Clones in Nature
What are clones? - A clone is an organism that contains identicle genetic material to its parent. Prokaryotes divide by binary fission. Eukaryotes asexually divide by mitosis.
Advantages of asexual reproduction -
- quick allowing organisms to take advantage of current environment.
- can be completed if sexual reproduction is not possible.
- offspring have identicle genetic information to enable them to survive in their environment.
Disadvantages of asexual reproduction -
- does not produce genetic variety so all genetically identicle organisms are equally susceptable.
Clones in Nature
Natural vegetative propagation in plants - English elm is adapted to reproduce asexually if the parent plant is damaged. New growth of root suckers or basal sproats grow from the meristem tissue in the trunk near to the ground.
Advantages of elm vegetative propogation -
- Root suckers allow the elm to spread as they grow around original trunk.
- The suckers grow in a circle called a clonal patch.
- This patch puts out more suckers so the patch can keep expanding.
Diadvantages of elm vegetative propogation -
- Dutch elm disease spread across Eaurope and English elm reponded by putting out root suckers. Then fungal disease carried by beetkes came.
- However, the clones are the same as the old one which do not have any immune to the fungal attack so they are just as vulnerable as the original tree.
- There was no genetic variation within the cloned population, natural selection could not occur.
Artificial Clones and Agriculture
Artificial vegetative propagation -
Taking cuttings: a section of stem is cut between leaf joints, then treated with plant growth hormones to encourage root groth and is then planted. The cutting is then genetically identicle to the original plant.
Grafting - shoot section from woody plant is joined to an already growing a root and stem(root stock). The graft grows and is genetically identicle to parent plant but root stock is genetically different.
Artificial propogation using tissue culture: Large sclae cloning:
Taking cutting and grafting cannot produce large numbers of clones plants. Plant tissue culture however can, and can produce large numbers of daughter plants from a small amount of plant material.
Tissue culture can produce new plants very quickly, which are known disease free.
Artificual Clones in Nature
Micropropogation by callus tissue culture - most common method.
- small peice of plant tissue taken to be clones from shoot tip EXPLANT.
- explant is placed on growth medium and the cells in the tissue divide.
- they cannot differentiate so a mass of cells called a CALLUS.
- Single callus cells can be removed from mass and put on growth medium to encourage shoot growth.
- growing shoots are then are put in growing medium to encourage root growth. They are then put into the greenhouse to be grown further.
Advantages of plant cloning in agriculture -
- farmers know what crop will be produced; high yeild, taste, colour etc.
- farmers costs are reduced as all plants ready to harvest at same time.
- its much faster than selective breeding.
Disadvantages of plant cloning in agriculture -
- no genetic variation so all plants are susceptable to same diseases/pests.