Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021

Recent Papers of MicrobiologicalInterest Published in Scientific American

* Compiled by Gordon W. Robertstad,Department of Biology, Universityof Texas at El Paso, El Paso, Texas * Pasquale V. Scarpino, EnvironmentalHealth Engineering, Universityof Cincinnati,Cincinnati, Ohio

The popular monthly magazine, Scientific 1959 American,has been of immensevalue to not June, 1959 only teachers and their students in high SELF-REPRODUCING MACHINES, L. S. schools and colleges, but also to scientists Penrose keeping abreast of recent developments in "In which simple units are built which assem- other fields. The papers contained in the ble themselves into larger units, which in turn make copies of themselves from other simple magazineare authoredby experiencedscien- units. The process sheds light on the self-repro- tists and are unusuallywell-written, informa- duction of biological molecules." tive, and timely. Abstractsof articlesrelating to microbiology that have appeared from August, 1959 June, 1959 to July, 1968 THE ENZYME-SUBSTRATE COMPLEX, follow. Offprintsof Earl Frieden these and others may be obtained from W. "The fleeting union of the enzyme and the H. Freeman and Company, 660 Market substance on which it acts holds a key to our Street, San Francisco,California 94104. The understandingof life processes. Many ingenious cost is 20 cents per article in any assort- techniques are in use today to isolate it for ment or quantity. study."

549 September,1959 combined into a precise tool for the study of IONIZING RADIATION AND THE LIV- protein chemistry." ING CELL, Alexander Hollaender and 1960 George E. Stapleton May, IN THE "'The primary site of the biological effects of ENERGY TRANSFORMATION radiationis in the cell. The specialized structures CELL, Albert L. Lehninger energy of the cell, including the genes, are damaged "How does the living cell convert the not only by direct hits but also by the chemical of foodstuff into a form that can be utilized and stored? The process involves the sequential ac- products of radiation." tion of many enzymes, some of which are part October, 1959 of the cell membranes." LICHENS, I. Mackenzie Lamb 1960 "These humble incrustations of rocks, trees May, ANIMAL INFECTIONS AND HUMAN and soil are composedof two distinct organisms: DISEASE, Meir Yoeli a fungus and an alga. Together they are able to "During most of man's history his worst dis- survive in some of the harshest environments eases were carried by animals and transmitted Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 on earth." by insects and other arthropods.These 'zoonoses' November, 1959 are still a threat over most of the world." INSECTS AND PLANT GALLS, William June, 1960 Hovanitz FLEMING'S LYSOZYME,Robert F. Acker their eggs in specific plant "Certaininsects lay and S. E. Hartsell the formationof a protuberance tissues, causing "The discovererof penicillin also found a sub- How does the in- that nourishesthe insect larva. stance that dissolvesbacteria. Occurring in many plant to grow this abnormal sect induce the human tissues and secretions, lysozyme is pres- tissue?" ently used to investigate the structure of the December, 1959 bacterialcell." NUCLEIC ACIDS AND PROTEINS, Mah- July, 1960 lon B. Hoagland THE BIOLOGY OF HEAVY WATER, Jo- "The nucleic acid molecules inherited by the sephJ. Katz living cell bear the plan of all the cell's protein "What happens to experimental organisms It now appears that another kind of molecules. that have been raised on water in which the hy- nucleic acid plays a key role in translatingthe drogen is not the common isotope of mass one into plan protein." but the heavy isotope of mass two?" December, 1959 August, 1960 DIFFERENTIATION IN SOCIAL AMOE- FRIENDLY VIRUSES, Karl Maramorosch BAE, John Tyler Bonner "Manyviruses, like many bacteria, help rath- "Certain amoebae gather to form a mass of er than harm the organismsthey live in." spores and a stalk. The way in which spore cells and stalk cells segregate may shed light oni November, 1960 how the cells of many-celled organismsdifferen- THE POLYOMAVIRUS, SarahE. Stewart tiate into various types." "This recently discovered organism causes a variety of malignant tumors in laboratory ani- 1960 mals. Studies of its action lend weight to the idea that viruses may be responsiblefor human February,1960 cancers. YEASTS,Anthony H. Rose "These single-celled fungi, essential in the December, 1960 making of bread and alcoholic beverages, pro- THE VIRUSES OF THE COMMONCOLD, duce enzymes and vitamins as well. They have ChristopherH. Andrewes also helped to throw light on many areas of cell "For years the cold virus stubbornly refused physiology." to multiply in tissue culture. Now, with new techniques, researchershave been able to cul- March, 1960 ture some 20 strains of the virus." IMMUNOELECTROPHORESIS,Curtis A. Williams, Jr. 1961 "This formidable word and the technique it Januarv,1961 identifies are derived from immunochemistry THE MECHANISM OF IMMUNITY, Sir and electrophoresis.These methods have been MacfarlaneBurnet

