Showing papers on "Mutation (genetic algorithm) published in 1971"
TL;DR: The hypothesis is developed that retinoblastoma is a cancer caused by two mutational events, in the dominantly inherited form, one mutation is inherited via the germinal cells and the second occurs in somatic cells.
Abstract: Based upon observations on 48 cases of retinoblastoma and published reports, the hypothesis is developed that retinoblastoma is a cancer caused by two mutational events. In the dominantly inherited form, one mutation is inherited via the germinal cells and the second occurs in somatic cells. In the nonhereditary form, both mutations occur in somatic cells. The second mutation produces an average of three retinoblastomas per individual inheriting the first mutation. Using Poisson statistics, one can calculate that this number (three) can explain the occasional gene carrier who gets no tumor, those who develop only unilateral tumors, and those who develop bilateral tumors, as well as explaining instances of multiple tumors in one eye. This value for the mean number of tumors occurring in genetic carriers may be used to estimate the mutation rate for each mutation. The germinal and somatic rates for the first, and the somatic rate for the second, mutation, are approximately equal. The germinal mutation may arise in some instances from a delayed mutation.
7,051 citations
TL;DR: To identify new genes controlling UV-induced mutation, it is desirable to select strains directly for defective mutation induction, thereby avoiding the prior condition that all such mutants be UV-sensitive.
Abstract: NDUCED mutations are thought to arise as a result of enzymatic processes uti‘lizing DNA damage as a substrate (BRIDGES 1969). Although the molecular mechanism is not known, evidence reviewed by WITKIN (1969) suggests that in E. coli mutations are produced during postreplication repair of lethal damage induced by ultraviolet light (UV) and controlled by r e d and ezrf (or lexf) genes. Strains carrying rec or ezr, although normal in excision repair, exhibit reduced or no UV mutability compared to wild type. In addition, such strains are UV sensitive, X-ray sensitive, and recombination deficient in varying degrees ( WITKIN 1969). In previous studies of UV-induced mutation in fungi, UV-sensitive strains have been selected on the assumption that UV mutagenesis might be related to dark repair of lethal damage. In some of these UV-sensitive strains, the frequencies of UV mutation are reduced compared to wild type at equal UV doses (CHANG, LENNOX and TUVESON 1968; NASIM 1968; WOHLRAB and TUVESON 1969). whereas in others these frequencies are enhanced (AVERBECK et al. 1970; RESNICK 1969; ZAKHAROV, KOZINA and FEDOROVA, 1970). To identify new genes controlling UV-induced mutation, it is desirable to select strains directly for defective mutation induction, thereby avoiding the prior condition that all such mutants be UV-sensitive. Mutants of Saccharomyces cereuisiae were selected ( LEMONTT and MORTIMER 1970) for reduced ability to undergo UV-induced locus reversion of the ochresuppressible (GILMORE 1967; HAWTHORNE 1969) argl-17 allele. This paper describes the isolation and some characteristics of these “reversionless” mutants, The results are discussed in relation to current ideas about induced mutagenesis.
315 citations
TL;DR: Mutants of Saccharomyces cerevisiae capable of growth on a minimal medium supplemented with ureidosuccinic and glutamic acids have been isolated from a pyrimidineless strain and it is suggested that the mutation is nonchromosomal and could be mitochondrial.
Abstract: Mutants of Saccharomyces cerevisiae capable of growth on a minimal medium supplemented with ureidosuccinic and glutamic acids have been isolated from a pyrimidineless strain. One of these mutants consistently yielded a non-Mendelian meiotic segregation. Moreover, the mitotic transmission of the mutation was very high. It is suggested that the mutation is nonchromosomal and could be mitochondrial. However, this mutation behaves very differently from other mitochondrial mutations.
310 citations
TL;DR: A hypothesis that mutants are selectively neutral at the majority of sites but are selected at a relatively small number of sites was examined, and the roles of associative overdominance and subdivided population structure in maintaining genetic variability were considered.
187 citations
TL;DR: It is suggested that at least some variations may arise in somatic cells by stable shifts in phenotypic expression rather than by changes in genetic information.
Abstract: Fluctuation tests of the Luria-Delbruck type have been used to examine the frequency of spontaneous variations in cultures of diploid, tetraploid, and octaploid Chinese hamster cells. Resistance to 8-azaguanine and altered response to thermal shock were chosen as marker systems. Mutation frequencies of approximately 10−6 and 10−5 have been estimated for heat resistance and azaguanine resistance respectively. Rates of mutation for these markers remain constant or decline slightly in cells with increasing numbers of chromosome sets. This trend is not in accordance with expectations based on the assumption of dominant, co-dominant, or recessive changes at gene or chromosome levels. It is suggested that at least some variations may arise in somatic cells by stable shifts in phenotypic expression rather than by changes in genetic information.
152 citations
120 citations
TL;DR: Among a number of suppressors ofAdenine requirement arising in a hetero-allelic adenine-requiring diploid used in this laboratory was one, SQ2 which, in a tetrad analysis of the diploids strain, gave the results summarised in tables 1 and 2.
