6 - MZH - Cloning Flashcards
Define cloning
cloning = The production of genetically identical cells or organisms
State 3 ways in which natural clones can be produced
- Binary fission - prokaryotes
- Asexual reproduction by mitosis - eukaryotes
- Vegetative propagation - asexual reproduction in plants
What are the 3 example of vegetative propagation in horticulture / agriculture?
- Take cuttings
- Use grafting - join the shoot of one plant to the growing stem and root of another plant
- Use layering - bending a stem of a growing plant downwards so it enters the soil and grows into a new plant
Steps to produce clones from cuttings in vegetative propagation (6)
- Use scalpel to take a cutting between 5-10cm long from the end of the parent plant
- Remove leaves from lower end of the cutting (if there’s any), leaving just one tip
- Dip the lower end of the cutting in rooting powder whcch contains hormones that induce root formation
- Plant cutting in a pot containing a suitable growth medium e.g. well drained compost
- Provide cutting with a warm / moiste environment by either covering whole pot with a plastic bag or by putting it in a propagator
- When the cutting has formed it’s own roots and it strong enoguh, you cna plant it elsewhere and let it grow
What is tissue culture and what is another name for it?
Tissue culture (micropropagation) = another form of vegetative propagation - artificially cloning plants
Steps to clone plants by tissue culture (4)
- Cells are taken from original plant that’s going to be cloned. Cells from the stem & root tip are used as these cells are their stem cells
- Cells are sterilised using using a sterilising agent of bleach or ethanol to kill any microorganisms
- Bacteria & fungi compete for nutrients w/ plant cells which decrease growth rate
- Cells are placed on a culture medium containing organic nutrients (e.g. glucose and amino acids) and a high conc of plant hormones. This is carried under asceptic conditions.
- The cells divide to produce a mass of undifferentiated cells. The mass can be subdivided to produce lots of plants very quickly through micropropagation
- When cells have divided and grown into a small plant, they’re taken out of the medium and planted in soil - they’re genetically identical to the parent plant
When is micropropagation useful? (3)
- Doesn’t readily produce seeds
- It’s required to be pathogen free e.g. foods like potatos
- Has been GM or selectively bred with difficulty
- Plant is endangered
What is micropropagation + how is it done?
Example of when it is used
Micropropagation is when tissue culture is used to produce lots of cloned plants very quickly.
- Cells are taken from developing cloned plants and subcultured (grown in a fresh culture medium)
- Repeating this process creates arge no’s of clones
This technique is used extensively in horticulture and agriculture e.g. to produce a field full of a crop tht have been genetically engineered to be pest-resistant
Advantages and disadvatages: (4 of each)
Artifical cloning of plants
Advantages:
- Desirable genetic characteristics are always passed onto clones e.g. high fruit production
- Tissue culture allows plants to be reproduced in any season
- Less space needed by tissue culture than for the same number of plants by the conventioal growing methods
- Produces lots of plants quickly
Disadvantages:
- Undesirable characteristics always passed onto clones e.g. fruit w/ lots of seeds
- No genetic variability ∴ one single disease could wipe them all out
- Production costs are high
- Contamination by microorganisms during tissue culture could lead to the loss of the whole batch being cultured
3 examples of natural plant clones produced by vegetative propagation
- What is the name of the type of plant
- How does it grow
- Example
Rhizomes:
- Stem cultures that grow horizontally underground away from the parent plant. They have ‘nodes’ from which enw shoots and roots can develop
- E.g. bamboo
Bulbs:
- Underground food stores used by some plants
- New bulbs are able to develop form the original bulb and form new individual plants
- E.g. onion
Stolons (runners):
- Similar to Rhizomes but grow above ground, on the surface of the soil
- New shoots and roots can either develop from nodes or from at the end of the stolon
- E.g. Strawberry
Give an example fo natural cloning in animals
Identical twins (monozygotic twins)
Name the 2 ways in which animals cana be artificially cloned
Artificial twinning
Somatic cell nuclear transfer (SCNT)
Stages carried out for artificial embryo twinning (5)
- Egg cell is extracted from female cow and fertilised in a petri dish
- Fertilised egg is left to divide at least once to form an embryo in vitro
- Individual cells from the embryo are seperated and each is put into a seperate petri dish. Each cell divides and develops normally, so an embryo is formeing in each petri dish
- Embryos are then implanted into surrogate mothers. One per surrogate mother
- Embryos continue to develop as normal inside surrogate cows and eventually born - genetically identical to each other
Stages to carry out somatic cell nuclear transfer (5)
- Somatic cell (any cell that’s not a reproductive cell) is taken from sheep A. Nucleus is extracted and kept
- An oocyte (immature egg) is taken from sheep B. It’s nucleus is removed to form an enucleated oocyte
- Nucleus from sheep A is inserted into the enucleated oocyte. The oocyte from sheep B now contains genetic info from sheep A
- The nucleus and enucleated oocyte are fused together and stimulated to divide
- Embryo is then implanted into a surrogate mother and eventually a lamb is born that’s a clone of sheep A
Uses of animal cloning (4)
Research:
- Test new drugs on cloned animals - they’re genetically identical so variables that come from genetic differences are removed
Agriculture:
- Farmers can increase the no’ of animals w/ desirable characteristics
Animals are GM to produce a useful substance that they wouldn’t normally produce:
- A goat have been GM to produce beneficial protein in its milk could be cloned
Save endangered species:
