Biochemical Genetics
Some Recollections

Essay from Phage and the Origins of Molecular Biology

by George W. Beadle

Cold Spring Harbor Laboratory Press, 1992

© 1992 by Cold Spring Harbor Laboratory Press. Used with permission.

(Posted July 11, 1997 · Issue 12; archived July 25, 1997)

Editor's Note: Max Delbrück, the physicist turned biologist, was a pioneer in the field of molecular biology and phage, which revealed a new world underlying that of classical biology. Delbrück shared the Nobel Prize in physiology in 1969 for discoveries concerning the replication mechanism and the genetic structure of viruses. Three years earlier, he had been given another honor with the publication of Phage and the Origins of Molecular Biology (Cold Spring Harbor Laboratory Press, 1966), a collection of essays assembled by his colleagues to celebrate his sixtieth birthday and his career. In 1992, the Press published an expanded edition of the original, adding several new essays. Here, George W. Beadle (a 1958 Nobel laureate in physiology for the discovery that genes act by regulating definite chemical events) shares his memories of an early fascination that would become a revolution.

I have often thought how much more interesting science would be if those who created it told how it really happened, rather than reported it logically and impersonally, as they so often do in scientific papers. This is not easy, because of normal modesty and reticence, reluctance to tell the whole truth, and protective tendencies toward others.

My first exposure to genetics came during the summer after my second year at the University of Nebraska. Professor F.D. Keim had just returned from a leave of absence at Cornell University, where he worked on a Ph.D. thesis on the genetics of spelt-club wheat hybrids. I was employed at the rate of thirty cents an hour to take data on the progeny - kernel color, size, and weight; rachis internode length; glume texture and shape; plant height; and an array of other traits.

To find out what genetics was all about, I spent my spare time reading H.E. Walter's textbook Genetics. It was a simple book - just about right for me - and I was fascinated. I decided then and there to investigate wheat genetics on my own. But I did little more than make some crosses in the greenhouse.

Keim, no longer living, was a truly remarkable man. I do not suppose anyone would claim he was a scholar of special distinction. Nor was he a brilliant teacher in the usual sense. He could not always solve the problems in the book we used as a text in his course, and he sometimes asked me if I could. The flattery was effective, though I suspect not premeditated. He won respect through his honesty and lack of pretense. He had an abundance of infectious enthusiasm and a fabulous understanding and judgment of students. During his career as a Professor of Agronomy he advised hundreds of students and, so far as I knew, never made a mistake. He sent George F. Sprague, now one of the world's top corn breeders, into genetics and plant breeding. He urged me to go to Cornell to take graduate work, rather than returning to the farm as I had intended - and arranged for an assistantship to make it possible. He sent Earl Patterson and Francis Haskins to the California Institute of Technology to become geneticists, and convinced Adrian Srb that hs would make a better geneticist than English scholar.

As I look back, I wonder if an understanding of people may not be more important in a teacher than knowledge of the subject or the brilliance with which he teaches it.

After going through phases during which I wanted to be an English major, an entomologist or a plant ecologist, I ended up as a graduate student at Cornell University working with Rollins A. Emerson and Lester W. Sharp on the genetics and cytology of maize. Those were exciting times, for Barbara McClintock, Marcus Rhoades, Ian Phipps, H.W. Li, T.H. Shen, H.S. Perry and a number of others were students at the same time.

Unlike A.C. Fraser who taught the beginning genetics course, which rated very high with students, Emerson did little or no formal teaching. Fraser was a superb teacher, in the sense of organizing the facts of genetics known at the time and presenting them clearly and logically. He was little concerned with what remained to be discovered, and I have often suspected that was the reason few, if any, of his many hundreds of students were inspired to become geneticists.

Emerson, on the other hand, was little interested in what was already known but fascinated with what remained to be discovered. He infected his students and colleagues with his own enthusiasm for adding to known knowledge. During corn pollinating season we all worked from dawn to dark, with Emerson setting the pace and presiding over lunch and rest-period intellectual bull sessions. In my book, he was a truly great teacher - not unlike Max Deibrück, in many respects.

In working with genes for pollen sterility, I discovered the three genetic types of abnormal chromosome behavior: asynapsis, polymitosis and sticky chromosomes. I shall never forget the incomparable thrill of discovering the asynaptic character. My enthusiasm was shared - so much so in the case of Barbara McClintock that it was difficult to dissuade her from interpreting all my cytological preparations. Of course she could do this much more effectively than I.

