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  • 1
    Electronic Resource
    Electronic Resource
    The molecular organisation of a B chromosome tandem repeat sequence from Brachycome dichromosomatica (1996)
    Springer
    Chromosoma 105 (1996), S. 223-230 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A high copy, tandemly repeated, sequence (Bd49) specific to the B chromosome and located near the centromere in Brachycome dichromosomatica was used to identify lambda genomic clones from DNA of a 3B plant. Only one clone of those analysed was composed entirely of a tandem array of the B-specific repeat unit. In other clones, the Bd49 repeats were linked to, or interspersed with, sequences that are repetitious and distributed elsewhere on the A and B chromosomes. One such repetitious flanking sequence has similarity to retrotransposon sequences and a second is similar to chloroplast DNA sequences. Of the four separate junctions analysed of Bd49-like sequence with flanking sequence, three were associated with the same A/T-rich region in Bd49 and the fourth was close to a 25 bp imperfect dyadic sequence. No novel B-specific sequences were detected within the genomic clones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004120050178
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  • 2
    Electronic Resource
    Electronic Resource
    Linkage disequilibrium and gametophytic self-incompatibility (1986)
    Springer
    Theoretical and applied genetics 73 (1986), S. 102-112 
    Details
    ISSN: 1432-2242
    Keywords: Linkage ; Linkage disequilibrium ; Gametophytic self-incompatibility ; Sheltering of lethals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The approach to linkage equilibrium of a locus linked to the locus determining gametophytic self-incompatibility (S) is considered. For the simplest case of three alleles at the S locus and two at the linked locus it is necessary to consider 3 measures of linkage disequilibrium. These are found to approach their equilibrium value of zero in one of three ways: 1) steadily declining to zero; 2) oscillating as decline proceeds; 3) a combination: 2) followed by 1). Linkage equilibrium may be established before genotype frequencies reach their expectation under random crossing. Earlier studies (Li 1951; Moran 1962) of the approach to S allele equilibrium have been based on the assumption that all types of pollen take part in fertilizations equally frequently. Such an assumption leads to simpler expressions for changes in S gene frequencies but is extremely unrealistic and, in particular, leads to a different rate of approach to equilibrium from the more comprehensive model. It is shown that even in the absence of selection it is not possible to predict the equilibrium gene frequency of a linked locus until S allele equilibrium is reached. This frequency may be either higher or lower than that calculated from a gene count in the starting genotype pool. However, these two gene frequencies may stabilize long before linkage equilibrium is achieved. An examination of selection against one genotype at the linked locus is undertaken. If linkage is complete, lethality can be less effective at reducing the gene frequency than is less intense selection (in only a few generations of selection). Here too linkage equilibrium may be established with selection still effective in bringing about a decline in gene frequency. An examination of the analysis and conclusions of Rasmuson (1980) shows that because these were based on the inadequate formulae previously discussed and exclude phenomena discussed above, they are misleading. The possibility of a gametophytic self-incompatibility system providing a sufficient condition for the sheltering of lethals in the absence of the condition of complete linkage to the S locus (r=0) is shown to be unlikely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00273726
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  • 3
    Electronic Resource
    Electronic Resource
    Fluctuations in heteromorphic self-incompatibility systems (1983)
    Springer
    Theoretical and applied genetics 66 (1983), S. 307-312 
    Details
    ISSN: 1432-2242
    Keywords: Heterostyly ; Oxalis compressa ; Modifier gene ; Self-incompatibility ; Isoplethy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic determination of heterostyly is briefly reviewed and experimental data are presented on the inheritance of tristyly in Oxalis compressa. It is shown that the model appropriate to Lythrum salicaria, of two diallelic loci, is inadequate to explain segregation patterns found in O. compressa, especially the reversal of dominance of the short phenotype. An extended model having an additional allele at the short locus, and a separate modifier gene, is presented and its deterministic genotype frequency dynamics examined numerically. It is shown that fixation of these extra genes or alleles is unlikely. Problems of testing the extended model are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251165
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  • 4
    Electronic Resource
    Electronic Resource
    Detection and estimation of linkage for a co-dominant structural gene locus linked to a gametophytic self-incompatibility locus (1988)
    Springer
    Theoretical and applied genetics 75 (1988), S. 882-888 
    Details
    ISSN: 1432-2242
    Keywords: Gametophytic self-incompatibility ; Linkage ; Disturbed segregations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The operation of gametophytic self-incompat ibility systems may lead to disturbed segregation ratios for genes at loci linked to the self-incompatibility loci. An exhaustive consideration of the types of crosses, methods of linkage estimation, progeny sizes and controls needed for accurate analysis of disturbed segregation ratios is presented. Examples of the application of these methods are included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00258049
