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DP IB Biology: SL

Topic Questions

Home / IB / Biology: SL / DP / Topic Questions / 3. Genetics / 3.3 Inheritance / Structured Questions: Paper 2


3.3 Inheritance

Question 1a

Marks: 1
a)

Huntington's disease is a disease caused by a dominant allele.

State what is meant by the term dominant, in the context of alleles. 

[1 mark]

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    Question 1b

    Marks: 3
    b)

    Gregor Mendel conducted experiments that established the basis of modern genetics. 

    i)
    State the type of organism that Mendel used in his studies.

    [1 mark]

    ii)
    State why the organism you named in part (i) was a good choice for Mendel's experiments.

    [2 marks]

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      Question 1c

      Marks: 2
      c)

      As well as Mendel discovering modern genetics, his experiments also set an important precedent that defines all good scientific experiments. In particular, his methods demonstrated good practice in the collection of reliable data.

      Which aspect of Mendel's experimental set-ups can claim to have achieved this?

      [2 marks]

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        Question 1d

        Marks: 2
        d)

        In snapdragon plants, a cross between a red and white flowered plant results in pink flowered offspring due to codominance of alleles.

        In the species that Mendel used for his experiments, a cross between a red-flowered plant and a white-flowered plant, did not result in any pink flowered plants in the next generation.

        Suggest why. 

        [2 marks]

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          Question 2a

          Marks: 2
          a)

          The diagram shows a human egg and three sperm cells at the moment of fertilisation. 9WOrJSD6_e-2a

          Suggest why the egg is so much larger than one sperm, even though they carry the same amount of genetic information as each other. 

          [2 marks]

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            Key Concepts
            Gametes

            Question 2b

            Marks: 1
            b)

            State the number of chromosomes in a human egg. 

            [1 mark]

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              Key Concepts
              Gametes

              Question 2c

              Marks: 1
              c)

              Name the cell that forms when a sperm fertilises an egg. 

              [1 mark]

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                Key Concepts
                Diploid Zygotes

                Question 2d

                Marks: 1
                d)

                In a genetic diagram where H denotes the dominant allele responsible for causing Huntington's disease, and h denotes the recessive allele, state:

                i)
                the meaning of the genotype Hh

                ii)
                the phenotype that Hh will display

                [2 marks]

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                  Question 3a

                  Marks: 2
                  a)

                  The diploid number of a species of rodent is 64.

                  The table below has been incorrectly completed; some of the numbers in the second column are correct, while others are not. 

                  Cell Type Number of chromosomes
                  Zygote 64
                  Sperm cell 64
                  Muscle cell 32
                  Fur-producing cell 16

                  Complete the table below with correct numbers in the second column. 

                  [2 marks]

                  Cell Type Number of chromosomes
                  Zygote  
                  Sperm cell  
                  Muscle cell  
                  Fur-producing cell  
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                    Key Concepts
                    Diploid Zygotes
                    Diploid

                    Question 3b

                    Marks: 2
                    b)

                    A genetic cross is performed between two heterozygous parents with the genotype Qq.

                    Complete the Punnett grid for this cross.

                    punnett-grid---sq

                    [2 marks]

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                      Question 3c

                      Marks: 2
                      c)

                      When writing out genetic crosses by hand, which of the following pairs of letters is the best choice for denoting the dominant and recessive alleles?

                      Give a reason for your answer. 

                      • Cc
                      • Oo
                      • Hh
                      • Vv

                      [2 marks]

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                        Question 3d

                        Marks: 1
                        d)

                        State the name used to describe different alleles of the same gene, that have a combined effect on the phenotype of the organism. 

                        [1 mark]

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                          Question 4a

                          Marks: 2
                          a)

                          A pedigree chart is shown below.

                          MIvO8gH5_e-4a

                          i)
                          State the number of generations shown in the pedigree chart. 

                          [1 mark]

                          ii)
                          State the numbers of males and females shown in the pedigree chart. 

                          [1 mark]

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                            Key Concepts
                            Pedigree Charts

                            Question 4b

                            Marks: 1
                            b)

                            The pedigree chart from part (a) can be adapted with shading as follows:

                            yh_tdceS_e-4b

                            Suggest a meaning for the shaded squares and circles. 

                            [1 mark]

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                              Key Concepts
                              Pedigree Charts

                              Question 4c

                              Marks: 2
                              c)

                              A sperm cell is shown below.mRSrnqqO_e-4c

                              i)
                              Label the diagram with an X to show the position of mitochondria in this cell.

                              [1 mark]

                              ii)
                              State the purpose of the mitochondria in a sperm cell

                              [1 mark]

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                                Key Concepts
                                Gametes

                                Question 4d

                                Marks: 2
                                d)

                                Define the term sex linkage. 

                                [2 marks]

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                                  Question 5a

                                  Marks: 4

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

                                  a)

                                  State the differences between the terms phenotype and genotype. 

                                  Give one example of each

                                  [4 marks]

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                                    Question 5b

                                    Marks: 3
                                    b)

                                    8000 offspring were produced from a cross between two heterozygous parents, Hh and Hh. 

                                    Calculate how many of these offspring would have the genotype hh. Show your working. 

                                    [3 marks]

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                                      Question 5c

                                      Marks: 8
                                      c)

                                      i)
                                      Define the term mutation.

                                      [2 marks]

                                      ii)
                                      List four factors that can increase the rate of mutation within cells. Describe the possible consequence of exposure to that factor.

                                      [6 marks]

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