In 1928 or 1929 Bernard O. Dodge, then of the New York Botanical Garden, gave a seminar at Cornell University on Neurospora. He had dissected in order and grown ascospores of crosses between a normal strain and one lacking asexual spores. He had found 4:4 segregations, with first division separation of the two types, in most asci. But there were some asci showing alternate pairs of spores of the two types. This was at a time when many cytologists and geneticists regarded the first meiotic division as reductional and the second as equational or mitotic. Dodge was at a loss for an explanation of the apparent second division segregation. Several of us, who had just been reviewing Bridges' and Anderson's evidence for four-strand crossing over in Drosophila, suggested the explanation - crossing over between the centromere and the segregating gene pair. This was my first introduction to Neurospora.

A year or so prior to this, Dodge was insisting to T.H. Morgan, then at Columbia University, that Neurospora was a more favorable organism for genetic studies than was Drosophila. Finally, after much persuasion, for Dodge was a most enthusiastic and persistent persuader, Morgan was induced to take some Neurospora stocks and try them. He carried them to the California Institute of Technology, on occasion transferring them to new culture media, as instructed by Dodge.

Soon thereafter, there appeared a young man who proposed to do graduate work in Morgan's new Division of Biology at Caltech. It was Carl C. Lindegren. Morgan asked his background, and when Lindegren said "Bacteriology," it was suggested he work on the genetics of Neurospora. In 1931 when I arrived at the California Institute of Technology, this work was in full swing.

On nearing the completion of my graduate work at Cornell, I had applied for, and was awarded, a National Research Council Fellowship. But there was a condition. I had proposed to remain at Cornell, for I wanted to continue with corn cytogenctics and thought Cornell was the best possible place to do so. But the Chairman of the Fellowship Committee, then Professor C.E. Allen of the University of Wisconsin, had other views. He and his Committee believed a change of institution was good in principle and said I could have the fellowship if I would elect my second choice, namely, the California Institute of Technology.

I have had many occasions to thank that Committee, not because Cornell was not a good place, but because a change of laboratories was the best thing that could have happened in my case. Ever since, I have argued that moves to different institutions after undergraduate work, after graduate work, and after postdoctoral work are much to be desired, other things being anywhere near equal.

Before leaving Cornell, H.S. Perry and I had worked out what we - I, at least - thought was a marvelous theory of crossing over. In brief, it held that chiasmata arise by pairwise separation of the four chromatids in alternate planes - always reductional at the centromere and equational or reductional elsewhere - with subsequent breakage of the chiasmata at anaphase and recombination of the broken chromatids.

We corresponded with E.C. Anderson, then at Caltech, about it. He replied that he did not know about the hypothesis, but he was pleased to know that we at least understood the genetic facts of crossing over. Ours was a fine hypothesis, later elaborated and published by Karl Sax of Harvard University. Unfortunately it proved to be wrong.

On arriving at Caltech in early 1931, I was anxious to talk with C.B. Bridges about our hypothesis. I was almost overwhelmed at the thought of approaching such a distinguished and brilliant geneticist, for I thought he would be so quick of mind that I would not be able to keep up my end of the discussion. It was with much amazement and relief that I discovered Bridges to be not only most friendly but quite slow and methodical in our discussion. He insisted on going over each point carefully and fully before going on to the next one. With Sturtevant, Dobzhansky, Emerson, and Schultz, on the other hand, I was often quite lost, for those were the days of the so-called scute subgenes, Oenothera analysis, and translocations in Drosophila. My head often buzzed on listening in on conversations about scute-8, scute-4, gaudens-velans, hookeri and so on, but finally I learned the new jargon.

The early 1930s were depression days and laboratory work was done at minimal expense. I recall that Sterling Emerson and I once needed a Harvard trip balance - cost about ten dollars. We were certain that Morgan would not approve such an expenditure, for he knew that geneticists did not need elaborate equipment of that kind. So we persuaded James Bonner to request it and then give it to us. He was a plant physiologist and really did need things of that kind.

I soon discovered that Morgan was likely to be in his most agreeable mood on Sunday mornings, when he could work in his small downstairs laboratory on Ciona. It was on such an occasion that I got him to approve the purchase of a new 90X achromatic oil immersion objective for the research microscope I was using. That was indeed a triumph.

Speaking of Morgan, I well recall the occasion on which my morale was given a substantial boost. I had shown a manuscript on sticky chromosomes to Sturtevant. After reading it, he asked, "May I show this to the Boss?" To me this was a high compliment, for Morgan, who was affectionately known as "The Boss" by close associates both at Columbia University and at Caltech, did not by any means have every manuscript referred to him. As an indication of the depth of the affection with which the term "the Boss" was held, several years after Morgan's death a postdoctoral fellow at Caltech who had been a graduate student in our laboratories at Stanford continued to refer to me by that term; he was promptly told, "That term is never to be used in this laboratory for anyone other than Doctor Morgan!"

