What is a clone?

To understand cloning, we must first understand a few things about cells.  All living things, from the simplest to the most complex, are made up of cells. Cells are specialized to perform a variety of functions. There are muscle cells, skin cells, nerve cells, and so on.

Cells group together to form tissue and tissues group together to make organs like the heart, liver, and kidneys. An organism grows and develops through a process called cell division. One cell divides into two, then each of those two divides again, and so on until eventually, in the case of human beings, trillions of cells have been produced to make up a complete living person. All cells in multicellular organisms contain a nucleus, which acts as the command center of the cell. The nucleus contains all of the organism’s genetic material, including the DNA, or deoxyribonucleic acid, which determines whether a rose will be red or yellow, whether a person will have curly hair or straight.

The word “clone” can refer to a group of cells that share the same genetic material or to two or more complete organisms that are genetically identical. That means that the clone is an exact copy of one of its parents (whereas we are made up of the combined features of both our parents). Cloning does occur naturally simple organisms like bacteria, for example, reproduce asexually, which means new organisms come from only one parent and share that parent’s genetic material. When humans and other animals produce identical twins, those twins are clones of each other (though not of either parent).

But the kind of cloning we hear about in school or on the news is engineered by scientists. Scientists have been conducting experiments for years in an attempt to create a complex organism that is a clone of another organism. While they had some success over the years cloning frogs and salamanders, nothing captured the world’s attention like the breakthrough scientists made at the Roslin Institute in Scotland in 1996.

After 276 failed attempts, a group of scientists led by Ian Wilmut successfully cloned a sheep (named Dolly), the first mammal ever to be cloned. The process used to create the cloned sheep, called somatic cell nuclear transfer, began with an egg cell from one sheep. The scientists destroyed that egg cell’s nucleus and then injected the nucleus from the cell of another sheep into the egg cell. With a little encouragement from electronic stimulation, the donated nucleus fused with the egg cell, and the new cell began to divide. The cluster of cells was then implanted into the uterus of the sheep that had provided the egg cell, and five months later Dolly was born an exact replica not of the sheep that had carried her in the womb but of the sheep that had supplied the nucleus.

While cloning mammals is very controversial, some scientists argue that it could have many benefits. Under the right circumstances, cloning could be used to increase the population of animals that are listed as endangered species. Cloning also has advantages to livestock farmers, who could use the technology to breed only high quality animals that produce the most milk or the finest wool.