Cloning

Cloning is the process of making an identical DNA copy of another organism. Cloning is referred to as asexual or nonsexual means of reproduction (even growing a plant from a cutting is a type of cloning). The word “clone” comes from the Greek word referring to plant cutting.
There are two major classes of cloning, natural cloning and unnatural or artificial cloning. Natural cloning happens in all plants and animals that reproduce asexually. Hydras, sponges, worms, and some other simple marine life can use a few different methods like budding, sending out runners, or by getting cut in half. Even at times animals and humans produce “clones” that we call identical twins. Identical twins come from the same fertilized egg that unexpectedly divided at an early stage of development and become two separate zygotes but still with the same genetic make-up.
Unnatural or artificial cloning has several ways of being done. We will look at two of the ways it is done: artificial embryo twinning and somatic cell nuclear transfer (SCNT). Artificial embryo twinning uses the same approach as what naturally happens when identical twins are formed, but in a Petri dish instead of in the uterus. This is done manually, separating a very early embryo into individual cells and then allowing each cell to divide and develop on its own. All the embryos are placed into surrogate mothers, where they are carried and delivered.
Somatic cell nuclear transfer, or SCNT, uses a very different method than artificial embryo twinning, but with the same result of an exact genetic copy of an individual. To better understand how SCNT works, we will need to take it apart and examine what it does. First we will look at a somatic cell; a somatic cell is any cell of the body except for male and female gametes, sperm and egg cells. Next we’ll look at a nucleus; a nucleus is the core of the cell and contains all the genetic information of the cell.
The process of SCNT begins by isolating a somatic cell from an adult animal. Next, transfer the nucleus from the cell into an egg cell that has had its nucleus removed. After a few chemical tweaks, the egg cell (with the new nucleus) divides and behaves just like a newly formed zygote. It develops into a blastocyst, and then an embryo, which is implanted into a surrogate mother to be carried and later delivered.
Cloning is one of the most controversial issues of this century. While scientists have been able to successfully clone animals, it remains to be seen how the genetic lineage of the clones will be affected. Dolly the cloned sheep, before she died, was weaker than the original, and suffered through a series of illnesses. On the one hand, we could use the technology to bring back recently extinct species, or thicken the ranks of endangered ones, but in the other hand, all clones usually succumb to illness after being born and are not as strong as the originals.
I used material from the University of Utah, Howstuffworks.com, Extinctanimal.com, Nelson Biology, and the book titled Time Life Human Body.