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    • Rights: The University of Waikato
    Published 21 November 2007 Referencing Hub media
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    Why are zebrafish that have been mutated to model human diseases1 difficult to identify?

    Transcript

    Peter Cattin (Auckland University): You actually wouldn’t know if you had mutant fish here because they would be heterozygotes. Often those mutations that we are interested in, and by mutations we are looking at things like muscle2 mutants or blood vessel3 - or blood itself – mutants … They would typically be fatal if they were homozygotes. So they will tend to be present in the population4 as hets [heterozygous]. You wouldn’t know they were there because they are able to survive with the dominant5 allele6. So any one of these could be mutants.

    It’s through doing back crosses that you look. You look then at the phenotype7 of the developing embryos and take if from there. Then you go to your more genetic8, PCR-type things to identify what genes9 have been affected, and look for upstream/downstream effects, those sorts of things.

    Alice Lan (PhD student, Auckland University): When I have a mutant I will have mismatched DNA10, and when I hybridise this it will create kinks [DNA from the fish is bound by complementary base pairing11 to wildtype DNA. Where the DNA is the same as the wildtype it will bind; where it differs because of a mutation12 it will ‘kink’].

    So Cel1 [a restriction enzyme13] will cut through the kinks and create a different band. If I run a profile in gel electrophoresis, I will be able to see the extra band. Then I will know that’s the mutant; that’s the interesting fish. Now I want to have a look.

    Peter Cattin (Auckland University): You’ve got to very carefully monitor where each of your fish progeny14 have gone, and the crosses. It’s got to be a very deliberate and carefully managed mathematical and logistical exercise, as well as the genetic side of it.

    1. diseases: 1. An abnormal condition of an organism that impairs bodily functions. 2. In plants, an abnormal condition that interferes with vital physiological processes.
    2. muscle: The tissue that makes it possible for an animal to move and to maintain its posture. Muscles also make the heart beat, force blood to circulate and move food along the digestive system. The human body has more than 600 muscles.
    3. blood vessel: Any of the vessels, as arteries, veins, or capillaries, through which the blood circulates.
    4. population: In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.
    5. dominant: An allele that is expressed if it is present.
    6. allele: An alternative form of the same gene that occupies the same location on a chromosome.
    7. phenotype: The observable physical or biochemical characteristics of an organism, determined by both genetic make-up and environmental influences.
    8. genetic: Of, relating to, or determined by genes.
    9. genes: A segment of a DNA molecule that carries the information needed to make a specific protein. Genes determine the traits (phenotype) of the individual.
    10. DNA: Deoxyribonucleic acid (DNA) is a molecule that contains the instructions needed for an organism to develop and function. These instructions are stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C) and thymine (T).
    11. complementary base pairing: The joining of specific nucleotides, for example, in a DNA double helix, the base adenine (A) only pairs with thymine (T) and cytosine (C) only pairs with guanine (G).
    12. mutation: Occurs when the DNA is damaged or changed in such a way that it alters the genetic message carried by that gene.
    13. restriction enzyme: An enzyme that causes a break, or cut, in both strands of DNA at a specific sequence, usually about 4-8 base pairs long. Also called a restriction endonuclease.
    14. progeny: Offspring of animals or plants.
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      diseases

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      2. 1. An abnormal condition of an organism that impairs bodily functions.

      2. In plants, an abnormal condition that interferes with vital physiological processes.

      population

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      3. In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.

      phenotype

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      4. The observable physical or biochemical characteristics of an organism, determined by both genetic make-up and environmental influences.

      DNA

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      5. Deoxyribonucleic acid (DNA) is a molecule that contains the instructions needed for an organism to develop and function. These instructions are stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C) and thymine (T).

      restriction enzyme

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      6. An enzyme that causes a break, or cut, in both strands of DNA at a specific sequence, usually about 4-8 base pairs long. Also called a restriction endonuclease.

      muscle

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      7. The tissue that makes it possible for an animal to move and to maintain its posture. Muscles also make the heart beat, force blood to circulate and move food along the digestive system. The human body has more than 600 muscles.

      dominant

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      8. An allele that is expressed if it is present.

      genetic

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      9. Of, relating to, or determined by genes.

      complementary base pairing

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      10. The joining of specific nucleotides, for example, in a DNA double helix, the base adenine (A) only pairs with thymine (T) and cytosine (C) only pairs with guanine (G).

      progeny

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      11. Offspring of animals or plants.

      blood vessel

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      12. Any of the vessels, as arteries, veins, or capillaries, through which the blood circulates.

      allele

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      13. An alternative form of the same gene that occupies the same location on a chromosome.

      genes

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      14. A segment of a DNA molecule that carries the information needed to make a specific protein. Genes determine the traits (phenotype) of the individual.

      mutation

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      15. Occurs when the DNA is damaged or changed in such a way that it alters the genetic message carried by that gene.

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