IF YOUR tO parents    bonded just o t be s    bonded in a preciselytimely manner, you    be s    done likes before tely, you    be here.

        Pusime and tral debts begin to add up. Go back just eigions to about time t Cimely couplings your existence depends.

        tinue furto time of Sors early excic material in a    ually and miraculously, result in you.

        At ty geions ago, ting on your beo1,048,576. Five geions before t, and ted couplings your existence depends. By ty geions ago, yourtotal number of forebears—remember, t cousins and aunts and otalrelatives, but only parents and parents of parents in a line leading iably to you—is overone billion (1,073,741,824, to be precise). If you go back sixty-feions, to time oftive efforts your eventual existencedepends o approximately 1,000,000,000,000,000,000, otal number of people who have ever lived.

        Clearly somet may i you tolearn, is t your line is not pure. You couldn’t be    a little i—actually quitea lot of i—albeit at a geically discreet remove. itors inyour background, tive from your moted ant cousin from your fat, if you are in a partnersry, t t you are at some level related. Indeed, if you look around you on abus or in a park or café or any cro of tives. s to you t    once: “Me, too!” In t literal andfual sense we are all family.

        e are also unily alike. pare yenes    99.9 pert t is inydifferences in t remaining 0.1 pert—“rougide base ihousand,”

        to quote tisicist a Nobel laureate Joon—are y. Muc years of t, t. Otical. It is tions of enomes—eacical, but not quite—t make us h as individualsand as a species.

        But ly is t, e to t, are genes?

        ell, start y-six little bundles of plexity, of y-ty-tions, every cell in yourbody—99.999 pert of t of s are red blood cells, some immune system cells, and egg and sperm cells,    carry tic package.) Citutete set of instrus necessary to make and maintain you and are made of longstrands of ttle raordinary molecule o has been called.

        Ds for just one reason—to create more DNA—and you    of it inside you:

        about six feet of it squeezed into almost every cell. Eacters of g, enougo provide 103,480,000,000possible binations, “guaraobe unique against all ceivable odds,” in tian de Duve. t’s a lot ofpossibility—a one follo ake more t to print t figure,” notes de Duve. Look at yourself in t upon t t you are been trillion cells, and talmost every one of ted DNA, and you begin toappreciate just uff you carry around o a single firand, t to stretco t once or t again and again. Altogeto onecalculation, you may y million kilometers of DNA bundled up insideyou.

        Your body, in s, loves to make DNA and    it you couldn’t live. Yet DNA is notitself alive. No molecule is, but DNA is, as it    is “among tive, c molecules in ticistRi. t is cigations and coaxed from t Neaals. It also explainsook stists so long to    anystifyingly lo t of life itself.

        As a knoity, DNA    t     tyof tübingen in Germany. ance    reize and called it nu (because itresided in t time, Miesctle more te its existence, butnu clearly remained on y-ter in a letter to y t sucs bey. traordinary insig one so far in advance of tific requirements t itattracted no attention at all.

        For most of t ury tion    terial—no a subsidiary role in matters of y. Itoo simple. It    four basipos, called ides,    four letters. e tory of life ary alp? (t you do it in muc you create plexmessages s and dasdo anyt all, as far as anyone could tell. It just sat ty on and or fulfilling someotrivial task t no o of. ty, it ,o exist in proteins in the nucleus.

        t, t:

        teemed it in some important op of t kept turning up, like t in a murder mystery, in experiments. In tudies in particular, one involving terium and anoteriop i bacteria), Drayed an importa could only beexplained if its role ral t alloed t DNA al to life,yet it    proteins side t ing their assembly.

        No one could uand ting messages to teins. ts as an interpreter bet is a notable oddity of biology t DNA and proteins don’t speak t four billion years t double act, ao mutually inpatible codes, as if one spoke Spanisher hindi.

        to unicate tor in translates information from a cell’s DNA into terms proteins uand and act upon.

        ory, ill a very long anding t, or indeed almost anyto do y.

        Clearly tation, and itude to uake it.    Man, and in 1904, just four years after timely rediscovery of Mendel’sexperiments s and still almost a decade befeh osomes.

        Co see uurn of tietury it rongly suspected t traits,but no one knew his.

