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Exam questions · Biology · Selective Breeding and Genetic Engineering

Tissue Culture

  • 6 exam questions
  • 20 marks
  • 9 quick checks
  1. 1 State [2 marks]

    State two conditions that must be provided for explants to grow in tissue culture.

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    Model answer

    Any two from: sterile conditions, nutrients, plant hormones, warmth, light.

    Mark scheme

    • First condition — 1 mark
    • Second condition — 1 mark
  2. 2 Name [2 marks]

    Name the mass of undifferentiated cells that forms in tissue culture, and the small plants that grow from it.

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    Model answer

    A callus, and plantlets.

    Mark scheme

    • Callus — 1 mark
    • Plantlets — 1 mark
  3. 3 Explain [3 marks]

    Explain why all of the tools and equipment used in tissue culture must be sterile.

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    Model answer

    Microorganisms such as bacteria and fungi grow much faster than plant cells. If they got into the culture they would compete with the plant cells for nutrients and might kill them or spoil the culture.

    Mark scheme

    • Microorganisms grow faster — 1 mark
    • They compete for nutrients — 1 mark
    • Could kill the cells / spoil the culture — 1 mark
  4. 4 Calculate [3 marks]

    A grower takes 40 explants from a rare orchid. Each explant produces a callus that makes 25 plantlets. Calculate the total number of plantlets, and state the genetic relationship between them.

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    Model answer

    40 × 25 = 1000 plantlets. They are genetically identical clones of the parent orchid.

    Mark scheme

    • 40 × 25 — 1 mark
    • 1000 plantlets — 1 mark
    • Clones, genetically identical — 1 mark
  5. 5 Explain [4 marks]

    Explain two advantages of using tissue culture in a plant breeding programme.

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    Model answer

    It can produce a large number of identical plants quickly, so a plant with a useful characteristic, such as disease resistance, can be copied in large numbers. It can also produce plants that are free of disease, because the cells from the shoot tip may not contain viruses, so the plants are healthier and give a better yield.

    Mark scheme

    • Many plants quickly — 1 mark
    • Developed: copy useful feature — 1 mark
    • Disease-free plants — 1 mark
    • Developed: viruses not in tip — 1 mark
  6. 6 Evaluate [6 marks]

    Evaluate the use of tissue culture to produce plants and for medical research.

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    Model answer

    In plant breeding, tissue culture produces large numbers of identical plants quickly, all year round, in a small space, and the plants can be disease-free. It can save rare species. In medical research cultured cells can be used to test drugs and study diseases such as cancer, which reduces the use of animals. However, it is expensive and needs a sterile technique and skilled workers, and contamination can ruin the cultures. The plants are clones, so there is no variation, and a disease could harm all of them. Overall it is very useful when it is used carefully, but it should be combined with other methods to keep genetic variation.

    Mark scheme

    • Many identical plants quickly — 1 mark
    • Disease-free / saves rare species — 1 mark
    • Medical research use — 1 mark
    • Expensive, skilled workers, contamination — 1 mark
    • Clones, no variation — 1 mark
    • A reasoned conclusion — 1 mark

Quick check

  1. 1

    What is a callus?

    1. AA root
    2. BA type of hormone
    3. CA mass of undifferentiated cells
    4. DA kind of agar
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    C: A mass of undifferentiated cells

    A callus is a mass of undifferentiated plant cells that grows in tissue culture.

  2. 2

    Why is the agar used in tissue culture sterile?

    1. ATo make it stronger
    2. BTo stop microorganisms growing
    3. CTo give nutrients
    4. DTo make it set
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    B: To stop microorganisms growing

    Sterile agar stops microorganisms growing and competing with the plant cells.

  3. 3

    What is added to the agar to make plant tissue grow?

    1. ANutrients and plant hormones
    2. BAntibiotics only
    3. CSoil
    4. DSalt only
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    A: Nutrients and plant hormones

    The agar contains nutrients and plant hormones, which make the cells grow and differentiate.

  4. 4

    Which describes plants made by tissue culture?

    1. AThey are all different
    2. BThey are produced by meiosis
    3. CThey have two parents
    4. DThey are genetically identical clones
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    D: They are genetically identical clones

    They all come from one parent by mitosis, so they are genetically identical clones.

  5. 5

    Which is an advantage of tissue culture?

    1. AIt increases variation
    2. BIt is cheap
    3. CIt makes many identical plants quickly
    4. DIt needs no skill
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    C: It makes many identical plants quickly

    Many identical plants can be produced quickly, all year round.

  6. 6

    Which is a disadvantage of tissue culture?

    1. AThe plants have no genetic variation
    2. BIt cannot make many plants
    3. CIt needs a lot of soil
    4. DIt only works in summer
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    A: The plants have no genetic variation

    The plants are clones with no variation, so a disease could affect all of them.

  7. 7

    Why can tissue culture be used to make disease-free plants?

    1. AIt uses antibiotics
    2. BShoot tip cells are often virus-free
    3. CIt uses vaccines
    4. DThe plants are cloned from roots
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    B: Shoot tip cells are often virus-free

    Cells in the tip of the shoot are often free from viruses, so the plants grown from them are disease-free.

  8. 8

    How can cultured human cells help to develop a new cancer drug?

    1. ABy growing a whole person
    2. BBy making the drug
    3. CBy curing the cancer
    4. DBy allowing the drug to be tested on cells
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    D: By allowing the drug to be tested on cells

    The drug can be tested on the cells in a dish, without using a person or animal.

  9. 9

    A grower wants to keep a rare orchid from extinction. Why is tissue culture useful?

    1. AMany plants can be grown from a small piece of tissue
    2. BIt creates new alleles
    3. CIt makes the orchid grow faster in the wild
    4. DIt makes seeds
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    A: Many plants can be grown from a small piece of tissue

    A small piece of tissue can be made into hundreds of plants, without taking plants from the wild.