American - Writer | -
The grand saga of how humans spread across the globe will need some amendments and annotations - rendezvous here, elopements there, and the commingling of genes most everywhere.
Sam Kean
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Geneticists in the early 1900s believed that nature - in an effort to avoid wasting precious space within chromosomes - would pack as many genes into each chromosome as possible.
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Before the Human Genome Project, most scientists assumed, based on our complex brains and behaviors, that humans must have around 100,000 genes; some estimates went as high as 150,000.
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Most mutations involve typos: Something bumps a cell's elbow as it's copying DNA, and the wrong letter appears in a triplet - CAG becomes CCG.
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All human beings are, in fact, born with dozens of mutations their parents lacked, and a few of those mutations could well be lethal if we didn't have two copies of every gene, so one can pick up the slack if the other malfunctions.
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Whereas recessive traits require two bad copies of a gene to become noticeable, a dominant trait expresses itself no matter what the other copy does. A benign example of dominance: If you inherit one gene for sticky wet earwax and one gene for dry earwax, the sticky earwax gene wins out every time.
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Most people who have encountered mercury have done so after breaking a mercury thermometer. And many of us who saw the liquid balls of mercury scatter across a floor or countertop considered the element the most beautiful on the periodic table.
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On a submicro scale, pure diamond is billions of billions of carbon atoms bonded to one another. If you shrunk yourself down and stood inside the diamond, you'd see nothing but carbon in a perfect pattern in every direction.
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Atoms of Element 118 fill an outer shell with electrons, creating a special type of element called a noble gas. Noble gases are natural turning points on the table, ending one row and pointing to the next.
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Atoms consist of a positive nucleus and negative electrons flying around outside it. Electrons closest to the nucleus feel a strong negative-on-positive tug, and the bigger atoms get, the bigger the tug. In really big atoms, electrons whip around at speeds close to the speed of light.
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Polonium is, frankly, pretty useless, and no country in the world except Russia bothered to refine it by the late 2000s.
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Despite the disreputable company it keeps, bismuth is harmless. In fact, it's medicinal: Doctors prescribe it to soothe ulcers, and it's the 'bis' in hot-pink Pepto-Bismol. Overall, it seems like the most out-of-place element on the periodic table, a gentleman among scoundrels.
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