Recombinant DNA (rDNA) is DNA which is composed of one or more genes from two different organisms (usually different species); foreign DNA is transferred into the genome of the host organism, and is then expressed in the host. The host organism is then called a transgenic organism, or a genetically modified organism (GMO). The introduced gene instructs the transgenic organism to produce the desired trait through gene expression. The trait may be passed onto future generations.

Recombinant DNA is produced by first isolating a DNA sequence, then inserting it into the DNA of a different organism. Two key DNA tools used in the production of rDNA are:

• Restriction enzymes (enzymes which separate DNA at specific recognition sites, forming DNA fragments)

• DNA ligase (a 'gluing' enzyme which catalyses the formation of phosphodiester bonds)

Process

1. 2 pieces of DNA are cut using the same restriction enzyme, producing fragments with sticky (overhanging ends) [Note: it is crucial to state that they are cut using the same restriction enzymes, otherwise they would not anneal to each other]

2. Fragments with complementary sticky ends can be joined via complementary base-pairing rules; this anneals or hybridises the DNA

3. Fragments of DNA are joined together by DNA ligase, producing a new molecule of DNA

4. Joined fragments will usually either form a linear or circular molecule (such as plasmid DNA), and are reinserted into the desired host organism to be expressed

Recombinant DNA technology is widely used in a number of science disciplines, including:

• Agriculture

• Environmental conservation

• Medicine

Many careers that require the use of technology also include fields of study in;

• Agricultural careers

• Environmental careers

• Medical careers

• Veterinary science

• Forensic science