Transgenic mice are a unique tool for understanding how interactions between individual genes and the environment affect human health. Most transgenic mice are made by injecting a transgene into fertilized eggs. The eggs are removed from the oviduct, and an ultrafine glass pipet is used to inject a solution containing a few hundred copies of the transgene DNA into the nucleus. The injected eggs are put into the oviduct of a surrogate mother, and pups are born 19 days later. Some of these mice will have the transgene into their genome and their descendants for generations to follow will also carry the transgene.
Transgenic mice are powerful tools for solving human gene puzzles.
The methods to make transgenic mice were developed in the early 1980s by John Gordon and by Ralph Brinster and Richard Palmiter and their co-workers. Although all of the cells in the body contain an identical set of genes, some genes are active in only one or a few tissues. It is this diversity of gene expression that produces the distinct cell types and tissues of the body, making a muscle cell different from a liver cell. The two main parts of a gene are the regulatory region and the protein-coding region. When the right combination of proteins binds to specific sites along the DNA in the regulatory region, the gene is switched on, and the protein-coding region becomes active.