bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some details and effects of the premeiotic controls of recombination frequencies inNeurospora crossa
Authors: Lamb B. C. 
Published: September 2009

SUMMARYRecombination data from crosses made at a single constant temperature of incubation were compared with those from crosses transferred to a different temperature at either the time of conidiation of protoperithecia by the strain of opposite mating-type, or after fertilization when crozier stages were first visible. Results were also compared from reciprocal crosses, from crosses made in different ways and from crosses in which protoperithecia were conidiated at different stages of maturity.Different temperature regimes during vegetative growth and proto-perithecial development had highly significant effects on subsequent meiotic recombination, while temperature differences during later premeiotic stages (between conidiation of protoperithecia and the crozier stage) had no or little effect. It was found that premeiotic controls could have as great, or greater, effects on meiotic recombination than those operating directly during meiosis. The possible adaptive significance of this is discussed.Recombination frequencies were affected by the method of making a cross (joint-inoculation of strains of opposite mating-type, or conidiation of protoperithecia), and by protoperithecial age at the time of conidiation by the opposite mating-type. Differences in recombination between reciprocal crosses were obtained and were dependent on temperature of incubation and age of protoperithecia at the time of conidiation. Recombination was not affected by different lysine concentrations in the medium. Genetic differences in premeiotic effector-production between the strains used were inferred.
Inactivation of whole chromosomes in mammals and coccids: some comparisons
Authors: Chandra H. Sharat 
Published: September 2009

SUMMARYGenetic systems involving developmental inactivation of entire chromosomes occur in two widely different groups of organisms: mammals and coccids (Homoptera: Insecta). The two groups show several similarities and some interesting contrasts with respect to this unusual cytogenetic phenomenon. Although mammalianXchromosomes and coccid paternal sets are components of different genetic systems, comparisons between them nevertheless suggest approaches that might prove to be of value. Further, the occurrence of facultative heterochromatization in these two wholly unrelated taxa must mean that this type of heterochromatization represents a fundamental capacity of chromosomes.
Associative overdominance caused by linked detrimental mutations
Authors: Ohta Tomoko 
Published: September 2009

SUMMARYAssociative overdominance due to linked detrimental mutations was investigated using the method of moment equations based on diffusion models. The expectation of the apparent selective value at the marker (neutral) locus has been evaluated. Assume two linked loci, at one of which the steady flux equilibrium is reached under constant mutational input of deleterious mutations (with ratev) having disadvantageshsin heterozygote andsin homozygotes. At another locus, the neutral alleles are segregating with frequencies near 0·5. Let Nebe the effective size of the population andcbe the recombination fraction between the two loci. Then the coefficient of associative overdominance at the neutral locus can be obtained by taking the expectation with respect to chromosome frequencies at steady flux equilibrium. It becomes approximatelywhere (LI−L0) is the inbreeding depression caused by deleterious mutations under complete inbreeding, andNehs≫ l andhs≫vare assumed. More generally, if the inbreeding depression of a chromosome segment with a length of recombination fraction C is (LI−L0) then s′ at the neutral marker at the edge of the segment iswherehsis the average heterozygote disadvantage of detrimentals.The significance of the associative overdominance is discussed in relation to actual observations. It is proposed that the most of the observed heterozygote superiority including inversion chromosomes ofDrosophila, isozyme alleles inAvenaand ABO blood group genes in man could be explained by the associated detrimentals.
Recombination and complementation between R factors inEscherichia coliK 12
Authors: Foster T. J. , Howe T. G. B. 
Published: September 2009

SUMMARYRecombination between chloramphenicol-sensitive (Cms) mutants of Rl, and R100, has been demonstrated inEscherichia coliK12rec+; it occurs at reduced frequency inrecBandrecC, and is not detectable inreeA, indicating that R factor recombination depends on host functions. Some mutants of R1 also recombine with an R100 mutant in a similar way.recAcells carrying an R1 and an R100 Cmsmutant (hetero-R state) have a low level of chloramphenicol-resistance, and form a chloramphenicol acetyl transferase that has lower specific activity than enzyme from hosts carrying wild-type or recombinant factors. These results suggest the occurrence of interallelic complementation between mutant R factors.
p–Fluorophenylalanine-induced mitotic haploidization inUstilago violacea
Authors: Day A. W. , Jones J. K. 
Published: September 2009

