Genetic engineering

Genetic engineering of animals

Two main types of genetic engineering are cloning and transgenesis . Cloning has been in the news through Dolly the lamb in Scotland, and more recently a lamb called Matilda and a calf called Suzi in Australia. Transgenesis is in the news because researchers in Adelaide are trying to create transgenic pigs for use in transplants.

Cloning

  1. Cloning involves taking donor eggs, usually from ovaries collected from slaughterhouses. The nucleus, which contains the genetic material, is removed from these eggs.

  2. The next stage involves collecting cells from the animal to be cloned, either a foetus surgically removed from the womb, or an adult animal.

  3. The nucleus is taken from these cells and injected into the donor eggs. Each nucleus contains the same genetic material, so all the eggs are identical.

  4. The eggs begin to divide and form an embryo, which is cultured in the laboratory for about 7 days.

  5. The embryos are implanted into surrogate mothers. All the offspring will be genetically identical.

Cloning doesn't have a very good success rate. Many embryos die soon after they are implanted. Some foetuses die much later in the pregnancy when they are already well developed. Cloned foetuses are often over-sized, leading to more birth difficulties. Many also die soon after they are born. Dolly the sheep was the only one of 29 implanted embryos to survive.

Transgenesis

  1. Female animals are treated with hormones to produce many eggs, which are fertilised and then removed.

  2. One piece of genetic material (one gene rather than a whole nucleus) is injected into each embryo.

  3. The genetically altered embryos are implanted into surrogate mothers.

Transgenic animals have the same problems as cloned animals - poor survival of embryos, birth difficulties, reduced survival. They have another problem as well. Injecting genetic material into embryos is a very imprecise process and very few embryos take up the gene as intended. Most of the animals born, often over 90%, are not transgenic. They of no use to the experimenters, so they are killed.

Purposes of genetic engineering

  1. To produce livestock with desired characteristics, such as fine wool, milk with more protein, meat with less fat, and so on.

  2. To produce biopharmaceuticals, such as blood clotting factor for haemophiliacs.

  3. To produce animals that have similar diseases to humans to test possible cures.

  4. To produce animals for transplant organs.

Problems with these purposes

Remembering that in the process of genetic manipulation animals are suffering and dying, some of the purposes it is to be used for seem very trivial. For example, one suggestion is to manipulate dairy cows so that their milk will be easier to make into cheese.

Important biopharmaceuticals are already being produced in genetically engineered bacteria and cell cultures. For example, human insulin for diabetics is produced by bacteria, and blood products are produced in cell cultures.

Animals engineered to have human-like diseases suffer as a result of this ill-health. However, the diseases are often a very poor model of the human condition. For example, there are 3 mouse models of cystic fibrosis, but none of them develop the lung congestion that plagues human sufferers.

There are other ways to get more organs for transplants than to breed animals for the purpose. Many more human organs become available when there is a system of presumed consent, where everyone is assumed to be an organ donor unless they officially register an objection.

There are ways to avoid the increasing exploitation of animals involved in genetic engineering.

For more detailed information on this issue, including references, go to More on genetic engineering .