GAZETTE - Adm.monash.edu.au - Monash University

More documents

Recommendations

Info

MONASH UNIVERSITY GAZETTETHE CODE FOR LIFEBy B. W. Holloway, Professor of GeneticsThe abbreviation DNA hasn't reached the popularity ofothers like VFL, SEATO (or my own current favouriteICPOTA), but more and more people are beginning torealize from articles in the daily press that these threeletters mean something which has general and scientificimportance. They stand for Deoxyribonucleic Acid, thechemical substance which is responsible for the basichereditary functions of life.Just as computer tape can store all the informationnecessary for the accounting procedures of a largebusiness, so DNA is the substance which stores the biologicalinformation necessary to maintain all those processeswhich comprise life. It is found in the nucleusof each living cell, located in structures called chromosomes.The chromosomes are assemblages of genes,each gene being composed of DNA and determining aparticular heritable characteristic. This DNA is preciselyduplicated at each cell generation, and by meansof the germ cells (eggs and sperm) is passed on tosucceeding generations to ensure the stability of eachliving species. Just as information on prices and salesin business must be coded before it can be read by thecomputer, so biological information is stored in theDNA molecule by means of a code. Determining howthis information is stored and read from this chemicalsubstance has been a major achievement for the collectionof scientific disciplines now known as molecularbiology, and by "cracking the code" new fields ofendeavour have been opened up for many branches ofbiology.Many of the experiments which contributed to thisknowledge of the genetic code came from the study ofthe genetics of micro-organisms - fungi, bacteria andviruses. The history of genetics abounds with examplesof the intensive study of individual creatures for thesolution of particular genetic problems. Just as Mendelused garden peas in the garden of the monastery atBrno and Morgan and his co-workers selected the fruitfly (Drosophila melanogaster) for the solution of particularproblems in genetics, so in the last ten to fifteenyears significant advances particularly related to geneticcoding have been made with microbial genetics.There are good reasons for such a choice of experimentalmaterial. In the first place it is relatively easy tohandle large numbers of micro-organisms, numberswhich would be physically impossible with plants oranimals. Because of the ease with which selectiveenvironments can be imposed on micro-organisms, it iscommonplace to be able to isolate a single variant bacterium(for example an antibiotic resistant form) fromamongst a thousand million other non-variant individuals.Most micro-organisms have very short generationtimes, thirty minutes or so in the case of bacteria, sothat in a few weeks of bacterial growth it is possible tosimulate evolutionary experiments which approximateall the generations of man's development on this planet.Finally, some bacteria show sexual differences so that itis possible to do hybridization experiments.Another group of micro-organisms which have alreadymade significant contributions to general geneticknowledge are the viruses, a group of creatures whichcan only multiply inside a living cell, be it either animal,plant or bacterial. The bacterial viruses, called bacteriophage(colloquially phage, to rhyme with age), whilesuperficially giving the appearance of parasites, arebetter thought of as examples of "infective heredity".They are very much smaller than bacteria, and generallyshaped like a tadpole with a head and a tail (seefigure). In interacting with a bacterium they firstattach themselves by their tail to the bacterium andinject the DNA from their head through the tail into theinterior of the bacterium. AU the rest of the phageparticle stays outside. This infection with DNA can thenresult in a variety of genetic events ranging in differentcircumstances from destruction of the bacterium withthe production of a hundred or so new phage particles,to the survival of the bacterial cell with additional geneticcapabilities which may even include acquired infectioussexual potency!Genetic studies on bacteria and phage have not onlycontributed to many details of the code of DNA, butto other general genetic problems including that of thecontrol mechanisms for reading thc code. It is one thingto have the information in the cell but deciding whenand how it is to be read is an entirely different problem.For example, most of the cells of the human body arecontrolled in their rate of division. It is believed thatloss of this control from one mechanism or another leadsto the initiation of some forms of cancer in which celtsare dividing without regard to the rate of division ofneighbouring cells.The important general point which has come out ofthese studies is that not only are the basic genetic principleswhich operate in such simple creatures as bacteriaand viruses the same as those in higher plants, animalsand man, but the genetic code by which information isstored in DNA is the same in all types of life, fungi orferns. viruses or vipers, bacteria or baboons.It is easy to see how knowledge of this type is usefulto the theoretical understanding of genetics, but how canone equate a study of this type with the exhortation ofFrancis Bacon that 'The real and legitimate goal of