SUMMARYHaploid segregante from vegetative diploids ofUstilago violaceaappear as spherical colonies (papillae) growing above a background of dead diploid cells on complete medium containing DL-p–fluorophenylalanine (PFP). Most mutants segregate normally but one-third of the mutants were expressed infrequently in 0–5% papillae only. These mutants, designated ‘missing-markers’, were found to be on either of two chromosomes that remained disomic after treatment with PFP. When cells from a disomic papillum were streaked on complete medium, monosomics in which ‘missing-markers’ were expressed segregated spontaneously at a low frequency. Thus, of 10–12 linkage groups identified inU. violacea, two remain disomic after PFP treatment. Possible reasons for these differences between chromosomes in the same genome are discussed.Haploid and diploid stock cultures did not differ either in resistance to PFP, or in the production of papillae on PFP medium. Haploid segregante from a diploid were slightly more resistant to PFP than the wild-type haploid cultures under some conditions, but were very different in that they no longer produced papillae on PFP medium. These haploid segre-gants resembled one of three PFP-resistant mutants (pfp-A) isolated from a wild-type haploid stock grown on PFP medium. The significance of these results to the mechanism of haploidization inU. violaceais discussed.
The position of a locus on chromosome 5B ofTriticum aestivumaffecting homoeologous meiotic pairing
Authors: Wall A. M. , Riley Ralph , Gale M. D. 
Published: September 2009

SUMMARYAn investigation was made of the chromosomal position of the mutant locus, in Mutant 10/13 ofTriticum aestivum(2n= 6x= 42), affecting homoeologous chromosome pairing at meiosis. In hybrids between Mutant 10/13 and rye (Secale cereale2n= 14), homoeologous chromosomes frequently pair at meiosis although normally, in wheat-rye hybrids, this happens infrequently.The association of the mutant condition with chromosome 5B was determined by (i) the absence of segregation in hybrids obtained when Mutant 10/13 monosomic 5B was pollinated by rye; (ii) the occurrence of trisomie segregation for pairing behaviour in 28-chromosome wheat-rye hybrids, obtained from SB trisomie wheat parents with two 5B chromosome from a non-mutant and one from a mutant parent; (iii) the absence of segregation for pairing behaviour in the 29-chromosome wheat-rye hybrids obtained from the same trisomie wheat parents.The alternative pairing behaviours segregated independently of the centromere when wheat plants that were simultaneously heteromorphic, 5BLtelocentric/5B complete, and heterozygous for the Mutant 10/13 state, were pollinated by rye. The alternative chromosome-pairing patterns segregated to give a ratio not different from 1:1, so that the association of homoeologous pairing with Mutant 10/13 probably derived from the occurrence of mutation at a single locus on 5BL. In the disomic heteromorphic state, 5BLwas 91 map units in length.Trisomie wheats with two complete 5B chromosomes and one 5BLtelocentric, that were also heterozygous for the Mutant 10/13 condition, were pollinated by rye. Among the resulting 28-chromosome hybrids there was a 2:1 segregation of hybrids with low pairing: high (homoeologous) pairing and also of hybrids with complete 5B: telocentric 5BL. However, there was no evidence of linkage in this trisomie segregation. All the 29-chromosome hybrids from this cross had low pairing and it could be concluded that the single mutant allele, in Mutant 10/13, was recessive. In the trisomie condition, relative to a simplex situation, 5BLwas 33·05 map units in length.The critical locus on 5BLwas designatedPairing homoeologous. The normal dominant allele was symbolizedPhand the recessive allele, in Mutant 10/13,ph.The prevention of homoeologous pairing by the activity of a single locus makes the evolution of the regular meiotic behaviour ofT. aestivummore readily comprehensible.
Two-environment selection with inbreeding inSchizophyllum commune
Authors: Connolly V. , Simchen G. 
Published: September 2009

SUMMARYIn two-way selection for growth rate in the fungusSchizophyllum communein two environments (20 °C and 30 °C) response for low growth rate was always greater than for high. This asymmetry was due to inbreeding depression combined with a greater selection differential associated with the low lines in the high temperature environment. Despite the high level of inbreeding applied, two low selection lines derived from the same source (parental isolate 2) showed no decrease in genetic variance during selection. This maintenance of genetic variance was associated with a decrease in stability of development relative to the corresponding high selection lines.
Bare-patches, a new sex-linked gene in the mouse, associated with a high production of XO females: I. A preliminary report of breeding experiments
Authors: Phillips Rita J. S. , Hawker S. G. , Moseley H. J. 
Published: September 2009