550 The AmericanBiology Teacher,August, 1968 "How does an animal make an antibody that molecularunity." neutralizes a single foreign substance, or anti- September, 1961 gen? The evidence favors the theory that cells THE LIVING CELL, Jean Brachet able to make antibody are 'selected' by the anti- "Presentingan issue on the fundamentalpar- gen and then multiply." ticle of life. Anatomical and chemical views of February, 1961 the cell have now converged to show that it is THE CHEMICAL STRUCTURE OF PRO- not a droplet of protoplasmbut a highly orga- TEINS, William H. Stein and Stanford nized molecularfactory." Moore September, 1961 "The atom-by-atom structural formulas of HOW CELLS TRANSFORMENERGY, Al- three proteins have now been worked out. This bert L. Lehninger knowledge should help in understanding how "In the chloroplastsof plant cells the energy the structuresof protein are related to their bio- chemical fuels. In logical activity." of sunlight is transformedinto the mitochondriaof animal cells these fuels are March, 1961 oxidized to run the cellular machinery." Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 NEW PENICILLINS, Anthony H. Rose September, 1961 "By altering the groups of atoms that are at- HOW CELLS MAKE MOLECULES, Vin- tached to the 'core' of the penicillin molecule, cent G. Allfrey and Alfred E. Mirsky chemists have produced penicillins that are ef- "The inherited master plan of the cell is con- fective against resistant strains of microorga- tained in the molecules of deoxyribonucleicacid. nisms." They direct the manufactureof protein enzymes, April, 1961 which in turn engineer all the chemical reac- PINOCYTOSIS,Ronald C. Rustad tions of life." "The word means 'drinkingby cells.' Actually September, 1961 it is the term for a complex process whereby a HOW CELLS DIVIDE, Daniel Mazia cell can take in nutrientsand other substancesto "All cells arise by division. In the process of which the cell membrane seems impermeable." mitosis each cell is apportioned a complete set May, 1961 of hereditary instructions when the chromo- INTERFERON, Alick Isaacs somes replicate and are separatedby the mitotic "This natural product of animal cells protects apparatus." them against attack by a variety of viruses. If it September, 1961 proves to be effective in humans, it should have HOW THINGS GET INTO CELLS, Heinz considerablemedical importance." Holter June, 1961 "It seems that some things passively flow VIRUSES AND GENES, Francois Jacob and through the cell membraneunder various pres- Elie L. Wollman sures, others are somehow actively pumped "When a virus infects a bacterium, the genes across the membrane and others are engulfed of the virus sometimesact as genes of their host. when the membranefolds inward." The phenomenonhas illuminatedthe mechanism of both heredity and infection." November, 1961 CHROMOSOMESAND DISEASE, A. G. August, 1961 Bearn and James L. GermanIII ENZYMES IN MEDICAL DIAGNOSIS, "Advances in the visualization of human Felix Wr6blewski chromosomes have made it possible to link "Certaindiseases are accompaniedby changes chromosomalabnormalities with certain diseases in the enzyme content of the body fluids. Al- and have opened up a new frontier in the study ready used in some diagnoses, these changes of human heredity." may make it possible to detect a cancer before it is a malignancy." December, 1961 THE THREE-DIMENSIONAL STRUC- September, 1961 TURE OF A PROTEIN MOLECULE, HOW CELLS MOVE, Teru Hayashi John C. Kendrew "A paramecium moves by the beating of its "The way in which the chain of amino acid cilia, an amoeba, by the streaming of its cyto- units in a protein molecule is coiled and folded plasm, a muscle, by its over-all contraction.All in space has been worked out for the first time. these processes appear to share an underlying The protein is myoglobin,the molecule of which

