For example, scientists might add a gene for resistance to a particular disease to a plant of economic importance, such as wheat. When a new gene has been added, the cell is said to be transformed. The transformed cell can be grown into a wheat plant that also has the gene. The plant grown from the transformed cell is described as a transgenic wheat plant, as are any offspring carrying the gene. Enzymes are used in both techniques.
Restriction enzymes make breaks in the DNA, at specific sites.
Another enzyme present in cells, DNA ligase, joins fragments of DNA together and can join DNA fragments from different organisms as easily as DNA fragments from the same organism. If DNA fragments from two different sources are mixed in a test tube with DNA ligase, sometimes the re-joining will put together the DNA from the two sources. DNA molecules composed of sequences derived from different sources are described as recombinant. How scientists add a gene to an organism Identifying a gene. To identify the gene for a particular characteristic from the huge amount of DNA within an organism is a daunting task.