Cloning: Overview

Introduction

Cloning is the process of creating a direct genetic copy of an organism or piece of organic material. Certain forms of cloning occur naturally, such as in the cellular process of mitosis or the asexual reproduction of many prokaryotic species. However, the term "cloning" is most commonly used in relation to processes specifically carried out by human researchers, or artificial cloning. There are three types of human-directed cloning: DNA cloning, therapeutic cloning, and reproductive cloning. All three have attracted some degree of debate, but reproductive cloning is by far the most controversial.

DNA cloning is the process of copying a single gene or short segment of DNA, which can be useful for many scientific purposes. For example, agricultural scientists can use cloned DNA to genetically modify crop species. DNA cloning is largely accepted, although some activists oppose it. Therapeutic cloning is used to make stem cells. Stem cells are undifferentiated cells that are capable of becoming whatever type of cell is needed, and therefore are highly valuable in medical research. Stem cells have great potential to treat disease, but because they are usually sourced from embryos, and some people believe that human embryos represent human life regardless of their origin, stem cell research has proved controversial.

Reproductive cloning is the highest-profile form of cloning, and focuses on the creation of entire living organisms. Famously, in 1997, scientists created the first cloned mammal, a sheep named Dolly. This breakthrough stimulated intense debate over the ethical implications of cloning from many different angles. Proponents of reproductive cloning tend to see it as a major scientific advancement with great potential benefits in areas such as conservation biology and agriculture. A few even advocate for the potential advantages that human cloning could offer to society. However, many critics are opposed to reproductive cloning on religious or other ethical grounds, while others are concerned about the viability of reproductive clones, as many early experiments with cloned animals produced stillborn, malformed, or sickly offspring. The concept of human cloning, in particular, remains a deeply controversial subject and has been explicitly banned in many US states as well as other countries.

Understanding the Discussion

Alzheimer’s Disease: A degenerative neurological disease often suffered by older people. Alzheimer’s patients suffer from memory loss progressing to dementia. Symptoms are caused by the death of nerve cells in the brain.

Chimera: An organism containing genetic material from two or more sources.

DNA: Deoxyribonucleic acid, a double-stranded helical molecule in the nucleus of a cell. DNA encodes genetic information and passes it to the next generation.

Embryo: An organism before birth or hatching that is in a very early stage of development. A five-day-old human embryo is a microscopic ball of undifferentiated cells.

Gene: A segment of DNA that encodes a specific product, often a protein.

Undifferentiated Cells: Cells that have not become a specific cell type. They have the potential to become any type of cell, and thus have applications in the treatment of disease.

History

In 1997, scientists at the Roslin Institute in Scotland polarized world opinion when they created the first cloned mammal, a sheep named Dolly. The clone was created by inserting DNA from an udder cell of a six-year-old ewe into a denucleated ovum. Dolly was the single successful outcome of 277 cloning attempts.

US president Bill Clinton was concerned that technology used to clone a sheep could be applied to the cloning of humans. Within a month of the Roslin Institute success, he banned the use of federal funds for human cloning. The same year, the National Bioethics Advisory Committee considered the issue and recommended that human cloning be considered morally unacceptable. One of the factors in the decision was the risk of a cloned child being born with genetic problems.

Beginning in 1997, individual US states began enacting legislation to ban human cloning. Privately funded efforts remained legal, but a voluntary moratorium was signed in 1998 by over 64,000 scientists. The Catholic Church became involved in the debate, opposing both human reproductive cloning and the use of embryos to obtain stem cells.

The bans were opposed by organizations including the Human Cloning Foundation and the Cloning Rights United Fund. Some groups expressed the opinion that every person should have the right to clone themselves as an alternative to traditional childbearing. Cloning would give infertile couples a chance to raise a child who shared the genetics of at least one parent.

Opponents of cloning pointed out the possibility of researchers creating whole clones for the sole purpose of harvesting organs for transplants. However, the Human Cloning Foundation advocated clone creation only for the donation of nonessential organs, such as kidneys or bone marrow.

In 2001, an endangered baby mouflon (a European wild sheep) was cloned using DNA from the ovary cells of a dead female. The mouflon DNA was transferred into a domestic sheep egg cell, and the embryo was carried to term by a female domestic sheep. A healthy infant mouflon resulted. This technology excited biologists, who realized the potential of cloning to increase the numbers of endangered animals. However, the breakthrough raised a new ethical issue: the possibility of cloning a dead person.

In 2001, a series of cattle cloning experiments replicated the high failure rate of previous attempts. Although some healthy clones were produced, the cloned calves were sometimes stillborn. Others had unusually high birth weights or genetic disorders resulting in cardiac or respiratory problems.

