DNA: the most unusual molecule on earth

DNA_methylation

DNA:  the most unusual molecule on earth.

DNA Franklin Crick Watson

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In the cell is a nucleus and in the nucleus are forty-six chromosomes and in the chromosomes are long strands of deoxyribonucleic acid. How long are the strands of DNA? About two meters. So, in every one of the ten thousand trillion cells in your body are roughly six feet of deoxyribonucleic acid.

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Do you feel strung out or tied down? You have twenty million kilometers of DNA inside you.

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Each strand of deoxyribonucleic acid has 3.2 billion letters of coding which will enable more combinations than I can write here, but let’s just say the number would be a one followed by more than three billion zeros. You think you are unique?  Well, you are. And yet you are 99.9 % the same as everyone else and we are all related, but that is another story for another time.

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Although, our human species has evolved with a two-strand DNA found in each of the twenty-three pairs of chromosomes in every cell of the body, this was not our original blueprint.  There are extra strands sometimes called “junk” DNA.  These disconnected strands are really an essential part of our original genetic blueprint, and, who knows, they could be the most important of all, used for something that we have no idea exists.

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DNA, the very source of life, is not alive itself. As geneticist Richard Lewontin puts it, deoxyribonucleic acid is “among the most nonreactive, chemically inert molecules in the living world.”

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Because DNA is so inert, it can last a long time as the saga of Monica’s blue dress reminds us.   License plate photos:  Max Clarke

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In 1869, Johann Friedrich Miescher at the University of Tübingen in southern Germany, upstream from Mannheim, where Big Brother played not so long ago, was looking at the pus in surgical bandages through a microscope. He noticed that there was a large amount of a material he called nuclein because it was in the nuclei of cells.

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He thought this material nuclein must be important because there was so much of it. Later, in a letter to his uncle, Miescher suggested that these unusual molecules could have to do with heredity.  This was such an amazing insight that everyone ignored it for eighty-five years.

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They all assumed that DNA was too simple to transmit heredity since it had only four parts, or nucleotides.

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How could anything with just four basic elements carry the whole story of life?

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When we were young, our father taught us the morse code. It has just two basic components, a dot and a dash. You can write War and Peace with the morse code, and you can write all the other books in the world with it too.

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It became clear over time that DNA was an important part of making proteins, but proteins were made outside of the nucleus so how was DNA, inside the nucleus,  communicating the protein making instructions?

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Finally investigators realized that the medium of communication between DNA and the proteins outside of the cell was ribonucleic acid (RNA).

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So now everyone grasped that DNA was indeed paramount in the transmission of heredity, but what was its structure?  How did it do that transmitting?

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Who was going to be the first to describe how deoxyribonucleic acid actually worked?

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Improbably enough, the first people to crack the DNA code were four scientists in England, who a. were new to biochemistry, b. didn’t work together as a team, and c. were rather childish, competitive individuals who often didn’t speak to each other.

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James Watson (right) could have been Seymour Glass. He was a child prodigy, a member of The Quiz Kids, a highly popular radio program, he entered the University of Chicago at age fifteen, earned a PhD by twenty-two, and he had a full head of academically willful hair.

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“It was my hope,” wrote Watson, “that the gene might be solved without my learning any chemistry.”

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Maurice Wilkins was convinced from the outset that the DNA structure was helical.  Wilkins, the boffin (British slang for a nerdy science type) of the group, had worked on the atom bomb during World War II.

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Francis Crick wrote the story of his life and called it What Mad Pursuit. He wrote a seven page letter to his son here explaining what he and Watson had discovered in 1953, the double helix as the molecular structure of DNA. This letter recently sold at auction for the most that has ever been paid for a private letter.

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For this breaking of the genetic code, Crick, Watson and Maurice Wilkins were awarded the Nobel Prize for medicine in 1962 and Rosalind Franklin was not since the Nobel is awarded only to the living. It must be said that Rosalind Franklin, who played a large part in the project, was treated very shabbily in this whole affair.

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Men of science do not always behave nobly. They are human, after all, and as apt to act ignobly as the rest of us.  Rosalind Franklin’s images of X-ray diffraction confirming the helical structure of DNA were shown to Watson without her approval or knowledge.

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Rosalind Franklin came to King’s College, London, in early 1951 and that summer she took the famous ‘Photo 51′ and made important studies of the DNA molecule. Francis Crick and James Watson of Cambridge University “obtained” Photo 51, and some of Franklin’s data and with their own deductions built the first correct model of the DNA molecule.

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Franklin’s habit of intensely looking people in the eye while being concise, impatient and directly confrontational to the point of abrasiveness unnerved many of her colleagues, but this is no excuse for some of the chicanery that went on with her private papers.

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Rosalind Franklin was female and Jewish, and Crick and Watson were male, immature and not a little pigheaded.

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Rosalind Franklin died in 1958 at the age of 37 of ovarian cancer.  One key ingredient to winning the Nobel is longevity. There are cases of Nobel laureates who won the prize fifty years after the work they had done. They had to be living, though. There are no posthumous Nobel awards.

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In 1921, Albert Einstein was awarded the Nobel prize for work he had done in 1905. This was for his explanation of the photoelectric effect, because relativity was considered still somewhat controversial in 1921.

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Francis Crick, the son of a Northampton shoemaker, worked until 1976 in the Cambridge Laboratory for Molecular Biology before accepting a post as a neurobiologist at the Salk Institute in La Jolla, California.

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James Watson returned to America in 1956 and taught at Harvard for the next twenty years. He was director of the National Center for Human Genome Research from 1989 to 1992.

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Watson’s book The Double Helix (1967), compulsory reading for future biology students, is an entertaining tell all that almost ruined his friendship with Crick, who tried in vain to prevent it from being published.

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The Double Helix has more in common with Truman Capote’s In Cold Blood than with, say, The History of the English Speaking Peoples. It’s not a scholarly history. It’s more like a memoir crossed with narrative non-fiction. As in the New Journalism, where the account of an event is inextricably mixed with the writer’s personal circumstances and biases, The Double Helix doesn’t represent the objective truth about the search for the structure and function of DNA, but Watson’s own take on that research.

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I wish I were DNA Helicase, so I could unzip your genes.

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What does DNA stand for?   National Dyslexics Association.

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I wish I was adenine, then I could get paired with U.

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Did you just mutate for a stop codon? Because you’re talking nonsense!

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What did the shepherd say when he read that scientists were implanting human DNA in sheep?       Bloody hell, I’ve been doing that for years.

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Doctor:  Bad news, your DNA is backwards.       Patient:     And…?

RomneyCare DNA cartoon

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Ménage à trois!  Ligand seeks two receptors into binding and mutual phosphorylation. Let’s get together and transduce some signals.

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One strand of DNA to another strand of DNA:  Do these genes make me look fat?

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See you next week?

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Kathi McDonald                                Sam Andrew

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