In 1934, Boris Ephrussi came to Caltech to work on embryology and genetics of mice, using transplantation technics There were times of much talk about gene action, with such questions being asked as whether aU genes act all the Cime. Morgan had just published a book, Embryology and Genetics. I remember Ephrussi once commenting that the difficulty was just that embryology and genetics - for the organisms investigated by the two branches of biology were not the same. The classical organisms of embryology - sea urchins, for example - were not favorable for genetic study and those favored for genetics, like Drosophila, were difficult embryologically.

We thought something should be done about it and finally proposed that we each gamble up to a year of our lives trying to do it. I would try this in Ephrussi's laboratory in Paris. Morgan inquired informally of the Rockefeller Foundation officers whether they might consider supporting me during such a venture. The reply was that this could not be done on the required short notice, for none of the fellowship officers had met me, and that was a requirement. Morgan thereupon said Caltech would pay my salary - the welcome sum of $1,500 per year - if I could manage. By leaving my family in a house renovated by me and provided rent-free by Caltech at the "corn farm," I could manage, by living on approximately two dollars per day in Paris. I do not know, but I have often suspected that Morgan personally provided the $125 per month.

I arrived in Paris in May, 1935, and we immediately began to attempt to culture Drosophila tissues. This proved technically difficult; so, on Ephrussi's suggestion, we shifted to transplantation of larval embryonic buds destincd to become adult organs. We sought advice from Professor Ch. Perez of the Sorbonne, who was a widely recognized authority on metamorphosis in flies. He said we had selected one of the worst possible organisms and that his advice was to go back and forget it. But we were stubborn and before many weeks had devised a successful method of transplantation. The first transplant to develop fully was an eye. It was the occasion for much rejoicing and celebration at a nearby cafe. In this way, we confirmed the nonautonomous development of eye-pigmentation that Sturtevant had earlier discovered for the character vermilion eye in gynandromorphs.

Before long, we had established the existence of two diffusible eye-pigment precursors that we believed to be sequential in the formation of the brown component of eye pigment, according to the scheme

This was the beginning in our minds of the one-gene-one-enzyme concept, but we did not then use that expression.

At the end of 1935, Ephrussi and I returned to Caltech and continued our transplantation work in collaboration with C.W. Clancy. In the fall Ephrussi returned to Paris and I moved to Harvard University as an assistant professor. We both attempted to determine the origin and nature of the diffusible pigment precursors, which we then called hormones because they were produced in one part of the body and had their effects elsewhere.

It was busy year, for I not only gave the lectures in the botany semester of the general course in biology but also managed to get a respectable amount of research done. In March of 1936 I was invited to accept a professorship in the School of Biological Sciences at Stanford with superb provisions for research support. The decision whether to accept was drawn out over a period of weeks. During this period, I sought the advice of Edward M. East, Professor of Genetics. I shall never forget the discussion.

"The fellows at Stanford seem to think they want me to join them," I said.

"Well, what do you want me to say about it?" East asked.

"I just want to know what you think about it."

"Oh, you want to know what I think of it? Well, I'll tell you what I think of it. Stanford never was any good, it isn't any good, and it never will be any good. That's what I think about it."

A month later, after the decision to move, East came to my laboratory and said, "Beadle, I knew you were going to Stanford." East was a fine friend and colleague. As those who had the privilege of knowing him appreciate, his gruffness and extravagant manner of speech was purely synthetic, deliberately cultivated to spur students and colleagues to greater efforts.

My nine years at Stanford were both pleasant and productive. Charles V. Taylor, Dean of the School, possessed boundless energy, enthusiasm and confidence. He had in fact promised support for research beyond his financial resources. But his confidence stood him in good stead, for after I accepted he immediately applied to the Rockefeller Foundation for the research support he had promised. I have often wondered what he would have done had the Foundation declined to make the grant. I am sure he would have found a way out. With the funds provided we built laboratories, equipped them and induced Edward T. Tatum to accept a position as Research Associate.

We spent three years trying to identify eye-pigment precursors and came pretty close to doing so. Tatum had in fact obtained an active substance as a product of bacteria metabolism of tryptophan. It was kynurenine esterified with sucrose, but because of the molecu1ar weight of the complex we failed to identify it. Butenandt in Germany did so by testing known relatives of tryptophan, an approach that is obvious in retrospect.

