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Cloning
Clones – genes, cells or whole organisms that carry identical genetic material because they are derived from the same original DNA.
Reproductive cloning
- Reproductive cloning generates genetically identical organisms.
Non-reproductive cloning
- Non-reproductive cloning generates cells, tissues and organs – can replace those damaged by diseases or accidents.
Advantages of Using Cloned Cells
- Cells will not be rejected as they are genetically identical to an individual’s own cells.
- Prevent waiting for donor organs to become available for transplant.
- Cloned cells can be used to generate any cell type because they are totipotent.
- Damage caused by some diseases and accidents cannot currently be repaired by transplantation or other treatments.
- Using cloned cells is less likely to be dangerous than a major operation such as a heart transplant.
Possibilities for Non-reproductive Cloning
- The regeneration of heart muscle cells following a heart attack.
- The repair of the nervous tissue destroyed by diseases such as multiple sclerosis.
- Repairing the spinal cord of those paralysed by an accident that results in a broken back or neck.
- These techniques are often referred to as therapeutic cloning.
- However, there are some ethical issues concerning whether cloning should be used in humans.
- There are ethical objections to the use of human embryonic material and some scientific concerns about a lack of understanding of how cloned cells will behave over time.
When it comes to A2/A-level Biology, do you know how the natural clones are produced using the example of vegetative propagation in elm trees?
Natural Vegetative Propagation
- Vegetative propagation is form of asexual reproduction of a plant.
- Only one plant is involved and the offspring is the result of one parent.
- The new plant is genetically identical to the parent.
(1) Runners – stems that grow horizontally above the ground.They have nodes where buds are formed, which grow into a new plant, e.g. strawberries and spider plant.
(2) Tubers – new plants will grow out of swollen modified roots called tubers.Buds develop at the base of the stem and then grow into new plants, e.g. potato and daliahs.
(3) Bulbs – a bulb contains an underground stem, with leaves containing stored food attached.
- At the centre of the bulb is an apical bud, which produces leaves and flowers.
- Also attached are lateral buds, which produces new shoots, e.g. daffodils.
(4) Basal sprouts (root suckers) – the suckers grow from meristem tissue in the trunk close to the ground, where least damage is likely to have occurred, e.g. elm trees and mint.
- Root suckers help the elm spread, because they can grow all around the original trunk.
- When the trunk dies, the suckers grow into a circle of new elms called a clonal patch.
- This, in turn, puts out new suckers so that the patch keeps expanding as far as resources permit.
Advantages
- A large number of elm trees can grow in one area as asexual reproduction is much faster = larger supply of wood.
- Elm trees grow quite close together = easy to harvest.
- Dense patches of trees encourage woodland animals = may be good for ecotourism/ bringing money to the area.
Disadvantages
- Dutch elm disease – a fungal disease that affected Europe’s elm trees.
- Once an elm is destroyed by the Dutch elm disease, it grows root suckers which shortly after become destroyed too.
- Since the new trunks are clones of the old one, they do not have any resistance to the fungal attack.
- There is no genetic variation within the cloned population, so natural selection cannot occur. - Cannot stop the growth of elm trees in unwanted places.
Drafted by Bonnie (Biology)