THE JOURNAL OF BIOLOGICAL CHEMISTRY 2005 by The American Society for Biochemistry and Molecular Biology Inc Vol 280 No 12 Issue of March 25 p e9 2005 Printed in U S A Classics A PAPER IN A SERIES REPRINTED TO CELEBRATE THE CENTENARY OF THE JBC IN 2005 JBC Centennial 1905 2005 100 Years of Biochemistry and Molecular Biology Launching the Age of Biochemical Genetics with Neurospora the Work of George Wells Beadle George Wells Beadle 1903 1989 grew up on a 40 acre farm near the small town of Wahoo Nebraska Beadle might have become a farmer himself had it not been for the influence of his high school science teacher Bess MacDonald who persuaded him to enroll at the University of Nebraska College of Agriculture After earning a B S in 1926 Beadle remained at Nebraska to obtain an M A with Franklin D Keim Through his work with Keim Beadle became interested in fundamental genetics and was persuaded to apply to graduate school at Cornell University rather than return to the farm Beadle entered Cornell in 1927 and joined Rollins Adams Emerson s laboratory to work on the cytogenetics of maize Over the next 5 years he published 14 papers dealing with his investigations on maize all initiated while he was a graduate student at Cornell With the completion of his graduate work in 1931 Beadle headed off to the California Institute of Technology to work with future Nobel laureate Thomas Hunt Morgan There he became interested in Drosophila and began doing research on genetic recombination In 1934 Boris Ephrussi a Rockefeller Foundation Fellow from Paris came to Morgan s laboratory at Caltech to study Drosophila genetics Beadle and Ephrussi teamed up and began examining eye pigment development in Drosophila after devising a method for larval embryonic bud transplantation These studies were performed in Ephrussi s laboratory in Paris From these experiments they proposed that eye color changes in mutant strains of Drosophila could be caused by inactivation of specific proteins acting in a single biosynthetic pathway This suggested that development could be broken down into a series of gene controlled biochemical reactions and laid the foundation for the one gene one enzyme theory that Beadle would eventually propose and make famous The idea that specific proteins were produced by specific genes was first alluded to in 1909 by Sir Archibald Garrod an English physician Garrod proposed that alkaptonuria an inherited condition in humans in which the urine is black due to the presence of homogentisic acid was associated with a recessive gene Garrod called them Factors in some way responsible for the further metabolism of homogentisic acid In 1958 others showed that the liver of a patient with alkaptonuria was without measurable homogentisic acid oxidase activity 1 However the first explicit articulation of the one gene one enzyme phrase and probably the concept would have to wait until the 1940s when Beadle and biochemist Edward L Tatum performed several experiments with a simpler organism that confirmed the direct relationship between one gene and one enzyme In 1937 Beadle accepted an appointment as Professor of Biological Sciences at Stanford University and invited Tatum to join him as a research associate While auditing a course that Tatum was teaching on comparative biochemistry Beadle learned that although microbial species share the same basic biochemistry they differ in their nutritional requirements He reasoned that if these differences were genetic in origin it should be possible to induce gene mutations that would produce new nutritional requirements This would allow identification of the genes governing biochemical reactions that form known products For his experimental organism Beadle chose the red bread mold Neurospora crassa whose life cycle had been characterized making it an ideal organism for genetic study He and Tatum This paper is available on line at http www jbc org 141 Downloaded from www jbc org at University of California Berkeley on January 17 2007 An Inositolless Mutant Strain of Neurospora and Its Use in Bioassays Beadle G W 1944 J Biol Chem 156 683 690 142 Classics knew from the studies of others that Neurospora could grow on a minimal medium composed of a sugar salts and the one vitamin biotin Then they used x rays to attempt to produce Neurospora mutants that had lost the ability to grow on their minimal medium Beadle once recalled upon reflecting on these experiments We believed so thoroughly that the geneenzyme reaction relation was a general one that there was no doubt in our minds that we would find the mutants we wanted The only worry we had was that their frequency might be so low that we would get discouraged and give up before finding one 2 The 299th mutagenized culture they tested proved to be the lucky one It did not grow in their minimal medium but it did survive and grow when vitamin B6 was added To prove that a single gene had been mutated Beadle and Tatum performed a genetic cross between the mutant strain and a wild type strain and tested cultures derived from the eight single spores that were the progeny of a single meiosis Their tests showed that cultures from four progeny spores required vitamin B6 whereas the other four did not confirming that a single gene had been mutated 3 Before long mutants requiring amino acids purines and pyrimidines were also found and the science of biochemical genetics was born In the Journal of Biological Chemistry JBC Classic reprinted here Beadle discusses some of the practical applications in the isolation and characterization of one of his Neurospora mutants He and Tatum had produced five Neurospora strains that required inositol for normal growth and had established that each of these mutants was altered in the same gene Because mutant growth rate was a function of inositol concentration Beadle reasoned that any one of these mutants could be used to assay for inositol In the Classic Beadle focuses on one strain and shows that his bioassay is reproducible and fairly precise at quantitatively estimating inositol concentrations in a variety of natural materials Beadle and Tatum s Neurospora investigations further showed that the biosynthesis of any one substance is dependent upon the function of a set of nonallelic genes A mutation in any of these genes results in loss of synthesis due to the presumed inactivation of a single enzyme catalyzing a reaction in a multistep biosynthetic pathway Beadle summarized this concept in an
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