Showing papers on "Mutation (genetic algorithm) published in 1978"

Stepwise mutation model and distribution of allelic frequencies in a finite population.

Abstract: A mathematical theory is developed that enables us to derive a formula for the equilibrium distribution of allelic frequencies in a finite population when selectively neutral alleles are produced in stepwise fashion (stepwise mutation model). It is shown that the stepwise mutation model has a remarkable property that distinguishes it from the conventional infinite allele model (Kimura-Crow model): as the population size increases indefinitely while the product of the effective population size and the mutation rate is kept at a fixed value, the mean number of different alleles contained in the population rapidly reaches a plateau which is not much larger than the effective number of alleles (reciprocal of homozygosity).

A simple model for the balance between selection and mutation

Abstract: A model for the variation in time of the fitness distribution in a large haploid population is shown to have simple limiting properties which can be elucidated in fairly explicit terms. The novel feature is that mutation is not assumed to cause a small perturbation in fitness but to bring down the evolutionary ‘house of cards’. A threshold phenomenon appears: if a certain inequality holds the limiting distribution is a skewed version of the mutant fitness distribution, but otherwise an atom of probability builds up at the upper limit of fitness.

Environmental Mutagens and Carcinogens

Abstract: INTRODUCTION METHODOLOGY Mutation Tests Using Microbes .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . Repair test and rec-assay .. Mutation test .

Relative sensitivities of forward and reverse mutation assays in Salmonella typhimurium

Abstract: Forward mutation to 8-azaguanine resistance and reverse mutation to histidine prototrophy were measured in Salmonella typhimurium after treatment with 16 mutagens of both base-substitution and frameshift classes. The two approaches were found to be equisensitive for all 16 mutagens--i.e., induction of significant mutation occurred at similar concentrations in the forward mutation assay and in the most sensitive of the five Ames tester strains.

A suppressor mutation in the nematode acting on specific alleles of many genes

Abstract: A suppressor mutation has been isolated in Caenorhabditis elegans through reversion analysis of a muscle-defective mutant The suppressor mutation acts on specific alleles of at least six genes and in one case we have been able to show that it partially restores functional gene product to a mutant otherwise lacking that product These and other features of the suppressor suggest that it acts at some step in information transfer, perhaps through mechanisms similar to those described previously in microorganisms

The design of a prototype mutation system for program testing.

Abstract: When testing software the major question which must always be addressed is "If a program is correct for a finite number of test cases, can we assume it is correct in general. " Test data which possess this property is called Adequate test data, and, although adequate test data cannot in general be derived algorithmically, 1 several methods have recently emerged which allow one to gain confidence in one's test data's adequacy. Program mutation is a radically new approach to determining test data adequacy which holds promise of being a major breakthrough in the field of software testing. The concepts and philosophy of program mutation have been given elsewhere, 2 the following will merely present a brief introduction to the ideas underlying the system. Unlike previous work, program mutation assumes that competent programmers will produce programs which, if they are not correct, are "almost" correct. That is, if a program is not correct it is a "mutant"-it differs from a correct program by simple errors. Assuming this natural premise, a program P which is correct on test data T is subjected to a series of mutant operators to produce mutant programs which differ from P in very simple ways. The mutants are then executed on T. If all mutants give incorrect results then it is very likely that P is correct (i.e., T is adequate). On the other hand, if some mutants are correct on T then either: (1) the mutants are equivalent to P, or (2) the test data T is inadequate. In the latter case, T must be augmented by examining the non-equivalent mutants which are correct on T: a procedure which forces close examination of P with respect to the mutants. At first glance it would appear that if T is determined adequate by mutation analysis, then P might still contain some complex errors which are not explicitly mutants of P.

Defective particle assembly in wild type P2 bacteriophage and its correction by the lg mutation.

Abstract: Summary The mutation lg of phage P2 has been located on the genetic map of P2 to the right of, and closely linked to, the del2 deletion, probably within tail gene F. The lg mutation causes larger burst sizes, compared with the wild type, especially at high incubation temperatures. The frequency of defective particles is lower in preparations of P2 lg than in those of wild type P2. It seems that the mutation lg improves the efficiency of particle assembly.

