How Cloning Works

Cloning Types

Cloning is a generic term than can mean one of three things. It can refer to molecular cloning, reproductive cloning to generate an animal that grows to adulthood, or embryonic cloning in which the goal is to provide researchers with certain cell types used only for therapeutic treatments.

Molecular Cloning

Molecular cloning happens all of the time in biotech research. In this process, genetic DNA, in the form of a DNA fragment called a gene, is removed from one organism and inserted into another one. The process begins by isolating the desired DNA from an organism and then cutting it out of the genome. The ends of this DNA fragment contain molecules that make them want to stick to the DNA where it will be inserted. The gene is inserted into a plasmid, or piece of bacterial DNA found outside of the organism's chromosomal DNA. The plasmid DNA has unique characteristics that allow it to be cut and the desired gene DNA inserted. Once this is accomplished, the plasmid is then inserted into bacteria where many copies can be made over several generations. Lab technicians select these bacteria for certain traits, looking specifically for the ones that contain the gene they were originally interested in. This type of cloning is done on a daily basis in most research centers around the world.

Reproductive Cloning

Reproductive cloning is what many people think of when they hear the term "clone." This is the process by which a genetic twin is made of an already developed organism. This process begins with two things--genetic material, in the form of nuclear DNA taken from an organism, and an egg from which all genetic material has been removed. The next step is to insert the genetic material into the host egg. This is called fertilization and when done properly, the fertilized egg starts dividing and becomes an embryo. The embryo can then be implanted into a host mother for development and birth. Dolly the sheep was the first adult mammal to be cloned in this manner. According to the cloning fact sheet at the Human Genome Project, this type of cloning has a low success rate and it took 276 tries before there was success with Dolly.

Therapeutic Cloning

Therapeutic cloning is done in a similar fashion as reproductive cloning, except the final goal is to halt the development of the egg at Day 5 and harvest the stem cells that were created in the process of cell division. This is stem cell research. Such practices are regulated by federal government statute in the United States. In March 2009, President Obama changed the way stem cell research is regulated. This new "order will allow researchers to use federal funds to work with new cell lines, (however) a legislative ban on the use of federal dollars to create new stem cell lines remains in place." Therapeutic cloning is the most controversial of the three types because of the ethics involved. Some feel that it is wrong to create life just to destroy it, but others believe this technology will lead to faster discovery and cures for many serious and untreatable diseases--and ultimately lead to the growth of organs and tissues than can be transplanted.

References

• Human Genome Project (See References 1)
• Obama Lifts Restrictions on Stem Cell Research (See References 2)

Resources

• Read this Article in Spanish
• Learn More About Cloning
• Molecular Cloning Steps