13. What is the difference between therapeutic cloning and reproductive cloning?
Reproductive cloning is the process by which an embryo is created by nuclear transfer and implanted into a surrogate mother in the hope of bringing it to term. Therapeutic cloning is the process by which an embryo is created through nuclear transfer in order to obtain stem cells from it for therapeutic purposes.

Reproductive cloning means creating a new individual from a single cell by replacing the nucleus in an egg cell with the nucleus (containing the genetic material) from another cell of the body. The cloned egg cell grows and develops into an embryo. The embryo is implanted inside a surrogate mother's womb to mature and produce a viable fetus. After birth the clone would, in theory, be the genetic copy of the adult whose nucleus was used for cloning. Reproductive cloning performed in animals is burdened by many technical and biological problems. Only about 1 percent of all the eggs that receive donor DNA can develop into normal surviving clones. In addition, the clones that survive often present many health problems.

Therapeutic cloning uses cloning technology to develop stem cells for research, and ultimately for therapy. The nucleus of the egg cell is replaced with the nucleus of another cell from the body and the egg cell is allowed to grow for about 4-5 days and develop to the blastocyst stage. The inner cell mass of the blastocyst is then removed and used for the creation of an embryonic stem cell line that has the genetic makeup of the donated nucleus. The goal of therapeutic cloning is to produce human stem cells, and subsequent tissues and organs, which can be used to replace damaged tissue. It is an application of the cloning technology which does not result in the production of genetically identical fetuses. One of the major problems facing the widespread use of this stem cell therapy is the fact that the transplanted cells, or tissues, are likely to be rejected by the patient's immune system. Therapeutic cloning would allow the production of cells and tissues matching each individual patient because the donated nucleus would come from the patient. Thus, the cells would genetically match the patient and would not elicit rejection when they are transplanted into the patient.

There continue to be great differences in the way countries around the world regulate human cloning and related technologies. For instance, it appears to be well accepted that a distinction must be made between the application of cloning techniques to the replication of a person, and the application of cloning techniques to the creation of tissues and cell lines with the aim of developing therapies. The use of cloning techniques for reproductive purposes has brought international condemnation and there appears to be a consensus against reproductive cloning.

14. Why is stem cell research confused with cloning?
Stem cell research is often confused with cloning because both areas involve the use of embryonic cells. The public and the media often equate "cloning" with the manipulation of embryonic cells to produce an organism, and stem cell research was first brought to the spot light when human stem cells were isolated from human "embryonic tissues". Both fields got even more confused when the term therapeutic cloning was introduced as a means to produce embryonic stem cells. But stem cell research does not always involve embryonic stem cells.

While reproductive cloning (the production of a whole new individual from one original cell by cloning technology) and therapeutic cloning (the use of cloning for the isolation of stem cells) both use techniques involving embryos, stem cell research involves the use of several different types of cells besides embryonic stem cells, such as adult stem cells from humans or animals, or stem cells from fetuses, umbilical cord or amniotic fluid.

Thus, a clear line should be drawn between cloning for the production of a cell or organism with the same nuclear genome as another cell or organism and stem cell research, which is based on the isolation of adult and embryonic stem cells in order to find cures for many degenerative diseases.

15. What is somatic cell nuclear transfer?
Somatic cell nuclear transfer, also called SCNT, is a technique in which the nucleus of a somatic cell (any cell of the body except sperm cells and egg cells) is injected, or transplanted, into an egg, that has had its nucleus removed. If the new egg is then implanted into the womb of an animal, an individual will be born that is a clone. The clone has the identical genetic material as the somatic cell that was transplanted because the nucleus that carries the genetic material.

This procedure is very inefficient and was first developed for agricultural purposes. However, in human medicine, this technique can be used to isolate embryonic stem cells from eggs that undergo nuclear transplantation. When the somatic cell is supplied from the cells of a person, the stem cells isolated from the developing eggs can be used to make a tissue that will not be rejected by that person, because they have the same genetic material. In this way, 'customized' embryonic stem cells could be made for everyone who needed them.

16. How are stem cells grown in the laboratory?
Stem cells are generally grown in culture dishes in incubators at body temperature (37ºC) under high humidity. Because there are many different types of stem cells, the components of the culture solutions for each type of stem cell, are different. The challenge for scientists is to grow enough stem cells in an undifferentiated state, that is without having them differentiate into more specialized cell types, and also to learn how to make the cells differentiate into specialized cells, when that becomes necessary.

Human embryonic stem cells can be grown as small colonies on layers of skin cells in the presence of serum from the blood. The skin cells are known as "feeder cells" and together with the serum, provide unknown factors that nourish and support the embryonic stem cells in their undifferentiated state. When the colonies of embryonic stem cells grow too big for their culture dishes, they are divided into smaller colonies, or single cells, and transferred into new culture dishes. The cells then continue to grow. This transfer process, known as "passaging", can theoretically be repeated indefinitely.

Hematopoietic stem cells can be derived from either bone marrow, placenta or umbilical cord blood. It is currently very difficult to grow hematopoietic stem cells in culture, as they tend to differentiate into more advanced cell types very quickly. Therefore, hematopoietic stem cells are not generally grown in culture.

Human mesenchymal stem cells, or bone marrow stromal stem cells, are isolated from the bone marrow and grown in culture media supplemented with serum from the blood. Mesenchymal stem cells attach to the plastic on the bottom of the culture dishes and can grow for several weeks before they will differentiate into other cell types.

Human neural stem cells can grow from fetal or adult brain tissue in culture media. They grow in suspension, meaning they do not attach to a culture dish, and they do not need serum from blood. In culture, one single neural stem cell can divide to make more cells that together form a round hollow structure known as a neurosphere. Neurospheres continue to grow in culture and when they get too big, are disaggregated into single cells.

These single cells are a mixed population of neural stem cells and more mature cells. The neural stem cells can be selected from this mixed population and once again grown into round and hollow neurospheres. This process of disaggregation and neurosphere formation can be repeated several times. Eventually all the neural stem cells differentiate into more mature cells.