From Wahoo, Nebraska to the Nobel Prize—George Beadle and His Work

Nov 4, 2020 by

In this series of interviews about Molecular Biologists, Manuel Varela and Ann Varela discuss George Beadle and his many contributions to molecular biology.

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https://en.wikipedia.org/wiki/File:File-AMNHBeadletatum.jpg

Beadle and Tatum‘s prize commemorated on the monument at the American Museum of Natural History in NYC.

Michael F. Shaughnessy

1) First of all, George Beadle was born in Wahoo, Nebraska—where exactly is Wahoo, Nebraska. And when was he born and where did he go to elementary school?

Dr. George Beadle is best known for his discovery that one gene specifies the production of a protein, which later became known as the famous “one gene-one protein” hypothesis. Beadle was born on October 22, 1903, on a farm near Wahoo, in Saunders county, in eastern Nebraska. Beadle’s parents, Chauncey Elmer Beadle and Hattie Albro, owned and worked a 40-acre farm near Wahoo, Nebraska. Their main crop consisted of potatoes, asparagus, and strawberries. At some point, they even kept bees. When Beadle was only five years old, his mother died. It is unclear where he attended elementary school, but it is known that he attend Wahoo High School. Beadle’s hobbies include gardening, rock-climbing, and skiing. His childhood friends called him “Beets.”

2) As an alumnus from the University of Nebraska-Lincoln, I (M.S.) am proud to say that he attended the University of Nebraska-Lincoln. Exactly when did he attend, what did he study, and under whom did he study?

Despite the reluctance of Beadle’s father to send his second son to college, Beadle went to the College of Agriculture in Lincoln, Nebraska, and completed his Bachelor of Science degree, in 1926, from Beadle’s beloved University of Nebraska. In 1927, Beadle completed his Master of Science degree from the University of Nebraska, under the direction of Professor F.D. Keim.

3) And his graduate work? Beadle later moved to New York to study at Cornell—what did he study there?

Between 1927 and 1931, Beadle was a teaching assistant at Cornell University with Professors R.A. Emerson and L.W. Sharp. Beadle focused his studies on Mendelian asynapsis in Zea mays. Beadle took his Doctor of Philosophy degree for this work in 1931. The title of his Ph.D. thesis project was “Genetical and Cytological Studies of Mendelian Asynapsis in Zea mays.”

The first encounter between Beadle and corn occurred in early 1928 as a second-year graduate student at Cornell University’s College of Agriculture. Unfortunately for Beadle, he had been, at first, assigned in the fall of 1926 to work in the ecology department under Professor Herbert Press Cooper. The expertise of the latter was in the area of grassland ecology.

Beadle’s burgeoning interest in corn research, however, was sparked by three major early influences. First, he had an intrinsic interest in cytology and genetics from his undergraduate school years. In graduate school, he had been influenced by the enthusiasm of students who were members of Professor Rollins Adams Emerson’s group discussions of corn genetics. Dr. Emerson was the newly appointed dean of the Cornell Graduate School and professor and chair of the plant breeding department. In the meantime, Beadle had already spent about two less-than-satisfying years working under Dr. Cooper. A third influence was his time spent in a graduate course on plant genetics taught by the inspiring Professor A.C. Fraser. His conversion all but complete at the start of the spring semester in 1928, Beadle transferred to the department of plant breeding, where Dr. Emerson’s field laboratory was stationed.

Sponsored a graduate fellowship under Professor Emerson, the newly arrived Beadle was trained by another graduate student named Barbara McClintock, who was a year older than Beadle but already widely recognized by fellow graduate students and faculty alike as being a true genius. McClintock showed Beadle how to plant, cultivate, and study corn. Beadle’s training by McClintock included learning how to remove or cover corn tassels and stigmas to prevent unwanted pollination. He learned how to pollinate the corn plants artificially. Moreover, McClintock showed Beadle how to collect corn ears, label the kernels properly, and keep meticulous records of their research activities. Importantly, McClintock taught Beadle how to perform her famous acetocarmine dye staining and smear technique for preparing corn chromosomes on microscope slides.

