Cloning has brought a revolution in the world of medical science. This process of creating embryos to produce stem cells holds great promise for treating life-threatening diseases like diabetes, Parkinson’s, and many types of cancers.

Cloning is a clear-cut process, yet delicate. Here, we have a step-by-step process showing the cloning of egg cells to produce embryonic stem cells in the lab.

Step 1

The scientists first isolate the nucleus from an egg cell, which is unfertilized. The scientists use a microscope to examine the fine surgical extraction, as the egg cell is just 100 micrometers in size (tenth part of a millimeter). The egg cell is held with the help of a suction pipette and its nucleus is removed with a glass needle.

Step 2

The scientists gently push the needle through the hard shell around the egg cell. This shell is known as zona pellucida and it safeguards the egg while it moves down the fallopian tube and enters the uterus. The shell also controls fertilization to see that only one sperm penetrates the egg.

Step 3

After removing the nucleus of the egg cell, it is discarded. What is needed is the cell without the nucleus, which is now known as “enucleated” egg. It still harbors RNA molecules, protein, and other important factors, which are going to help in creating the embryonic stem cells.

Step 4

After that, the scientists remove the nucleus from a donor cell and inject into the enucleated egg cell. After several years, this donor cell can be a skin cell taken from an ill patient whom doctors wish to treat by making use of the patient’s own cells that are grown in culture. Once again, the scientists ease the needle tip through the zona pellucida and penetrate deep into the cell without the nucleus. Here, they inject the donor nucleus.

Step 5

After completion of the nuclear transfer process, scientists “stimulate” the unfertilized egg cell with the help of electrical or chemical treatment, which activates cellular division. The very first division produces two cells; the second division produces four cells, and the multiplication goes on. This is the formation of an embryo.

Step 6

Eighty-four hours after the commencement of division, the multiplying cells generate a mass of cells known as blastocyst, which is similar to the size of egg cell. Blastocyst has three components - internal cell mass, trophoblast cell layer, and internal cell cavity. The first component is that part which forms the embryo after the fertilized egg is implanted in the womb. Hence, it also possesses embryonic stem cells. The second component forms a section of the placenta.

Step 7

When the blastocyst is placed onto a dish that promotes tissue culture, various types of cells get a favorable condition to grow the following: embryonic stem cell colonies from the internal cell mass, cells that are membrane-like, and placental cells. Out of these, the stem cells are the only one to have the capacity of continuing growth under these conditions. In due course of time, they are going to multiply to such an extent that scientists can expand their culture to several dishes. This process is called “passaging.”

Step 8

The human as well as the mouse embryonic stem cells produce dense colonies having hundreds of individual cells, which look amazingly similar and are difficult to distinguish even by a trained eye. There are “feeder cells” too, which are actually connective-tissue cells of mouse. They supply essential hormones and nutrients to the growing embryonic stem cell cultures. Scientists are finding methods to abolish the dependency on “feeder cells” and maintain embryonic stem cell cultures without them.  There are around 50-80 individual cells in a small human embryonic cell colony. Each of them is about 10 micrometers (or 0.000010 meters) in size.

The cloning is done. Scientists use these clones to study the growth of specific tissues and cells. These specialized tissues and cells developed from embryonic stem cells through nuclear transfer hold a tremendous potential to treat big diseases, hence, this process is also referred to as “therapeutic cloning.”

You have heard a lot about the controversial cloning. Cloning is not just creating an identical. Know more and find the connection between stem cells and Dolly!