        Man c of study a tiny, delicate fly formally called Drosoper, but more only kno fly (or vinegar fly, banana fly, e fly). Drosopo most of us as t frail, colorless i seems too droory spes fruit flies ainvery attractive adva almost noto tles,    from egg to productive parenten days or less, and    four c tly simple.

        out of a small lab ( bia Uy in Neiculous breeding and crossbreeding involving millions of flies (onebiograp is probably an exaggeration), eaco becaptured iny variations ininance. For six years tried to produce mutations by any means tion and X-rays, rearing t ligly in ovens, spinning trifuges—but notable mutation—a fly te eyes ratants o gee useful deformities, alloo track a trait tions. By suc tioicular ceristid individual cually proving to more or lesseveryone’s satisfa t c t of inance.

        t level of biological intricacy: tiesand t posed trickier to isolate and uand. Aslate as 1933,    vi genes eveed. As Man    time, to itious.” It may seemsurprising t stists could struggle to accept ty of sometal to cellular activity, but as allace, King, and Sanders point out in Biology: t rarest text), oday al processes sud memory. e kno    kno    time you could plue from your body and take it audy o many of Man’s peers as t stists today migure a strayt and exami under a microscope.

        ainly true    someted ingcell replication. Finally, in 1944, after fifteen years of effort, a team at titute in Mantan, led by a brilliant but diffident adian named Osricky experiment in eria ly iious by crossing it    DNA    certainly ive agent in y. trian-born bioc Ered quite seriously t Avery’s discovery wo Nobel Prizes.

        Unfortunately, Avery itute, a strong-ei named Alfred Mirsky,    Avery’s    ies at titute in Stock to give Avery a Nobel Prize. Avery by time y-six years old and tired. Uo deal ress and troversy, ion and never    near a lab again. But ots elseructure of DNA.

        ting person in t certaio crack tructure of DNA.

        Pauling erminiure of molecules and allograpec o peering into t of DNA. In an exceedingly distinguis    tructureriple    a double one, and never quite got on t track. Instead, victory fellto an unlikely quartet of stists in England eam, often    onspeaking terms, and    part novices in the field.

        Of t to a ventional boffin omib. tis—Crick of type t bloype t produce coal.

        t unventional of tson, an Ameri prodigy    least part of tion for some of tered ty of C fifteen. y-ttaco tory in Cambridge. In1951, y-trikingly lively    appearsin pograpo be straining to attacself to some po just out of frame.

        Crick, till    a doctorate, son’s at ed as blustery, nosy, cative, impatient o sion, and stantly in danger ofbeing asked to go elsewrained in biocry.

        tion    if you could determio see—correctly, as it turned out— did    did. to ac tle    tely necessary. As atson coucobiograp    be solved my learning any cry.” t actually assigo one point o stop it. atson ensibly mastering t of crystallograpo be pleting a tion of large molecules.

        Altson enjoy nearly all t in popular ats for solving tery of DNA, t on experimental itors, ts of uitously,” in tactful orian Lisa Jardine. Far a least at tKing’s College in London, ilkins and Franklin.

        tiring figure, almost to t of invisibility. A1998 PBS dotary on tructure of DNA—a feat for o overlook irely.

        t enigmatic cer of all tering portrait,atson in ted Franklin as a o irritate    tractive and mige stunning aken even a mild i in clot in ted all expectations. Seven use lipstick, ed in s.”

        1 images ience of tructure of DNA,acallograpeced by Linus Pauling.

        Crystallograpo map atoms in crystals (allograp DNA molecules o get good results from t to ilkins’s perennial exasperationso share her findings.

        If Franklin     be altoget King’s ied dazzles modern sensibilities (actually any sensibilities).    alloo t instead o take tilitarian c even atson ceded opof tantly pressed—at times actively o ss rio of men o get a peek at tcies, like respect. “I’m afraid o adopt—let’s say a patronizing attitudetoing institution and t s s s locked away.

        t ilkins and Franklin did not get along    t atson and Crick seem to ed to t. Altson respassing raterritory, it     altogeto a a decidedly queer ss DNA definitely o all t it . toilkins’s presumed dismay and embarrassment, in ted a mootice around tment t said: “It is    regret t    is    Dr. M.h.F.

        ilkins e helix.”

        te of all t in January 1953, ilkins sson Franklin’simages, “apparently    .” It atement to callit a signifit er atson ceded t it “ . . . it mobilizedus.” Armed as of its dimensions, atson and Crick redoubled ts. Everyto go t one point Paulio a feren England at o correct tions t     tai Idle in Need,on t oo liberal of temperament to be alloo travel abroad. Crid atson also    good fortu Pauling’s son tly kept t of any nes abacks athome.

        Still fag ty of being trumped at any moment, atson and Crick appliedto t    DNA y Press celed publication of ter Crid ilkinsplained about its cerizations, uitouslyful." tions quoted above are after atson softened s.

        pos—called adenine, guanine, cytosine, and t ticular    into tsonand Crick o     toget famous in modern sce—sisting of metal plates boltedtogeted ilkins, Franklin, and t of to have a look.

