Showing papers on "Mutation (genetic algorithm) published in 1975"

Spontaneous mutation in man.

Abstract: Mutation is one of the basic phenomena of life. Without mutation, the gradual development of life from inorganic material would have been impossible, and the evolution of living beings from the first groups of molecules in which a primitive, information-carrying unit cooperated with an energy gaining device59 up to the present diversity of highly refined living organisms could not have occurred. Therefore, one would expect that mutation, and especially “spontaneous” mutation, i.e., that occurring naturally and without any detectable external reasons, would attract the research activity of many biologists, especially geneticists. Surprisingly, however, this is not the case. In most experimental studies—for example, on microorganisms, Drosophila or the mouse—research on spontaneous mutation is being carried out more or less as a sideline of other work, and the results are widely scattered.

Genetical aspects of [URE3], a non-mitochondrial, cytoplasmically inherited mutation in yeast.

Abstract: [URE3], a non-mitochondrial non-mendelian mutation which modifies drastically yeast nitrogen metabolism has been genetically studied. Cytoduction experiments show definitely that the inheritance of the determinant is not linked to the nucleus. The maintenance of the [URE3] determinant seems controlled by the product of a conventional nuclear gene (ure2) which is itself involved in nitrogen metabolism. The (ure2) mutation alone gives the same phenotype as [URE3] but it is impossible to obtain a stable recombinant containing simultaneously the (ure2) mutation and the [URE3] determinant. Application of the Newcombe respreading experiment demonstrates that the [URE3] mutational event occurs before the selection procedure and is therefore not strictly adaptative. Nevertheless, the nature of the selection medium changes considerably the frequency of the [URE3] mutants recovered.

Inversion heterozygosity and the origin of XO daughters of Bpa/+female mice.

Abstract: THERE has long been an interest in developing mouse stocks carrying chromosome inversions for mutation testing. This interest stems from the fact that heterozygosity for a paracentric inversion, that is, a structural rearrangement in which a chromosome segment that does not include the centromere is rotated through 180°, results in suppression of recombination in the inversion region. This is caused by the failure of recovery of the products of single crossovers in this region, because dicentric chromatids and acentric fragments are produced that either fail to give functional meiotic products or result in the formation of unbalanced zygotes which are generally eliminated. Recombination between the pair of chromosomes concerned is, therefore, confined to any crossovers in the non-inverted regions and to the rare two-strand double crossovers which may occur within the inversion region if it is a long one. This property of inversion heterozygotes enables the recovery, in the progeny, of the structurally normal homologue largely intact and any recessive mutation located on it can be readily detected if suitable genetically marked stocks are used. In the simplest case, when the mutation is a recessive lethal and the inversion is located in the X chromosome, detection is either by the absence of half the males, or if the inversion itself is marked by a recessive lethal (as in the C1B method devised by Muller for Drosophila melanogaster), by the absence of all the males.

Polyallelic mutational equilibria.

Abstract: A new deterministic formulation is derived of the equilibrium between mutation and natural selection, which takes into account (a) the possibility of many allelic mutation states, (b) selection coefficients of the order of magnitude of the mutation rate and (c) the possibility of further mutation of already mutant alleles. The frequencies of classes of alleles 0, 1, 2, n mutant steps removed from the type allele are shown to form a Poisson distribution, with a mean and variance of the mutation rate divided by the coefficient of selection against each incremental mutational step. — This formulation is interpreted in terms of the expected frequencies of electromorphs , defined as classes of alleles characterized by common electrophoretic mobilities of their protein products. Electromorph frequencies are predicted to form stable unimodal distributions of relatively few phenotypic classes. Common electromorph frequencies found throughout the ranges of species with large population sizes are interpreted as being a uniquely electrophoretic phenomenon; band patterns on starch and acrylamide gels are phenotypes, not genotypes. It is predicted that individual electromorphs are highly heterogeneous with regard to amino acid sequence.

The deterministic behavior of self-incompatibility alleles

Abstract: For a system of n self-incompatibility alleles, neglecting mutation and random drift, it is shown that the completely symmetric equilibrium is locally stable, and any allelic frequency less than q equals 1 + a minus the square root of 1 + a-2, where a equals [2(n minus 1)]- minus 1, will increase. For all n, q greater than (2n)- minus 1, but if n greater than 1, q is approximately equal to (2n)- minus 1.

Induction, selection, and experimental uses of temperature-sensitive and other conditional mutants of yeast.

Abstract: Publisher Summary This chapter focuses on temperature-sensitive ( ts ) and other conditional mutants of yeast. A conditional mutant is an organism that resembles the wild type under some environmental conditions, but displays a characteristic mutant phenotype under other environmental conditions. The mutation responsible for this phenotype is a conditional mutation. If a conditional mutant is incapable of prolonged vegetative growth under the restrictive conditions, the mutation it harbors is a conditional lethal mutation, and the gene and function that are defective are referred to as indispensable or essential. Various conditional lethal mutants can lose viability (the ability to resume vegetative growth on return to the permissive conditions) at very different rates during a period of exposure to the restrictive conditions. In the chapter, induction and isolation of mutants is discussed and the problem of genetic complexity is explained. Experimental uses of ts mutants are described as well. The study discussed in the chapter is based on experience with Saccharomyces cerevisiae and refers specifically only to that organism.

Spontaneous Male Recombination and Mutation in Isogenic-Derived Chromosomes of Drosophila melanogaster

Abstract: Spontaneous male recombination and visible mutations were observed in second and third chromosomes derived from an isogenic line, ID, previously found to exhibit a high recessive lethal mutation rate. All three types of events tend to occur very early in spermatogenesis resulting in large clusters of identical recombinant or mutant progeny from a single male. Mutations and male recombination exchange points tend to be located more frequently in the right arm than in the left in both second and third chromosomes but for a trivial reason in the case of chromosome 2. No significant differences in male or female recombination were found between the progeny of reciprocal crosses. Male recombination in chromosome 2, like recessive lethal mutation, is independent of the presence of ID third chromosomes in the same genome. Both quantitative and qualitative differences in male recombination were found when ID chromosomes were compared with others extracted from natural populations.