Mutation and disease in man

Abstract: Efforts to evaluate the burden of genetic disease maintained by mutation pressure are reviewed, Various individuals and committees have suggested that approximately 1800 per 100,000 liveborn infant...

Requirements for suppression of a dnaG mutation by an I-type plasmid.

Abstract: We have confirmed and further characterized the phenomenon of suppression of a dnaG mutation by an I plasmid and determined the requirements for the complete expression of suppressibility. The authentic derepressed mutation of the conjugal fertility system, described earlier, was shown to be one of the requirements. The second requirement is a previously undescribed type of mutation leading to a far higher degree of derepression of this system than the authentic drd mutation. This second mutation leads to extremely high conjugal fertility and pilus production. A third requirement for the complete expression of suppressibility is that the host recA function remain intact. recA function is required not merely for the fulfillment of the other two requirements described above, but also for an additional step or steps leading to its complete expression. The nature of this step(s) is unknown, but it is not insertion of the plasmid into the host genome.

Genetic analysis of the mutation female-lethal in Drosophila melanogaster.

Abstract: A genetic analysis was made of the Female-lethal (Fl) locus of Drosophila melanogaster. This is an Jf-linked mutation which causes lethality only in females. Other alleles do not complement Fl and are either lethal or sterile when homozygous in females. Complementation studies on Fl alleles demonstrate that there is no simple ranking of these alleles in terms of severity of phenotypic effect. Dosage manipulation of Fl alleles indicates that the sex-specificity is not a consequence of gene dosage effects. Viability studies on males carrying Fl alleles show that Fl alleles have no effect on viability regardless of the presence or absence of a Y chromosome. The Fl locus is therefore sex-specific. The hypothesis that Fl is involved in the establishment of imaginal phenotypic sex cannot be substantiated on the basis of experiments utilizing sex-change mutations.

Theory of mutations. II. Physical model of genetic stability

Abstract: A physical model for genetic stability of DNA is constructed in terms of the “microscopic” model for uninduced point mutations and the electromechanical thermoelastic properties of the macroscopic “global” DNA system. Theoretical considerations show how experimental data from one of the least complicated but useful genetic systems, T4 bacteriophage, support the proton-code model of DNA discussed by Lowdin. The stability of an unperturbed DNA system is treated to illustrate the dynamical coupling between the “global” motion of DNA and the stability at local genetic sites. The method for analyzing a DNA system perturbed by “low-energy” optical or acoustical frequencies is indicated. The model provides a physical explanation for “hot spots” (genetic sites highly susceptible to mutation) and suggests that quantum theory may be as useful in the biological sciences as it is in the physical sciences with respect to designing and interpreting certain experiments in genetics. The incidence of human cancer as a function of chronological age is discussed in terms of the model.

Second Acriflavine Sensitivity Mutation, acrB, in Escherichia coli K-12

Abstract: A novel acriflavine-sensitive mutant was isolated. The mutation was referred to as acrB1 and was demonstrated to be located at min 82.

Site specificity and variability in the mutator and antimutator effects of phage T4 gene 43 mutants.

Abstract: Spontaneous, 2-aminopurine- and 5-bromouracil-induced mutations at six rII nonsense codons were studied in phage T4 strains possessing wild-type and mutant gene 43 alleles. The mutation pathways studied included interconversions and reversions of nonsense codons. The tsCB87 allele, which specifies an antimutator DNA polymerase, reduced base-analogue-induced mutation frequencies along all pathways. However, GC base pairs were less affected than AT base pairs. The frequency of spontaneous UAA leads to UAG conversions was also reduced by tsCB87, but that of spontaneous UAA leads to UAG UGA conversions was often increased. Mutation in the presence of the mutator allele tsL56 was increased along all pathways, with no preference for either AT or GC base pairs. Mutation frequencies in the presence of the two mutant DNA polymerases were highly variable. A strong correlation was found between 2-aminopurine-induced mutation frequencies in ts+ tsCB87 phage along the reversion and UAA changed to UAG (but not UAA changed to UGA) pathways.