A third project, involving corn genetics, dealt with a new mutant corn plant. The new mutant was defective in several later steps of meiosis. Thus, the mutant corn appeared to be affected by more than one genetic locus. It was consequently called polymitotic. As before, Beadle performed the same techniques he learned from McClintock. The resulting genetic crossings showed that the sterility defect seemed to occur at a later step in meiosis, presumably after synapsis. He had attributed the defect in the mutant plant to a related factor, which regulated the timing of cell division and the growth patterns of corn. Beadle published the results in a preliminary paper in Science in 1929 as a single author and later in 1930 with a complete genetic analysis.

Beadle, still a graduate student, conducted another corn study, which could not be included in his thesis due to the type of funding available for the project. The study involved the relationship between a wild Central American or Mexican corn variety, called teosinte, and the corn that he studied as a graduate student in the Ph.D. program at Cornell. The project would later feature prominently during the notorious Corn Wars.

4) Mendelian asynapsis was one area of investigation. We all hopefully studied Gregor Mendel in high school biology—but what is meant by Mendelian asynapsis?

Beadle would make tremendous contributions to the molecular biological study of corn, also known as maize. Mendelian asynapsis is one of these contributions, and it occurred early on in his scientific career. The term refers to the inability of newly made chromosomes to pair together during meiosis when corn was undergoing reproduction. Thus, the inability to synapse is referred to as “asynapsis,” and it was a process that was affecting corn.

At Cornell, the remarkable Barbara McClintock and Beadle conducted a research project together as graduate students. They were interested in understanding the genetic nature of corn plants that mutated into a sterile form. These corn mutants could not make mature anthers on their tassels, or could not produce pollen, or perhaps both. Beadle and McClintock self-pollinated plants that contained one mutated allele and planted the resulting kernels after the artificial plant mating techniques were performed. The graduate students then examined the pollen-producing cells under the microscope. The results showed that the cells were abnormally developed in their chromosome morphologies. Under the scope, the chromosomes of the corn mutants failed to pair up together during meiosis, as would be expected for normal corn cells. Beadle and McClintock interpreted these data as an inability of the sterile mutants to produce pollen. They further concluded that during meiosis, the affected genetic element responsible for the corn sterility had failed to permit chromosome pairing, a process called synapsis. Therefore, Beadle and McClintock named the affected corn gene asynaptic, for its inability to undergo synapsis. They published their work together in the prestigious journal Science in 1928, with Beadle as first-author. The report was to be Beadle’s first scientific publication after having arrived at Cornell two years earlier.

Beadle’s second project dealing with corn involved a follow-up study of the corn sterility phenomenon, a project carried out without McClintock. At the time, she had felt that Beadle was sufficiently trained and could continue the work independently. In contrast, Beadle understood the situation differently. He had felt somewhat abandoned and still dependent upon McClintock for her expertise, especially with her famous invention for preparing the chromosome dye. Nevertheless, Emerson seemed to agree with McClintock, and Beadle continued on his own.

Beadle spent the next two planting seasons examining the genetics of the asynaptic mutant corn plants from a Mendelian perspective, examining the cytological outcomes of new generations involving crosses with normal corn plants. Beadle confirmed the heterozygous recessive nature of the allelic mutation and published the full account on the genetics of the mutant on his own in 1930.

Beadle’s scientific exploration of corn would span decades. He had begun with his graduate thesis work on corn genetics. He ended up with his entry into the so-called “Corn Wars,” involving a massive investigative effort to the study of corn evolution, the latter of which was conducted after his retirement.

5) He taught genetics at Harvard (not too shabby for a cornhusker from Nebraska). How long was Beadle there, and what did he study?

In 1936, Beadle accepted a teaching position at Harvard University. He remained there as Assistant Professor of Genetics for only one year. Before that, between 1931 and 1936, Beadle had been at the California Institute of Technology in Pasadena, CA, having studied corn and crossing-over in fruit flies.