Recent Papers of Microbiological Interest in Scientific American 551 contains 2,600 atoms." October, 1962 THE GENETIC CODE, F. H. C. Crick 1962 "How does the orderof bases in a nucleic acid January,1962 determine the order of amino acids in a pro- THE FINE STRUCTURE OF THE GENE, tein? It seems that each amino acid is specified Seymour Benzer by a triplet of bases, and that triplets are read "The question 'What is a gene?' has bothered in simple sequence. geneticists for fifty years. Recent work with a 1962 small bacterial virus has shown how to split the November, David Joravsky gene and make detailed maps of its internal THE LYSENKOAFFAIR, structure." "A case study of one aspect of the celebrated controversythat still troubles Soviet science: the February, 1962 dispute between Lysenkoitesand others over the MESSENGERRNA, JerardHurwitz and J. J. practical problem of curing virus diseases of the Furth potato."

"New experimentshave found a kind of ribo- Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 December, 1962 nucleic acid (RNA) that acts as a messenger to BIOLOGICAL LUMINESCENCE, William carry instructionsfrom the genes to the particles D. H. Seliger in the cell where proteins are manufactured." McElroy and Howard "A remarkablevariety of organismsfrom bac- February, 1962 teria to fishes shine by their own light. The AMOEBOID MOVEMENT,Robert D. Allen light is produced by diverse chemical systems, "In a new theory to explain the mechanismof the best understood of which is the system iso- motility in amoebae and similar cells, the author lated from fireflies." proposes that streaming cytoplasm contracts at the front of the cell and literally pulls it along." December, 1962 ULTRAVIOLET RADIATION AND NU- March, 1962 CLEIC ACID, R. A. Deering THE SMALLEST CELLS, Harold J. Moro- "The damaging effects of ultravioleton living witz and MarkE. Tourtellotte things have long been known. Now they are be- "A microbe known as the pleuropneumonia- ing explained in terms of specific changes in like organismgives rise to free-living cells small- molecules of the genetic material." er than some viruses. They suggest the question: What are the smallest dimensions compatible 1963 with life?" January,1963 THE STRUCTURE OF VIRUSES, R. W. May, 1962 Horne MALARIA, Carlos A. Alvarado and L. J. "The electron microscope reveals that these Bruce-Chwatt infectious particles possess three principal types "It still disables more people than any other of symmetry.Each species of virus is ingenious- disease. Many nations in which it is a major ly assembled from just a few kinds of building problem now aim, with the aid of the World block." Health Organization,at its total eradication." January,1963 June, 1962 SKIN TRANSPLANTS AND THE HAM- THE PATH OF CARBON IN PHOTOSYN- STER, Rupert E. Billinghamand Willys K. THESIS, J. A. Bassham Silvers "The carbon atoms of the carbon dioxide as- "Thisfamiliar laboratory rodent is an anomaly similated by plants traversean intricate cycle of of the animal kingdom in several respects, not chemical reactions. The immediate products are least of which is the unique hospitality it shows not only carbohydratesbut also amino acids, to many kinds of foreign-tissuegrafts." fats and other compounds." February, 1963 July, 1962 THE FUNGI OF LICHENS, VernonAhmad- Robert L. Sin- SINGLE-STRANDED DNA, jian sheimer "Lichensare composite plants, associationsof "The molecule of the hereditarymaterial de- fungi and algae. The problem is to separate the oxyribonucleicacid (DNA) normallyconsists of two partners and study the fungi in isolation. two interwovenstrands. The discovery of a form and then to try to put the lichen together again." with onlv one strand promises to clarify how the molecule replicates." March, 1963

