What do you get when you cross a goat with a spider? A silk shirt, of course. This may sound like just another silly joke, but nowadays, scientists are actually able to mix and match genes from different animals to create transgenic animals.

What are Transgenic Animals?

Like all living things, animals have genes that are made up of DNA. Genes affect characteristics like length of fur, coloring and size. Because of advancements in technology, scientists are now able to adjust the DNA of animals to change these and other characteristics. Animals who have had their DNA changed are called transgenic animals.

How Does it Work?

There are three main ways to transfer genes into an animal: DNA Microinjection, Retrovirus-Mediated Gene Transfer and Embryonic Stem Cell-Mediated Gene Transfer. While the wording sounds complex, the methods are actually fairly easy to understand.

DNA Microinjection

In this method, a foreign gene is directly injected into a fertilized egg that is put into a female animal that acts as a surrogate mother for the egg.

Retrovirus-Mediated Gene Transfer

A retrovirus is a virus that attaches to an organism’s DNA and changes it to include a new characteristic. Scientists expose ordinary cells to a retrovirus when they are trying to create transgenic animals.

Embryonic Stem Cell-Mediated Gene Transfer

Stem cells are blank cells that can turn into any type of cell. Scientists modify these cells, and then add them to an embryo, which is a fertilized egg that develops and grows until it hatches or is born.

What is the Purpose?

Scientists modify the genetic makeup of animals for several reasons. Sometimes, transgenic animals are created to help with medical advancements. Others are beneficial to farmers. Transgenic animals can also be beneficial for manufacturers of certain products.


Transgenic animals have been beneficial to the medical field by providing organs for transplants. Transgenic animals produce milk with extra nutrients.


Scientists can create transgenic animals that are larger, produce more milk, and are more disease resistant than other animals.


Some transgenic animals can produce materials that are lightweight and extra strong. These materials are used in products such as tennis rackets or clothing.