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitatively determined self-incompatibility (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 641-644 
    Details
    ISSN: 1432-2242
    Keywords: Borago officinalis ; Isozyme ; Polymorphism ; Self-incompatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It is shown by simulation that a hypothetical multilocus, quantitatively determined self-incompatibility system, whether gametophytic or sporophytic, should maintain variability in small populations at a higher level than would panmixia. Studies of more than 20 isozyme loci show that borage has almost no variability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226731
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitatively determined self-incompatibility (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 427-430 
    Details
    ISSN: 1432-2242
    Keywords: Borago officinaux ; Inbreeding depression ; Outcrossing ; Self-incompatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It has been claimed that Borage (Borago officInalis L.) has a multifactorial self-incompatibility system. Such systems may have a high level of ineffective pollination, and we show that this is the case in borage. The ranking of seed set from highest to lowest is as follows: bee-pollination; natural pollination in the absence of bees; artificial cross-pollination between unrelated plants; artificial cross-pollination between related plants; artificial self-pollination. In diallel crosses, significant parental effects were detected but no consistent patterns of seed set, which suggest a simple self-incompatibility system, were detected. The level of outcrossing with natural pollination was very variable but greater than 50%. Thus, there appears to be no straightforward self-incompatibility system in borage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186090
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  • 7
    Electronic Resource
    Electronic Resource
    The heritability of fitness: some single gene models (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 278-284 
    Details
    ISSN: 1432-2242
    Keywords: Heritability ; Fitness ; Additive-genetic variance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Because directional selection exhausts additive-genetic variance, it is frequently claimed that the heritability of fitness should be very close to zero. However, mutation-selection balance generates a certain amount of additive-genetic variance, so that even parent-offspring measures of heritability may be greater than zero at equilibrium. Intra-generation heritability may also be non-zero, providing the potentials for genetic change following environmental change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225964
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  • 8
    Electronic Resource
    Electronic Resource
    Why are there so few homomorphic multi-locus sporophytically determined self-incompatibility systems? (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 955-958 
    Details
    ISSN: 1432-2242
    Keywords: Dominance ; Gametophytic ; Homomorphyic ; Self-incompatibility ; Speciation ; Sporophytic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Homomorphic multi-locus sporophytically determined self-incompatibility systems are much rarer than multi-locus gametophytic systems. This note examines some of the possible reasons for this disparity and concludes that, while each additional locus in a gametophytic system allows increased crossing among related plants as well as a lower mutation rate to maintain a given level of variability, the same conclusion cannot be drawn for sporophytic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211047
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  • 9
    Electronic Resource
    Electronic Resource
    Quantitatively determined self-incompatibility (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 375-378 
    Details
    ISSN: 1432-2242
    Keywords: Self-incompatibility ; Simulation ; Polygenes ; Borago officinalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary It has been reported that incomplete self-incompatibility could be determined in Borago officinalis by many genes. Simple ten-gene models for such enforced cross-fertilization have been developed and their properties examined by computer simulation. Mutation rates necessary to maintain a given level of variability in small populations are high, as already determined theoretically for oligogenic self-incompatibility systems. However, the extent of ineffective pollination is very much greater in the ten-gene system. This finding may be verifiable in borage if it is indeed self-incompatible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305831
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  • 10
    Electronic Resource
    Electronic Resource
    Quantitatively determined self-incompatibility. 5. Detection of multi-locus systems (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 562-566 
    Details
    ISSN: 1432-2242
    Keywords: Bioassay ; Coefficient of crossability ; Self incompatibility ; Linkage estimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Multi-locus self-incompatibility systems may be distinguished from single-locus systems by reciprocal differences in backcrosses and between crossed progeny of individual clearly compatible crosses. Such crosses are extremely laborious, so other methods have been suggested. In this note, it is shown that the coefficient of crossability is not a useful discriminant of self-incompatibility, as indeed should be expected from the properties of multi-locus systems, and that linkage methods are also unlikely to be successful. Until more self-incompatibility genes have had their sequences characterised, there is no substitute for the traditional genetical methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00838709
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