Non-Darwinian evolution

Comparative biochemical and immunological study of malic enzyme from two species of lactic acid bacteria: evolutionary implications

Representatives of both Streptococcus faecalis and Lactobacillus casei produce isofunctional malic enzymes. All 10 strains of S. faecalis tested could be induced to synthesize malic enzyme and readily adapted to growth on malate. Although 17 of 21 L. casei strains could be induced to produce malic enzyme, only 9 of 14 strains tested grew at the expense of malate. A comparison of catalytic and regulatory properties suggested that the malic enzymes from S. faecalis and L. casei were very similar. Immunological analyses showed that the numerous similarities in function actually reflected partial protein homologies; however, two distinct forms of the malic enzyme were detected among different strains of L. casei by immunochemical and serological procedures. The division of L. casei into two subgroups based on the immunological type of malic enzyme synthesized corresponds to two subspecies currently recognized by microbial taxonomists.

Induced mutations and barley improvement

Seven barley varieties, originating from three X-ray induced mutations, have been officially approved in Sweden since 1958. Some have gained a wide area of cultivation. The list is as follows: Pallas, isolated 1947, approved 1958, mutant ert-k (32) of Bonus barley. - Mari, isolated 1950, approved 1960, mutant mat-a (8) of Bonus. - Hellas, approved 1967, mutant cross of Pallas × Herta. - Kristina, approved 1969, mutant cross of Domen × Mari. - Visir, approved 1970, Pallas × Long Glumes back-crossed to Pallas. - Mona, approved 1970, mutant cross of Mari × Monte Cristo back-crossed to Mari. - Gunilla, approved 1970, hybrid cross of the mutant 44/3 arisen from Gull barley in 1939; evolved in a series of steps, using one six-row and four two-row varieties, with mutant characters prevailing and Gull genes reiterated. - After the first approval of Pallas in 1958, 12 more years have led to the approval of a second mutant case and five mutant crosses. In addition, chromosome translocations, induced by irradiation in Bonus, have been instrumental in the production of hybrid barley in USA and are used in the barley improvement program of Sweden, as well as for theoretical analysis in numerous countries.

Gibbon fibrinopeptides: identification of a glycine-serine allelism at position B-3

The fibrinopeptides A and B of the gibbon (an Asian ape) have been characterized and their relation to other primate types examined. An allelic situation was discovered at location B-3; two of the gibbons studied had both glycine and serine at that position, whereas four others were homozygous for glycine.

Evaluation of the effects of chemical mutagens on man: the long road ahead

By analogy with the problem of evaluating the genetic risks of radiation, it appears that it will be extremely difficult to assess the mutagenicity for man of the wide range of chemicals to which human populations are currently exposed. Nevertheless, the potential significance of this problem calls for a major effort at such an evaluation.

Fitness of an Escherichia coli mutator gene

Competition experiments between Escherichia coli mutT1 and mut(+) populations show that the mutator gene confers selective advantage on the strain that carries it. The observed increase in fitness varies, with an average increase in mutator growth rate of 1.4 percent when mutator and wild-type strains are grown together in chemostats.

Evolution of higher-organism DNA

A great deal of information about evolutionary events and processes has been inferred from careful studies of fossil records. Other forms of evidence have also contributed greatly to the understanding of evolution. Comparative biochemistry (Florkin, 1949), immunology (Boyden, 1942), protein sequencing (Dayoff, 1969; Anfinsen, 1959), and early DNA studies (McCarthy & Bolton, 1963; Schildkraut, Marmur & Doty, 1961) have for the most part corroborated earlier evolutionary findings, and at the same time provided new understanding of molecular processes in evolution. Of these approaches the comparison of DNA seems most promising since a relatively precise quantitative comparison can be made of all of the genetic material of different species.

Comparative immunological studies of two Pseudomonas enzymes

Crystalline preparations of muconate lactonizing enzyme and muconolactone isomerase, two inducible enzymes that catalyze successive steps in the catechol branch of the beta-ketoadipate pathway, were used to prepare antisera. Both enzymes were isolated from a strain of Pseudomonas putida biotype A. The antisera did not cross-react with enzymes of the same bacterial strain that catalyze the chemically analogous steps in the protocatechuate branch of the beta-ketoadipate pathway, carboxymuconate lactonizing enzyme and carboxymuconolactone decarboxylase. The antisera gave heterologous cross-reactions of varying intensities with the muconate lactonizing enzymes and muconolactone isomerases of P. putida biotype B, P. aeruginosa, P. stutzeri, and all biotypes of P. fluorescens, but did not cross-react with the isofunctional enzymes of P. acidovorans, of P. multivorans, and of two bacterial species that belong to other genera. The evolutionary and taxonomic implications of the findings are discussed.

