Genetic modification

Genetic modification changes an organism’s genetic material by removing, changing or inserting individual genes. Genes contain instructions for making proteins. Changing the genes an organism has can therefore change the proteins it makes, alter its characteristics or enable it to produce a desired protein.

Genetic modification of bacteria

A human gene can be inserted into a bacterium. The bacterium can then use the gene’s instructions to produce the human protein. For example, bacteria can be genetically modified to produce human insulin.

Genetic modification of crop plants

Genes can be inserted into crop plants to give them useful characteristics. For example, a gene may make a crop resistant to a herbicide, so the crop can survive when that herbicide is applied. Another gene may give a crop resistance to insect pests, reducing the damage they cause.

Genes can also be inserted to improve a crop’s nutritional qualities, such as by increasing the amount of a useful nutrient it produces.

Production of human proteins using recombinant plasmids

A human gene contains instructions for making a particular protein. By inserting that gene into bacteria, the bacteria can be used to produce the human protein. A small circular piece of bacterial DNA called a plasmid carries the gene into the bacteria.

Making a recombinant plasmid

A restriction enzyme cuts the DNA containing the human gene, isolating the section needed. The cut leaves short, exposed sequences of bases called sticky ends.

The same restriction enzyme cuts a bacterial plasmid. This produces sticky ends on the plasmid that are complementary to those on the human DNA. The complementary bases pair, bringing the human DNA and plasmid together. An enzyme called DNA ligase then joins the DNA pieces, forming a recombinant plasmid: a plasmid containing DNA from another source.

Producing the human protein

The recombinant plasmid is inserted into a bacterium. As bacteria containing the plasmid multiply, the plasmid and its human gene are carried into more bacterial cells.

The bacteria can express the human gene: they use its instructions to make the human protein. As the bacteria multiply, more cells carry the gene and can produce the protein.