The term “clonal” refers to the group of organisms which are genetically related but not necessarily reproductively or behaviorally identical. For example, two individuals from different species may have some genetic similarities such as the same mother, father and offspring, but they will not be considered clones because their reproductive systems are not identical. Cloning refers to the ability of one individual to produce gametes (eggs) from another individual.
A clone is genetically similar to its parent, but it does not possess all the characteristics of that parent. Clonogenicity is the capacity of human cells to divide and then give rise to two identical daughter cells. The ability to divide into more than two daughter cells is known as multipotency.
Clonogenicity – normal human cells can not easily be cloned. Most dividing cells are considered “clonogenic” which means they can undergo more than one cycle of division. For example, fibroblasts are clonogenic.
They are easily trapped in the cell cycle and can become cancerous when exposed to certain types of chemicals. That’s why they are considered “normal” human cells. This does not mean that you can make a whole body from them, or that they are responsible for the growth of tumors.
How do they do it?
The process of producing a cloned animal involves two distinct stages. The first involves taking the nucleus from an unfertilized egg and injecting it into a “host” mother. At this point, the egg begins to behave as if it has been fertilized. That is, it begins to divide and multiply until it forms a blastocyst: a tiny ball of perhaps 100 cells that looks like a yolk. At this point, the ball of cells is removed and placed in the cavity of a “breeding” mother. The cytoplasm of the unfertilized egg in the blastocyst contains all the nutrients and organelles necessary for a new animal to develop. As the cells of the blastocyst divide and multiply they also lose their dependence on the cytoplasmic nutrients and begin to behave as new individuals.
The process can be repeated over and over again. By changing the host mother (the one who receives the injection of egg cytoplasm) and by changing the breeding mother (who receives the blastocyst), you can create a whole litter of cloned offspring. All the offspring will be exact copies of each other and of the host mother.
The process was first successfully accomplished in the 1960s with a species of sheep. The technique has also been used with a few species of cattle. One of the reasons that cloning has never been attempted with humans is that the process is tremendously difficult and inefficient.
Although many types of animals can easily be cloned, few mammals are able to reproduce this way. The few that can include goats, sheep, cats, and pigs. After years of research, mammals such as dogs and monkeys have been cloned, but each attempt is difficult and costly. One of the difficulties with human cloning is the problem of bringing a cloned embryo to term. For many years, no one was able to develop an animal from a clone to term. Most died during the early stages of their growth. By the late 1990s, however, several rhesus monkeys were brought to term and survived.
What are some of the risks?
The moment a mother’s egg and a father’s seed unite, a new life begins. The process of human cloning takes that life and makes an exact copy without the natural process of creation. Many people have expressed concern with the morality behind such an act. Those who are in favor of human cloning believe that it could be a valuable tool in medicine. For example, scientists could use human embryos to create new skin for burn victims or new organs for transplant patients. The technology could also be used in agricultural applications. Some people, however, believe that human life should not be created for the sake of scientific advancement. They argue that the process is immoral and could lead to the creation of “soulless” human beings.
In addition to the moral and ethical concerns, there are many risks involved with human cloning. For example, because the process is so inefficient, hundreds of eggs may be needed to create just one viable clone. This creates the possibility that many of these eggs will be from fertilized eggs, creating hundreds of human embryos.
These embryos would then have to be destroyed in the process of taking the eggs. Other risks involve the health of the individual receiving the new organs or skin. As with any organ transplant, there is always the possibility that the body will reject the new tissue. Another concern is that human clones would have to be created through the use of cancer-causing agents, such as radiation or certain chemicals. The long-term effects of these agents, as well as those that may be involved in creating the human embryos necessary for the process, are still unknown.
What are some of the possible benefits of human cloning?
The main area of concern with human cloning is that it is unethical. However, some people believe that if it is done under strict guidelines, there may be benefits to human cloning. Perhaps one of the greatest benefits of human cloning is the potential for medical uses. Many scientists are interested in using human embryos to create new organs for transplant patients and skin for burn victims. In addition, some individuals have proposed the possibility of using human embryos to propagate cells, which could be used to treat Parkinson’s disease and other degenerative nerve disorders. Another potential use for human cloning is the creation of “designer babies.” Scientists believe they may be able to take an embryo and design it so that the child will have specific traits or abilities. For example, a child could be designed to be a perfect athlete or have the best possible immune system.
What is Dolly?
Dolly is the first cloned mammal. She was created at the Roslin Institute in Scotland by Ian Wilmut and his associates. In 1997, Wilmut and his team successfully cloned a sheep by taking the nucleus from a cell in an adult ewe’s udder and placing it in an egg that had its own nucleus removed. The egg was then tricked into thinking it has been fertilized. The egg began to divide and eventually became a blastocyst, which was implanted into a second ewe. Almost instantly the clone began to develop. Dolly was born on July 5, 1996 and was a perfect genetic duplicate of the “donor ewe.” Within hours of her birth Dolly became an international celebrity.
What are some of the objections to Dolly and why are they considered to be valid?