552 The AmericanBiology Teacher,August, 1968 THE GENETIC CODE: II, Marshall W. stances are called endotoxins.How they act on Nirenberg the body is the subject of much current study." "A sequel to F. H. C. Crick'sarticle of Octo- ber 1962, which discussed how the hereditary May, 1964 materialembodies the code for the manufacture HYBRID NUCLEIC ACIDS, S. Spiegelman acid will combine with of proteins. The nature of the code has now "One strand of nucleic strands been further elucidated. anotherwherever the subunitsof the two are complementary.Artificial combinations clar- May, 1963 ify the flow of informationin the living cell." THE LYSOSOME,Christian de Duve May, 1964 "This small acts particle as the digestive tract LEUKEMIA,Emil Frei III and Emil J. Frei- of the living cell. Its the sub- enzymes dissolve reich stances ingested by the cell and under certain "Although this disease characterizedby the circumstancescan dissolve the cell itself." accumulationof white blood cells is almost al- August, 1963 ways fatal, advances in knowledge of its cause HOW SLIME MOLDS COMMUNICATE, and managementgive promisethat it may some- Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 John Tyler Bonner day be curable." "Slime-mold amoebae are free-living micro- June, 1964 organisms that periodically gather together to A DEFECTIVE CANCER VIRUS, Harry form macroscopicfruiting bodies. It now seems Rubin that secreted gases play several importantroles "The Rous sarcomavirus is uniquely efficient in this development." in producing tumors. Its carcinogenic effect October, 1963 seems to be related to an inability to form a FOREIGN NUCLEIC ACIDS, Alick Isaacs protein coat and reproduce itself without help "In 1957 it was found that the cell defends from another virus." itself against viruses with a protein called inter- July, 1964 feron. It now seems that this substance protects GERM-FREE ISOLATORS,P. C. Trexler the cell against all the nucleic acids other than "They are widely used to raise laboratoryani- its own." mals in an environmentthat is entirely free of are December, 1963 microorganisms.Other potential applications in the manu- POLYRIBOSOMES,Alexander Rich in surgery on human patients and "These collections of the particles called ribo- facture of spacecraft." somes appear to be the assembly lines on which August, 1964 the living cell manufacturesprotein molecules. WINE, MaynardA. Amerine How the assemblyline works is just now becom- "This happy invention of man is a solution of ing clear." hundreds of subtly interactingsubstances. Mod- ern understanding of the wine-making process 1964 cannot explain a great wine but guarantees a February, 1964 good one." HOW CELLS ATTACK ANTIGENS, Rob- ert S. Speirs October, 1964 "An army of defensive cells protects the body THE GENETIC CODE OF A VIRUS, Heinz against invasion by foreign substances: the anti- Fraenkel-Conrat gens. The specialized functions of these various "The tobacco mosaic virus consists of heredi- 'inflamatory'cells are now being clarified." tary material and a single protein. Artificial changes in the hereditarymaterial elucidate how February, 1964 it directs the synthesis of the three-dimensional THE BLACK DEATH, William L. Langer molecule of protein." "The plague that killed a quarter of the peo- ple of Europe in the years 1348-1350 is still December, 1964 studied to shed light on human behavior under HOW CELLS MAKE ANTIBODIES, G. J. conditionsof universalcatastrophe." V. Nossal "The process has now been clarified by ex- March, 1964 periments with single antibody-producingcells BACTERIAL ENDOTOXINS, A. I. Braude grown in culture. These experiments indicate "Some disease bacteria excrete toxin; others that antibody manufacture is directed by the do not excrete it but contain it. These latter sub- genes.

