The Age of Genomes PDF – Tales from the Front Lines of Genetic Medicine
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In each of our beginnings was our personal genome, created when we were less than a single cell and with us every moment since. Our genome has helped define what we have, and haven’t, done with our lives. This precise DNA barcode, because of its enormous length and complexity, distinguishes each of us not only from the other eight billion people alive today on the planet, but also from each and every other of the twenty-something billion human beings who have ever lived since the dawn of humanity two hundred thousand years ago. Indeed, distinguishing each of us from every other living organism, whether flora, fauna, virus, or archebacteria for the past four billion years. What could be more personal than that?
Even when it’s hot outside, we don’t walk around naked. People are typically squeamish about public nudity because they don’t want every detail of their reproductive anatomy put out on display for all the world to see, and prudence prevails. But this particular modesty only runs skin deep. What is more profoundly revealing than being naked in a crowd? Today, certainly one answer to this question, mechanistically more than skin deep and down to the core of our very being, is the sequence of our very own genome.
However, even if we generally don’t like getting naked in public, we will when there’s a good reason to do so. One place people typically do this is their doctor’s office. We bare ourselves despite that slightly awkward feeling we have waiting there, exposed on the usually cold examining table, to allow our doctor to see our most intimate parts because we know this can help keep us healthy and so it’s worth the discomfort. Conversely, hiding some of these parts and refusing a doctor’s examination could cause a lot of pain, or worse, in the end. This is essentially the same reason why people decide to share this intimacy in silico by giving their personal genome information to their doctor. Such information provides a tool to help navigate us to a healthy one hundred and fifty years or so of life. This is not astrology: this is bona fide biological science. But what does it all add up to?
About twenty years ago, having all a person’s DNA fully analyzed (commonly referred to as whole genome sequencing) cost about the same as an aircraft carrier. Now, it costs less than a Vespa and doesn’t require a prescription. How incredible and astonishing is this era that we live in? Whole genome sequencing has become an established technology to identify previously undiagnosed diseases in patients and their families, to find missed drug targets in cancers, or even to embark on a journey of self-discovery about our roots and how we each became the person we are today. There are currently serious academic discussions promoting Generation XX/XY—sequencing the genomes of all newborn American babies from a drop of heel blood—beginning in the next decade or so. There are also thought leaders table thumping for ending the century-old practice of doctors diagnosing disease primarily by signs and symptoms and instead retooling medicine into a practice based on genetic and biochemical mechanisms of ailments. These are promising and profound changes.
It takes about twenty thousand or so genes to make a human being. Somewhat humbling, this is near the same number of genes as the mustard weed plant, and less than double the number of genes to make tiny fruit flies that we hardly notice. Yet, this is our personal instruction manual, and perhaps eventually the key to bringing us back from beyond the grave centuries after we have passed.
When geneticists and genetic counselors look at a person’s genome, we look for specific changes, called mutations, that we think should be there. One can think of a strand of DNA as being something like a sentence, albeit laid out on the familiar twisting double helix. Individual “letters” in the words of that sentence comprise pairs of only four nitrogen-rich compounds: adenine, guanine, cytosine, and thymine, respectively represented by the letters A, G, C, and T. Mutations can be a misspelling by a single such letter (referred to as a “base”) of DNA, such as “porcxpine” instead of “porcupine,” or reshuffled letters (“pucropine”), and additions or losses can stretch for millions of bases. This code ultimately defines each of our personal destinies.
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