        Any informed person could see at o question a brilliant piece of detective    t of Franklin’s picture.

        tion of Nature carried a 900-icle by atson and Crick titled“A Structure for Deoxyribose Nucleic Acid.” Apanying it e articles byilkins and Franklin. It ful time in t about toclamber to top of Everest o be cro of life ly overlooked. It received a smallmention in the News icle and was ignored elsewhere.

        Rosalind Franklin did not s t ty-seven in 1958, four years before ted. Nobel Prizes are nota certainly arose as a result of co X-rays t ed t Franklin rarely en steppedcarelessly in front of a beam. Oserity, t least isfa of living just longenougo see ed. he died in 1955.

        atson and Crick’s discovery    actually firmed until t took over ty-five years for our model of DNA to go from being onlyrato being very plausible . . . and from to being virtually certainlycorrect.”

        Even so, ructure of DNA uoress iics , and by 1968ticle titled “t as t as,”

        suggesting—it    it is so—t tics    anend.

        In fact, of course, it    beginning. Even no deal about DNA tand, not least    actually seem to do anything.

        y-seven pert of your DNA sists of not long stretcs prefer to put it. Only rand do you fiions t trol and aal funs. thecurious and long-elusive genes.

        Genes are notrus to make proteins. tain dull fidelity. In te and notrifle monotonous. But bie ce variety.

        Put all togeto tiap sympenohe human genome.

        An alternative and more on ard truanual for ters and trus for making proteins. trus are ten are called s, and tters are knoters of tic alp—sist of tides mentioned a page or two back:

        adeosine. Despite tance of ances are not made of anytic. Guanine, for instance, is tuff tabounds in, and gives its o, guano.

        taircase orted rope ladder: ts of tructure are made of a typeof sugar called deoxyribose, and teps) are formed by tosine and tters appear as youmove up or doitutes t .

        Noicular brilliance of DNA lies in its manner of replication.    is time toproduce a nerands part do, and ea a nenerside along astrand pairs up ide, ead serves as a template for tion of a ned. If you possessed just orand of your o terships:

        if topm orand    topm on td must be cytosine. ork your ide pairings, aually you     t nature does it really quickly—inonly a matter of seds, .

        Most of time our DNA replicates iful accuracy, but just occasionally—aboutoime in a million—a letter gets into tidepolymorpo biocs as a “Snip.” Generally tretcectable sequence for the body.

        But occasionally t leave you predisposed to some disease,but equally t fer some sligage—more protective pigmentation, forinstance, or increased produ of red blood cells for someone living at altitude. Over time,t modifications accumulate in botions, tributing totinctiveness of both.

        tion is a fine ooo many errors andt fun, but too fe sacrifices adaptability. A similar balance mustexist betability in an anism and innovation. An increase in red blood cells     ions to move and breat additional red cells also too many,and “it’s like pumping oil,” in temple Uy ant Cz.

        t’s . to live at itude get increased breat pay for it s. By sucuralsele look after us. It also o explai you bee too different—not    being a new species anyway.

        t differeed for by our Snips.

        Nocorrespondence, but t part, be in different places. Add morepeople to t yet more Snips i more places. For every one ofyour 3.2 billion bases, some g in t position. So not only is it o refer to “t in a sense    even    t equally, in t David Cox, “you could sayall    , too.”

        But o explain    DNA    startsto get a little unnerving, but it does really seem t to perpetuate DNA.

        t of our DNA only called junk is largely made up of clumps of letterst, in Ridley’s    for t t gettingted.”

        2Most of your DNA, in ot devoted to you but toitself: you are a maot it for you. Life, you    s tobe, and DNA is    so.

        Even ions for making genes—ists put it—it is not necessarily ioning of the anism in mind.

        One of t genes ranscriptase, does do is make itpossible for retroviruses, suco slip unnoticed into tem.

        In ote siderable energies to produg a protein t doesnot is beneficial and sometimes clobbers us. Our bodies    to do sobecause t. e are vessels fet    proportio found in any anism—don’t do anyt all, as far asell, except reproduce themselves.

        All anisms are in some sense slaves to t’s ures more or less beyond ting are prepared to die in ting. to breed, to disperse one’s genes, is t poure.

        As S it: “Empires fall, ids explode, great sympten,and be is a single instinct t demands satisfa.” From an evolutionary pointof vie a reo pass on eic material.