SUMMARYBare-patches (Bpa), a semi-dominant, sex-linked, male-lethal gene in the mouse is described. It shows 14·5 ± 3·0% recombination with Blo and 5·4 ± 2·2 % with Ta and may, therefore, be allelic with Str.Only about half the expected number of heterozygous females is observed; the remainder appear to lose their mutant chromosome and become XO females as there is an excess of non-Bpa females, at least 24% of which proved to be XO. It is not yet certain whether the lost X chromosome is always the mutant one nor is it certain whether the loss is a property of the Bpa gene or due to a closely linked factor: a separate factor seems more likely. Some possible mechanisms for XO production are discussed.
Corresponding-site interference, synaptinemal complex structure, and 8+:0mand 7+:1moctads fromwild-type×mutantcrosses ofAscobolus immersus
Authors: Lamb B. C. , Wickramaratne M. R. T. 
Published: September 2009

SUMMARY‘Wider ratio’ octads (8:0, 0:8, 7:1 and 1:7) regularly occurred inwild-type(+) ×whiteascospore(w) crosses of the Pasadena strains ofAscobolus. Control crosses showed that phenocopies and false octad clusters were absent or rare; no reversion fromwto + occurred, but mutation from + towwas found at a number of loci, with nearly all 0+:8wand many 2+:6woctads in + ×wcrosses arising from mutation, not conversion. Nearly all 8+:0w, 7+:1wand 6+:2woctads appeared to arise by conversion.The finding of genuine wider ratio octads implies hybrid-DNA formation at corresponding sites inbothpairs of non-sister chromatids in the same bivalent, which conflicts with models of the synaptinemal complex requiring that only two of the four chromatids pair intimately at any point. Octad types arising from hybrid-DNA formation at corresponding sites in both pairs of non-sister chromatids were described and formulae were derived for their frequencies. The lack of genuine wider ratio octads in several otherAscobolusstudies was shown to be explicable quantitatively in terms of their conversion frequencies.‘Corresponding-site interference’ is defined as interference between the two pairs of non-sister chromatids of a bivalent in hybrid-DNA formation at exactly corresponding sites. Formulae based on observed octad frequencies were derived for calculating coincidence values for this kind of interference. Corresponding-site interference was found to be weak, with coincidence values differing between crosses with high and with low conversion frequencies.
Further studies on the maintenance of mate-killer (mu) particles in Stock 540Paramecium aurelia
Authors: Franklin J. 
Published: September 2009

SUMMARY1. Mu particles can be removed from stock 540Paramecium aureliaby incubation in a solution of 1·0 mg/ml RNAase for 12 h. Only a relatively small percentage of cells become mu-free and it is suggested that this variation is due to the activity of the M genes producing metagons at different times.2. Paramecia, made mu-free by growth at elevated temperatures, can be re-infected with mu by allowing the cells to swim in a brei of stock 540 paramecia. The re-infection is only permanently successful with cells that were made mu-free 10 days earlier.
The position on chromosome 5B of wheat of the locus determining crossability with rye
Authors: Lange Wouter , Riley Ralph 
Published: September 2009

SUMMARYThe allelekr1, conditioning ready crossability between wheat and rye when wheat is the female parent, is at a locus already known to be on chromosome 5B of wheat. This locus was mapped using a telocentric chromosome consisting of the long arm of chromosome 5B. Mapping was carried out by analyses ofF2and testcross progenies. The two experiments gave a mean recombination frequency, between the locus and the centromere, of 11·45 ± 3·0%. The possibility of different recombination frequencies in male and female meiosis is discussed.
Variability of recombination frequencies in theftrcistron ofCoprinusand its influence on the identification of marker effect alleles
Authors: Moore David 
Published: September 2009

