The process of producing genetically identical cells or organisms from the cells of an existing organism. Natural clones occur in humans and other mammals as identical twins.The two types of artificial cloning used for animals are reproductive cloning and non-reproductive cloning.
A technique for cloning animals which involves taking a nucleus from an adult body cell and inserting it into an enucleated egg cell. Both reproductive and non-reproductive cloning use nuclear transfer.
A body cell is taken animal A. The nucleus is extracted and kept.
An egg cell is taken from animal B. Its nucleus is removed to form an enucleated egg cell.
The nucleus from animal A is inserted into the enucleated egg cell - the egg cell from animal B now contains genetic information from animal A.
The egg cell is stimulated to divide and an embryo is formed.
In reproductive cloning the embryo is implanted into a surrogate mother. A infant is produced that's genetically identical copy from animal A.
In non-reproductive cloning stem cells are harvested from the embryo. The stem cells are genetically identical to the cells in animal A.
Advantages and Disadvantages
Advantages:Desirable characteristics are passed onInfertile animals can be reproducedCloning can happen at any time - wouldn’t have to wait for breeding seasonRepopulate endangered animalsAids in medical research - all subjects standardised
Disadvantages:Undesirable characteristics are passed onSome evidence suggest clones don’t live as longReproductive cloning is difficult, time-consuming and expensiveGenetic diversity is decreasedSusceptibility to disease
Ethical Issues of Human Cloning
There are many ethical issues surrounding the issue of human cloning. Reproductive cloning of humans is currently illegal in the UK, however, non-reproductive cloning is allowed under licence. Ethical issues include:
Some believe that it undermines sexual reproduction.
Some believe clones may have a lower quality of life due to social exclusion or difficulties developing their own personality.
Unknown psychological effects to the clone.
Puts both the surrogate and clone at risk as many cloning experiments have resulted in failures in the form of miscarriages, stillbirths, and life-threatening anomalies.
Some evidence suggest that clones may have shorter lifespans.
Might foster an understanding of people as objects that can be designed and manufactured to possess specific characteristics. Decrease the value of human life.
The use of human embryos as a source of stem cells is controversial as the embryos are usually destroyed after they have been harvested.