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ashone26 (Chapter 26 ** )

Chapter Twenty-six — The Stuff of Life

A Short History of Nearly Everything – by Bill Bryson

Chapter 26 — The Stuff of Life

  • If you go back just 8 generations, to about the time of Abraham Lincoln, there are already over 250 people on whom your existence depends.  Continue farther, to the time of Shakespeare, and you have no fewer than 16,384 ancestors, all of whom contributed genetic material to you.  At 20 generations, the number of people who procreated on your behalf has risen to over 1 million.
  • If you are in a partnership now with someone from your own race and country, the chances are excellent that you are at some level related.  In fact, most of the people you see around you are probably relatives.
  • Compare your genes with the genes of any other human being and, on the average, they will be about 99.9 percent the same.  The tiny difference is represented by roughly one nucleotide base in every 1000.  Almost every cell in your body (99.999% of them) carries the same complement of chromosomes (red blood cells, egg cells, and sperm cells are exceptions).
  • DNA exists for one purpose – to create more DNA.  You have a lot of DNA inside you: about six feet of it squeezed into almost every cell.  Each length of DNA comprises 3.2 billion letters of coding.
  • A human adult is comprised of ten thousand trillion cells, and almost every one of those cells holds two yards of densely compacted DNA.  You have about 20 million kilometers of DNA bundled up inside of you.
  • In 1953, an edition of Nature carried a 900-word article by Watson and Crick titled “A structure for Deoxyribose Nucleic Acid”.  It was an eventful time in the world, with Edmund Hillary about to climb Mount Everest and Elizabeth II about to be crowned queen of England.  The discovery of the secret of life was mostly overlooked.
  • 97% of your DNA consists of nothing but long stretches of ‘non-coding’ DNA.  Only here and there along each strand do you find sections that actually control and organize vital functions.
  • Single genes are nothing more or less than instructions to make proteins.  However, by combining genes you create combinations of instructions that make life possible.
  • The shape of a DNA molecule is like a spiral staircase or twisted rope ladder, the famous double helix.
  • The brilliance of DNA lies in its manner of replication.  When it is time to produce a new DNA molecule, the two strands part down the middle and each half goes off to form a new partnership.  Each nucleotide along a strand pairs up with a specific partner nucleotide, and the template creates a new matching strand.
  • The balance between accuracy and errors in replication is a fine one.  Too many errors and the organism can’t function, and too few and it sacrifices adaptability.
  • Scientists can insert human DNA into certain cells of flies, and the flies accept it as if it were their own.  Over 60% of human genes are fundamentally the same as those found in fruit flies.
  • 35,000 genes functioning independently is not nearly enough to produce the kind of physical complexity that makes up humans.  Genes clearly must cooperate.
  • Proteins are the workhorses of all living systems.  As many as 100 million of them may be busy in any cell at any moment.  Protein behavior and function are based not simply on their chemistry, abut also on their shapes.  Properly assembled, each protein must be folded into an extremely specific shape to be fully functional.
  • All the intricate chemical processes that animate cells – the cooperative efforts of nucleotides, the transcription of DNA into RNA – evolved just once and stayed pretty well fixed ever since across the whole of nature.

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