thesciences is the endowment of human life with new inventionsand riches"? There is an increasing and justifiabledemand from the man in the street (who providesthe money) and the politicians (who decide how tospend it) that scientists can no longer claim that "researchfor research's sake" is sufficient logic to justifytheir continued and expensive support,However, it seems to geneticists that to "know thyself"is an instruction as important today as when first madecenturies ago, and that the basis of knowledge of whatman is, and the most valuable of his existing riches, liesin the DNA carried in his own forty-six chromosomes.This represents his entire potential not only for thepresent but for every human being in the future. Just asa nation must explore its natural wealth in mineralsand natural products, so it is necessary for man to knowand understand his own genetic wealth. Just as mineralwealth must be husbanded and protected, so must thegenetic potential of man be guarded. While man's instinctis to preserve life at any cost, to do so may lead8
to progressive genetic devaluation.For example we know of many diseases which are inherited.These arise through genes directing particularbodily functions which have mutated to a form causingmodified metabolic function and hence disease. Includedin this group are haemophilia, diabetes, phenylketonuria,rheumatoid arthritis and perhaps schizophrenia. Researchinto these conditions has in many cases Led totreatment which has allowed sufferers to live nearnormal lives, have children and hence increase the Irequencyof the gene for that disease in the population atlarge. This means that we could be decreasing thefitness of the population (the fit being defined by J. M.Thoday as "those who fit their existing environmentand whose descendants will fit future environments").A further way in which fitness of the world populationcan be decreased is by increased frequency of mutationrates due to increased Levels of radiation from nuclearweapons testing. Mutations are chemical changes in theDNA resulting from certain chemical and radiationtreatments, the changes causing variations in the codeof the DNA which result in permanent alteration ofgenetic traits. The danger of such radiation-causedmutations is that, in a population like man, almost allwould result in changes that would decrease the levelof fitness.What then can we do about this? The solution toobtain decreased levels of atmospheric radiation is clearenough and most nations have undertaken the necessarysteps. The other dangers are less easily solved, Twosuggestions can be made. There might have to be somecontrol of the freedom that individuals now possess tobreed with other individuals of their choice, a notionclearly repugnant to current ideas of social freedom.Secondly, it may be possible to devise some form of"genetic engineering" to repair regions of the genomewhich are deleterious for the individual possessing them.Current ideas of how genetic engineering might be accomplishedare based on genetic phenomena whichhave been studied in micro-organisms, and microbialgenetics will no doubt supply the experimental modelsfor this type of work,I think it unlikely that either of these procedures willbe initiated in the near future. However it is importantfor people to realize that our knowledge of genetics isincreasing to the point where it will almost certainly bepossible to impose significant genetic alterations on thehuman race. We must be prepared to decide whether thisshould be done and not to leave such a decision entirelyto scientists.Some of the unexpected complexities of any directionof human heredity are easily seen in a few cases whichAn electron micrograph 0/ two bacteriophage particles clearly showing the head and tail structure. The head COlItainsthe DNA which appears as light-coloured material. The tail is a complex structure which functions verymuch like a hypodermic syringe. The particle on the right clearly shows the fibres on the tail, which are used toattach the phage to the bactrriut suriace, The sheath of the tail has contracted (it is intact in the particle on theleft) and clearly reveals the core of the fail, which is injected into the bacterial cell and through which the DNApasses on its way to the interior of the bacterial cell. If 100,000 phage particles were placed end to end they wouldextend over I inch (electron micrograph by Dr. H. S. Slater)9
Page 1 and 2: VOLUME V NUMBER 1 - NOVEMBER, 1968P
Page 3 and 4: esidence of which three have so far
Page 5 and 6: •into subsequent years is restric
Page 7: Architect's sketch 0/ Mannix Colleg
Page 11 and 12: FOUR HONORARY DEGREES CONFERREDFour
Page 13 and 14: country his concern and anxiety abo
Page 15 and 16: eading reference files has already
Page 17 and 18: Ibody compiles a notebook of number
Page 19 and 20: DEDICATION OF THE RELIGIOUS CENTRET
Page 21 and 22: edly atheist, denying the existence
Page 23 and 24: matriculation physics in Victoria i
Page 25 and 26: OPENING OF THE LAW SCHOOLThe law sc
Page 27 and 28: "1 do not believe that is a true di
Page 29 and 30: trained to eat the kind of food tha
Page 31 and 32: in a similar market situation to hi
Page 33 and 34: projections of water requirements a
Page 35 and 36: not two worlds, or three, or four,
Page 37 and 38: FIRST PART-TIME PROFESSORDr. Harry

GAZETTE - Adm.monash.edu.au - Monash University

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?