11 mark
Which base pair has a mistake?
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Syllabus Edition
First teaching 2023
First exams 2025
|
Structure of Nucleic Acids & Replication of DNA (CIE A Level Biology)
Exam Questions
3 hours46 questions
21 mark
Which row correctly identifies the features of DNA and RNA molecules? Â Â Â
| Â | DNA and RNA both contain a 5- carbon sugar | DNA and RNA contain both purine and pyrimidine bases | forms hydrogen bonds with bases in RNA molecules |
|
A B C D |
✓ ✓ ✓ X |
✓ X ✓ ✓ |
✓ ✓ X X |
key
✓= correct statement
X= incorrect statement
              Â
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31 mark
DNA was extracted from the pancreas of a walrus and a human liver cell.
In which way did the DNA molecules differ?
the ratio of guanine to cytosine
the type of pentose sugar
the types of nucleotides
the sequence of the nucleotidesÂ
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41 mark
Which row correctly describes guanine?
| Â | ring structure | component on nucleotide strand it is attached to | complementary base |
| A | double | pentose sugar | cytosine |
| B | double | phosphate | cytosine |
| C | single | phosphate | cytosine |
| D | single | pentose sugar | thymine |
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51 mark
What is the minimum number of hydrogen bonds in a length of DNA containing 900 base pairs?
450
900
1800
2700
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61 mark
The diagram shows part of a DNA molecule
Â
Which part is a nucleotide?Â
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71 mark
The diagram shows the outcomes from four different models of DNA reproduction after one nuclear division. The parent DNA is shown in black and the newly synthesized DNA is shown in grey.
Which diagram shows conservative DNA replication?
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81 mark
This diagram shows a section of a DNA molecule.
What is part X on the diagram?
Cytosine
Uracil
Thymine
Guanine
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91 mark
This diagram shows a section of DNA
How many hydrogen bonds would be involved in holding these two strands together?
10
11
12
14
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101 mark
Which row correctly describes adenine on a strand of DNA?
| Â |
component on nucleotide strand it is attached to |
complementary base |
|
A |
deoxyribose |
uracil |
|
B |
ribose |
uracil |
|
C |
deoxyribose |
thymine |
|
D |
ribose |
thymine |
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11 mark
Which base pair has the mistake? Â
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21 mark
A short piece of DNA 19 base pairs long was analysed to find the number of nucleotide bases in each of the polynucleotide strands. Some of the results are shown below
| Â | number of nucleotide bases | |||
|
strand 1Â strand 2 |
A 8 - |
T - 8 |
G - 3 |
C - 4 |
How many nucleotides containing adenine (A) were present in strand 2?
2
4
6
8
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31 mark
During semi-conservative replication of DNA, the following processes occur:
|
1 |
Free nucleotides are hydrogen bonded to those on the exposed strand. |
|
2 |
The cell receives the signal to begin to divide. |
|
3 |
Hydrogen bonds are broken between the complementary base pairs. |
|
4 |
Covalent bonds form between adjacent nucleotides on the same strand. |
|
5 |
The DNA double helix is unwound. |
Which is the correct order of the processes?
2 → 5 → 3 → 4 → 1
2 → 5 → 3 → 1 → 4
2 → 1 → 4 → 3 → 5
2 → 1 → 5 → 4 → 3
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41 mark
The table shows the percentages of bases in DNA from various types of cell.
|
source of DNA |
adenine |
cytosine |
guanine |
thymine |
|
human hair |
30 |
20 |
21 |
Z |
|
human liver |
W |
40 |
40 |
11 |
|
dog liver |
24 |
26 |
24 |
26 |
|
mouse bone marrow |
23 |
X |
27 |
25 |
|
sunflower leaf |
11 |
41 |
Y |
10 |
What is a valid deduction from this data?
W = 9 Â X = 24 Â Y = 38 Â Z = 29
W= 9 Â X = 26 Â Y = 37 Â Z = 31
W= 9 Â X = 25 Â Y = 38 Â Z = 29
W= 10 Â X = 25 Â Y = 37 Â Z = 30Â
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51 mark
Which of the following would be a result of analysing a DNA molecule?
An equal ratio of pentose sugars to phosphates and an equal ratio of thymine to adenine bases.
Twice as many pentose sugars as phosphates and an equal ratio of guanine to cytosine bases.
An equal ratio of hexose sugars to phosphates and an equal ratio of thymine to cytosine bases.
Twice as many hexose sugars as phosphates and an equal ratio of guanine to adenine bases.
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61 mark
The diagram shows part of a DNA molecule
Which row correctly describes the highlighted sections of DNA?
| Â |
contains a base |
hydrogen bonding present |
|
A |
2, 3 and 4 |
1 only |
|
B |
2, 3 and 4 |
3 only |
|
C |
1 ,2, 3 and 4 |
3 and 4 only |
|
D |
1 ,2, and 4 |
3 only |
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71 mark
In 1957, Meselson and Stahl conducted an experiment that provided overwhelming evidence to support the theory than DNA replication was semi-conservative. They used E. coli which has a generation time of around one hour.