During the course of this work Tatum's late father, Arthur Tawrie Tatum, then Professor of Pharmacology at the University of Wisconsin, visited Stanford. On this occasion he called me aside and expressed concern about his son's future. "Here he is," he said, "not clearly either biochemist or geneticist. What is his future?" I attempted to reassure him - and perhaps myself as well - by emphasizing that biochemical genetics was a coming field with a glowing future and that there was no slightest need to worry.

In 1940 we dccided to switch from Drosophila to Neurospora. It came about in the following way: Tatum was giving a course in biochemical genetics, and I attended the lectures. In listening to one of these - or perhaps not listening as I should have been - it suddenly occurred to me that it ought to be possible to reverse the procedure we had been following and instead of attempting to work out the chemistry of known genetic differences we should be able to select mutants in which known chemical reactions were blocked. Neurospora was an obvious organism on which to try this approach, for its life cycle and genetics had been worked out by Dodge and by Lindegren, and it probably could be grown in a culture medium of known composition. The idea was to select mutants unable to synthesize known metabolites, such as vitamins and amino acids which could be supplied in the medium. In this way a mutant unable to make a given vitamin could be grown in the presence of that vitamin and classified on the basis of its differential growth response in media lacking or containing it.

There was never any slightest doubt that this approach would be successful - in my mind at least - for we had complete confidence in the one-gene-one-enzyme hypothesis. The only question in doubt was the frequency of the kinds of mutations we were in a position to produce and identify with the metabolites and methods available to us. The mutants came, first one requiring thiamine, then pyridoxine, and soon paraaminobenzoic acid.

These results were reported at the 1940 American Association for the Advancement of Science meetings in Dallas, Texas. I recall vividly the discussion period, where a fellow scientist we knew well commented that either we were incredibly industrious or he would have to be skeptical. I strongly suspect he did not believe the results. The hypothesis seemed much too simple to him, a view I shall have occasion to refer to again.

It was clear to us that we had an approach capable of adding rapidly to our understanding of the relation of genes and specific known chemical reactions. It was equally clear that we would require additional financial support. The need for such support posed an interesting problem. Three years earlier, the experimental biology group at Stanford headed by C.V. Taylor had applied for a large grant from the Rockefeller Foundation. It was made: $200,000 for ten years, with a stipulation we were not to apply for more for a period of ten years. The Foundation knew Taylor well!

That meant we could not properly ask for further support from the Rockefeller Foundation. The Research Corporation seemed a logical possibility. So in 1941 I went to New York to see Frank Blair Hanson of the Rockefeller Foundation to tell him that I knew of the ten-year pact and to ask if there were any objection to my going to the Research Corporation for additional funds. Of course he said there was no objection.

On the same day, I went to see Howard Andrews Poillon at the Research Corporation and told my story. He called in Robert Waterman. Not knowing he was the Waterman of Williams and Waterman vitamin B-1 fame, I retold the story. Waterman was ahead of me and tremendously enthusiastic. He and Poillon said they would give support - $10,000 right off.

At that point there was a telephone call for me. It was Hanson, who said he had been thinking that, since the Rockefeller Foundation had got us started, they might give added support, despite the pact. Poillon and Waterman said that was only reasonable and proper; and that I should by all means go back to Hanson. They said I should send the Research Corporation a carbon copy of our application to the Rockefeller Foundation and that, if the grant were not made, they would promise then and there to make the grant. That was a marvelous example of foundation flexibility and speed of decision. The Rockefeller Foundation made the grant without delay. This plus further grants enabled us to invite David M. Bonner, Norioan H. Horowitz and Herschel K. Mitchell to join our group and to move forward with dispatch.

In 1945 I held a Sigma Xi National Lectureship under which I gave lectures on biochemical genetics and the one-gene-one-enzyme interpretation. I was much impressed with the resistance to this notion, especially in agricultural colleges where workers were familiar with the genetics of such characteristics as egg production, and milk production in dairy cattle. They were sure gene action could not be generally described in the simple way we had postulated. It seems to me the status of the concept dropped to an all-time low at the Cold Spring Harbor Symposium of 1951. In rereading the volume on those meetings, I have the impression that the number whose faith in one-gene-one-enzyme remained steadfast could be counted on the fingers of one hand - with a couple of fingers left over.