At Harvard, Beadle was unhappy. He fretted about getting his research and teaching programs established. Beadle worried about funding, such as those for his salary, equipment, and supplies. He also worried about having enough laboratory workers. While he was, to his surprise, funded quite adequately, he failed to garner research successes in the laboratory.

Working with another new Harvard faculty member, Dr. Kenneth V. Thimann, they set out to identify and purify the biochemical agents responsible for producing eye colors of the fruit flies. These were agents that Beadle had been studying in Thomas Hunt Morgan’s famous laboratory, the “fly room,” at Columbia University. Two of these agents were called vermillion (v substance) and cinnabar (cn substance), and they were believed to convey a bright red eye color. Thimann and Beadle used so-called “tester flies,” which were mutants incapable of producing one or another of the eye colors or perhaps even no eye color, making the eyes of their flies pale in appearance.

They managed to purify several candidate biochemicals in the laboratory. They injected these agents into the larvae of the mutant lab flies, the testers, hoping to generate new eye colors in the fly testers. In short, they failed to produce flies with the desired vermillion and cinnabar colors. Beadle and Thimann reasoned that the v and cn substances were not proteins or fats in their nature. Thus, they predicted that the candidates were amino acids. Thus, they injected each of the known amino acids into their tester flies, but none of them reproduced the eye colors. Therefore, unfortunately, they were unable to isolate the eye color-producing biochemicals. It was a significant disappointment. The Harvard experience was not a positive one for Beadle. It was an outcome that his colleague Alfred H. Sturtevant had predicted before Beadle had accepted the Harvard offer.

After Harvard, Beadle was selected for a position as Professor of Biology, specifically, Genetics, at Stanford University in 1937. This tenure lasted for nine years before returning to the Caltech campus in 1946 as Professor of Biology and Chairman of their Biology Division.

In January 1961, Beadle moved to the Midwest, and he was voted Chancellor of the University of Chicago. By the fall semester, he had become the University President.

6) His big collaboration seemed to be with Edward Lawrie Tatum—how would you describe their collaboration?

Beadle’s Nobel Prize-winning work with Edward Tatum entails their discovery that a gene specifies the production of a protein. Beadle and Tatum had been interested in how genes, proteins, and biological traits related to one another. Feeling somewhat dissatisfied with the Drosophila melanogaster fly as a model organism for studying the gene’s functional nature, Beadle and Tatum turned their attention to a fungus, called Neurospora crassa, a microorganism with features that proved beneficial to the advancement of genetics and later to molecular biology. See Figure 4.

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Figure 4. Neurospora crassa fungus.

First, the microbe was relatively easy to culture in the laboratory for closer study. The nutritional requirements were clearly defined and simple in their manipulation in culture. It was an extensively studied organism, with readily discernable morphological structures within its various developmental stages. For instance, Neurospora crassa formed distinctive spore pair numbers indicating whether recombination occurred during crossing experiments using different mutants. Many mutants of the fungus could be generated with ease if suitably coaxed to do so with physical mutagens, such as ultraviolet (U.V.) light. Lastly, the metabolic behavior of the mutants could be evaluated in the laboratory. Various biochemicals that were newly purified and available could be added back to their culture media and mutant growth measured with ease.

Figure 5. The first step of Beadle and Tatum experiment: mutagenesis of Neurospora crassa.

Beadle’s experimental design would prove advantageous in his study of the hypothesis that the gene directs the production of an enzyme. The methodology involved first exposing the fungal spores to doses of X-rays and U.V. radiation. See Figure 5. Next, Beadle and Tatum permitted the irradiated mutagenized fungal spores to germinate. Then, they plated the germinating mutant in a variety of culture media. See Figure 6.

Figure 6. Next, Beadle and Tatum grew mutants and transferred each auxotroph to various culture media.