Recent Papers of Microbiological Interest in Scientific American 553 1965 malignant to normal." January,1965 GENES OUTSIDE THE CHROMOSOMES, December, 1965 Ruth Sager RHEUMATIC FEVER, Earl H. Freimer and "Therehas been evidence for many years that Maclyn McCarty hereditary information exists apart from the "It is clear that this baffling disease, which chromosomalgenes. Now nonchromosomalgenes often damages the heart, stems from streptococ- have been identified by the traditionalmethods cal infection. No link has yet been found, how- of genetic analysis." ever, between the infection and the rheumatic process. February, 1965 THE GENETICS OF A BACTERIAL 1966 VIRUS, R. S. Edgar and R. H. Epstein January, 1966 "The T4 virus is a simple form of life with a THE BACTERIAL CHROMOSOME, John precise architecture dictated by genes in its Cairns DNA molecule. By mappingthe genes and learn- "When bacterial DNA is labeled with radio- ing their function one learnshow the virus is put active atoms, it takes its own picture. Autoradio- Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 together." graphs reveal that the bacterial chromosome is a single very long DNA molecule and show how April, 1965 it is duplicated." THE CONTROL OF BIOCHEMICALRE- ACTIONS, Jean-PierreChangeux February, 1966 "The cell is a factory and enzymes are its THE NUCLEOTIDE SEQUENCE OF A machines.Two feedback systems controlproduc- NUCLEIC ACID, Robert W. Holley tion, one regulating synthesis of enzymes, an- "For the first time the specific order of sub- other their activity. Models of the two systems units in one of the giant molecules that partici- are described." pate in the synthesis of protein has been deter- July, 1965 mined. The task took seven years." FLIES AND DISEASE, Bernard Greenberg March, 1966 "Do flies spread disease? Surprisinglythe evi- THE FOOTPRINTS OF TUMOR VIRUSES, dence is still inconclusive. Efforts to provide an Fred Rapp and Joseph L. Melnick answer have nonetheless yielded significant in- "Some viruses that cause tumors in animals formationon the nature of infection." are not found in the tumors but their antigens Julv, 1965 are. This suggests that the absence of a virus in THE ROLE OF CHLOROPHYLLIN PHO- a human cancer does not necessarily mean that TOSYNTHESIS, Eugene I. Rabinowitch a virus did not cause it." and Govindjee April, 1966 "The pigments of plants trap light energy and ANTIBIOTICS AND THE GENETIC store it as chemical energy. They do this by CODE, Luigi Gorini catalyzing an oxidation-reduction process in "The meaning of the code that directs the which hydrogen atoms are boosted from water synthesis of proteins can be changed by the ac- to organic matter." tion of streptomycin and related drugs. They October, 1965 cause 'misreading' by altering the structure of PROTEIN FROM PETROLEUM, Alfred ribosomes." Champagnat June, 1966 "Certain microorganismsthrive on hydrocar- THE BLUE-GREEN ALGAE, Patrick Echlin bons. In growing they synthesize protein rich in "These primitive plants more closely resemble amino acids that plant foods lack. Protein from bacteria than they do other algae. They live in petroleummay help solve the world'sfood prob- an extraordinary range of environments, and lem." they have both beneficial and harmful effects in human affairs." November, 1965 THE REVERSAL OF TUMOR GROWTH, June, 1966 Armin C. Braun MOLECULAR MODEL - BUILDING BY "The fact that cancers are usually irreversible COMPUTER, Cyrus Levinthal is sometimes taken as showing that they are "In which biochemists observe models of giant caused by mutation.Some 'multipotenial'cells in molecules as they are displayed on a screen by plants and animals, however, can change from a computer and try to fold them into the shapes

554 The AmericanBiology Teacher,August, 1968 that they assume in nature." ject to damage. Experiments with bacteria re- veal that the cell has a remarkable ability to July, 1966 repair such damage." GERMAN MEASLES, Louis Z. Cooper "This mild infection can have grave results April, 1967 during pregnancy. In 1964 an epidemic in the THE INDUCTION OF CANCER BY VI- U. S. caused defects in 20,000 infants. Isolation RUSES, Renato Dulbecco of the virus has led to intensive efforts to de- "Normal cells cultured in glassware can be velop a safe vaccine." transformedinto cancer cells by several viruses. Such 'model' systems are studied to find how October, 1966 the virus, with fewer than 10 genes, can produce THE GENETIC CODE: II, F. H. C. Crick the change." "The central theme of molecular biology is confirmed by detailed knowledge of how the July, 1967 four-letter language embodied in molecules of BUILDING A BACTERIALVIRUS, William nucleic acid controls the 20-letter language of B. Wood and R. S. Edgar the proteins." "T4 viruses with mutations in certain genes Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 produce unassembled viral components. These November, 1966 particles are combined in the test tube in an THE THREE - DIMENSIONAL STRUC- effort to learn how the genes of a virus specify TURE OF AN ENZYME MOLECULE, its shape." David C. Phillips "The arrangement of atoms in an enzyme October, 1967 molecule has been worked out for the first time. THE STRUCTUREOF ANTIBODIES,R. R. The enzyme is lysozyme, which breaks open Porter cells of bacteria. The study has also shown how "The basic pattern of the principal class of lysozyme performs its task." molecules that neutralize antigens (foreign sub- stances in the body) is four cross-linkedchains. November, 1966 This pattern is modified so that antibodies can ACETABULARIA: A USEFUL GIANT fit differentantigens." CELL, Aharon Gibor "Thismarine alga grows to a length of an inch November, 1967 but has only one cell and one nucleus. It is LYSOSOMESAND DISEASE, Anthony Alli- therefore almost ideal for studying the relations son between the nucleus and other parts of the cell." "Lysosomes are organelles of the living cell that contain digestive enzymes. They play an December, 1966 important part in normal life processes, and THE GENETIC CONTROL OF THE there is evidence that they are also involved in SHAPE OF A VIRUS, Edouard Kellenber- pathologicalones." ger "The protein shell of a virus is an assembly November, 1967 of subunits. In simple viruses the subunits them- THE FUNGUS GARDENS OF INSECTS, selves may specify the shape of the shell. Com- Suzanne W. T. Batra and Lekh R. Batra plex viruses seem to be formed on an interior "Severalkinds of insects live only in associa- core, or scaffold." tion with one kind of fungus, and vice versa. In some instances the insect actively cultivates the 1967 fungus, browsing on it and controlling its January,1967 growth." THE KINSHIP OF ANIMAL AND HUMAN DISEASES, Robert WV.Leader December, 1967 "Knowledgeof humandiseases has been great- INFECTIOUS DRUG RESISTANCE. Tsu- ly advanced by inducing similar diseases in ex- tomu Watanabe perimentalanimals. It now appearsthat there is "Bacteria can suddenly become resistant to still much to be learned from animal diseases several antibacterial drugs. The resistance is that occur naturally." transferred from one strain to another by an 'episome' that carries the gene for multiple re- February, 1967 sistance." THE REPAIR OF DNA, Philip C. Hanawalt and Robert H. Haynes 1968 "The two-strand molecule that incorporates January,1968 the genetic informationof the living cell is sub- HOW PROTEINS START, Brian F. C. Clark