Study of H-2 mutations in mice. VI. M523, a new K-end mutant.

Abstract: A newH-2 mutation was found in a mouse belonging to CBA/CaLacSto (H-2k) strain and designated 523, the proposed haplotype symbol for which isH-2ka. The line CBA.M523 carries this mutation and is fully congenic with the parental strain, except for the mutant site 523. The mutation 523 is located within theK- end of theH-2 gene complex. Phenotypically, it causes prompt skin graft rejection and pronounced graft-versus-host activity in strain combination CBA/Sto⇄C-BA.M523. Attempts to produce active alloantisera in the same strain combination have so far been unsuccessful.

Tests for the mutagenic actions of a number of chemicals on Haemophilus influenzae with special emphasis on hydrazine.

Abstract: A number of chemicals have been tested for their ability to produce novobiocin-resistant mutants in Haemophilus influenzae. Of these, hydrazine (HZ) proved unique because it induced a fairly high incidence of mutation without killing significant numbers of cells at concentrations ranging over nearly four orders of magnitude. Moreover, its dose-effect curve increased very slowly initially and reached a relatively low maximum. It is suggested that HZ may be acting as both a mutagen and an antimutagen in this system. HZ has sometimes been characterized as primarily an inactivating agent rather than as a mutagen. Obviously, quite the opposite is true for H. influenzae. Moreover, a survey of the literature shows that HZ has been used effectively to produce mutations in phage, bacteria, higher plants and Drosophila. There is reason to suspect that it produces mainly single locus mutations rather than chromosomal aberrations, but the amount of information on this point is still very small. The effectiveness of a mutagen can be markedly affected by the criterion of effectiveness used. If a high incidence of mutation with reasonably high cell survival is the criterion, then mutagens that are relatively nontoxic would probably be considered highly effective. In this case, the maximum mutation rate that can be achieved in practice may be controlled either by toxicity or by maxima like the one found for HZ. If, on the other hand, the important criteria are the concentration and exposure time needed to produce a detectable increase in mutation, then some quite toxic mutagens would be considered quite effective even though the maximum mutation that can be produced in practice is low. The first criterion is the one to use in choosing mutagens for detailed analysis of the mutation process, but the second set of criteria may be more suitable for generalizing to other organisms, for example from microorganisms to man, since toxic effects can be quite different in different cell types.

mut-25, a mutation to mutator linked to purA in Escherichia coli.

Abstract: The mutation mut-25 that results in a mutator phenotype is closely linked to purA on the chromosome of Escherichia coli. The gene order in this region is ampA mut-25 purA. purA mut-25 double mutants retained mutator activity indicating that mut-25 is not a mutation in the purA gene. The repair mutations uvrA6, recA56, and exrA1 had no effect on mutation frequencies in mut-25 strains, and mut-25 strains were normally resistant to ultraviolet irradiation. Frequencies of host range mutations were not increased in phages T1, T2, and T7 grown on mut-25 strains. mut-25 could act trans, reverting the trpA46 mutation either on the chromosome or on an F episome. The transitions AT yields GC (adenine-thymine yields guanine-cytosine) and GC yields AT were induced by mut-25.

Mutagenicity tests with aflatoxins in the mouse.

Abstract: Introduction Aflatoxins, a collective term for eight compounds of related molecular configuration (i.e., aflatoxins BI, B2, B2a, GI, G2, G2a, MI, and M2), are metabolites of Aspergillus flavus, a common contaminant of stored human and animal foodstuffs (refs. I, 5, 24). Aflatoxin BI and GI are the most abundant and active compounds of this group. They are acutely hepatotoxic and have been shown to be potent carcinogens in the rat 4,7,15,2., and rainbow trout 3. Aflatoxin BI is known to inhibit protein synthesis and DNA-dependent RNA synthesise,~5,2s. Various types of genetic effects following aflatoxin t reatment of whole organisms, or cells in culture, have been described in different organisms. Aflatoxin BI has been shown to be mutagenic in the Bacillus subtilis transforming DNA assay in vitro 19 and in Neurospora crassa2°, ~1. I t inhibits the mitotic process in human embryonic lung cells 16 and produces chromosome aberrations in seedling roots of Vicia faba is, in Al l ium cepa 2~, in a cell line derived from the rat Kangaroo 12, and in human leucocytes in vitrog,22, 27. Aflatoxin BI is able to induce autosomal recessive-lethal mutations in Drosophila melanogaster ~4 whereas a mixture of aflatoxins BI and GI causes an increase in the dominant lethals in male mice 1°. In the present experiments the capacity of aflatoxin BI to produce heritable chromosomal changes in mice has been tested by analysing the spermatocyte I chromosomes of the treated males (spermatocyte test on treated males) and of their offspring (VI translocation test) 17.

Interlocus variation of genetic distance and the neutral mutation theory.

Abstract: Theoretical distributions of genetic distance between reproductively isolated taxa are derived by means of computer simulation, taking into account mutation and random genetic drift. The distributions obtained are in good agreement with the observed distributions of interracial and interspecific genetic distances for enzymes loci in Drosophila. This indicates that the gene substitution at enzyme loci can be explained by the neutral mutation theory.

Dental reduction and the probable mutation effect.

Abstract: A recent test of the probable mutation effect can be interpreted to suggest the operations of mutations under conditions of reduced selection in the late Pleistocene reduction of the human dentition.