Spider silks are protein based polymers secreted by a number of glands in the abdomen of spiders. A company named Nexia (Osbourne, 2002) has been successful in making spider silk which they intend to use in several products, they have done this by introducing the gene responsible for making silk in spiders into goats.
Why not just use spiders? Spiders cannot be farmed the way silk worms can because they are territorial carnivores (they wind up eating each other when in close proximity for too long ).
So this is where the goats come into play. The mammary gland is a perfect natural factory (Lazaris,2002 ) for the synthesizing and production of proteins. Given the enormous expense of making drugs artificially, transgenic goats offer a brilliant way to make dirt cheap drugs, it is estimated that $50,000 worth of proteins (Osbourne,2002 ) could be extracted from a few buckets of milk at the cost of about $12 worth of hay. Nexia raises goats that are part spider in order to produce the silk protein they need. You might picture these goats as some sort of mutant looking spider-goats, but they look and act just like normal goats with the exception being they are 1/70,000th spider (Robbins, 2002 ) .The female goats eventually produce a silk-milk mix, which according to one article looks and tastes just like normal milk, (where do you find someone willing to drink spider- goat milk?).
How do you make a spider-goat.
The first step is to collect the gene responsible for making the silk from the spider. Nexia uses 2 different types (Osbourne, 2002 ) of spiders for this ; the common garden spider (Araneus diadematus ), and tthe Golden orb weaver (Nephila clavpipes ). The spiders are ground into a fine powder and since the silk gene is present in almost all of the spiders cells (Hayashi, 2000 ) it is extracted from this powder. Next the gene is altered so that it will only be expressed inside the mammary gland of the female goats, after which the altered gene is pushed into a goat egg.