Here are the steps in their experiment in a mixed-up order
|
1 |
Bacteria contain either all 14N DNA or hybrid DNA |
|
2 |
Bacteria grown in a 15N medium for many generations |
|
3 |
Bacteria transferred to a 14N medium and sampled every hour |
|
4 |
All bacteria contain hybrid DNA (14N DNA and 15N DNA). |
|
5 |
All bacteria contain 15N DNA |
4 → 3 → 1 → 2 → 5
3 → 1 → 2 → 4 → 5
5 → 4 → 3 → 1 → 2
2 → 5 → 3 → 4 → 1
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81 mark
The diagram shows part of an RNA molecule.
Which row of the table below is correct?
Â
| Â |
uracil |
phosphate |
ribose |
guanine |
|
A B C D |
W W X X |
Z Y Z Y |
Y Z Y Z |
X X W W |
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91 mark
Which nucleic acid bases are pyrimidines?
adenine and guanine
thymine and adenine
thymine and guanine
cytosine and uracil
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101 mark
How many mistakes are there in this DNA sequence?
1
2
3
4
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11 mark
A piece of DNA 153 base pairs long was analysed to find the number of nucleotide bases in each of the polynucleotide strands. Some of the results are shown below
| Â | number of nucleotide bases | |||
|
strand 2 |
A |
T 31 |
G 22 |
C 52 |
How many nucleotides containing Thymine (T) were present in strand 2?
22
29
34
48
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21 mark
What would be the result of analysing a DNA molecule 14 000 base pairs in length?
28 000 pentose sugars, 14 000 phosphates, an equal ratio of cytosine to thymine bases and an equal ratio of guanine to adenine bases
28 000 pentose sugars, 28 000 phosphates, an equal ratio of cytosine to guanine bases and an equal ratio of thymine to adenine bases
14 000 pentose sugars, 28 000 phosphates, an equal ratio of cytosine to thymine bases and an equal ratio of guanine to adenine bases
28 000 pentose sugars, 28 000 phosphates, an equal ratio of cytosine to thymine bases and an equal ratio of guanine to adenine bases
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31 mark
Meselson and Stahl proved that DNA replication was semi-conservative. Bacteria were grown for many generations in a medium containing 15N (a heavy isotope of nitrogen). They were then transferred to a medium containing 14N (a lighter isotope of nitrogen). They were given time to replicate DNA and divide once. Their DNA was extracted, spun in a centrifuge and observed using ultraviolet light. They then repeated this experiment, this time allowing the bacteria to replicate DNA and divide twice. Again, the DNA was extracted, spun in a centrifuge and observed using ultraviolet light.
Which shows the predicted results after zero, one and two generations of replication in the medium with the light isotope?
X = 0 Â Y = 1 Â Z = 2
X = 0 Â Y = 2 Â Z = 1
X = 2 Â Y = 1 Â Z = 0
X = 2 Â Y = 0 Â Z = 1
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41 mark
The table shows the percentages of bases in DNA from various types of cell.
|
source of DNA |
adenine |
cytosine |
guanine |
thymine |
|
human hair |
30 |
20 |
21 |
29 |
|
human liver |
9 |
40 |
40 |
11 |
|
dog liver |
24 |
26 |
24 |
26 |
|
mouse bone marrow |
23 |
26 |
27 |
24 |
|
sunflower leaf |
11 |
41 |
38 |
10 |
What is a valid deduction from this data?
Larger organisms have a greater thymine abundance.
All cells have roughly the same amount of DNA.
The structure of DNA in sunflower leaves and human liver is similar.
The four bases exhibit complementary base pairing.
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51 mark
The diagram shows DNA strands that have undergone replication. The parent DNA is shown in black and the newly synthesised DNA is shown in grey.
Which would be the resulting DNA strands formed after two cycles of semi-conservative replication? Â
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61 mark
Which enzymes are needed for DNA replication?
|
1 |
Helicase |
|
2 |
DNA ligase |
|
3 |
RNA polymerase |
|
4 |
DNA polymerase |
1 and 2 only
2, 3 and 4 only
1, 2 and 4 only
1 and 4 only
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71 mark
Which diagram shows the bond linking the individual units of a nucleic acid?
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81 mark
The following events occur in the replication of DNA.
Here are the steps in their experiment in a mixed-up order
|
1 |
opposite strands are separated |
|
2 |
free DNA nucleotides pair with complementary nucleotides on each strand |
|
3 |
bonds between complementary bases are formed |
|
4 |
bonds between complementary bases are broken |
|
5 |
phosphodiester bonds are formed |
Which is the correct order of the processes?
1 → 3 → 4 → 2 → 5
3 → 1 → 2 → 4 → 5
2 → 1 → 3 → 4 → 5
4 → 1 → 2 → 3 → 5
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91 mark
Which type of sugar and types of bonds are found in a DNA molecule?
| Â | type of sugar | nucleotides in strand joined by | adjacent strands joined by |
| A | non-reducing | phosphodiester bonds | hydrogen bonds |
| B | reducing | phosphodiester bonds | hydrogen bonds |
| C | non-reducing | ester bonds | covalent and hydrogen |
| D | reducing | ester bonds | covalent and hydrogen |
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101 mark
In 1957, Meselson and Stahl conducted an experiment that proved that DNA replication was semi-conservative. They took bacteria containing only 15N in their DNA and transferred them to a medium only containing 14N. They allowed the bacteria to divide once then centrifuged the DNA to reveal the following results
Which shows the predicted results after one generation in the medium with the light isotope?
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