Transgenic Goats

Original paragraph

The animals look and act just like regular goats: Workers milk them like they would at any dairy, and the goats raid their handlers’ pockets for stuff to chew on—a risk you face around any kid, doe, or billy goat. But scientists have added an extra protein or two to their already nutrient-rich milk.

One of those proteins is from the golden orb-weaver spider. Its silk, tougher than Kevlar, is a hundred times stronger than human ligaments. The potential for a light, incredibly resilient fiber is immense: The future might hold anything from spider knee replacements to spider parachutes. But aside from being viscerally disgusting, a spider farm just won’t work. Golden orb weavers are cannibalistic. In 2000, Nexia Biotechnology figured out a solution to that problem that reads like science fiction—it bred goats that can produce the silk instead.

To make the goats, scientists ferreted out the chunk of the golden orb weaver’s genetic code that’s responsible for directing the production of the single protein that makes up its dragline silk, a kind of safety line that connects the spider to its web. Next they tucked that gene into the DNA of goat embryos, alongside the natural milk production genes, to take advantage of the ready-made machinery. The embryos were then implanted into female goats, which gave birth to kids with a little something extra. Now, keeping the line going is easy—just breed a spider-goat with a normal one; half of the babies will carry the spider gene.

The only way to find out if they have the gene is by genetic testing. Lewis has several sets of fraternal twins where only one is part spider. He often asks visitors to guess which makes silk. “Nobody’s better than fifty-fifty guessing which is which,” he said.

Like any other goats, the transgenic ones mature around 18 months. That’s when they start lactating, and the spider silk proteins are mixed in with the milk—which Lewis and his crew extract from the goats’ udders with good old-fashioned milking. “All they want you to do is scratch their head,” Lewis said. “And to milk them, you just turn ’em loose, and they hop up to get milked.”

While getting the silk out is trickier than pouring milk into a bottle, it’s not fundamentally more complicated than making cheese. First the fat is skimmed off, and then the silk proteins are processed out, like separating curds from whey.

Key ideas:

• Scientists added protein from the golden orb-weaver spider into goats' milk
• Scientists found out which of the spider's genetic code is responsible for the production of the single protein that makes up its dragline silk
• They put that gene into the DNA of goat embryos next to the natural milk production genes
• The embryos were implanted into female goats
• The only way to find out if a goat has a gene or not is by genetic testing
• The goats mature after 18 months and then they start lactating
• To get silk out of the milk, first the fat is skimmed off and then the silk proteins are processed out

Source 
Ferguson, Cat. "Mixing Spider DNA and Goat Embryos Produces Milk With a Side of Silk." TakePart. N.p., n.d. Web. 09 Oct. 2014. <http://www.takepart.com/article/2014/04/10/gmo-goats>.
O'Brien, Miles, and Marsha Walton. "Research Areas." Nsf.gov. N.p., 03 May 2010. Web. 05 Oct. 2014. <http://www.nsf.gov/news/special_reports/science_nation/spidersilk.jsp>. 

Paraphrasing

The goats may look like any other but they are not. They are transgenic and have spider DNA in them. Scientists have added protein from the golden orb-weaver spider into the goats' milk in order to make it easier to harvest spider silk. First, the scientists found out which of the spider's genetic code is responsible for the production of the single protein that makes up its dragline silk. Next, they put that gene into the DNA of goat embryos next to the natural milk production genes. Those embryos were then implanted into female goats.

The only way to find out whether or not a goat has the spider gene is through genetic testing. Otherwise, they look just the same. Like normal goats, transgenic ones mature after around 18 months which is also when they start lactating. The spider silk proteins are in the goats' milk so to get them out you just have to milk the goats. However, getting the silk out of the milk is a bit harder. First, the fat is skimmed off and then the spider silk proteins are processed out. The video below from the National Science Foundation explains the things above further.

Video 1: All about transgenic goats

https://www.youtube.com/watch?v=ktgACq4zcAU