Recombinant DNA techniques have been used for genetic modification, such as introducing a gene into an organism that will alter or create specific functions. For example: adding a heat resistance gene to agricultural crops. Recombinant DNA is also used to create therapeutic products such as vaccines, proteins and hormones.
According to IS Johnson in an article in Science, the first FDA approved commercial health care product derived from recombinant DNA was biosynthetic "human" insulin. Insulin is a relatively simple protein to copy so it was an ideal candidate.
First, the desired DNA molecule is isolated by cutting the DNA around the gene of interest using restriction enzymes. The gene is then inserted into a vector, or a piece of DNA capable of propagating itself, creating a recombinant DNA strand. Vectors are usually bacterial plasmids or viral phages. The vector is then taken up into the specially prepared DNA of a host cell.
Bacteria as a host
The most common host used to create recombinant DNA is E. coli bacteria. The E. coli cells take up the vector containing the desired gene, and insert it into its own DNA. Replication occurs as normal, creating multiple new strands of DNA containing the new gene.
The host cell will start expressing proteins created from the recombinant DNA that can be isolated and purified. For example, the insulin gene can be inserted into bacteria, causing it to create the insulin protein, which is used as a therapeutic product.
Recombinant DNA technology is the means by which a DNA molecule is artificially engineered in vitro, or in a controlled environment outside the cell, by combining DNA segments from at least two sources. The newly constructed DNA molecule contains specific genes or characteristics that can be beneficial in human health research.