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DP IB Biology: SL

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Home / IB / Biology: SL / DP / Topic Questions / 2. Molecular Biology / 2.5 Nucleic Acids: Structure & DNA Replication / Structured Questions: Paper 2


2.5 Nucleic Acids: Structure & DNA Replication

Question 1a

Marks: 2
a)

Describe the main role of DNA. 

[2 marks]

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    Question 1b

    Marks: 2
    b)

    The image below shows a representation of several nucleotides in a molecule of DNA.

    e-1b

    Identify the structures marked Y and Z.

    [2 marks]

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      Question 1c

      Marks: 2
      c)

      Identify the nitrogenous bases in part b) marked X and W.

      [2 marks]

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        Key Concepts
        Double Helix Structure

        Question 1d

        Marks: 1
        d)

        DNA and RNA are referred to as polynucleotides.

        State the meaning of the prefix 'poly' in the term polynucleotide

        [1 mark]

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          Question 2a

          Marks: 2
          a)

          In a section of DNA 17 % of the nucleotides were found to contain cytosine.

          Calculate the percentage of thymine in this section of DNA. 

          [2 marks]

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            Key Concepts
            Double Helix Structure

            Question 2b

            Marks: 1
            b)

            State one reason why the calculation from part a) could not be performed for a piece of RNA. 

            [1 mark]
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              Key Concepts
              DNA & RNA: Comparison

              Question 2c

              Marks: 3
              c)

              The diagram below shows a representation of part of a DNA molecule.

              diagram-5_letters

              Identify the structures labelled A, B, and D.

              [3 marks]

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                Question 2d

                Marks: 1
                d)

                Identify one type of bond found within the structure labelled C in the diagram at part c).

                [1 mark]

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                  Key Concepts
                  Double Helix Structure

                  Question 3a

                  Marks: 1
                  a)

                  State the purpose of DNA replication. 

                  [1 mark]

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                    Key Concepts
                    DNA Replication

                    Question 3b

                    Marks: 2
                    b)

                    The diagrams below show two models of DNA replication.

                    dna-replication-sq

                    State, with a reason, which diagram, A or B, is correct.

                    [2 marks]

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                      Question 3c

                      Marks: 2
                      c)

                      Identify two enzymes that are involved with the process of DNA replication.

                      [2 marks]
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                        Question 3d

                        Marks: 2
                        d)

                        Calculate the fraction of a cell’s original DNA that will be present after 3 full cycles of DNA replication.

                        [2 marks]

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                          Question 4a

                          Marks: 1
                          a)

                          Both DNA and RNA contain pentose sugars in their sugar-phosphate backbones. 

                          Define the term pentose in reference to sugar molecules. 

                          [1 mark]

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                            Question 4b

                            Marks: 2
                            b)

                            During DNA replication the new bases are added to the new strand by the enzyme DNA polymerase in the 5' to 3' direction. 

                            Use your knowledge of enzymes to explain why it would not be possible for DNA polymerase to add the new bases in the 3' to 5' direction. 

                            [2 marks]
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                              Question 4c

                              Marks: 2
                              c)

                              When bases are bonded to the new DNA strands during replication they undergo a condensation reaction. 

                              Describe the events that occur during a condensation reaction.

                              [2 marks]

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                                Key Concepts
                                Formation of Sugars

                                Question 4d

                                Marks: 2
                                d)

                                In a length of DNA 1 000 nucleotides long there are 382 guanine nucleotides in one of the strands.

                                Explain why it is not possible to calculate the number of guanine nucleotides in the opposite strand from the information provided.  

                                [2 marks]

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                                  Key Concepts
                                  Double Helix Structure

                                  Question 5a

                                  Marks: 4

                                  One mark is available for clarity of communication throughout this question. 

                                  a)
                                  Draw on and annotate the diagram below to show the correct structure of double-stranded DNA.
                                  bTZZnTVZ_e-5a
                                  [4 marks]
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                                    Question 5b

                                    Marks: 5
                                    b)
                                    Compare and contrast the structures of DNA and RNA.
                                    [5 marks]
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                                      Key Concepts
                                      DNA & RNA: Comparison