Recent Papers of Microbiological Interest in Scientific American 555 and Kjeld A. Marcker wound can produce enough toxin to cause the "The chain of amino acid units that consti- severe and often fatal symptoms of this disease. tutes a protein molecule begins to grow when a Tetanus is hard to treat, but it could be eradi- variant of one of the standard amino acids is cated by immunization." delivered to the site of synthesis by a specific transferagent." April, 1968 POLLEN, Patrick Echlin February, 1968 "The tiny grains that carry the male genetic THE MEMBRANE OF THE MITOCHON- material of plants are closely studied with, DRION, Efraim Racker am.ongother instruments,the scanning electron "The folded inner membrane of this intra- microscope. Their baroque architecture raises cellular body is the site of the major process of fundamentalquestions." energy metabolism in the living cell. It is stud- ied by taking it apart and attemping to put t April, 1968 together again." THE SEXUAL LIFE OF A MOSQUITO, Jack Colvard Jones

February, 1968 "Modern methods of insect control call for Downloaded from http://online.ucpress.edu/abt/article-pdf/30/6/549/24268/4442168.pdf by guest on 02 October 2021 DEATH FROM STAPHYLOCOCCI, Ian detailed knowledge of an insect'sphysiology and Maclean Smith behavior. Reproduction in Aedes aegypti, the "When someone dies of staphylococcalinfec- yellow-fevermosquito, is surprisinglyelaborate." tion, what is the specific cause of death? The answeris sought by study of the chemical events June, 1968 that accompany the course of fatal infection in THE DISCOVERYOF DNA, Alfred E. Mir- laboratoryanimals." sky "In 1869 Friedrich Miescher found a sub- March, 1968 stance in white blood cells that he called 'nu- THE AUTOMATIC SYNTHESIS OF PRO- clein.' Cell biologists saw that it was a constitu- TEINS, R. B. Merrifield ent of chromosomes and hence must play a "By anchoring an amino acid to a plastic majorrole in heredity." bead one can add other amino acids one by one 1968 in automatically controlled steps. This method July, X-RAYCRYSTALLOGRAPHY, Sir Lawrence has already been used to make the small protein insulin." Bragg "The new knowledge of the atomic structure April, 1968 of matter uncovered over the past half-century TETANUS, W. E. Van Heyningen by the X-ray-diffractiontechnique has led to a "Bacteria that may barely infect a trivial fundamentalrevision of ideas in many sciences."

556 The AmericanBiology Teacher,August, 1968