Abstract: SUPER-SUPPRESSOR mutations are readily isolated in certain auxotrophic strains of yeast by selecting for prototrophic variants. They arise spontaneously or after treatment with mutagens (Hawthorne and Mortimer, 1963; Hawthorne, 1969b; Inge-Vechtomov, 1965). Since, often, they are dominant, they can as readily be found in diploid as in haploid auxotrophs. All the evidence suggests that they act, as do the better-known amber and ochre suppressors in bacteria, through the misreading of mutant nonsense codons by means of altered amino-acid-accepting transfer RNA species (Gilmore and Mortimer, 1966; Gilmore, Stewart and Sherman, 1968). Among a number of suppressors of adenine requirement arising in a hetero-allelic adenine-requiring diploid used in this laboratory was one, SQ2 which, in a tetrad analysis of the diploid strain, gave the results summarised in tables 1 and 2. Four facts stand out. First, a recessive lethal mutation
93 citations
76 citations
Journal Article•
TL;DR: A genetic hypothesis of cancer has to comprise mutation of both nuclear and cytoplasmic genetic determinants.
01 Jan 1971
TL;DR: As single-cell eukaryotes that can exist either as stable haploids or diploids, the yeasts afford many advantages as test organisms for examination of the genetic effects of chemicals and radiations.
Abstract: As single-cell eukaryotes that can exist either as stable haploids or diploids, the yeasts afford many advantages as test organisms for examination of the genetic effects of chemicals and radiations. The suitable characteristics of these higher fungi include clonability, a short generation time, adaptability to replica plating, and a well-developed genetics. Two species, Saccharomyces cerevisiae and Schizosaccharomyces pombe, have been used for most of the mutation studies with yeast.
TL;DR: A mutation which increases about sixfold the activity of glucose 6-phosphate dehydrogerase in Escherichia coli is described, and according to antibody titration zwfL1 acts to increase the amount of normal enzyme, rather than by specifying an altered enzyme.
TL;DR: The isolation, properties, and genetic analysis of a strain of Escherichia coli K-12 with an amber recA mutation demonstrate that the recA product is a protein that is probably not essential for growth.
Abstract: The isolation, properties, and genetic analysis of a strain of Escherichia coli K-12 with an amber recA mutation are described. The experiments demonstrate that the recA product is a protein that is probably not essential for growth.
TL;DR: A mutant strain of Escherichia coli K-12 was found in which spontaneous mutation to phage T 7 resistance occurred at a very low frequency, and the mutation preventing T7 resistance, non-9, inhibited capsule formation when transduced into capsulated strains.
Abstract: A mutant strain of Escherichia coli K-12 was found in which spontaneous mutation to phage T7 resistance occurred at a very low frequency T7 resistance in the parental strain from which this mutant was derived resulted from a mutation to excess capsular polysaccharide synthesis The mutation preventing T7 resistance, non-9, inhibited capsule formation when transduced into capsulated strains The non-9 mutation was cotransducible with his, the gene order in this region being non-9 his Su-1
TL;DR: 8-methoxypsoralen (8-MOP) given before far ultra violet (254 nm, herein-) causes genetic damage to Escherichia coli in the presence of near ultra-violet light (365 nm, hereinafter NUV).
Abstract: ~-METHOXYPSORALEN(I) is a synthetic member of the furocoumarins, a class of compounds widely distributed in the plant kingdom. It has been shown by Igali er al. [ 11 to cause genetic damage (both mutational and lethal) to Escherichia coli in the presence of near ultra-violet light (365 nm, hereinafter NUV). In the course of that work it was found that 8-methoxypsoralen (8-MOP) given before far ultra violet (254 nm, herein-
TL;DR: A genetic and epidemiological study of muscular disease in Poland finds methods of detection of gene carriers crucial for genetic counselling and important for accurate planning of services such as rehabilitation centres, hostels for crippled children, hospital and sanatorium beds.
Abstract: A genetic and epidemiological study is especially important in those hereditary diseases for which no effective treatment is known, since then genetic counselling is the only means of prevention. The progressive muscular dystrophies are typical conditions of this sort. Knowledge of the type of hereditary transmission for a given form of muscular dystrophy is the basis for correct genetic prognosis. Finding methods of detection of gene carriers is crucial for genetic counselling. Estimation of such parameters as relative fitness, mutation rate, incidence, and prevalance types of progressive muscular dystrophy is important not only from a purely academic point of view but also from a practical one as well. It is important for accurate planning of services such as rehabilitation centres, hostels for crippled children, hospital and sanatorium beds. For this reason we undertook a genetic and epidemiological study of muscular disease in Poland.
TL;DR: In recent years many examples of what are conveniently referred to as enzyme and protein polymorphisms have been discovered in the course of surveys of human populations and of naturally occurring populations of other animal species.
