Facts About Cloning
Dolly the Sheep in a field at The Roslin Institute.
Credit: Photo courtesy of The Roslin Institute, The University of Edinburgh

Cloning is the process of taking genetic information from one living thing and creating identical copies of it. The copied material is called a clone. Geneticists have cloned cells, tissues, genes and entire animals. 

Although this process may seem futuristic, nature has been doing it for millions of years. For example, identical twins have almost identical DNA, and asexual reproduction in some plants and organisms can produce genetically identical offspring. And scientists make genetic doubles in the lab, though the process is a little different.

There are three different types of cloning, according to the National Human Genome Research Institute (NHGRI):

  • Gene cloning, also called DNA cloning, creates copies of genes, or segments of DNA.
  • Reproductive cloning makes duplicates of whole animals.
  • Therapeutic cloning creates embryonic stem cells, which are used to create tissues that can repair or replace damaged tissues. 

In gene cloning, a genetic engineer extracts DNA from an organism and then uses enzymes to break the bonds between nucleotides (the basic building blocks of DNA) and snip the strand into gene-size pieces, according to the University of Nebraska

Plasmids, small bits of DNA in bacterial cells, are combined with the genes. Then, they are transferred into living bacteria. These bacteria are allowed to grow into colonies to be studied. When a colony of bacteria containing a gene of interest is located, the bacteria can be propagated to make millions of copies of the plasmids. Then, the plasmids can be extracted for gene modification and transformation. 

Gene modification, or gene design, is when a genetic engineer cuts the gene apart and replaces regions of it with new material. Transformation is the step in which the new genetic material is transferred to a new organism, which changed it genetically. The organism, such as a plant, is grown, and the seeds they produce have inherited the new genetic properties.

Reproductive cloning

In reproductive cloning, a genetic engineer removes a mature somatic cell (any cell except for reproductive cells) from an organism and transfers the DNA into an egg cell that has had its own DNA removed, according to the NHGRI. Then, the egg is jump-started chemically to start the reproductive process. Finally, the egg is implanted into the uterus of a female of the same species as the egg.

The mother gives birth to an animal that has the same genetic makeup as the animals that donated the somatic cell. This was the process that produced Dolly the sheep.

Therapeutic cloning

Therapeutic cloning works in a similar way to reproductive cloning. A cell is taken from an animal's skin and is inserted into the outer membrane of a donor egg cell. Then, the egg is chemically induced so that it creates embryonic stem cells. These stem cells can be harvested and used in experiments aimed at understanding diseases and developing new treatments. [Infographic: How Stem Cell Cloning Works]

The first study of cloning took place in 1885, when German scientist Hans Adolf Eduard Driesch began researching reproduction. In 1902, he was able to create a set of twin salamanders by dividing an embryo into two separate, viable embryos, according to the Genetic Science Learning Center. Since then, there have been many breakthroughs in cloning.

In 1958, British biologist John Gurdon cloned frogs from the skin cells of adult frogs. On July 5, 1996, a female sheep gave birth to the now-famous Dolly, a Finn Dorset lamb — the first mammal to be cloned from the cells of an adult animal — at the Roslin Institute in Scotland. 

"The birth of Dolly and the new understanding of the opportunity to change the functioning of cells made researchers consider other possible ways of modifying cells," Ian Wilmut, the scientist who led the team that created Dolly, told Live Science. 

Since Dolly, many more animal clones have been born, and the process is becoming more mainstream. Research has also been conducted on human-cell cloning. In 2013, scientists at Oregon Health and Science University took donor DNA from an 8-month-old with a rare genetic disease and successfully cloned human embryonic stem cells for the first time. Unfortunately, the researchers didn't remove the cells to save the child. The project was to prove that mature donor cells could be used to produce new ones. This research has evolved into using stem cells for many different applications, including hair regrowth, treatments for burns and more.

Several companies are currently providing services that use cloning technology. For example, South Korea-based Sooam Biotech clones pets for around $100,000. And a Texas-based company, Viagen Pets, clones cats for $25,000 and dogs for $50,000. 

Even plants are being cloned. One company is cloning maple trees to provide lumber for guitar-makers, with the aim of duplicating a quality in the wood, called figuring, that gives a guitar a sort of shimmering appearance.

There are many other applications for cloning. The movie "Jurassic Park" stirred the public's imagination and asked the question, "Can we use cloning to bring back extinct species through cloning?" For this process to be successful, scientists would need living DNA from the extinct animal and a living animal egg that is closely related to the extinct creature. 

On July 30, 2003, a group of scientists led by Jose Folch at the Center of Food Technology and Research of Aragon, in northern Spain, brought back an extinct wild goat called a bucardo, or Pyrenean ibex. The cloned animal lived for only 10 minutes, according to National Geographic, but the scientists proved that an extinct animal could be brought back. Researchers at Harvard are currently working to clone woolly mammoths, and they say they should be able to do so by 2019. 

While cloning a human is currently illegal in most parts of the world, cloning stem cells from humans is a very promising field of research. Stem cells can be reprogrammed to become any type of cell needed to repair or replace damaged tissue or cells in the body. Stem cell research has the potential to help people who have spinal injuries and other conditions.

Another area of research, the cloning of hair follicles, began more than a decade ago. It's just one potential application of human-cell cloning: treating hair loss. "We have learned recently that human hair cells lose their potential to multiply when expanded in cell cultures in a petri dish," said Ken L. Williams Jr., a surgeon and founder of Orange County Hair Restoration and author of "Hair Transplant 360: Follicular Unit Extraction" (Jp Medical Ltd., 2015). "Global gene expression analysis of the human hair follicle, however, has revealed that a special 3D spheroid culture may be able to allow cloning of hair cells in the future years. By manipulating the environment that the human hair cells grow, induction or expansion of hair cells occurs."

Another example of practical human-cell cloning is to use stem cells to help burns heal. A biotech company, RenovaCare, has created what it calls the CellMist System. In this process, stem cells are applied to the burned area on the patient, and that application triggers new skin-cell growth. Though it's still experimental, this process could help burn victims heal faster and experience less scarring. 

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