        Stists    most of our DNA doesn’t doanyted findings began to turn up. First in Germany and tzerland researcs t produced curiouslyunbizarre outes. Iook t trolled t of a mouse’seye and ied it into t fly. t    it migerestingly grotesque. In fact, t only made a viable eye int fly, it made a fly’s eye. ures t    sor for 500 million years, yet could sic material as if ters.

        tory    to certain cells of flies, and t it as if it heir own.

        2Junk DNA does    is tion employed in DNA fingerprinting. Its practicality for tally by Alec Jeffreys, a stist at ty of Leicester in England. In 1986Jeffreys udying DNA sequences feic markers associated able diseases    to to ly for solving criminal cases-and so it proved. A young baker ced to terms in prison for the murders.

        Over 60 pert of    turns out, are fually t flies. At least 90 pert correlate at some level to tail, if only tcer field,researc ode udying essentially t appeared,    of blueprints.

        Furtence of a clutcer trol genes, eagt of a se of tic (from a Greek iA, knoo do—t tretc of ting is t instruct t for all anisms in muche same way.

        Iingly, t of geic material and    is anized doesn’t necessarily, oreven generally, reflect tication of ture t tains it. e y-six e ferns    evolved of all plex animals, y times as muc is meically splendorous tor of five.

        Clearly it is not t aken a big    lately. Until retly it t    least 100,000 genes, possibly a good many more, but tnumber ically reduced by t results of t,    t came as botment.

        It    tention t genes ed in anynumber of ies. Exultant stists    various times declared toy, scy, criminality,violence, alg and erminism udy publisending tically inferior at matics. In fact,    notyou is so aodatingly simple.

        ty in one important sense, for if you    determined or propensity to diabetes or to baldness or any otinguisrait, t ively easy anyo isolate and tinker unately, ty-five tioning indepely is not nearly enougo produce ty t makes a satisfactory cooperate. A feon’s disease, andcystic fibrosis, for example—are caused by lone dysfunal genes, but as a rule disruptivegenes are    by natural sele long before tlytroublesome to a species or population. For t part our fate and fort—and even oureye color—are determined not by individual genes but by plexes of genes ’s     all fits toget beprodug designer babies anytime soon.

        In fact, t years ted matters eo bee. Even t turns out, affects t a man’s beardgroance, is partly a fun of    sex (because t sex produces a testosterone surge). In tists made an even moreprofound discovery al genes fromembryonic mice, and t only often born    sometimes uallyfitter ters ampered ain importantgenes royed, it turned out, otepping in to fill t    so good for our uanding of    introduced ara layer of plexity to somet and anyway.

        It is largely because of ting factors t crag t at once as only a beginning. t    it, is likea parts list for t tells us    says not ’s needed noing manual—instrus for o make it go.

        e are not close to t poi.

        So no is to crack teome—a cept so    termproteome didn’t eve a decade ago. teome is tion tcreates proteins. “Unfortunately,” observed Stific Ameri in teome is muced the genome.”

        t’s putting it mildly. Proteins, you ems; as many as a    any moment. t’sa lot of activity to try to figure out. orse, proteins’ beions are based notsimply on try, as    also on to fun, a protein mustnot only s, properly assembled, but t also befolded into aremely specific serm t’s used, but it’s amisleading one as it suggests a geometrical tidi doesn’t in fact apply. Proteins loopand coil and kle into s are at oravagant and plex. t owels.

        Moreover, proteins are (if I may be permitted to use a abolic circumstao be ped, glycosylated, acetylated, ubiquitinated, farneysylated,sulfated, and lio glycopidylinositol anc else. Often ittakes relatively little to get t appears. Drink a glass of ificAmeriotes, and you materially alter types of proteins at large in yoursystem. t feature for drinkers, but not nearly so icists o uand w is going on.

        It    all begin to seem impossibly plicated, and in some is impossiblyplicated. But ty in all too, oo an equallyelemental underlying unity in tiny, deft imate cells—tive efforts of ides, transcription of DNA into RNA—evolved just ond ayed pretty ure. Aste Frencicist Jacques Monod put it, only : “Anyt is true of E.

        ust be true of eleps, except more so.”

        Every living tion on a single inal plan. As s—eacy arts, adaptations, modifications, andprovidential tinkerings stretceclosely related to fruit aables. About ions t take pla abanana are fually tions t take pla you.

        It ot be said too often: all life is o is, and I suspect o be, t profound true statement there is.

        PARt    VItO USDesded from t us    it is not true, but if it is,let us pray t it    beegenerally known.

        -Remark attributed to ter afterDarion o her
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