I have several times been asked when the one-gene-one-enzyme hypothesis was first proposed and by whom. I have thought about this question many times and have reread a number of papers to see if I could discover the answer. I have not been successful. The first reference in so many words that I know of is in a review of biochemical genetics that I wrote for the 1945 volume of Chemical Reviews. I am sure Ephrussi and I had the concept in mind. Clearly Tatum and I also had when we planned our Neurospora work. I have read it into the papers of A.R. Moore, L.T. Troland, R.B. Goldschmidt, S. Wright, J.B.S. Haldane and others. Prior to any of these, A.E. Garrod was quite clear in his view that an enzyme concerned with the cleavage of the ring of 2,5-dihydroxyphenylacetic acid (homogentisic acid) is controlled by a gene. One must remember that the protein nature of enzymes was not clearly demonstrated until 1926 when J.B. Sumner crystallized urease. Even then the evidence was not widely accepted for several years.

Why was Garrod's work unappreciated and forgotten? It was well known to Bateson and he referred to it in his 1909 Mendel's Principles of Heredity. W.E. Castle's textbook, Genetics and Eugenics, 1920 edition, lists Garrod's 1902 paper on alcaptonuria in the bibliography but does not refer to it in the text. Thereafter it seems to have been dropped from all standard textbooks of genetics, until 1942 when J.B.S. Haldane in New Paths in Genetics discussed alcaptonuria in the context of phenylalanine-tyrosine metabolism and its genetic control.

I referred to this remarkable situation in a seminar at the University of California some years ago and pointed out that these derelict textbooks included Sturtevant and Beadle's 1939 An Introduction to Genetics as well as Goldschmidt's 1938 Physiological Genetics. Following my presentation, Professor Goldschmidt explained to me that he could not understand how this could have happened in his case, for he had known of Garrod's work and had referred to it in his own earlier works. It seems clear that Goldschmidt, like the many others who had read Garrod's papers and books, simply failed to see the significance of his view. He was in good company, for as Bentley Glass has recently pointed out, Muller referred to the analysis of alcaptonuria in 1922 without recognizing its basic significance.

It seems to me that, like Mendel, Garrod was so far ahead of his time that biochemists and geneticists were not ready to entertain seriously his gene-enzyme-reaction concept. Like Mendel's, Garrod's work remained to be rediscovered independently at a more favorable time in the development of the biological sciences. I strongly suspect that an important common component of the unfavorable climate for receptiveness in these two instances is the persistent feeling that any simple concept in biology must be wrong. Here are some classical examples of such concepts:

The synthesis of urea by Wohler.
Darwin's theory of evolution.
Mendel's principles of inheritance.
Garrod's gene-enzyme-reaction concept.
The crystallization of urease by Sumner.
The crystallization of tobacco mosaic virus by Stanley.
The transformation of pneumococcus by Avery, MacLeod, and McCarty.
The Watson-Crick structure of DNA.

In connection with the last of the examples listed, I have a vivid recollection of a 1956 discussion with two distinguished biochemists, X and Y, about the significance of the Watson-Crick structure of DNA. I was not making much of an impression. Finally I asked X, who I assume must be the "Old Chemist" in Erwin Chargaff's incredible essay Amphisbaena (in Essays on Nucleic Acid, Elsevier, 1963), "Do you believe that the Watson-Crick structure is essentially correct?" The amazing answer: "Yes, I think it is correct, but I don't think it has anything to do with replication."

Moral: Do not discard an hypothesis just because it is simple - it might be right.

Tell us about your favorite essay.

Endlinks

Phage and the Origins of Molecular Biology - edited by J. Cairns, G.S. Stent, and J.D. Watson. Cold Spring Harbor Laboratory Press's Web site has a description and the table of contents.

George W. Beadle - a brief biography of Beadle. This page is maintained by the Institute Archives of the California Institute of Technology, which holds Beadle's papers.

Protocols on the Internet - links to nearly two dozen molecular biology protocol resources.

Molecular Biology of Bacteriophage T4- edited by J.D. Karam. The sequel to the 1983 edition, this Blackwell Science textbook "highlights the value of this biological system as a research and teaching tool." This page lists the contents and has a link to related books.

How Scientists Think :Twenty-One Experiments that Have Shaped Our Understanding of Genetics and Molecular Biology - by George B. Johnson. A book of discussions of classic experiments that illustrate scientific logic. This page contains the table of contents and an excerpt from the preface.

National Center for Genome Resources - NCGR facilitates the sharing of resources in public and private genome research and policy development.

Survey of Molecular Biology Databases and Servers - a "list of lists" (with links) of databases and servers, including SWISS-PROT and MEDLINE. Some servers link between multiple databases.

Model Organism Databases - links to more than 50 organism databases from the Sanger Centre. (Note: The Sanger Centre was an HMS Beagle Webpick for July 3.)

History of Genetics Timeline - major events in the history of genetics, from the populational to the molecular level.

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