There are few issues in our society that raise as many emotional and ethical concerns as cloning and stem cells. Scientists, journalists, special interest groups, and even patients themselves regularly bombard us with their particular views on this issue. How are we to know what to think regarding these issues? How do we separate fact from fiction? Since cloning and stem cells are two separate (but related) issues, we will deal with them individually.
What Is Cloning?
Cloning is a process by which a genetically identical copy of a gene, an entire cell, or even an organism is produced. We will confine the discussion primarily to the cloning of an entire organism. This is a topic about which there is much misinformation. It is also a subject that raises some very serious ethical issues.
Cloning as usually understood is an artificial process, meaning it is carried out in a laboratory setting. It can and does, however, occur regularly in nature. There are organisms (e.g., bacteria, protists, and some plants) that typically reproduce by asexual reproduction. Here a genetically identical copy of the parent is produced by the splitting of a single cell (the parent cell).
Identical twins are also clones. In fact, identical twins have been called "natural clones" since splitting of a fertilized egg causes this, producing two copies of the same organism.
It is the issue of artificial cloning that has captured the interest of so many in our society. This process has garnered much attention in recent years, especially with the birth of the famous sheep, Dolly. Actually, many different types of animals have been cloned including tadpoles, mice, cats, sheep, cattle, a horse, and others.
How Is a Clone Made?
The simplest method for making a clone is to remove the nucleus (containing the organism's DNA) from a somatic (body) cell in the animal you want to clone. You then take an egg cell (from the same type of animal) that has had its own nucleus removed, and you place the donor nucleus into the egg cell. This is called somatic cell nuclear transfer (SCNT). This egg is grown briefly in a test tube and then implanted into the womb of an adult animal. If there are no complications, at the end of gestation an animal is born with an identical genetic makeup of the donor animal. As one might imagine, the process is technically quite difficult. Let's use the aforementioned Dolly as an example. It took 277 eggs that ultimately produced 29 embryos and only one living sheep to create Dolly. This is consistent with the failure rate for other animals. As can be seen, many embryos are wasted in these attempts.