To an aspiring animal owner, Petco presents an embarrassment of riches. Here, in the basement of a New York City store — where the air carries the sharp tang of hay and the dull musk of rodent dander — is a squeaking, squealing, almost endless menagerie of potential pets. There are the spindly-legged lizards scuttling across their sand-filled tanks; the preening cockatiels, a spray of golden feathers atop their heads; and, of course, the cages of pink-nosed white mice training for a wheel-running marathon. There are chinchillas and canaries, dwarf hamsters, tree frogs, bearded dragons, red-footed tortoises, red-bellied parrots, and African fat-tailed geckoes.
But one of these animals is not like the others. The discerning pet owner in search of something new and different merely has to head to the aquatic display and keep walking past the speckled koi and fantail bettas, the crowds of goldfish and minnows. And there they are, cruising around a small tank hidden beneath the stairs: inch-long candy-colored fish in shades of cherry, lime, and tangerine. Technically, they are zebrafish (Daniorerio), which are native to South Asian lakes and rivers and usually covered with black and white stripes. But these swimmers are adulterated with a smidgen of something extra. The Starfire Red fish contain a dash of DNA from the sea anemone; the Electric Green, Sunburst Orange, Cosmic Blue, and Galactic Purple strains all have a nip of sea coral. These borrowed genes turn the zebrafish fluorescent, so under black or blue lights they glow. These are GloFish, America's first genetically engineered pets.
Though we've meddled with many species through selective breeding, these fish mark the beginning of a new era, one in which we have the power to directly manipulate the biological codes of our animal friends. Our new molecular techniques change the game. They allow us to modify species quickly, rather than over the course of generations; doctor a single gene instead of worrying about the whole animal; and create beings that would never exist in nature, mixing and matching DNA from multiple species into one great living mash-up. We have long desired creature companions tailored to our exact specifications. Science is finally making that precision possible.
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Though our ancestors knew enough about heredity to breed better working animals, our ability to tinker with genes directly is relatively new. After all, it wasn't until 1944 that scientists identified DNA as the molecule of biological inheritance, and 1953 that Watson and Crick deduced DNA's double helical structure. Further experiments through the '50s and '60s revealed how genes work inside a cell. For all its seeming mystery, DNA has a straightforward job: It tells the body to make proteins. A strand of DNA is composed of individual units called nucleotides, strung together like pearls on a necklace. There are four distinct types of nucleotides, each containing a different chemical base. Technically, the bases are called adenine, thymine, guanine, and cytosine, but they usually go by their initials: A, T, C, and G. What we call a "gene" is merely a long sequence of these As, Ts, Cs, and Gs. The order in which these letters appear tells the body which proteins to make — and where and when to make them. Change some of the letters and you can alter protein manufacturing and the ultimate characteristics of an organism.
Once we cracked the genetic code, it wasn't long before we figured out how to manipulate it. In the 1970s, scientists set out to determine whether it was possible to transfer genes from one species into another. They isolated small stretches of DNA from Staphylococcus — the bacteria that cause staph infections — and the African clawed frog. Then they inserted these bits of biological code into E. coli. The staph and frog genes were fully functional in their new cellular homes, making E. coli the world's first genetically engineered organism. Mice were up next, and in the early 1980s, two labs reported that they'd created rodents carrying genes from viruses and rabbits. Animals such as these mice, which contain a foreign piece of DNA in their genomes, are known as transgenic, and the added genetic sequence is called a transgene.
Encouraged and inspired by these successes, scientists started moving DNA all around the animal kingdom, swapping genes among all sorts of swimming, slithering, and scurrying creatures. Researchers embarking on these experiments had multiple goals in mind. For starters, they simply wanted to see what was possible. How far could they push these genetic exchanges? What could they do with these bits and pieces of DNA?
There was also immense potential for basic research; taking a gene from one animal and putting it into another could help researchers learn more about how it worked and the role it played in development or disease. Finally, there were promising commercial applications, an opportunity to engineer animals whose bodies produced highly desired proteins or creatures with economically valuable traits. (In one early project, for instance, researchers set out to make a leaner, faster-growing pig.)
Along the way, geneticists developed some neat tricks, including figuring out how to engineer animals that glowed. They knew that some species, such as the crystal jellyfish, had evolved this talent on their own. One moment, the jellyfish is an unremarkable transparent blob; the next it's a neon-green orb floating in a dark sea. The secret to this light show is a compound called green fluorescent protein (GFP), naturally produced by the jellyfish, which takes in blue light and reemits it in a kiwi-colored hue. Hit the jelly with a beam of blue light, and a ring of green dots will suddenly appear around its bell-shaped body, not unlike a string of Christmas lights wrapped around a tree.
When scientists discovered GFP, they began to wonder what would happen if they took this jellyfish gene and popped it into another animal. Researchers isolated and copied the jellyfish's GFP gene in the lab in the 1990s, and then the real fun began. When they transferred the gene into roundworms, rats, and rabbits, these animals also started producing the protein, and if you blasted them with blue light, they also gave off a green glow. For that reason alone, GFP became a valuable tool for geneticists. Researchers testing a new method of genetic modification can practice with GFP, splicing the gene into an organism's genome. If the animal lights up, it's obvious that the procedure worked. GFP can also be coupled with another gene, allowing scientists to determine whether the gene in question is active. (A green glow means the paired gene is on.)
