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The detection, in unordered octads, of 6+:2m and 2+:6m ratios with postmeiotic segregation, and of aberrant 4:4s, and their use in corresponding-site interference studies

Published online by Cambridge University Press:  14 April 2009

Aglaia Ghikas  and
B. C. Lamb
Aglaia Ghikas
Affiliation:
Department of Botany, Imperial College, London SW7 2BB
B. C. Lamb
Affiliation:
Department of Botany, Imperial College, London SW7 2BB

Summary

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Systems for the detection of postmeiotic segregation in unordered octads are described for 4:4(2), 6:2(2), 2:6(2), 5:3(3), 3:5(3) and 4:4(4) segregations, where the number in parentheses is the number of pairs of non-identical sister-spores. Linkage relations, centromere distances and phenotypic detectability of suitable combinations of markers for initial selective identification of such segregations, and subsequent confirmation tests, are discussed; correction formulae are given to allow for non-detection of certain classes in particular circumstances. Using one such system in Ascobolus immersus, we detected 4:4(2), 6:2(2) and 2:6(2) segregations at the w-78 site: 2:6(2)s were previously unknown. Initial visual detection in this system was from octad phenotype ratios for w-78 (white ascospore) and gr-3 (granular ascospore pigmentation), with mating type and parafluorophenylalanine resistance as confirmatory markers after germination. Corresponding-site interference for wider ratio and – for the first time – narrower ratio unique classes was determined: it was moderately positive or moderately negative, depending on the cross and segregation class involved.

Type
Research Article
Information
Genetics Research , Volume 29 , Issue 3 , June 1977 , pp. 267 - 278
Copyright
Copyright © Cambridge University Press 1977

References

REFERENCES

Emerson, S. (1966). Quantitative implications of the DNA-repair model of gene conversion. Genetics 53, 475–485.CrossRefGoogle ScholarPubMed
Emerson, S. (1969). Linkage and recombmation at the chromosomal level. In Genetic Organisation, vol. 1 (ed. by Caspari, E. W. and Ravin, A. W.), p. 289. New York: Academic Press.Google Scholar
Emerson, S. & Yu-Sun, C. C. C. (1967). Gene conversion in the Pasadena strain of Ascobolus immersus. Genetics 55, 39–47.CrossRefGoogle ScholarPubMed
Kitani, Y. & Whitehouse, H. L. K. (1974). Aberrant ascus genotypes from crosses involving mutants at the g locus in Sordaria fimicola. Genetical Research 24, 229–250.CrossRefGoogle Scholar
Lamb, B. C. (1972). 8:0, 0:8, 7:1 and 1:7 conversion ratios in octads from wild-type x mutant crosses of Ascobolus immersus. Heredity 29, 397.Google Scholar
Lamb, B. C. & Wickramaratne, M. R. T. (1973). Corresponding-site interference, synaptinemal complex structure, and 8+: 0m and 7+: 1m octads from wild-type x mutant crosses of Ascobolus immersus. Genetical Research 22, 113–124.CrossRefGoogle Scholar
Leblon, G. (1972). Mechanism of gene conversion in Ascobolus immersus. I. Existence of a correlation between the origin of mutants induced by different mutagens and their conversion spectrum. Molecular and General Genetics 115, 36–48.CrossRefGoogle Scholar
Leblon, G. & Rossignol, J.-L. (1973). Mechanism of gene conversion in Ascobolus immersus. III. The interaction of heteroalleles in the conversion process. Molecular and General Genetics 122, 165–182.CrossRefGoogle Scholar
Stadler, D. R., Towe, A. M. & Rossignol, J.-L. (1970). Intragenic recombination of ascospore color mutants in Ascobolus and its relationship to the segregation of outside markers. Genetics 66, 429–447.CrossRefGoogle Scholar
Whitehouse, H. L. K. (1957). Mapping chromosome centromeres from tetratype frequencies. Journal of Genetics 55, 348–360.CrossRefGoogle Scholar
Wickramaratne, M. R. T. (1974). Gene conversion in Ascobolus immersus and the control of recombination in Neurospora crassa. Ph.D. thesis, Imperial College, London.Google Scholar
Wickramaratne, M. R. T. & Lamb, B. C. (1975). The determinants of gene conversion properties in Ascobolus immersus. Heredity 35, 428.Google Scholar
Yu-Sun, C. C. C. (1966). Linkage groups in Ascobolus immersus. Genetica 37, 569–580.CrossRefGoogle Scholar
Yu-Sun, C. C. C., Wickramaratne, M. R. T. & Whitehouse, H. L. K. (1977). Mutagon specificity in conversion pattern in Sordaria brevicollis. Genetical Research 29, 65–81.CrossRefGoogle Scholar