One especially important culture medium was minimal media, which consisted of various salts, a buffer, and one of many biochemical agents, such as amino acids, sugars, nucleic acids, fats, vitamins, etc. See Figure 7. Then, if a mutant of a type called an auxotroph failed to grow on any of these minimal media cultures, the missing necessary nutrient could then be added back systematically. Thus, if the added nutrient recused the mutant by its reacquisition of growth, then the rescued mutant could be hypothesized to have the gene responsible for utilization affected. It would be the first case in scientific history that a gene was involved in the metabolism of a rescuing biochemical. In other words, a gene was experimentally associated with a gene product, let say an enzyme. The gene was directly connected to the production of a dedicated enzyme. The work was a bombshell with ramifications that spread like wildfire throughout the scientific world.

Beadle and Tatum found individual genes important in the biochemistry of many amino acids, sugars, and vitamins. The list of genes that specified putative enzymes involved in their biochemical pathways grew with each round of mutagenesis, germination, plating, culturing, nutrient testing, and analysis of the genetic patterns. With each round of studies, using their highly productive experimental process, Beadle and Tatum would be increasingly encouraged to conclude that a single gene controlled the biosynthesis in the cell of a single enzyme.

Figure 7. Beadle and Tatum culture auxotroph fungal mutants on supplemented minimal media.

Though Beadle and Tatum never quite stated it precisely in these terms, the so-called “one gene codes for one enzyme” hypothesis would be attributed to the two scientists. It would form the basis of a Nobel for them. When their work was published in 1944, the one-gene/one-enzyme theory flew in the face of many contemporary geneticists, who were under the impression that many genes were needed to specify one trait.

Time would vigorously test the one-gene/one-enzyme hypothesis, and it resulted in several revisions for subsequent studies to be rectified with the original notion. First, it was discovered that the gene could encode more than merely an enzyme. The gene could encode a protein that was not an enzyme, like a structural or a regulatory protein, for instance. Secondly, as the geneticists had hoped, a fully intact protein for a trait might be composed of two or more individual proteins, called polypeptides. Thus, it was more accurate to conclude that a gene encodes a polypeptide, rather than a fully functional protein. Therefore, more than one gene could specify a product. Along these lines, certain traits did require the participation of several gene products to express those characteristics. Fourth, genes don’t necessarily have to encode proteins, per se. For instance, a given gene might code for a functional RNA molecule, instead. Transfer (tRNA) is just one example. When charged with dedicated amino acids, the tRNA molecules bring these building blocks to the translational apparatus to make proteins. Lastly, one genetic element could encode several different gene products. In this case, once mRNA is transcribed from a gene, the newly made RNA could cut and re-splice its various broken segments to produce dissimilar RNA forms and thus make different polypeptides, a process called alternative splicing.

Nevertheless, the work of Beadle and Tatum in which they discovered that a gene directs the expression of a protein, would lead future investigators to refine the one-gene/one-enzyme concept. The astonishing discovery of Beadle and Tatum would also lead to the advancement of new avenues for biochemistry and especially of molecular biology. Specific genes could be implicated in the disruption of specific biochemical defects, say for a nutritional mutant, like a defective ability to utilize an amino acid, a sugar, or a vitamin. The list of metabolites and their genes responsible in their biochemistry would be limitless. The work of Beadle and Tatum would also lead to the cloning of genes with the advancement of recombinant DNA technology, and gene cloning, in turn, would pave the way for genetic diseases to be studied in molecular detail. The molecular biological advances would lead to genomics, bioinformatics, gene therapy, and genome editing. These various sciences will undoubtedly continue to advance as new studies reveal newer discoveries of a molecular nature.

7) And he spent time in Paris, France, amazingly—Who did he study with and what did he study there?

Between 1931 and 1936, Beadle was awarded a National Research Council to support his research, which included work on Indian corn and work on crossing-over in fruit flies. Beadle visited in 1935 and began a six-month collaboration with Professor Boris Ephrussi at the Institut de Biologie Physico-Chimique, in Paris, France.

