State the main role of DNA.
The image below shows a representation of several nucleotides in a molecule of DNA.
Identify the structures marked Y and Z.
DNA and RNA are referred to as polynucleotides.
State the meaning of the prefix 'poly' in the term polynucleotide.
Was this exam question helpful?
In a section of DNA 17 % of the nucleotides were found to contain cytosine.
Calculate the percentage of thymine in this section of DNA.
State one reason why the calculation from part a) could not be performed for a piece of RNA.
The diagram below shows a representation of part of a DNA molecule.
Identify the structures labelled A, B, and D.
Identify one type of bond found within the structure labelled C in the diagram at part c).
Was this exam question helpful?
One mark is available for clarity of communication throughout this question.
Draw on and annotate the diagram below to show the correct structure of double-stranded DNA.
Compare and contrast the structures of DNA and RNA.
Was this exam question helpful?
The 3D shape of DNA is know as a double helix.
State why RNA does not form a double helix
State the part of a DNA molecule that contains nitrogen.
Was this exam question helpful?
The diagram below shows a base pair within a molecule of DNA.
Identify part P of this section of DNA
Scientists sequenced the gene for a hormone, in order to understand more about why some individuals stop producing this hormone. The scientists determined that the gene consisted of 1 500 base pairs; 30% of the total bases were cytosine.
Deduce the number of nucleotides of adenine and guanine within this sample of DNA
Describe the conventional numbering system for carbon atoms in a pentose sugar such as the ribose or deoxyribose sugars found in RNA and DNA. You may sketch a diagram to illustrate your answer.
Was this exam question helpful?
The diagram below shows the process of DNA replication. The horizontal lines represent the positions of bases.
Identify the parts of the DNA molecule represented by the labels W, X, Y and Z.
The table shows the percentage of different bases in the DNA of some organisms.
Organism | Percentage of each base | |||
Adenine | Guanine | Cytosine | Thymine | |
Human | 32.8 | 17.2 | 17.2 | 32.8 |
Caterpillar | 33.1 | 16.9 | 16.9 | 33.1 |
Mouse |
| 22.4 |
|
|
Virus | 24.7 | 24.1 | 18.5 | 32.7 |
Calculate the missing figures for mouse DNA and complete the table.
Humans and caterpillars have very similar percentages of each base in their DNA but are not the same class of organism.
Use your knowledge of DNA structure and function to explain how this is possible.
The DNA of the virus is different from that of the human, caterpillar and mouse. Some viruses contain single-stranded DNA that is not base-paired to a complementary strand.
Explain how the data from the table in 4(b) provide evidence for this difference.
Was this exam question helpful?
Within the nucleus, DNA is replicated semi-conservatively in order to produce new cells.
State two features of DNA and explain how these features are important in the process of semi-conservative replication of a cell’s DNA.
Was this exam question helpful?
The ends of a DNA strand are referred to as the 3’ end and the 5’ end.
Describe the aspects of DNA structure that give rise to this naming system.
The structure of DNA has many characteristics that enable it to carry out its function.
(i) Identify two structural features that help DNA to carry out its function.
[2]
(ii) For each feature identified at part i), explain how it assists with DNA function.
[2]
Was this exam question helpful?
Even the smallest DNA molecules are very long.
A kilobase (Kb) is a unit equivalent to 1000 base pairs of a DNA molecule.
One Kb of double stranded DNA has a length of 0.34 μm.
The DNA in the nucleus of a cell from a fruit fly (Drosophila) is 5.6 cm long.
Calculate the number of Kb in the DNA of the fruit fly. Give your answer to the nearest whole number.
The amount of DNA found in the nucleus of cells can vary amongst people, with each human chromosome containing between 5 x 104 and 26 x 104 Kb of DNA.
Suggest one reason why people might have different quantities of DNA to each other.
Other than for use in replication, explain one advantage of DNA molecules having two strands.
Was this exam question helpful?
A section of DNA contains 1,200 base pairs.
The number of guanine molecules on strand one was counted as 156.
The number of cytosine molecules on strand one was counted as 209.
The number of adenine molecules on strand two was counted as 264.
Deduce the total number of each base present in the section, and the % composition of each base. Complete the table below.
| Number of molecules present | % composition |
Adenine |
|
|
Cytosine |
|
|
Guanine |
|
|
Thymine |
|
|
The image below shows a section of the skeletal formula of a DNA molecule.
Label the image below to show all the carbon atoms on each pentose sugar using the standard numbering format.
The DNA nucleotides are covalently bonded together in the sugar-phosphate backbone between the pentose sugar and the phosphate group, however, they are hydrogen bonded together between the bases.
Explain why both types of bonds are important for the functioning of DNA.
Was this exam question helpful?
ATP is a source of energy used in cells and is produced from processes such as respiration.
The structure of ATP is shown in the diagram below.
Use the information in the diagram, as well as your own knowledge, to compare and contrast the structure of ATP with an adenine DNA nucleotide.
Explain how the structure of DNA allows replication.
Was this exam question helpful?