Some scientists have objected to the creation of Dolly on moral grounds. They believe that human cloning should not be allowed under any circumstances because it is unethical. They believe that cloning results in cloned individuals being denied their right to “life, liberty, and the pursuit of happiness” because they are deny the right to be an unique individual. They do not believe it is morally correct to create human beings and then destroy them.
Other scientists oppose Dolly because of the process used create her. They believe that creating human embryos for the purpose of experimentation is morally reprehensible. One of the main concerns is that not all of the embryos can be implanted in surrogate mothers.
This means that some of the cloned human embryos have to be destroyed. These critics believe that the creation of human embryos is wrong and using these embryos for any purpose, even experimentation, is immoral.
Still other scientists have raised concerns about safety. They believe that creating human embryos and then destroying them for experimentation purposes is dangerous and could potentially create life threatening health risks for any individual who may be cloned from these embryos.
What is the current legal status of Dolly?
The current legal status of Dolly’s technology is unclear. Dolly herself was not the result of any sort of government regulated research. Dolly was a product of private research and as such, there are no laws prohibiting her existence. However, many people believe that laws or guidelines should be in place to govern experiments that lead to the creation of human embryos, whether they are eventually implanted into mothers or not.
Many people have pointed out that if Dolly had been the result of publicly funded research, it probably would be illegal for her to exist. The reason is because many governments have laws in place that ban human cloning. However, these laws generally refer to the cloning of entire human beings.
They do not specifically ban the creation of human embryos for experimental purposes.
What is the current state of cloning technology?
Current cloning technology is sufficient to clone simpler organisms like single-celled amoebas. However, when it comes to cloning mammals, the technology presents more challenges. To date, only five mammal species have been cloned. Four of these (mice, rats, goats, and sheep) were created by the same method used to create Dolly. These animals are referred to as “clones” but in reality, they are really the result of genetic engineering. The difference is that instead of impregnating an adult animal, the nucleus containing the animal’s genetic material is implanted into a egg whose original genetic material has been removed. The egg then acts as a “blank slate” that allows the copied genetic material to take hold and develop according to the copied instructions.
The fifth mammal species to be cloned (cats) was created using a different technology that is still under development. Scientists have successfully used this technology to create a cat embryo but not a full grown cat. This new cloning method is called “somatic cell nuclear transfer” or somatic cell cloning.
The technology involves removing the nucleus of an unfertilized egg and replacing it with the nucleus of a skin cell from the animal that is to be cloned. The egg is then fertilized with the donor animal’s spouse. The egg grows into a cloned embryo and, if all goes well, a cloned baby.
What is the current status of government regulation?
Governments have generally taken a cautious approach to human cloning. Many governments have outright banned human cloning for any purpose. Other governments allow cloning for purposes of scientific research. Still other governments have no laws at all regarding human cloning.
The United States government has announced that it will not fund any research into human cloning. However, private institutions are free to pursue such research if they choose. The National Academy of Sciences has called for a temporary ban on all human cloning.
The ban was originally supposed to be in place until a panel could determine if human cloning is ethically sound and safe. However, the ban remains in place due to political pressure. As a result of the ban, private companies have picked up human cloning research where universities have dropped it.
Cloning is difficult and expensive. However, some believe that these reasons are insufficient to ban human cloning. Instead, they argue that human lives are at stake.
These people believe that the risks of human cloning do not justify the potential benefits. They also argue that advances in fertility treatments have reduced the need for human cloning.
Others believe that the risks of human cloning can be reduced and that cloning can offer very important benefits to society. They argue that since the process is already being used on animals, it would be foolish to ban it from use on humans. They also argue that human cloning would allow parents to create offspring that are biologically related to them.
Who is right? What do you think? Should human cloning be allowed or not?
Consider all of the issues involved and then select a position.
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Thank you, and happy cloning!
Sources & references used in this article:
- Long-term renewal of hair follicles from clonogenic multipotent stem cells (S Claudinot, M Nicolas, H Oshima… – Proceedings of the …, 2005 – National Acad Sciences)
- Clonogenic neoblasts are pluripotent adult stem cells that underlie planarian regeneration (DE Wagner, IE Wang, PW Reddien – Science, 2011 – science.sciencemag.org)
- Isolation of a highly clonogenic and multipotential subfraction of adult stem cells from bone marrow stroma (JR Smith, R Pochampally, A Perry, SC Hsu… – Stem …, 2004 – Wiley Online Library)
- Clonogenic multipotent stem cells in human adipose tissue differentiate into functional smooth muscle cells (LV Rodríguez, Z Alfonso, R Zhang… – Proceedings of the …, 2006 – National Acad Sciences)
- Slowly cycling (label‐retaining) epidermal cells behave like clonogenic stem cells in vitro (RJ Morris, CS Potten – Cell proliferation, 1994 – Wiley Online Library)
- Stem cells in the dog heart are self-renewing, clonogenic, and multipotent and regenerate infarcted myocardium, improving cardiac function (A Linke, P Müller, D Nurzynska… – Proceedings of the …, 2005 – National Acad Sciences)
- Clonogenic multiple myeloma progenitors, stem cell properties, and drug resistance (W Matsui, Q Wang, JP Barber, S Brennan, BD Smith… – Cancer research, 2008 – AACR)