At the postdoctoral level, Beadle followed-up on his earlier polymitotic study he had conducted as a graduate student. He discovered that the nature of the mutations involved their proximity to two distinctive genetic elements, which, in turn, were closely linked to each other on the chromosomes of the mutant corn plant—these linked genes specified kernel color, such as purple or yellow.

8) Drosophila—the fruit fly—why did he study this small fly, and what did he learn about this particular fly? Why is it important?

Beadle had become a postdoctoral fellow at California Institute of Technology, in Pasadena, CA. Beadle studied fruit flies shortly after starting the new position, working under Professor Thomas Hunt Morgan.

Dr. Morgan had moved his famous “fly room” laboratory at Columbia University to Cal Tech, where Beadle joined Morgan’s fly group. Professor Morgan was a 1933 Nobel Laureate well known amongst geneticists and cell biologists as having provided sound evidence for Gregor Mendel’s theory of chromosome segregation and Mendel’s law of independent assortment of genes between different chromosomes. Morgan also discovered that during meiosis, a process involving crossing over occurred, substantiating the idea that closely linked genes favored enhanced genetic recombination between genetic elements.

In Morgan’s lab, Beadle studied the crossing-over phenomenon in the Drosophila melanogaster fruit fly with Alfred H. Sturtevant and Boris Ephrussi. Previous investigators William Bateson, Muriel Wheldale-Onslow, and Rose Scott-Moncrieff inspired the experimental approach adopted by Beadle and colleagues. The process involved crossing genetic mutants of flies with various shades of eye color, examining the outcomes upon the new generations on the eyes, and identifying the biochemical agent responsible for conferring the colors of fly eyes. They studied flies with distinctive eye colors, such as brown (wild type), vermillion, cinnabar, and white.

Unfortunately, the initial effort by Beadle and co-workers to grow fly eyes failed. The work had entailed excising tissues from fly head embryos where the eyes were supposed to emerge and then growing the tissue extracts in culture dishes. They were hoping to grow the eyes from lab flies in laboratory culture dishes. The attempt failed to work as Beadle and collaborators did not obtain eyes in their glass dishes.

Thus, Beadle, Sturtevant, and Ephrussi focused their attention on culture media, hoping that with the right combination of food, they might be successful. While that effort failed, too, it would help Beadle in future work with fungi. Meanwhile, they adopted a new experimental approach with the flies. The new method entailed cutting primordial eye tissue from embryo heads of genetic fly mutants and transplanting them onto the abdomens of recipient larval flies. Each donor and recipient harbored various mutant and wild-type eyes, hoping the new eye tissues would grow a third eye—on their fly abdomens!

Here, they grew new flies with three eyes, two on their heads, and the third eye on their abdomens. The new experimental design was more successful than their previous attempt to grow new eyes in the lab without their heads. The embryo fly tissue would grow on their recipient’s abdomens!

The resulting eye colors that emerged in the transplanted recipient flies would reveal which eye color was dominant or recessive, either the donor or recipient, the wild type, or one of the mutant eyes. It was an unusual experimental approach.

These experiments proved to be more fruitful. Beadle and colleagues transplanted various mutants with other mutants and the wild type flies, each with particular eye colors in the recipient abdomens of the new larva. Sometimes, a mutant eye color would dominate in certain recipients but not others. The resulting transplanted eye tissues provided a complex mix of outcomes. Next, they would add back candidate chemicals to replace the agent missing in certain fly mutants, hoping to identify the responsible eye color conferring chemicals. It was arduous work.

Accurately analyzing these complex data would successfully demonstrate the genius of Beadle, Sturtevant, and Ephrussi. They interpreted the eye color data by proposing a step-wise process of eye color production. That is, they hypothesized that one gene product would act first, and another gene’s product would act second, and so on, to produce the final eye color. In the case of the fly, Beadle and colleagues proposed that the substance produce by the vermillion gene worked first, then that of cinnabar worked next, and so on, such that in wild type flies, a brown color would be produced in the fly.

