36
DNA and RNA are both nucleic acids, but the genetic material of living organisms is DNA. Some viruses have RNA genomes.
I.
State the molecule used as the genetic material by living organisms.
[1]
II.
Outline why RNA viruses do not contradict the statement that living organisms use DNA as their genetic material.
[2]
Explain how the structure of nucleic acids allows hereditary information to be stored stably.
[2]
Discuss why DNA is suitable as a long-term store of hereditary information in cells.
[2]
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Question 37
The diagram shows a short RNA molecule being formed from nucleotide monomers.
I.
Identify the three components of one RNA nucleotide.
[1]
II.
Outline the reaction by which RNA nucleotide monomers form an RNA polymer.
[2]
Explain why an RNA polymer can have properties that separate nucleotide monomers do not have.
[2]
Evaluate the use of a simple circle-pentagon-rectangle diagram for representing RNA structure.
[2]
Question 38
DNA and RNA are nucleic acids with related structures but different cellular roles.
I.
State one similarity between DNA and RNA.
[1]
II.
State the nitrogenous base found in RNA instead of thymine.
[1]
III.
State the sugar found in DNA.
[1]
Compare and contrast the structures of DNA and RNA.
[3]
Sketch and label the chemical difference between ribose and deoxyribose at carbon 2 of the sugar.
[1]
Question 39
Chargaff measured the relative percentages of bases in DNA from several species. The tetranucleotide hypothesis predicted equal percentages of A, T, G and C in all DNA.
DNA source | / % | / % | / % | / % |
|---|---|---|---|---|
Human | 30.5 | 29.8 | 19.9 | 19.8 |
Wheat | 27.1 | 27.3 | 22.7 | 22.9 |
Yeast | 31.2 | 31.0 | 18.9 | 18.9 |
E. coli | 24.7 | 24.3 | 25.5 | 25.5 |
Mouse | 29.0 | 28.8 | 21.1 | 21.1 |
Tetranucleotide hypothesis | 25.0 | 25.0 | 25.0 | 25.0 |
Describe the relationship between the percentages of adenine and thymine in the species shown.
[1]
Explain why the relationship between guanine and cytosine is expected in double-stranded DNA.
[1]
Use the data to evaluate the tetranucleotide hypothesis.
[2]
State how these data support DNA as a molecule with capacity to store information.
[1]
Question 40
Complementary base pairing is important in both replication and expression of genetic information.
I.
State the complementary base pairs in DNA.
[1]
II.
Outline the bonding that allows complementary bases to pair.
[2]
Explain how complementary base pairing allows semi-conservative replication of DNA.
[3]
Explain how complementary base pairing is involved in transcription.
[2]
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Question 41
A student claims that DNA cannot store much information because it uses only four different bases.
Base positions | Possible sequences |
|---|---|
1 | 4 |
2 | 16 |
3 | 64 |
4 | 256 |
5 | 1,024 |
6 | 4,096 |
7 | 16,384 |
8 | 65,536 |
9 | 262,144 |
10 | 1,048,576 |
I.
State the number of possible bases at each position in a DNA strand.
[1]
II.
Calculate the number of possible base sequences in a DNA molecule with 10 base positions.
[2]
Explain how DNA can have an enormous capacity for storing genetic information with great economy.
[2]
Evaluate the student's claim.
[2]
Question 42
Almost all living organisms use the same genetic code, despite having very different DNA base sequences.
I.
Define a codon.
[1]
II.
State why there are 64 possible codons.
[2]
Explain how base sequences can vary greatly while the genetic code remains conserved.
[2]
Discuss how conservation of the genetic code supports universal common ancestry.
[2]
Question 43
Nucleic acid strands have directionality because of the numbered carbon atoms in their pentose sugars.
I.
Identify the 5' terminal and the 3' terminal of a nucleic acid strand.
[2]
II.
State the direction in which a new DNA or RNA strand is synthesized.
[1]
Explain the significance of 5' to 3' linkages in replication and transcription.
[3]
Explain why directionality is also significant in translation.
[2]
Question 44
The stability of the DNA double helix depends partly on the pairing of purines with pyrimidines.
I.
State which DNA bases are purines and which are pyrimidines.
[2]
II.
State the complementary base pairs in DNA.
[1]
Explain how purine-to-pyrimidine bonding contributes to the stability of the DNA helix.
[2]
Discuss the consequences for DNA if purine-purine and pyrimidine-pyrimidine pairs occurred frequently.
[2]
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Question 45
A molecular visualization of a nucleosome can be used to study how eukaryotic DNA is packaged.
I.
Identify the central protein core of a nucleosome.
[1]
II.
Outline the role of linker DNA in a nucleosome arrangement.
[2]
Explain how nucleosomes help package eukaryotic DNA.
[2]
Suggest how molecular visualization software can provide evidence for the association between DNA and histone proteins in a nucleosome.
[2]
Question 46
Hershey and Chase used T2 bacteriophages labelled with radioactive phosphorus or radioactive sulfur to investigate whether DNA or protein is the genetic material.
I.
Explain why radioactive phosphorus was used to label DNA and radioactive sulfur was used to label protein.
[2]
II.
State the role of centrifugation in the experiment.
[1]
Explain how the results of the experiment support the conclusion that DNA is the genetic material.
[3]
Evaluate the importance of radioisotopes as a technological development in this investigation.
[2]
Question 47
Chargaff measured the relative amounts of bases in DNA from diverse life forms. His results were important in rejecting an earlier model of DNA.
Organism | Adenine / % | Thymine / % | Guanine / % | Cytosine / % |
|---|---|---|---|---|
Human | 30 | 30 | 20 | 20 |
Wheat | 24 | 24 | 26 | 26 |
E. coli | 22 | 22 | 28 | 28 |
Yeast | 40 | 40 | 10 | 10 |
Sea urchin | 15 | 15 | 35 | 35 |
I.
State the pattern in Chargaff's data for adenine and thymine, and for guanine and cytosine.
[2]
II.
State one way in which base composition varies across the organisms in the data.
[1]
Explain how Chargaff's data support complementary base pairing in double-stranded DNA.
[2]
Discuss how Chargaff's data addressed the tetranucleotide hypothesis and illustrate the certainty of falsification.
[3]
Question 48
Before the structure and role of DNA were accepted, many scientists expected protein to be the genetic material because proteins are chemically diverse. Evidence from several investigations changed this view.
I.
State one reason why protein was once considered a strong candidate for genetic material.
[1]
II.
Outline one feature of DNA that shows it can nevertheless store diverse hereditary information.
[2]
Compare the contributions of the Hershey-Chase experiment and Chargaff's data to the conclusion that DNA is the genetic material.
[3]
Evaluate why one experiment alone would have been less convincing than the combined evidence.
[2]
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