Until recently, scientists couldn't easily change the genetics of bacteria, plants or animals. Modern molecular laboratory methods allow researchers to add specific genes from one organism to the genetics of another, a process known as recombinant DNA technology or gene engineering. Scientists can use this technique to create a variety of new traits in bacteria, plants and even humans.
In recombinant DNA technology, scientists splice together segments of DNA from different sources to form a single, functional molecule called a recombinant DNA molecule. The first recombinant DNA was produced in 1972 by Stanford researcher Paul Berg who joined together fragments of DNA from two viruses with the help of restriction enzymes and ligase. The restriction enzymes act like aEURoemolecular scissorsaEUR that cut the DNA at specific sequences. The ligase joins together DNA fragments that have the same sequence of sticky ends. DNA ligase is the same enzyme used during cellular DNA replication to knit together Okazaki fragments.
Scientists can then introduce the recombinant DNA into the cells of an organism or cell culture. For multicellular organisms, this involves creating a vector that can deliver the DNA into the cells of the host. The vector can be a plasmid or viral particle. Plasmids work well in yeast and many cultured human cells, but cloning large eukaryotic genes is difficult using plasmid vectors. Viruses, however, have evolved to efficiently deliver their own DNA into host cells.
Adding new genes to the cells of an organism with the help of recombinant DNA technology has resulted in a variety of new technologies that benefit agriculture, medicine and environmental science. For example, scientists can now splice bacterial DNA into the genomes of crops to make them resistant to insects or herbicides. These crops are called genetically modified organisms or GMOs.