Electrophoretic Variation in
            <i>Escherichia coli</i>
            from Natural Sources

Milkman, Roger

doi:10.1126/science.182.4116.1024

Cited by 194 publications

(97 citation statements)

References 9 publications

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“…The present data seem to be consistent with those of other haploid organisms such as E. coli (Milkman 1973) and Neurospora intermedia (Spieth 1975), though there are significant differences between the above two organisms and the moss studied here in the way they face natural selection. The former often endure unfavorable environments as dormant spore while the latter species maintains its ordinary life style as a haploid plant under most environmental changes.…”

Section: Resultssupporting

confidence: 80%

Genic variabilities in natural population of haploid plant, Conocephalum conicum. I. The amount of heterozygosity.

Yamazaki

1981

The Japanese journal of genetics

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The amount of genetic variability expected in natural populations is different for diploid and haploid organisms under most selection models: diploid organisms are expected to be more polymorphic. I examined several natural Japanese populations of haploid moss, Conocephalum conicum by starch gel electrophoresis.Seven enzyme loci out of 11 examined turned out to be polymorphic. The average heterozygosity at the 11 loci was 0.167. This value is almost identical to those obtained in diploid organisms of various sources. Moreover, abundant genic variability was found within a local population, indicating the prevalence of sexual reproduction in natural populations of this species. The equality of genic variability between diploid and haploid organisms is most easily explained by the selective neutrality of allozyme polymorphisms, though other possibilities are not excluded from the present data alone.

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Section: Resultssupporting

confidence: 80%

Genic variabilities in natural population of haploid plant, Conocephalum conicum. I. The amount of heterozygosity.

Yamazaki

1981

The Japanese journal of genetics

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“…The possibility of more mutations being neutral in higher forms such as mamdtals with advanced homeostasis has been suggested by Kondo (24). Low physiological homeostasis and frequent local extinction of colonies must be the main reason why the heterozygosity (or 1, minus the sum of squares of allelic frequencies in haploid organismsv does not go very high in organisms having immense apparent population sizes such as neotropical Drosophila (25) and Escherichia coli (26). The mathematical model proposed in this paper represents my attempt to make the neutral mutation theory more precise and realistic.…”

Section: Discussionmentioning

confidence: 99%

Model of effectively neutral mutations in which selective constraint is incorporated

Kimura

1979

Proc. Natl. Acad. Sci. U.S.A.

202

171

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Based on the idea that selective neutrality is the limit when the selective disadvantage becomes indefinitely small, a model of neutral (and nearly neutral) mutations is proposed that assumes that the selection coefficient (s') against the mutant at various sites within a cistron (gene) follows a r distribution; Ass') = aPe-as's.-l/P(,B), in which a = fi/i and s' is the mean selection coefficient against the mutants (?'> 0; 1 _ ft > 0). The shown that we have roughly kg = ve. The situation becomes quite different if slightly advantageous mutations occur at a constant rate independent of environmental conditions. In this case, the evolutionary rate can become enormously higher in a species with a very large population size than in a species with a small population size, contrary to the observed pattern of evolution at the molecular level.Among difficult questions that confront the neutral mutation theory purporting to treat quantitatively the evolution and variation at the molecular level, the following two are particularly acute. 3440The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

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“…Several experimental studies have been thus far conducted on the genie polymorphisms of haploid microorganisms (Milkman 1973;Spieth 1975). These studies generally show no obvious differences between haploids and diploids.…”

Section: Introductionmentioning

confidence: 99%

The amount of polymorphism and genetic differentiation in natural populations of the haploid liverwort Conocephalum conicum.

Yamazaki

1984

The Japanese journal of genetics

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Natural populations of diploid organisms are expected to be more polymorphic than haploid organisms under most selection models. To test this prediction and to obtain data concerning the amount of allozyme polymorphism in a haploid plant, I examined two natural populations of the haploid liverwort Conocephalum conicum by starch gel electrophoresis.Abundant genie variability was found within local populations in Japan: 7 of 11 loci. Average heterozygosity of these 11 loci was 0.167. This value is similar to those obtained for various kinds of diploid organisms. Gene identity (I) between the two populations was 0.994, and another measure of genetic differentiation, Gst was 0.018, indicating virtually no genetic differentiation between the populations. High levels of genie variability and low levels of genetic differentiation in these haploid plants are consistent with a hypothesis of selective neutrality of allozyme polymorphisms, although other possible explanations cannot be excluded.

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Electrophoretic Variation in Escherichia coli from Natural Sources

Cited by 194 publications

References 9 publications

Genic variabilities in natural population of haploid plant, Conocephalum conicum. I. The amount of heterozygosity.

Genic variabilities in natural population of haploid plant, Conocephalum conicum. I. The amount of heterozygosity.

Model of effectively neutral mutations in which selective constraint is incorporated

The amount of polymorphism and genetic differentiation in natural populations of the haploid liverwort Conocephalum conicum.

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