Emerson wrote that every age has its geniuses, its masterminds who propel humanity in a new direction, for good or evil—though he also said you need circumstances to bring them out. I believe that the time is now. The circumstances are here. The masterminds are in place. The Prometheuses are bringing in the fire, the Florentines are carving Davids, Faustus is talking to the devil, and the Los Alamos boys are building the bomb.
*See pages 145–46.
THE LANGUAGE OF BIOTECH: A Genetic Primer
Science has given us the means to create utopia and dystopia, incinerate and mutate ourselves, build elevators into space, and tinker with the Lego blocks of life. Yet most people blanche when they see terms such as deoxyribonucleic acid—better known as DNA. Stare at your left hand and, if you could see them, you would glimpse billions of deoxyribonucleic acid molecules tucked just inside the cells that make up your hand. The eyes you are using to stare at your pinky contain deoxyribonucleic acid. Your eyes were made according to instructions stored in you in those nucleotides, and they continue to see thanks to eyeball maintenance programs stowed in your DNA.
Try saying deoxyribonucleic acid. It’s not too hard, even if it sounds sciency. Die-ox-ee-ribe-o-nuke-lay-eek acid. DNA is a three-dimensional information-storage molecule—a collection of atoms joined together by chemical bonds—drawn by chemists as a two-dimensional figure on a page that looks like this:
DNA is composed of three materials: first, a microscopic hunk of sugar called a deoxyribose that is joined to a second component, a phosphate, that links the deoxyribose sugars. This sugar-phosphate “ladder” is the superstructure of DNA, its outer backbone supporting the third ingredient, the nucleic acids, also known as bases. These bases are much like the zeros and ones in binary computer code, except that instead of two elements to the code, DNA contains four bases: adenine (A), cytosine (C), guanine (G), and thymine (T). And instead of encoding programs on a computer, the sequence of these bases provides instructions to create and maintain a living organism.
Are your eyes already glazing? Well, think of this as learning to drink wine, which most people don’t like at first but keep trying until it becomes quite a nice sensation. Scientific concepts will not be quite so sweet, or dry, for most nonscientists. Nor will they give you a pleasant buzz. But having at least a rudimentary knowledge of the language and concepts of modern biology could save your life, or your children’s. It could prevent you or others from becoming unduly frightened of new discoveries that are safe or it could make you knowledgeable enough to be frightened of science that is not. If you can use a recipe to bake mustard-lemon halibut, or comprehend the difference between a concerto and a symphony, you can get this stuff. Absorb these ideas as you might the basics of how to write a haiku poem or a rock lyric, or read box scores in the sports section.
You don’t need to know how to say the chemical name for DNA to read this book, but it’s a little like reading a Dickens novel without really learning the names of Oliver Twist, Nicholas Nickleby, and David Copperfield. Granted, mitochondria, enzyme, and polymorphism lack the ring of Twist and Copperfield. They seem to have been decided on by scientists whose imagination did not include concocting snappy names, a misfortune that has hardly helped the cause of enlivening the scientific debate. Scientists, along with lawyers and engineers, have created over the centuries a complicated language that makes it easy for members of their science-speak caste to talk to one another, but sounds like mumbo jumbo to everyone else.
The story begins with a cell—the basic unit of life, the universe where most of the action takes place in the science part of this story. Nearly all life-forms are comprised of cells, either just one or, in the case of humans, about 100 trillion. Many cells contain a central glob called a nucleus filled with chromosomes, twenty-three pairs in humans, and various numbers in other organisms. In most of the living creatures you see (such as ourselves, mice, goats, fish, plants, starfish), these chromosomes contain two complete sets of the genome, one each from the organism’s parents—except sperm and egg cells, which contain only one complete set, and red blood cells, which have no nucleus. (There a few exceptions to this, but they are not important to understanding the concept.) The chromosomes are made out of DNA, which in a human consists of around 3 billion base pairs from each parent, for a total of 6 billion. The DNA is arranged in pairs like the rungs on a ladder, the rungs twisted elegantly into the famous double helix, discovered by Watson and Crick in 1953. If each base pair were the size of a letter on the page of this book, the strand would run from my office in San Francisco to my hometown of Kansas City, Missouri. Writing it all down in a book would take 500,000 pages.
These pairs are arranged in linear sequences of up to several thousand bases called genes—some thirty thousand of them in a human, and a few hundred of them in the simplest single-celled bacterium. (The exact number of human genes is still debated; there also are millions of base pairs that apparently do nothing, so-called junk DNA, though recent findings suggest that more may be going on amid this “junk” than has been previously realized.) The arrangement of the base pairs into sequences of As, Ts, Cs, and Gs is the basic code of life. Remarkably, DNA figured out eons ago how to replicate itself and to be read by the cell to perform functions. (Little is known about how primordial DNA molecules on the ancient Earth figured out how to copy themselves; efforts to piece together a mechanistic picture of how this happened have been ongoing since the 1950s). This is because each nucleotide is designed by evolution to pair with another specific nucleotide. As like to pair with Ts, and Gs with Cs. When DNA replicates it splits in half, with the assistance of certain proteins, with each strand of the double-helix ladder separating like a zipper unzipping. The exposed bases then have the ability to pair with complementary nucleotides. Processes in the cell then help seek out loose nucleotides floating around and chemically incorporate them into the growing DNA chain—As pair with Ts, Gs with Cs, and so forth, voilà, a new set of complete chromosomes.
DNA’s second mission is to carry the code used to create proteins, which are encoded by genes. Proteins are sequences of amino acids; they look something like a linear pearl necklace bunched up into a ball, with each pearl being a different amino acid (there are twenty different types of amino acids generally used in proteins). Even though humans are thought to have only 30,000 genes, our cells make many times that number of different proteins. Proteins are the key structural components of life and also serve as the machines that accelerate chemical reactions (if a protein accelerates a chemical reaction, it is called an enzyme). Proteins turn genes on and off, proteins recognize and eliminate invading infectious organisms, proteins unzip and help copy DNA. In short, life as we know it is largely handled by these elegantly designed protein nano-machines designed over the millennia by evolution.
Proteins wad up into specific three-dimensional shapes that interact with other three-dimensional shapes, including other proteins, the blobs often attracted to each other by chemical and electrical bonds that cause reactions that regulate everything from memory storage in a brain cell to tears in our eyes when we are sad. Each amino acid is coded by a three-base sequence. For instance, the amino acid alanine—abbreviated A—is coded by GCG, and the amino acid histidine—an H—is coded by CAC. So let’s say the gene sequence of my crooked toe starts with GCG, which makes an A, and then CAC, which makes an H. Then repeat GCGCAC six times. The resulting protein would have an amino acid sequence like this: AHAHAHAHAHAH, and on and on, depending on the sequence of the DNA.
Proteins are not made directly from the master code recorded on your DNA. Rather, they are manufactured with the help of an intermediary molecule called RNA that carries nucleotide instructions to direct the assembly of each protein molecule (a single RNA molecule can be used to direct the synthesis of multiple copies of the same