Federal legislation to ban human cloning was introduced in 1998, but the bill failed to pass. In 2001, Italian fertility doctor Severino Antinori and US fertility expert Panos Zavos announced separate plans to clone humans. The announcements spurred a new attempt to pass a federal anti-cloning bill, but the attempt was unsuccessful. Antinori eventually announced the birth of a cloned baby but provided no proof of his claim.

Panos Zavos was affiliated with Clonaid, a human cloning company that was largely discredited due to its association with the Raëlians, a cult espousing the belief that extraterrestrials engendered humans. Their stated goal was to achieve eternal youth by cloning themselves and transferring their personalities into their clones. Clonaid claimed in 2003 to have created the first human clone, a baby girl called Eve. The company refused to allow the child to be examined, so the claim was not accepted by the scientific community. Later, in 2009, reports would circulate of Zavos's new assertions that he had succeeded in cloning and transferring more than ten human embryos; as in the past, no corroborating evidence was found, and these claims, along with other claims of successful human reproductive cloning, were widely disregarded and ignored.

In 2003, the cloned sheep Dolly had to be euthanized at age six due to arthritis and a respiratory infection. She only lived half the lifetime of a normal sheep. Dolly showed signs of premature aging, indicating that clones may age at an accelerated rate.

The administration of US president George W. Bush opposed human reproductive cloning as well as therapeutic cloning involving the destruction of new human embryos. Despite Bush’s efforts, however, no federal law against human cloning was enacted. In related legislation, a bill was passed in 2006 banning the production of human embryos to harvest tissues or organs.

Bush vetoed a 2006 bill that would allow federal support for research involving stem cells derived from newly created human embryos. Research using cell lines from embryos that had already been destroyed was permitted to continue receiving support, although scientists expressed concern about the continued usefulness of such lines. It was around this time that the debate around cloning and its research became further ignited when scientist Shinya Yamanaka announced a proven ability to reprogram specialized adult cells to behave like embryonic cells. Called induced pluripotent stem cells (IPS), their creation and use for potential individualized treatment were viewed as a more ethical alternative to cloning because the process did not involve embryo destruction. In 2009, however, President Barack Obama signed an executive order overturning the Bush era’s ban on federal funding for embryonic stem cell research.

As some scientists continued to advocate for the greater therapeutic potential and, possibly, quality of stem cells derived from cloned embryos, research into successfully cloning human embryos for this purpose continued. In 2013, it was announced that scientists working for an Oregon research institution had, by applying a form of the Dolly technique, achieved a breakthrough in cloning human embryos that could be used as healthy embryonic stem cell sources. While this development again raised ethical concerns and speculation about future attempts at cloning a human being, the lead researcher, Shoukhrat Mitalipov, argued that the embryos, which were not fertilized naturally, were likely incapable of developing beyond the production of the cells.

Research on cloning non-human animals also progressed. Although such work did draw opposition from many animal welfare activists, in general it attracted less controversy that the idea of human cloning. Several species of livestock animals were successfully cloned to aid in the breeding of preferred traits such as disease resistance, while various animals were also cloned specifically for research purposes. After a lengthy investigation, in 2008 the US Food and Drug Administration acknowledged the safety of meat and milk from cloned animals and their offspring. In 2018, it was reported that Chinese scientists had successfully cloned primates for the first time, creating two female macaque monkeys using the same somatic cell transfer techniques that had been used to create Dolly the sheep. Meanwhile, a market developed for cloning pets like cats and dogs, allowing wealthy clients to replicate their favorite animal companions.

Cloning Today

Cloning, and particularly human cloning research, remained a controversial subject into the 2020s. While the US did not establish a federal ban on human cloning as many other countries did, a patchwork of laws banning or restricting the practice in various forms had developed at the state level. For example, several US states, including Massachusetts, California, and Illinois, maintained bans on reproductive human cloning, while a handful of others, including Arizona, Arkansas, and South Dakota, had bans that extended to include therapeutic cloning. In many cases, debate around human cloning, including therapeutic cloning, tended to be closely connected to debate around abortion. While research into therapeutic cloning remained ongoing, no active medical procedures involving the process were officially in use anywhere in the world by the mid-2020s.

Developments in animal cloning also continued to make headlines. For example, in 2021, it was reported that scientists had cloned a black-footed ferret, marking the first successful cloning of an endangered species native to North America. This development brought fresh attention to the concept of using cloning to save species from extinction. However, while some conservationists embraced the potential of cloning, others argued it was a misguided effort that might even prove detrimental by reducing public pressure to protect threatened species in the first place.

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