5.4 - Cloning Flashcards
What is Micropropagation?
Tissue culture is a process in which very small (‘micro’) pieces of plants (‘tissue’) are grown (‘cultured’) using nutrient media
Because they are initially grown in petri dishes on nutrient agar we say they are grown ‘in vitro’ – outside a living organism
How are plants micro-propagated in vitro?
Cells are scraped from the parent plant (these cells are known as explants)
The surface of the explants are sterilised using a disinfectant followed by a rinse with sterile water
Sterilised explants are transferred to a sterile petri dish containing sterile nutrient agar
The growth medium encourages the explant cells to grow and divide into small masses of cells (known as a callus)
Each callus is transferred to a fresh growth medium that contains a range of plant growth regulators (hormones). The presence of these hormones causes the callus to develop roots, stems and leaves, forming a plantlet
Plantlets can be transferred to individual potting trays and develop into plants
What are the advantages of micropropagation?
Clones are genetically identical individuals
The cloning of plants has many important commercial uses
It allows a variety of a plant with desirable characteristics to be produced:
Cheaply
With a greater yield (a large number of plants can be produced per square metre)
Quickly (the plantlets are ready to grow into mature plants)
At any time of the year
Identical to each other (so they retain the desired characteristic)
Disease-free or resistant plants can be bred
It can also ensure diseases prevalent in other areas of the world are not imported and spread by ensuring native varieties of plants are produced in large enough quantities to supply demand in one country without importing plants from abroad
Tissue culture can also be an important process in preserving rare plant species
What are the disadvantages of micropropagation?
There are a number of drawbacks to using micropropagation:
Trained personnel and a sterile laboratory are required
All the plants produced are genetically identical and so will all be vulnerable to the same diseases and pests (the lack of genetic variation makes them less able to adapt to environmental change)
How are embryo’s cloned?
It is possible to clone animals using embryo transplants
Egg cells from the best cow are artificially fertilised using sperm cells taken from the best bull
This forms an embryo
The developing animal embryo is then split apart many times before the cells of the embryo become specialised
This forms many separate embryos that are genetically identical
These cloned embryos are then transplanted into host mothers
The calves born from these host mothers are all genetically identical
How are adult cells cloned?
The nucleus is removed from an unfertilised egg cell
The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
A very small electric shock stimulates the egg cell to divide (by mitosis) to form an embryo
These embryo cells contain the same genetic information as the adult skin cell
When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female (known as the surrogate mother) to continue its development until birth
This process was used to create the first clone (exact genetic copy) of a mammal in 1996
What are the benefits of cloning?
Cloning could be used to help preserve endangered species of plants and animals
Cloning makes it possible to quickly and cheaply produce commercial quantities of consistently high quality plants at any time of the year.
Cloning allows farmers to ensure consistently high quality of livestock
What are the risks with cloning?
Cloning can result is a reduced gene pool like selective breeding. Means there are fewer different alleles in a population leaving the population with a smaller chance of having resistance to a new diseases
Some evidence that clone animals may not be as healthy as normal ones
Humans may be cloned in the future which is very unethical. Early attempts might be unsuccessful
What is pharming?
A transgenic animal is bred that contains a foreign gene within its genome
This foreign gene causes the animal to produce a useful compound which gets expressed within its milk
Once this has been done the animal can be cloned to produce a whole herd or flock, all of which produce the same special milk
This process is known as pharming
What is pharming produce?
Antibodies for targeting cancer cells in humans
Blood clotting factor IX for haemophilia (blood clotting disorder)
Alpha-1-antitrypsin for cystic fibrosis sufferers