While the Drosophila melanogaster work helped elucidate the order of gene product function, it was fraught with its share of problems. When providing back the missing putative gene products, it was guesswork as to what the responsible substances were when eye colors were studied. Second, sometimes, they missed out entirely on the correct nature of the eye color material. When exposed to culture media with sugar, the eye color agent would be changed to form undetectable, missing out on isolating the agent entirely. Beadle never forgot this blunder. It would, however, help him later to win the Nobel.

9) The Nobel Prize was shared with another scholar—who did he share the Nobel with and for what discovery?

In 1958, the Nobel Prize in the category of medicine or physiology would be granted to Drs. Geoge Beadle, Edward Tatum, and Joshua Lederberg. The groundbreaking Nobel work of Beadle and Tatum was considered above. Lederberg had worked previously with Tatum, who was his graduate advisor at Yale University. In 1946 Tatum and Lederberg had found that bacteria contained genetic and behavioral characteristics indicative of sexual mating, a novel finding.

The Nobel work of Lederberg involved his studies of bacterial conjugation, also known as mating. He would show that conjugating bacteria could be exploited to map the locations of genetic elements which conferred certain metabolic properties, such as methionine and biotin synthesis. Then, in the early 1950s, Lederberg and Norton Zinder would discover the process of transduction, a method that bacteriophages used to infect Salmonella bacteria and inject foreign genetic determinants to confer amino acid synthesis. The Nobel work of Lederberg would prove useful for the development of genetic engineering technology in later years.

10) I know that he has received many honors on the campus of the University of Nebraska-Lincoln—but can you name a few?

Beadle’s accolades are numerous, including membership to the Member of the National Academy of Sciences (1944), the Albert Lasker Award of Basic Medical Research (1950), the Dyer Award (1951), the Emil Christian Hansen Prize of Denmark (1953), the Nobel Prize in Physiology or Medicine with E. L. Tatum and J. Lederberg (1958), the Albert Einstein Commemorative Award in Science (1958), the National Award of the American Cancer Society (1959), the Kimber Genetics Award of the National Academy of Sciences (1960), the Foreign Member of the Royal Society (1960), the Thomas Hunt Morgan Medal (1984), as well as numerous honorary D.Sc. from foreign and domestic universities.

11) What have I neglected to ask about this cornhusker from Nebraska?

Beadle has been married twice. He and his first wife, Marion Hill, a botanist, had a son named David, who lives in the Netherlands. His second wife, Muriel McClure, was a writer.

After the great scientist’s retirement as president of the University of Chicago in 1968, Beadle, who was 65 years old, picked up the hobby of corn, once again. Beadle had long been fascinated by the evolutionary origin of corn. It was a topic for which he had held a deep affection and occupied a great deal of his time as a graduate student at Cornell in the late 1920s and early 1930s. This time, however, in the late 1960s as a highly regarded Nobel Laureate and retired university president, he returned to the relationship between domesticated corn of the modern variety called Zea mays and the wild corn called teosinte. Beadle had postulated that teosinte was the parental ancestor of modern corn. A variety of ideas held Beadle’s notion in contention.

A large and vocal camp of investigators vigorously believed that the teosinte was not the ancestor of corn. Rather this group thought that corn and teosinte were two closely related modern varieties or even that wild teosinte arose evolutionarily speaking as a new variant of domesticated corn—that is, the exact opposite view maintained by Beadle. It was not yet experimentally demonstrated up to the late 1960s, when Beadle entered the fray, whether teosinte was the ancestor of corn. These different explanations of ancestral origins formed the essence of the Corn War, and it would last almost another 20 years before molecular studies would settle the matter. Both sides had their proponents and detractors, which frequently manifested themselves in print and, spectacularly, at scientific conferences, shouting matches, and dramatic walkouts during ongoing seminars.