Scientists discovered other potential uses, too. Zhiyuan Gong, a biologist at the National University of Singapore, wanted to use GFP to turn fish into living pollution detectors, swimming canaries in underwater coal mines. He hoped to create transgenic fish that would blink on and off in the presence of toxins, turning bright green when they were swimming in contaminated water. The first step was simply to make fish that glowed. His team accomplished that feat in 1999 with the help of a common genetic procedure called microinjection. Using a tiny needle, he squirted the GFP gene directly into some zebrafish embryos. In some of the embryos, this foreign bit of biological code managed to sneak into the genome, and the fish gave off that telltale green light. In subsequent research, the biologists also made strains in red — thanks to a fluorescent protein from a relative of the sea anemone — and yellow, and experimented with adding these proteins in combination. One of their published papers showcases a neon rainbow of fish that would do Crayola proud.
To Richard Crockett, the co-founder of the company that sells GloFish, such creatures have more than mere scientific value — they have an obvious aesthetic beauty. Crockett vividly remembers learning about GFP in a biology class. He was captivated by an image of brain cells glowing green and red, thanks to the addition of the genes for GFP and a red fluorescent protein. Crockett was a premed student, but he was also an entrepreneur. In 1998, at the age of twenty-one, he and a childhood friend, Alan Blake, launched an online education company. By 2000, the company had become a casualty of the dot-com crash. As the two young men cast about for new business ideas, Crockett thought back to the luminescent brain cells and put a proposal to Blake: What if they brought the beauty of fluorescence genes to the public by selling glowing, genetically modified fish?
At first, Blake, who had no background in science, thought his friend was joking. But when he discovered that Gong and other scientists were already fiddling with fish, he realized that the idea wasn't far-fetched at all. Blake and Crockett wouldn't even need to invent a new organism — they'd just need to take the shimmering schools of transgenic fish out of the lab and into our home tanks.
The pair founded Yorktown Technologies to do just that, and Blake took the lead during the firm's early years, setting up shop in Austin, Texas. He licensed the rights to produce the fish from Gong's lab and hired two commercial fish farms to breed the pets. (Since the animals pass their fluorescence genes on to their offspring, all Blake needed to create an entire line of neon pets was a few starter adults.) He and his partner dubbed them GloFish, though the animals aren't technically glow-in-the-dark — at least, not the same way that a set of solar system stickers in a child's bedroom might be. Those stickers, and most other glow-in-the-dark toys, work through a scientific property known as phosphorescence. They absorb and store light, reemitting it gradually over time, as a soft glow that's visible when you turn out all the lights. GloFish, on the other hand, are fluorescent, which means that they absorb light from the environment and beam it back out into the world immediately. The fish appear to glow in a dark room if they're under a blue or black light, but they can't store light for later — turn the artificial light off, and the fish stop shining.
Blake was optimistic about their prospects. As he explains, "The ornamental fish industry is about new and different and exciting varieties of fish." And if new, different, and exciting is what you're after, what more could you ask for than an animal engineered to glow electric red, orange, green, blue, or purple thanks to a dab of foreign DNA? Pets are products, after all, subject to the same marketplace forces as toys or clothes. Whether it's a puppy or a pair of heels, we're constantly searching for the next big thing. Consider the recent enthusiasm for "teacup pigs" — tiny swine cute enough to make you swear off pork chops forever.
Harold Herzog, a psychologist at Western Carolina University who specializes in human-animal interactions, has studied the way our taste in animals changes over time. When Herzog consulted the registry of the American Kennel Club, he found that dog breed choices fade in and out of fashion the same way that baby names do. One minute, everyone is buying Irish setters, naming their daughters Heather, and listening to "Bennie and the Jets" — welcome to 1974! — and then it's on to the next great trend. Herzog discovered that between 1946 and 2003, eight breeds — Afghan hounds, chow chows, Dalmatians, Dobermans, Great Danes, Old English sheepdogs, rottweilers, and Irish setters — went through particularly pronounced boom and bust cycles. Registrations for these canines would skyrocket, and then, as soon as they reached a certain threshold of popularity, people would begin searching for the next fur-covered fad.
Herzog identified a modern manifestation of our long-standing interest in new and unusual animals. In antiquity, explorers hunted for far-flung exotic species, which royal households often imported and displayed. Even the humble goldfish began as a luxury for the privileged classes. Native to Central and East Asia, the wild fish are usually covered in silvery gray scales. But ancient Chinese mariners had noticed the occasional yellow or orange variant wriggling in the water. Rich and powerful Chinese families collected these mutants in private ponds, and by the thirteenth century, fish keepers were breeding these dazzlers together. Goldfish domestication was born, and the once-peculiar golden fish gradually spread to the homes of less-fortunate Chinese families — and households elsewhere in Asia, Europe, and beyond.
As goldfish grew in popularity, breeders stepped up their game, creating ever more unusual varieties. Using artificial selection, they created goldfish with freakish and fantastical features, and the world's aquariums now contain the fantail, the veiltail, the butterfly tail, the lionhead, the goosehead, the golden helmet, the golden saddle, the bubble eye, the telescope eye, the seven stars, the stork's pearl, the pearlscale, the black moor, the panda moor, the celestial, and the comet goldfish, among others. This explosion of types was driven by the desire for the exotic and exquisite — urges that we can now satisfy with genetically modified pets.
Excerpted from Frankenstein's Cat: Cuddling Up to Biotech's Brave New Beasts by Emily Anthes, published in March 2013 by Scientific American / Farrar, Straus and Giroux, LLC. Copyright 2013 by Emily Anthes. All rights reserved.