Beadle and Tatum

Neurospora crassa is a filamentous pink mould. It became famous to scientists due to the work of Beadle and Tatum in the 1940s when they developed the one gene—one enzyme hypothesis. Its life cycle is shown in Fig. 2.9. Unforturrately, the full force of fungal nomenclature comes into play when considering this organism. Aerial hyphae... 

The introduction of techniques for mutagenesis by UV irradiation or by the use of chemicals considerably extended the applications of microbial studies to nutrition (Davis, 1954-1955). Auxotrophic mutants were produced with nutrient dependencies not shown in the untreated parental strains (Beadle and Tatum, 1940). The fortuitous discovery of penicillin by Fleming and its successful use in the treatment of infections (Florey) promoted exhaustive research into its mode of action. Eventually it was established that penicillin prevented the proliferation of gram-positive bacteria by blocking the synthesis of their cell walls... 

An important feature in the mechanism of inheritance from the stand-point of our discussion lies in the existence of what have been inelegantly called "leaky genes" or less picturesquely "partial genetic blocks." Observation of a phenomenon of this sort was first made by Mitchell and Houlahanl in 1946 and was an outgrowth of the earlier pioneer studies on the genetics of Neurospora by Beadle and Tatum.2... 

Beadle and Tatum had found that irradiation of Neurospora spores produced mutants which were incapable of carrying out certain well-defined chemical reactions, and it was at first supposed that as a result of the destruction of a specific gene, the potentiality for producing a particular enzyme was completely lost. The "wild type" of Neurospora could propagate satisfactorily when biotin was the only vitamin-like substance supplied in the culture medium. Of the many mutant strains produced, however, one needed, in addition to biotin, the vitamin riboflavin. Without a supply of riboflavin in the culture medium this so-called "riboflavinless mutant" would not grow. Since riboflavin is a part of an enzyme system always found in Neurospora, it is an obligatory cell constituent and either has to be produced by the cells themselves (as in the wild type) or supplied exogenously in... 

If one combines the classical One Gene—One Enzyme hypothesis, which won Beadle and Tatum the Nobel Prize in rgsS, with the generally accepted view of most biochemists that every enzyme has evolved to convert one substrate to one product, it seems... 

Beadle and Tatum deduced the one gene-one enzyme relationship. 

The second major breakthrough was discovered by Beadle and Tatum (1941) with their conceptual one-gene-one-enzyme hypothesis. This proved the biochemical basis for the mechanism of gene action and integrated... 

Obviously, what Beadle and Tatum suggested is not an axiom but a rule, and certain situations just represent exceptions to their profound rule. It... 

The one-gene-one-enzyme hypothesis implied that a mutant must have altered the protein. Beadle and Tatum could not demonstrate the defective nature of the protein in their mutants because of the lack of technology at that time. However, this was demonstrated first at the biochemical level by Mitchell and Lein (1948, Mitchell, et al. 1948) and by Yanofsky (1952, 2005 a,b) in tryptophan, which required mutants of Neurospora that lacked... 

This theory proposed by Beadle and Tatum (1941) implied that the structure of an enzyme or a protein is controlled by one gene, in the sense that one gene encodes one protein. This theory became useful in understanding... 

Thus, because of the split nature of the eukaryotic genes, the Beadle and Tatum concept of gene-enzyme relation has to be modified, as one gene can create many proteins and could be written in the language of central dogma as... 

Thus, the central dogma is no more an axiom and that is true of Beadle and Tatum s one-gene-one-enzyme concept as well. Indeed they represent certain profound rules in biology. However, these rules have to be modified to accommodate new facts regarding the nature of gene as new facts emerge. 

Yanofsky, C. 2005a. The favorable features of Tryptophan synthetase for proving Beadle and Tatum s one gene—one enzyme hypotheis. Genetics 169, 511 -516. 

This book is being published on the occasion of the 52nd anniversary of the awarding of the Nobel Prize to Beadle and Tatum in 1958 to reflect the progress made in the understanding of proteins, which was started by the conceptualization of the one-gene-one-enzyme hypothesis that provided the tool for analysis of proteins. 

In 1941, George W. Beadle (1903-89) and Edward L. Tatum (1909-75), working at Stanford University, discovered that specific mutations of a bread mold, induced by X-rays or UV light, cause the mold to lose its ability to synthesize specific molecules such as pyridoxine (vitamin Bg). This led them to propose the one gene-one enzyme theory. At that time, the chemical nature of the gene was unknown, although proteins were the prime suspects. Beadle and Tatum would later share the... 

The observed rate of growth of a pyridoxine-requiring Neurospora mutant (Beadle and Tatum, 1941), as function of the concentration of pyridoxine in the medium. 

The points in Figure 1-2 represent my measurement of the slopes of the growth curves shown in Figure I of Beadle and Tatum (1941). They agree closely with the points of their Figure 2, except for one point, that for 1.2 /[Pg.563]

The reported growth rate for the normal strain in a medium with 40 /greater than that for the basic medium, as shown by the slopes of the lines in Figure 1 of Beadle and Tatum (1941). 

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