6.4.6 Production of Artificial Clones in Animals Flashcards
What is embryo twinning?
The process of embryo twinning produces offspring that are clones of each other but not of their parents
It has been a routine procedure carried out to boost yields of livestock and promote desirable characteristics since the 1980s
The key step is the deliberate division of the embryo into two half embryos
These are then inserted into a surrogate mother for gestation and birth
The surrogate gives birth to identical twins
In some cases, embryos are split into single identical cells, each of which can be implanted into a separate surrogate mother animal
Although embryo twinning guarantees desirable characteristics in the offspring, it is not possible to predict how many offspring will be produced
What is reproductive cloning?
This is the method made famous by Dolly the sheep, cloned in Edinburgh, UK in 1996
Its name is Somatic Cell Nuclear Transfer (SCNT)
Dolly made headlines as being the first livestock animal to be created from a clone
Three separate animals are required:
The animal to be cloned by donating a cell
The female to donate an egg cell
The surrogate mother
How is SCNT carried out?
The animal to be cloned donates a somatic (body) cell eg. from an udder
The egg cell is extracted from the egg donor and enucleated (its nucleus is removed by suction and discarded)
The nucleus from the udder cell is injected into the enucleated egg cell
The hybrid zygote cell is now treated to encourage it to divide by mitosis
The embryo is implanted into the surrogate mother for gestation and birth
What is therapeutic cloning?
This is a technique designed to use cloned cells to replace dead or damaged cells that cause a loss of function in an individual
Embryos are cloned as in reproductive cloning, but the embryos are removed and subdivided
Each individual embryo cell is a totipotent stem cell that can be cultured and artificially differentiated into any type of specialised cell
In theory, any specialised cell can be derived by this method
Crucially, specialised cells with the same genome as the sufferer can be cloned and replaced
An example is replacing specialised brain tissue in sufferers of Parkinson’s Disease
At present, there is a lot of potential for therapeutic cloning but little clinical progress has been made
