Cloning

Biology: IB Diploma Higher Level, topic 13.3.6

Clones are groups of genetically identical organisms, derived from a single original parent cell.

When a single parent is able to produce exact genetic copies of itself, clones are produced.
This can happen at the cellular and organism level.
For example, when bacteria reproduce through the process of binary fission, they are producing clones.

Many plant species and some animal species have natural methods of cloning.
Humans can produce identical twins which are monozygotic. This means they were formed from the same zygote, therefore sharing the same DNA and being clones of each other.
Some plants, like strawberries, produce runners which allows them to produce clones of themselves.
Other plants, such as potatoes, produce tubers which can then grow into clones of the original plant.

Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cells.
When an embryo splits naturally this produces identical twins; however, this can also be done artificially e.g. in order to produce larger numbers of a desired animal.
For example, when a bull and a cow with desirable traits are mated the embryo produced will be split into several clusters of cells which can then be implanted into a number of surrogate mother cows. The resultant calves are all clones of each other.

Cells from adult animals can be harvested and their DNA used to grow a clone of that animal.
The nucleus of the harvested cell is placed into an enucleated egg cell.
A small current of electricity is then used to stimulate growth.
The egg cell can then be implanted into a surrogate mother.
The offspring created will be a clone of the original animal whose cells were harvested.
Dolly the Sheep was famously produced in this way.

Test yourself on Cloning

Which of the following is NOT a step in the cloning of adult animals such as Dolly the Sheep?