Cloning is the process of producing genetically identical organisms.
For IGCSE Biology, you should understand cloning processes for plants and for mammals.
Micropropagation (tissue culture)
Micropropagation is the main method for cloning plants in vitro. In vitro means that the experiment is done outside the normal biological context; in short, it means that the experiment is done in a controlled environment in a lab.
Stages of micropropagation (also called tissue culture):
- Small tissue samples from a parent plant are cut out
- These explants are placed in agar growth medium that contains nutrients and plant hormones.
- The samples divide and grow into masses of plant tissue.
- These plantlets are transferred to compost, where the plantlets grow into plants.
Why do we need to do micropropagation?
By cloning plants, it is possible to produce a large quantity of genetically identical plants.
- Farmers can produce the plant all year round.
- If the farmer starts with a plant that has desirable characteristics (e.g. good tasting, large fruits), all of the plants produced through micropropagation will have the same desirable characteristic.
Cloning Mammals
The first mammal to be cloned was Dolly the sheep. Dolly was born in 1996 in the UK and died in 2003.
The process that gave birth to Dolly:
- The nucleus is removed from an unfertilised egg cell.
- The nucleus is removed from a tissue cell, which is donated by another sheep.
- The nucleus that was removed from the tissue cell is fused with the enucleated egg cell by applying an electric shock.
- The electric shock also starts cell division of the fused egg.
- After approximately 6~7 days, the embryo is implanted into the uterus of another sheep, which becomes the surrogate mother.
- The sheep that is born is genetically identical to the sheep that donated the tissue cell.
Cloning Transgenic Animals
- Animals can be genetically engineered to contain beneficial traits. For example, transgenic animals may be able to produce human proteins, such as insulin.
- When these transgenic animals are cloned, all the animals that are newly produced will be able to produce the same human protein.