Monozygotic (identical) twins - zygote split at early stage and developed into two embryo's
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Examples of artificial cloning (3)
Plant cuttings, Micropropagation of plants, Cloning of animals
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Micropropagation - Sequence
Meristem - Explant - Callus - Plantlet
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Micropropagation - Steps 1-4/7
Desirable plant selected - Meristem removed from shoot (sterile conditions) - Meristem cut into Explants - Explants placed on sterile aerated medium (agar)
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Micropropagation - Steps 5-7
Explants grow into a Callus (undifferentiated cells) - Callus cut and allowed to grow and differentiate on agar and becomes a Plantlet - Plantlets transplanted into sterile soil
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What is improtant about Meristematic cells - Explain
Totipotent - Can become any type of cell and can develop into a new individual - Capable of cell division by mitosis
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Why must conditions be sterile?
Bacteria and fungi could grow and compete with the developing plants for nutrients
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Micropropagation - Advantages (5)
Large numbers of genetically identical plants (desirable characteristics maintained) - Higher survival rates - Quicker than sexual reproduction - Large number stored in small area (costs) - Unique genotypes preserved
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Why is it important that unique genotypes are preserved?
Genetically unstable (increased mutation) increases labour costs for finding abnormal plants - Hard and costly to maintain sterile conditions - Genetically identical plants have the same susceptibility to disease
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Animal cell tissue culture
Producing a large number of a particular type of cell from a small number of originals
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Tissue cultures - Uses
Production of cancer cells (Research for treatment) - Production of host cells for viruses (Delvelop vaccine) - Production of monoclonal antibodies (Pregnancy tests)
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Stem cells - Advantage
Totipotent - can differentiate into more than one type of cell
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Where are they found?
Bone marrow, Adult testis, Umbilical cord
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Where do most that are used come from?
Early Embryos from IVF
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What is the advantage of stem cell organ transplants?
Organ not rejected by immune system - Don't require immunosuppressive drugs
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Animal cloning - Types (2)
Splitting Embryos - Nuclear Transfer
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Splitting Embryos - Stages
Fertilisation - Cell division (to 8 cell stage) - Cells split into 4 - Cells develop into identical embryos - Placed into surrogate mother (contributes no genetic information)
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What would happen if a different egg or sperm was used?
Produce genetically different embryos to the other egg and sperm due to different combinations of alleles
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Why is the Embryo split at an early stage?
So that the cells haven't differentiated
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Nuclear Transfer - Stages
Nucleus removed from an unfertilised egg (enucleated) - Nucleus from anothers body cell inserted into enucleated egg (micropipette) - Laboratory culture to 16 cell stage - Placed in uterus of surrogate mother
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Animal cloning - Disadvantages (4)
Expensice and unreliable (low success rate) - Premature ageing - Large organ syndrome - Unethical?
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