Beadle’s idea, which he first published back in 1939, was that corn was a descendant from the wild corn called teosinte. That is, Beadle thought that teosinte was the ancient ancestor to modern domestic corn. While he had held the idea in his mind for years, he had not put it in print until he had read an article written in 1938 by Paul Christoph Mangelsdorf and Robert G. Reeves. The 1938 paper had claimed that an extinct variety of corn was the true ancestor. Reeves and Mangelsdorf proposed, furthermore, that the true corn ancestor was yet to be discovered. A third notion that teosinte emerged evolutionarily in more modern times, too novel to be the ancient ancestor to corn. Lastly, Mangelsdorf and Reeves had proposed the so-called “tripartite” hypothesis, which stated that teosinte was a hybrid formed by the combination of corn and a plant called by its genus Tripsacum.

Beadle began his arguments in favor of his idea that teosinte was the ancestral origin of domestic corn by pointing out that ancient peoples made popcorn out of teosinte. Beadle also claimed that, with some effort, the teosinte could be made edible. Towards this, Beadle found a way to process the teosinte and use the flour to make cookies, which he fed to this colleagues. The modern “experiment” did not work—the teosinte-based cookies tasted terrible!

To argue against the tripartite theory, Beadle pointed out the poor genetic relatedness of corn and Tripsacum. Furthermore, Beadle stated, the Tripsacum-corn hybrids were not likely to arise naturally, as Mangelsdorf and Reeves had claimed because the hybrids were so difficult to produce artificially.

At an impasse, Beadle invoked a three-pronged experimental approach to address the controversy. First, he sought to determine how related corn and teosinte were at the genetic level. Second, Beadle aspired to discover the functions of the genes that were distinctive to corn and teosinte. Lastly, he wanted to know whether he could artificially reproduce ancient ears of corn by hybridizing teosinte and primitive corn.

These three lines of investigations each required monumental effort. First, they tried to convincingly demonstrate relatedness between corn and teosinte. Thus, over 50,000 plants were cultured spanning three generations of hybrid corn and involving large plots of land. Beadle and colleagues studied the structural architecture of the so-called spikelet features of the hybrids. These spikelets would form the cobs and the kernels of the corn. They found that unrelated genes were responsible for the spikelet characters of the modern versus ancient corn plants.

To study gene function, mutant teosinte plants with modern corn traits were necessary, and the study required over two dozen laboratory workers and with 75 thousand corn plants grown with their seeds collected. The mutant hunt was epic in its scope. After several years of effort, they failed to find the badly needed mutants. A second push involved the help of Mexican scientists led by Dr. Mario Gutierrez, and their lab assistants, another 2 million seeds were collected and examined. Again, no teosinte mutants with modern corn genes were found.

Motivated by a public confrontation about the controversy with Mangelsdorf at a scientific conference in 1972, McClintock came out of recent retirement and entered the picture. She and her Mexican and Latin American collaborators quickly discovered the critical teosinte genomes that combined with those of modern corn. In particular, she and her group determined the genetic basis of the so-called knob structures known to associate with the chromosomes of corn and teosinte plants. Her data had supported the notion that teosinte and corn were genetically distinct, which was consistent with Beadle’s idea that teosinte was the ancestor of corn.

Unfortunately, the publications that resulted from these extensive investigations in the 1970s failed to convince Mangelsdorf and his followers. During the next 15 to 20 years, however, new molecular-based studies of gene and chromosome sequences and comparative analyses of these sequence data all pointed to Beadle’s hypothesis. The DNA sequence analyses definitively supported the idea that teosinte was the true ancestor of corn. Sadly, when one of these molecular biologists, a previous graduate student of Beadle’s, John Doebley, paid a visit to Beadle in 1980, the legendary pioneer of molecular biology was no longer fully lucid.

George Beadle died on June 9, 1989, in Pomona, California, from complications due to Alzheimer’s disease.

For detailed biographical information about the fantastic Beadle and a scholarship in his name, visit:

  1. Book: https://www.amazon.com/George-Beadle-Uncommon-Farmer-Emergence/dp/0879697636
  2. Scholarship: https://financialaid.unl.edu/george-beadle-scholarship-guidelines-2020-2021
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