Abstract: In recent years many examples of what are conveniently referred to as enzyme and protein polymorphisms have been discovered in the course of surveys of human populations and of naturally occurring populations of other animal species. The term polymorphism is used in this context for any situation where members of a population can be sharply classified into several distinct phenotypes in terms of particular characteristics of the enzyme or protein, and where at least two of the phenotypes have an appreciable incidence (greater than 2%). Most of these polymorphisms can be attributed to the occurrence of two or more alleles each coding for a structurally distinct form of a polypeptide chain in the particular enzyme or protein. It is thought that the structural difference between the polypeptides usually amounts to no more than a single amino-acid substitution, and that the allelic difference originated in a single mutational event involving the change of only one base for another in the sequence of several hundred or thousand bases in the DNA of the particular gene. But direct evidence for this has so far only been obtained in a limited number of polymorphisms, and there are certainly some exceptions where the polypeptide products of the two common alleles differ by more than one amino acid, eg, the sheep haemoglobins A and B (Boyer et al, 1967). Electrophoretic surveys of arbitrarily chosen enzymes and proteins have been carried out in various naturally occurring animal populations to see how often such polymorphisms occur. A number of very different species have been studied in this way. They include man (Harris, 1966 and 1969), Drosophila pseudoobscura (Hubby and Lewontin, 1966; Lewontin, and Hubby, 1966; Prakash, Lewontin, and Hubby, 1969), mouse (Ruddle et al, 1969; Selander, Hunt, and Yang,
TL;DR: It is shown that a particular base pair in the DNA may show variable mutability, depending on its nearest neighbors, and similar base pairs at different sites in the gene can vary in their mutability despite the fact that they are flanked by similar neighbors.
Abstract: In 15 sites in the T 4 rII gene, mutation from the ochre (UAA) codon to amber (UAG), opal (UGA) and the wild-type was measured with and without 2-aminopurine treatment. It is shown that a particular base pair in the DNA may show variable mutability, depending on its nearest neighbors. Also, similar base pairs at different sites in the gene can vary in their mutability despite the fact that they are flanked by similar neighbors.
TL;DR: One-locus, two-allele models are presented which describe the genetic consequences of naturally occurring and experimentally induced parthenogesis in triploid and diploid amphibians to provide a basis for understanding evolution in these populations.
Abstract: SYNOPSIS. One-locus, two-allele models are presented which describe the genetic consequences of naturally occurring andexperimentally induced parthenogesis in triploid and diploid amphibians. The models may in general be used to investigate genetic change resulting from apomictic (ameiotic) and automictic (meiotic) parthenogenetic reproduction.
These models quantify the influence of mutation, segregation, and selection upon genetic variability in parthenogeneticpopulations. They also allow an estimate of the relative importance of stochastic forces in altering this variability. They thus provide a basis for understanding evolution in these populations.
Some of the conclusions derived from this study contradict previous predictions regarding genetic variability in parthenogenetic populations. First, if mutation is the sole source of genetic change (i.e., strict apomixis), parthenogenetic populations should not become completely heterozygous. Second, small amounts of segregation occurring in apomictic populations have enormous effects upon the genetic variability of these populations, i.e. , they should lose much of their heterozygosity.
In addition to these conclusions, the results of this study suggest that studies of protein variability in parthenogenetic species should contribute toward answering the question: How much of the genetic variability observed in nature is evolutionarily relevant?
TL;DR: Nutritional requirements were introduced into wild-type, heterothallic strains of Candida lipolytica by exposing the cells to X rays, and genetic recombination was observed in individually isolated ascospores from the hybrid strains.
Abstract: Nutritional requirements were introduced into wild-type, heterothallic strains of Candida lipolytica by exposing the cells to X rays. Complementing hybrids were recovered from mixtures of the auxotrophic strains, and genetic recombination was observed in individually isolated ascospores from the hybrid strains.
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TL;DR: The authors produce evidence indicating that this is indistinquishable from heritable and deduce from that it is, therefore, identical with that gene that is Rh and favor the hypothesis that in this they are seeing the expression of a ‘gene of control’ and its effect on a ’gree of structure’ in the complex that isRh.
Abstract: . A consanguineous ♂R1R2 × ♀R1R1 mating is reported which produced one child, four R1R1 and two R1R2 children. Nonpaternity and nonmaternity are ruled out as an explanation for the anomalous phenotype. The authors produce evidence indicating that this is indistinquishable from heritable and deduce from that it is, therefore, identical with that gene. Three explanations are offered for its occurrence here and two discarded. The third is a mutation: they favor the hypothesis that in this they are seeing the expression of a ‘gene of control’ and its effect on a ‘gene of structure’ in the complex that is Rh.
TL;DR: The uvr502 mutation has been mapped on the chrosome of E. coli K 12 and the gene order was determined as ilv uvr(502) metE.
Abstract: The uvr502 mutation has been mapped on the chrosome of E. coli K 12. The gene order was determined as ilv uvr(502) metE.
Journal Article•