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Exam questions · Biology · DNA and the Genome

DNA, Genes and the Genome

  • 7 exam questions
  • 18 marks
  • 8 quick checks
  1. 1 State [1 mark]

    State where the DNA is found in an animal cell.

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    Model answer

    In the nucleus, in the chromosomes.

    Mark scheme

    • In the nucleus (or in the chromosomes) — 1 mark
  2. 2 Describe [2 marks]

    Describe the structure of DNA.

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    Model answer

    DNA is a polymer. It is made of two strands that coil around each other to form a double helix.

    Mark scheme

    • A polymer made of two strands — 1 mark
    • The strands form a double helix — 1 mark
  3. 3 Define [2 marks]

    What is a gene?

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    Model answer

    A gene is a small section of DNA on a chromosome. It codes for a particular sequence of amino acids, to make a specific protein.

    Mark scheme

    • A small section of DNA on a chromosome — 1 mark
    • Codes for a sequence of amino acids to make a specific protein — 1 mark
  4. 4 Name [3 marks]

    The diagram shows part of a human cell. Name the parts labelled A, B and C.

    A cell, a nucleus and a chromosome opening out to DNA, with three parts marked A, B and C.
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    Model answer

    A is the nucleus. B is a chromosome. C is a gene.

    Mark scheme

    • A: nucleus — 1 mark
    • B: chromosome — 1 mark
    • C: gene — 1 mark
  5. 5 Explain [3 marks]

    Explain the difference between a gene and the genome of an organism.

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    Model answer

    A gene is a small section of DNA on a chromosome that codes for one specific protein. The genome is the entire genetic material of the organism. So the genome contains all of the genes, and a gene is only one small part of it.

    Mark scheme

    • A gene is a small section of DNA that codes for a protein — 1 mark
    • The genome is the entire genetic material of an organism — 1 mark
    • The genome contains all the genes, so a gene is only part of it — 1 mark
  6. 6 Describe [3 marks]

    The whole human genome has now been studied. Describe three reasons why this is important.

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    Model answer

    Scientists can search the genome for genes that are linked to different types of disease. Understanding which genes cause inherited disorders helps scientists to understand and treat them. Comparing the genomes of people from different places can be used to trace how early humans migrated around the world.

    Mark scheme

    • Search for genes linked to different diseases — 1 mark
    • Understanding and treatment of inherited disorders — 1 mark
    • Tracing human migration patterns from the past — 1 mark
  7. 7 Explain [4 marks]

    A family has a history of an inherited disorder. Explain how knowledge of the human genome could help this family.

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    Model answer

    Scientists can search the genome to find the gene that is linked to the disorder. Knowing the gene means that family members can be tested to find out whether they carry the faulty allele. Understanding what the gene does helps scientists to understand how the disorder develops, which makes it easier to develop a treatment for it.

    Mark scheme

    • The gene linked to the disorder can be found — 1 mark
    • Family members can be tested for the allele — 1 mark
    • Understanding what the gene does explains the disorder — 1 mark
    • This helps scientists to develop treatments — 1 mark

Quick check

  1. 1

    Where is DNA found in an animal cell?

    1. AIn the cell membrane
    2. BIn the nucleus
    3. CIn the cytoplasm
    4. DIn the ribosomes
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    B: In the nucleus

    DNA is found in the nucleus, contained in chromosomes.

  2. 2

    What is the shape of a DNA molecule?

    1. AA single straight chain
    2. BA flat sheet
    3. CA double helix
    4. DA hollow sphere
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    C: A double helix

    DNA is made of two strands that coil together to form a double helix.

  3. 3

    What is a gene?

    1. AA small section of DNA that codes for a protein
    2. BA whole chromosome
    3. CA type of protein
    4. DA cell that makes DNA
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    A: A small section of DNA that codes for a protein

    A gene is a small section of DNA on a chromosome that codes for a protein.

  4. 4

    How many chromosomes are there in a normal human body cell?

    1. A23
    2. B44
    3. C92
    4. D46
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    D: 46

    Human body cells have 23 pairs of chromosomes, which is 46 in total.

  5. 5

    What does a gene code for?

    1. AA sequence of sugars
    2. BA sequence of amino acids
    3. CA sequence of fatty acids
    4. DA sequence of nucleotides in RNA
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    B: A sequence of amino acids

    Each gene codes for a particular sequence of amino acids, which join to make a specific protein.

  6. 6

    What is the genome of an organism?

    1. AIts largest chromosome
    2. BIts set of proteins
    3. CAll of its genetic material
    4. DIts most important gene
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    C: All of its genetic material

    The genome is the entire genetic material of an organism.

  7. 7

    Which of these is one use of the human genome?

    1. ATracing how early humans migrated around the world
    2. BMaking humans photosynthesise
    3. CMeasuring body temperature
    4. DPredicting the weather
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    A: Tracing how early humans migrated around the world

    The human genome can be used to trace human migration patterns, to search for disease genes and to understand inherited disorders.

  8. 8

    Which statement about genes and chromosomes is correct?

    1. AA gene is bigger than a chromosome
    2. BGenes are found outside the nucleus
    3. CEvery chromosome carries only one gene
    4. DA chromosome carries many genes
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    D: A chromosome carries many genes

    A chromosome is a long molecule of DNA that carries many genes.