Cloning

What is cloning?

Cloning is one of the most controversial areas of scientific research of recent times. The term 'cloning' means the asexual reproduction of identical copies of an original, and it is human cloning (and to a lesser extent animal cloning) for reproductive purposes that causes considerable public disquiet.

However, reproductive cloning is one of just three distinctive types of processes and technology covered by the term 'cloning'. The others are recombinant DNA technology or DNA cloning, and therapeutic cloning.

While there are numerous problems of technique, side-effects and technology still to overcome, the key issue in the cloning debate is generally still regarded as the ethical question - is cloning morally acceptable?


Background

The types of cloning differ widely from one another, both in their techniques and aims.

'Recombinant DNA technology', 'DNA cloning', 'molecular cloning' or 'gene cloning' all describe the process of transferring a DNA fragment from one organism to a self-replicating genetic element (a cloning vector) such as a bacterial plasmid, enabling the fragment to be propagated in an alien host.

DNA cloning is an important technique in researching gene therapy, genetic engineering of organisms, and sequencing genomes.

Reproductive cloning and therapeutic cloning both rely on the process of 'somatic cell nuclear transfer'. In this process, the nucleus of a donor adult cell is transferred to an egg whose nucleus, and thus its genetic material, has been removed. The egg is then treated with electricity in order to stimulate division.

For reproductive cloning - which creates animals with an identical genetic make-up to an already existing animal - the embryo must then be transferred to a host body, in which to grow.

For therapeutic or embryo cloning, the objective is not to create adult animals, but to extract stem cells for research from the cloned embryos created. Embryonic stem cells are extracted from the five day old embryo, or blastocyte, which is then destroyed.

There are hopes in the medical community that stem cell research and therapeutic cloning will facilitate organ cloning and enable the replacement of damaged cells with healthy ones for sufferers of degenerative diseases.

Although the first cloned animal - a tadpole - was created in 1952, the most publicly significant event in the history of cloning was the creation of Dolly the Sheep in 1996 at the Roslin Institute, near Edinburgh. Since Dolly, a number of other cloned animals have been bred, including sheep, goats, cows, mice, pigs, cats, rabbits, and a gaur (an endangered species of Asian bison).

However, almost as significant as Dolly's development to adulthood were the circumstances of her death. Dolly died in February 2003, with lung cancer and crippling arthritis, aged six - half the life expectancy for a sheep of her breed.

In November 2001, scientists from Advanced Cell Technologies, a biotechnology company in Massachusetts, announced that they had cloned the first human embryos for the purpose of advancing therapeutic research.

Since then, a number of more or less reputable organisations and scientists claim to have successfully brought a cloned human embryo to term - but none have been able or willing to confirm this.


Controversies

Controversies about cloning can be broken down into ethical and scientific problems, although there is a degree of overlap.

On the ethical side, it is frequently asked whether it is appropriate to 'play God' by interfering with genetics. Beyond this, critics cite the suffering of laboratory animals, the destruction of unwanted embryos and concerns about the future uses of this new technology.

On the scientific front, the principal objection to reproductive cloning is the enormous inefficiency of the process, which may require hundreds of attempts to create a viable animal. In addition to low success rates, clones seem to suffer numerous health problems for reasons that are yet unknown.

Cloned animals tend to have compromised immune function and higher rates of infection, tumour growth, and other disorders. Studies of cloned mice and cattle show considerably reduced life expectancy. In this context, many scientists feel that, although human cloning may be possible, it would be wrong.

In December 2006 a government white paper proposed a ban on the creation of part-animal, part-human embryos after a consultation revealed widespread unease with the practice.

MPs argued against the ban, however. The Commons' science committee said in May 2007 it should be allowed under licence because existing research practices provide "essential tools in understanding diseases".


Cloning statistics

Dolly the Sheep was the sole survivor of 276 attempts to create and implant an embryo

The experiments to create a cloned gaur, carried out at Advanced Cell Technology, saw 692 gaur skin cells combined with cow eggs; 81 embryos began to divide; eight cows became pregnant; five miscarried

In the UK, attempting to clone a human carries a maximum penalty of 10 years' imprisonment

Statistic 1: (Source: Human Genome Project Information website); Statistic 2: (Source: Guardian, October 2000); Statistic 3: (Source: Human Reproductive Cloning Act 2001)


Cloning Quotes

"A person who places in a woman a human embryo which has been created otherwise than by fertilisation is guilty of an offence."

Human Reproductive Cloning Act 2001, Section One

"Ministers in Britain have too easily swallowed the line that cloning human embryos is essential to medical progress. It is not. Like stuck records, ministers and policy makers continue to enthuse about therapeutic cloning even though the majority of bench scientists no longer think it's possible or practicable to treat patients with cells derived from cloned embryos. They have already moved on to investigating the alternatives."

New Scientist editorial, December 2001

"What we want is to stimulate an informed public discussion of the way in which the techniques might be misused as well as used and to ensure legislation was put in place to prevent misuse."

Dr Ian Wilmut, the embryologist who created Dolly the Sheep, February 1997