Mutagen specificity in conversion pattern in<i>Sordaria brevicollis</i>

Yu‐Sun, Clare C. C.; Wickramaratne, M. R. T.; Whitehouse, H. L. K.

doi:10.1017/s0016672300017122

Cited by 26 publications

(6 citation statements)

References 14 publications

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“…If it were true, one should see greater departures from equality in the 6:2/2:6 ratio for frame-shifts than for base-substitutions. This is certainly the case for the S. brevicollis data of Yu-Sun, Wickramaratne and Whitehouse (1977), and much of the A. inimersus data of Leblon (1972) and Rossignol, Paquette and Nicolas (1979), though with some exceptions; it is less apparent in the Ascobolus data of Lamb and Ghikas (1979) and Lamb and Helmi (1978). It also applies to the non-pairs for long deletions in yeast (see end of section 5(u)).…”

Section: Discussionmentioning

confidence: 88%

The properties of meiotic gene conversion important in its effects on evolution

Lamb

1984

Heredity

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SUMMARYIn order to determine how important gene conversion is as a force in populations, extensive surveys have been made to determine the limits, distributions and typical values of evolution-related conversion parameters from various fungi, Drosophila and maize. The conversion frequency, c, had an enormous range for different mutations within a species, with loci often having different means and limits for c. b, the frequency of a particular allelle in the products of meiotic tetrads or octads with aberrant segregation ratios, often showed values near the theoretical extremes; d, disparity in direction of conversion, was frequent and often extreme. b and d could only be studied in fungi, and their less extreme values in Saccharomyces than in Sordaria orAscobolus are clearly related to the lack of frame-shift mutations in the yeast data. For different mutations at a locus, neither c nor b showed normal distributions; both gave dispersed distributions, sometimes multi-modal for b; c and b were not usually correlated. y, the force of meiotic gene conversion on allele frequencies, had a large range of positive and negative values, with different loci often having quite different limits and mean absolute values. For different mutations at a locus, y showed dispersed distributions, with little tendency to cluster around zero. The high proportion of non-zero y values in all fungi where this could be studied, with large departures from zero being most extreme in Ascobolus and Sordaria brevicollis, shows that gene conversion could often be an important force in changing allele frequencies in favour of mutant or wild-type in these organisms. Even in organisms with much lower c or absolute d values, conversion could still be important, depending on dominance, selection coefficients and mutation rates. Presumed frame-shifts tended to have more extreme disparity and hence higher absolute y values than did presumed base-substitutions, but with no Consistent C differences. Induced mutations had similar or slightly higher absolute y values compared with spontaneous mutations.

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Section: Discussionmentioning

confidence: 88%

The properties of meiotic gene conversion important in its effects on evolution

Lamb

1984

Heredity

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“…For a new sequence variant to spread throughout a family of repeats, as the result of conversion events, the conversion must be biased (i.e., it must favor the new variant). This type of biased conversion has been observed for intragenic recombination involving spore color loci in Ascobolus immersus (21) and Sordaria brevicollis (22). In the present case, it is possible that biased gene conversion has been one of the mediating factors in the introgression of the Moreton rDNA into the Torresian subspecies, and we will discuss below how this process may be detected in the Moreton/Torresian hybrid zone.…”

Section: Discussionmentioning

confidence: 89%

Ribosomal RNA-encoding DNA introgression across a narrow hybrid zone between two subspecies of grasshopper

Arnold

Shaw

Contreras

1987

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

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A ribosomal RNA-encoding DNA (rDNA) cloned sequence, consisting of a 0.8-kilobase fragment from the 26S/nontranscribed spacer region, was used to identify diagnostic restriction enzyme fragments that distinguish the Moreton and Torresian subspecies of the grasshopper Caledia captiva. These restriction fragments were then used to study patterns of rDNA variation across a narrow geographical hybrid zone between the two subspecies. The pattern of rDNA variation that emerged after the analysis ofover 250 individuals clearly demonstrates the asymmetrical introgression of the Moreton ribosomal RNA genes into the Torresian subspecies. This asymmetric movement of genetic material occurs even though there exists extreme postmating F2 and backcross inviability between the two subspecies. From our data, as well as those of previous chromosomal and allozymic studies, we are able to support the occurrence of nonrandom processes such as biased gene conversion and/or natural selection. Because the rDNA loci in the Moreton and Torresian individuals are located in different regions on chromosomes 10 and 11, it should be possible to determine the relative contributions of conversion, natural selection, and these sorts of processes to the pattern of introgression of the Moreton rDNA into the Torresian subspecies.How reproductive isolation develops during the speciation process remains a fundamental and unanswered question in evolutionary biology. As a corollary ofthis question, one can inquire about the consequences of repeated hybridization between partially reproductively isolated populations. Grant (1) has stated, in reference to the findings of Anderson (2), that long-term backcrossing of hybrid individuals to the parental types can result in ".... convergences between previously separate phyletic lines ...." However, it is also apparent that the introduction, maintenance, and persistence of foreign genetic material, despite significant pre-and/or postmating isolation, must be mediated by factors such as genetic drift, migration, and/or natural selection. Thus, the definition of interacting processes that lead to introgression (2) of genetic material is of fundamental importance in understanding how genetic systems may be perturbed. Indeed, it has been advocated that a major stimulus to speciation involves hybridization (3). Furthermore, the quantitation of the effects of factors such as genetic drift, migration, and selection is equally fundamental in understanding the evolution of organisms.In order to examine the above parameters, it is necessary to identify hybridizing taxa that have the following characteristics: (i) significant levels of reproductive isolation; (ii) morphological, physiological, or genetic markers that can be used to identify genomic components in parental and hybrid individuals; and (iii) definable differences in the habitats occupied by the taxa. Such a system has been identified in the grasshopper Caledia captiva. In particular, two subspecies (Moreton and Torresian) of C. captiva meet and f...

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“…Repair of the hDNA intermediate results in gene conversion. The differential repair of such hDNA has been used to explain disparities in the frequency of converting small deletions and insertions in the fungi Ascobolus immersus and Sordaria brevicollis (22,23,50). On the other hand, the double-strand break repair (DSBR) model (42) has been proposed to explain recombination data for S. cerevisiae, in which virtually all mutations are repaired to the wild type with similar efficiencies (31).…”

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confidence: 99%

High-Frequency Gene Conversion between Repeated Cμ Sequences Integrated at the Chromosomal Immunoglobulin μ Locus in Mouse Hybridoma Cells

Baker

Read

1995

Molecular and Cellular Biology

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The occurrence of mitotic recombination between repeated immunoglobulin mu gene constant (C mu) region sequences stably integrated at the haploid chromosomal immunoglobulin mu locus in murine hybridoma cells was investigated. Recombination events are detected as changes in hapten-specific immunoglobulin M production. Recombination occurs with high frequency (0.5 to 0.8%) by a mechanism consistent with gene conversion. A double-strand break repair-like mechanism is suggested by the finding that repair of a 2-bp deletion mutation and a 2-bp insertion mutation occurs with parity in a donor-directed manner. The results also suggest that the gene conversion process is directional in that the 5' C mu region sequence is preferentially converted.

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Mutagen specificity in conversion pattern inSordaria brevicollis

Cited by 26 publications

References 14 publications

The properties of meiotic gene conversion important in its effects on evolution

The properties of meiotic gene conversion important in its effects on evolution

Ribosomal RNA-encoding DNA introgression across a narrow hybrid zone between two subspecies of grasshopper

High-Frequency Gene Conversion between Repeated Cμ Sequences Integrated at the Chromosomal Immunoglobulin μ Locus in Mouse Hybridoma Cells

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