6.2.1 Cloning and Biotechnology Flashcards
what is cloning
the process of producing genetically identical cells or organisms from the cells of an existing organism
- can occur naturally in plants and animals, but also artificially
what is vegetative propagation
the production of plant clones from non-reproductive tissue, e.g. roots, leaves and stems
what are the methods of vegetative propagation in plants
- rhizomes
- stolons/runners
- suckers
- tubers
- bulbs
what are rhizomes
stem structures that grow horizontally underground away from the parent plant
- have nodes from which new shoots and roots can develop
- e.g. bamboo
what are stolons/runners
- similar to rhizomes
- in stems growing horizontally away from the parent plant
- but ABOVE ground, on the surface of the soil
- new shoots and roots develop at nodes or can form at the end of the stolon
- e.g. strawberries
what are suckers
shoots that grow from sucker buds (undeveloped shoots) present on the shallow roots of a parent plant
- e.g. elm tree
what are tubers
- large underground plant structures that act as a food store for a plant
- covered in “eyes”
- each eye is able to sprout and form a new plant
- e.g. potatoes
what are bulbs
- also underground food stores used by some plants
- new bulbs can develop from the original bulb and form new individual plants
- e.g. onions
what is a horticulturist
plant growers
what are other “natural” methods of vegetative propagation that horticulturists may use to produce clones
- taking cuttings
- grafting
- layering
what is grafting
joining the shoot of one plant to the growing stem and root of another plant
what is layering
bending the stem of a growing plant downwards so that it enters the soil and forms another plant
from where do you take cuttings to make clones of the parent plant
stem
root
leaf
PRACTICAL: how would you take cuttings and grow a clone from a parent plant
1) use a scalpel or sharp secateurs to take a cutting, between 5 to 10 cm long, from the end of the stem of a parent plant
2) remove any leaves from the lower end of your cutting if they are present, leaving just one at the tip
3) dip the lower end of the cutting in rooting powder, containing hormones to induce root formation
4) plant your cutting in a pot containing a suitable growth medium, e.g. well drained compost
5) provide cutting with a warm and moist environment (cover whole pot with plastic bag or place in a propagator (which provides these conditions))
6) when cutting has formed its own roots and strong enough, plant it elsewhere to continue growing
PRACTICAL: how would you take a root cutting
- cut a piece of root from the plant with a straight cut (use scalpel or secateurs)
- remove the uncut end of the root with a slanted cut
- dip the end of the cutting in rooting powder and plant in suitable growth medium
PRACTICAL: how would you take a leaf cutting
- popular method includes split vein cutting
- where you remove the whole leaf
- and then score the large veins on the lower leaf surface using a scalpel
- put it on top of a growth medium with the broken
- veins facing down
- repeat growing steps, and new plants should form from each break in the veins
what method is used to artificially clone plants
tissue culturing
what are the steps of tissue culturing
1) cells are taken from plant that is being cloned
2) cells are taken from the stem and root tips: STEM CELLS, so can develop into any type of cell
3) cells are sterilised (with bleach for example) to kill any microorganisms (as the bacteria and fungi will compete with the plant cells for nutrients, decreasing their growth rate)
4) cells (the explant), are placed in a culture medium containing plant nutrients
- e.g. glucose for respiration
- e.g. growth hormones such as auxins
5) cells divide and grow into a small mass called callus, which is then divided and moved to new culture mediums with a different ratio of nutrients and hormones
6) callus grows into a small plant (plantlet), and are taken out of the medium and planted into soil
- will develop into plants genetically identical to the original plant
when is tissue culture mostly used
- used to clone plants that don’t readily reproduce and are endangered and rare, e.g. british orchids
- used to grow whole plants from genetically engineered plant cells
what is micropropagation
a method of tissue culture that produces lots of cloned plants very quickly
what is the specifics behind micropropogation
- the bit where the cells are taken from the developing cloned plants (callus) and subcultured (grown on another fresh culture medium)
- process is repeated to create a large number of clones
when may micropropagation be used
- widely in horticulture and agriculture
- e.g. to produce fields full of a crop that has been genetically engineered to be pest-resistant
what is agriculture and what is horticulture
- both involve cultivating plants
- AGRICULTURE: farming, so using land to grow crops for human use and consumption
- HORTICULTURE: the cultivation of any plant for any purpose, but usually smaller, garden scale
what are the arguments for tissue culture
- desirable genetic characteristics (e.g. high fruit production) are ALWAYS passed onto the clones, which doesn’t always happen in sexual reproduction
- means plants can be reproduced in any season, as the environment is controlled
- less space using tissue culture than making the same number of plants using conventional growing methods
- produces lots of plants quickly, as compared to time taken to grow from seeds
