； the technique perfected by linus pauling。
crystallography had been used successfully to map atoms in crystals （hence“crystallography”）； but dna molecules were a much more finicky proposition。 only franklinwas managing to get good results from the process； but to wilkins’s perennial exasperationshe refused to share her findings。
if franklin was not warmly forthing with her findings； she cannot be altogetherblamed。 female academics at king’s in the 1950s were treated with a formalized disdain thatdazzles modern sensibilities （actually any sensibilities）。 however senior or acplished；they were not allowed into the college’s senior mon room but instead had to take theirmeals in a more utilitarian chamber that even watson conceded was “dingily pokey。” on topof this she was being constantly pressed—at times actively harassed—to share her results witha trio of men whose desperation to get a peek at them was seldom matched by more engagingqualities； like respect。 “i’m afraid we always used to adopt—let’s say a patronizing attitudetoward her；” crick later recalled。 two of these men were from a peting institution and thethird was more or less openly siding with them。 it should hardly e as a surprise that shekept her results locked away。
that wilkins and franklin did not get along was a fact that watson and crick seem to haveexploited to their benefit。 although crick and watson were trespassing rather unashamedlyon wilkins’s territory； it was with them that he increasingly sided—not altogether surprisinglysince franklin herself was beginning to act in a decidedly queer way。 although her resultsshowed that dna definitely was helical in shape； she insisted to all that it was not。 towilkins’s presumed dismay and embarrassment； in the summer of 1952 she posted a mocknotice around the king’s physics department that said： “it is with great regret that we have toannounce the death； on friday 18th july 1952 of d。n。a。 helix。 。 。 。 it is hoped that dr。 m。h。f。
wilkins will speak in memory of the late helix。”
the oute of all this was that in january 1953； wilkins showed watson franklin’simages； “apparently without her knowledge or consent。” it would be an understatement to callit a significant help。 years later watson conceded that it “was the key event 。 。 。 it mobilizedus。” armed with the knowledge of the dna molecule’s basic shape and some importantelements of its dimensions； watson and crick redoubled their efforts。 everything now seemedto go their way。 at one point pauling was en route to a conference in england at which hewould in all likelihood have met with wilkins and learned enough to correct themisconceptions that had put him on the wrong line of inquiry； but this was the mccarthy eraand pauling found himself detained at idlewild airport in new york； his passport confiscated；on the grounds that he was too liberal of temperament to be allowed to travel abroad。 crickand watson also had the no less convenient good fortune that pauling’s son was working atthe cavendish and innocently kept them abreast of any news of developments and setbacks athome。
still facing the possibility of being trumped at any moment； watson and crick appliedthemselves feverishly to the problem。 it was known that dna had four chemical1in 1968； harvard university press canceled publication of the double helix after crick and wilkinsplained about its characterizations； which the science historian lisa jardine has described as 〃gratuitouslyhurtful。〃 the descriptions quoted above are after watson softened his ments。
ponents—called adenine； guanine； cytosine； and thiamine—and that these paired up inparticular ways。 by playing with pieces of cardboard cut into the shapes of molecules； watsonand crick were able to work out how the pieces fit together。 from this they made a meccano…like model—perhaps the most famous in modern science—consisting of metal plates boltedtogether in a spiral； and invited wilkins； franklin； and the rest of the world to have a look。
any informed person could see at once that they had solved the problem。 it was withoutquestion a brilliant piece of detective work； with or without the boost of franklin’s picture。
the april 25； 1953； edition of nature carried a 900…word article by watson and crick titled“a structure for deoxyribose nucleic acid。” acpanying it were separate articles bywilkins and franklin。 it was an eventful time in the world—edmund hillary was just about toclamber to the top of everest while elizabeth ii was imminently to be crowned queen ofengland—so the discovery of the secret of life was mostly overlooked。 it received a smallmention in the news chronicle and was ignored elsewhere。
rosalind franklin did not share in the nobel prize。 she died of ovarian cancer at the age ofjust thirty…seven in 1958； four years before the award was granted。 nobel prizes are notawarded posthumously。 the cancer almost certainly arose as a result of chronic overexposureto x…rays through her work and needn’t have happened。 in her much…praised 2002 biographyof franklin； brenda maddox noted that franklin rarely wore a lead apron and often steppedcarelessly in front of a beam。 oswald avery never won a nobel prize either and was alsolargely overlooked by posterity； though he did at least have the satisfaction of living just longenough to see his findings vindicated。 he died in 1955。
watson and crick’s discovery wasn’t actually confirmed until the 1980s。 as crick said inone of his books： “it took over twenty…five years for our model of dna to go from being onlyrather plausible； to being very plausible 。 。 。 and from there to being virtually certainlycorrect。”
even so； with the structure of dna understood progress in genetics was swift； and by 1968the journal science could run an article titled “that was the molecular biology that was；”
suggesting—it hardly seems possible； but it is so—that the work of genetics was nearly at anend。
in fact； of course； it was only just beginning。 even now there is a great deal about dna thatwe scarcely understand； not least why so much of it doesn’t actually seem to do anything。
ninety…seven percent of your dna consists of nothing but long stretches of meaninglessgarble—“junk；” or “non…coding dna；” as biochemists prefer to put it。 only here and therealong each strand do you find sections that control and organize vital functions。 these are thecurious and long…elusive genes。
genes are nothing more （nor less） than instructions to make proteins。 this they do with acertain dull fidelity。 in this sense； they are rather like the keys of a piano； each playing asingle note and nothing else； which is obviously a trifle monotonous。 but bine the genes；as you would bine piano keys； and you can create chords and melodies of infinite variety。
put all these genes together； and you have （to continue the metaphor） the great symphony ofexistence known as the human genome。
an alternative and more mon way to regard the genome is as a kind of instructionmanual for the body。 viewed this way； the chromosomes can be imagined as the book’schapters and the genes as individual instructions for making proteins。 the words in which the instructions are written are called codons； and the letters are known as bases。 the bases—theletters of the genetic alphabet—consist of the four nucleotides mentioned a page or two back：
adenine； thiamine； guanine； and cytosine。 despite the importance of what they do； thesesubstances are not made of anything exotic。 guanine； for instance； is the same stuff thatabounds in； and gives its name to； guano。
the shape of a dna molecule； as everyone knows； is rather like a spiral staircase ortwisted rope ladder： the famous double helix。 the uprights of this structure are made of a typeof sugar called deoxyribose； and the whole of the helix is a nucleic acid—hence the name“deoxyribonucleic acid。” the rungs （or steps） are formed by two bases joining across thespace between； and they can bine in only two ways： guanine is always paired withcytosine and thiamine always with adenine。 the order in which these letters appear as youmove up or down the ladder constitutes the dna code； logging it has been the job of thehuman genome project。
now the particular brilliance of dna lies in its manner of replication。 when it is time toproduce a new dna molecule； the two strands part down the middle； like the zipper on ajacket； and each half goes off to form a new partnership。 because each nucleotide along astrand pairs up with a specific other nucleotide； each strand serves as a template for thecreation of a new matching strand。 if you possessed just one strand of your own dna； youcould easily enough reconstruct the matching side by working out the necessary partnerships：
if the topmost rung on one strand was made of guanine； then you would know that thetopmost rung on the matching strand must be cytosine。 work your way down the ladderthrough all the nucleotide pairings； and eventually you would have the code for a newmolecule。 that is just what happens in nature； except that nature does it really quickly—inonly a matter of seconds； which is quite a feat。
most of the time our dna replicates with dutiful accuracy； but just occasionally—abo