Cloning is a process of artificially creating a new individual that is genetically identical to an existing individual.
Tissue culture technique involves the growth of cells or tissues outside the organisms in a suitable culture medium, which contains nutrient and growth hormones.
Cloning
Fusion cell cloning involves replacing the nucleus of an unfertilised egg with the nucleus from a different cell. The replacement nucleus can come from an embryo, but if it comes from an adult cell, it is called adult cell cloning.
Dolly the sheep was the first mammal to be cloned using adult cell cloning. She was born in the UK in 1996 and died in 2003. Here's how she was produced:
1. An egg cell was removed from the ovary of an adult female sheep, and its nucleus removed.
2. The nucleus from an udder cell of a donor sheep was inserted into the empty egg cell.
3. The fused cell then began to develop normally, using genetic information from the donated DNA.
4. Before the dividing cells became specialised, the embryo was implanted into the uterus of a foster mother sheep. The result was Dolly, genetically identical to the donor sheep.
Tissue culture technique
Another way of cloning plants is by tissue culture, which works not with cuttings but with tiny pieces from the parent plant. Sterile agar jelly with plant hormones and lots of nutrients is needed. This makes tissue culture more expensive and difficult to do than taking cuttings.
Tissue culture involves the following steps:
1. Small amounts of parent tissue or a number of cells are taken
2. The plant material is transferred to plates containing sterile nutrient agar jelly
3. Plant hormones are added to stimulate the cells to divide
4. Cells grow rapidly into small masses of tissue
5. More growth hormones are added to stimulate the growth of roots and stems
6. The tiny plantlets are transferred into potting trays where they develop into plants
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