Transgenics is the production of animals whose genetic make-up has been changed in some way. A gene
from humans or another species is inserted into the animal's DNA. Another method is to knock out or
disrupt one of the animals' own genes, scientists call these animals 'knockouts'. Knockouts are usually used
in biomedical research where they mimic a human disease. Transgenic animals are able to pass on their
new genes to their offspring thereby producing future generations of modified animals.
Transgenics is one of the fastest growing areas of research. Latest Home Office figures show that 511,607
experiments on transgenic animals were carried out in 1999. The first transgenic animal was created nearly
20 years ago, and was a giant mouse that had the gene for human growth hormone incorporated into its
genome (genetic make-up). Since then transgenic rats, rabbits, sheep, cows, pigs, goats, chickens and even
fish have all been 'designed'.
The first step is the identification and isolation of the relevant gene that will eventually be responsible for the
production of protein or feature that you wish to manifest in the animal. The piece of DNA containing that
gene is then inserted into a fertilised egg or embryo. This can be achieved in a number of ways:
microinjection of the DNA into the pronucleus, retroviral transfer and the use of embryonic stem cells. The
most successful of these is the microinjection technique.
Microinjection: Several hundred copies of the gene are injected directly into the pronucleus of the host egg.
Since the integration of the gene into the host is random there is no way of controlling what happens. The
mistakes made here can result in animals being born with terrible abnormalities. Microinjection is made
much more difficult in larger mammals than in mice because their...