Recombinant DNA

Recombinant DNA is a DNA molecule assembled in the laboratory by combining genetic material from two or more sources that would not normally be found together. A common example is a bacterial plasmid, a small circle of DNA, into which a human gene has been inserted. The pieces may come from different species or be made by chemical synthesis, so the result is sometimes called chimeric DNA.

To make it, scientists cut DNA with restriction enzymes, which recognize specific short sequences and often leave single-stranded overhangs, called sticky ends, that pair with matching ends on other fragments. The enzyme DNA ligase then seals the pieces together. The recombinant molecule is usually put into bacteria or yeast, which copy it as they divide and can read its genes to make the encoded protein, known as a recombinant protein.

The technology emerged in the early 1970s, when researchers first moved DNA from one bacterium into another, and it underpins molecular cloning and genetic engineering. Its first approved consumer product, in 1982, was human insulin made by bacteria; growth hormone, clotting factors and several vaccines are now made in similar ways.