A defect in pyruvate decarboxylase in a child with an intermittent movement disorder

A patient with an intermittent movement disorder has been found to have an inherited defect in pyruvate decarboxylase ((2-oxo-acid carboxy-lyase, E.C. 4.1.1.1.). The patient is a 9 yr old boy who since infancy has had repeated episodes of a combined cerebellar and choreoathetoid movement disorder. He has an elevated level of pyruvic acid in his blood, an elevated urinary alanine content, and less marked elevations in blood alanine and lactate. Methods were developed to study his metabolic abnormality in dilute suspensions of white blood cells and cultured skin fibroblasts, as well as in cell-free sonicates of fibroblasts. Oxidation of pyruvic acid-1-(14)C and pyruvic acid-2-(14)C by his cells and pyruvate decarboxylase activity in sonicates of his cells were less than 20% of those in cells from control subjects. Oxidation of glutamic acid-U-(14)C, acetate-1-(14)C, and palmitate-1-(14)C was normal, as was incorporation of alanine-U-(14)C into protein. The rate of oxidation of pyruvic acid by the father's cells and the activity of pyruvate decarboxylase in the father's sonicated fibroblasts were intermediate between those of the patient and those of controls. Values for the mother were at or just below the lower limits of the ranges in controls. Kinetic data suggested the posibility of several forms of pyruvate decarboxylase in this family. Possible mechanisms relating the chemical abnormality and the clinical symptoms in this patient are discussed.

Village and tribal genetic distances among American Indians, and the possible implications for human evolution

Pair-wise genetic distances based on six genetic systems (Rh, MNSs, Kidd, Duffy, Diego, and haptoglobins) are presented for seven villages of Makiritare Indians, seven villages of Yanomama Indians, and 12 Indian tribes of Central and South America. It is shown that the mean genetic distance between Indian villages is 85-90 per cent of the distance between tribes. Since in the past, the initial event in the formation of a new tribe was probably the breaking away of one or several related villages from an established tribe, it is clear that this initial event could have profound consequences for subsequent tribal gene frequencies. By the criterion of changes in gene frequency in polymorphic genetic systems, the maximal rate of evolution in the American Indian has been approximately 100 times more rapid than the mean rate suggested by calculations based on amino acid substitutions in certain polypeptides of a variety of organisms. The above-mentioned findings could account in part for this 100-fold difference. Some other factors which might diminish the apparent difference between the results of these two types of calculations are mentioned.

Hemoglobins A and A2 in New World primates: comparative variation and its evolutionary implications

Hemoglobin A(2) (alpha(2)delta(2)) in New World primates represents about 1/160 to 1/16 of total hemoglobin and, by virtue of this low proportion, is presumed to be functionally unimportant. Nonetheless, A(2) exhibits genetic polymorphism by electrophoresis in three out of five genera, whereas the major component, hemoglobin A (alpha(2)beta(2)), is electrophoretically invariant. Moreover, in four genera, including man, the evolutionary accumulation of mutations has been greater in delta than in beta Such findings suggest that both polymorphism and evolutionary changes can accrue to an effectively functionless and thus selectively nearly netutral gene.

The rate of molecular evolution considered from the standpoint of population genetics

The rate of amino acid substitutions in the evolution of homologous proteins is remarkably constant. Furthermore, estimated rates of amino acid substitutions based on comparisons of the alpha hemoglobin chains of various mammals with that of the carp are about the same as those based on comparisons of the carp alpha and mammalian beta or the alpha and beta chains in mammals. These uniformities are regarded as evidence for the hypothesis that a majority of amino acid substitutions that occurred in these proteins are the result of random fixation of selectively neutral or nearly neutral mutations. TWO IMPLICATIONS OF THIS POSSIBILITY ARE DISCUSSED: (a) Random gene frequency drift is playing an important role in determining the genetic structure of biological populations and (b) genes in "living fossils" may be expected to have undergone as many DNA base (and therefore amino acid) substitutions as corresponding genes (proteins) in more rapidly evolving species.