SUMMARYThe variability of recombination frequencies between alleles of theftrcistron is assessed and shown to be normally in the range of ± 25% though occasionally replicates differed by a factor of two and in rare cases even more extremely. It is shown that the variation results from biological differences between separate attempts at the same cross and cannot be ascribed to sampling error or any other controllable cause. In the light of this variability the marker effect alleles already recognized in this cistron are re-examined with a new series of crosses. It is confirmed that marker effect may act to enhance or reduce the recombination frequency but it is shown that enhancement can be expressed in two entirely different ways. There is one type of site which causes a uniform doubling of the recombination frequency in all crosses no matter where the second site is placed in the map. The second type of marker effect enhancement site causes a very great increase in recombination frequency in crosses against relatively closely linked mutants, but its effect diminishes as the distance between the marker effect site and the second site is increased.
A model of mutation appropriate to estimate the number of electrophoretically detectable alleles in a finite population
Authors: Ohta Tomoko , Kimura Motoo 
Published: September 2009

SUMMARYA new model of mutational production of alleles was proposed which may be appropriate to estimate the number of electrophoretically detectable alleles maintained in a finite population. The model assumes that the entire allelic states are expressed by integers (…,A−1,A0,A1, …) and that if an allele changes state by mutation the change occurs in such a way that it moves either one step in the positive direction or one step in the negative direction (see also Fig. 1). It was shown that for this model the ‘effective’ number of selectively neutral alleles maintained in a population of the effective sizeNeunder mutation rate υ per generation is given byWhen 4Neυ is small, this differs little from the conventional formula by Kimura & Crow, i.e.ne= 1 + 4Neυ, but it gives a much smaller estimate than this when 4Neυ is large.
Mutants of Coprinus selected for resistance to D-glucosamine and L-sorbose
Authors: Moore David 
Published: September 2009

SUMMARYMutants resistant to growth inhibition have been obtained by selecting on media containing inhibitory concentrations of either d-glucosamine or l-sorbose. All of the mutants isolated were found to be sugar transport-defective and cross-resistant to growth inhibition by the three analogues 2-deoxy-d-glucose, d-glucosamine and l-sorbose. Like the mutants previously selected for resistance to 2-deoxy-d-glucose, the new mutants described are all shown to be alleles of the ftr cistron.
General and specific effects of modifiers of mutant expression
Authors: Thompson James N. 
Published: September 2009

SUMMARYStrains homozygous for mutants affecting the length of the L4 vein in Drosophila melanogaster were selected for increased or decreased vein length. Substitution of chromosomes selected for their effect on one mutant into the genome of a non-homologous mutant has shown that many modifiers of mutant expression must be considered as acting generally on the character rather than affecting only a specific mutant.
Polarity of gene conversion and post-meiotic segregation at thebufflocus inSordaria brevicollis
Authors: Bond D. J. 
Published: September 2009

SUMMARYThe flanking markers of wild-type recombinant spores originating from crosses of spore colour mutants inSordaria brevicolliswere analysed. Recombinant asci were of two main types – either with one or with two wild-type spores. In most crosses the behaviour of flanking markers was significantly different for these two types of recombinant asci. The main differences were in the polarity of gene conversion (as inferred from parental outside marker combinations) and in the frequency of recombinant outside markers. These differences were interpreted in terms of hybrid DNA models of recombination and correction of heteroduplex DNA.
Genetic evidence for a polycistronic unit of transcription in the complex locus ‘14’ inPodospora anserinaII. Genetic analysis of informational suppressors
Authors: Picard Marguerite 
Published: September 2009

SUMMARYForty-one suppressors obtained after NG and EMS mutagenesis of two ‘polar’ mutants of segment ‘29’ inPodospora anserinawere genetically analysed. Three classes of suppressor could be distinguished on spectrum pattern criteria. One representative suppressor of each class was demonstrated to be non-gene specific. The class I suppressor was dominant and only suppressed polar mutants in segment ‘29’ and non-ICR-induced ones in genes where polarity cannot be determined. Class II and III suppressors were partially dominant and they suppressed polar, non-polar and even ICR-induced mutants. The difference between classes II and III seems to be only quantitative. According to whether class II and III suppressors are considered strongly or weakly allele-specific, two hypotheses are considered. First,tRNAs could be involved in all three classes of suppression: class I would be nonsense-specific and classes II and III would be nonsense-missense suppressors. Secondly,tRNA could be involved only in class I suppression, while ribosomal ambiguity could be responsible for class II and III suppression.
Developmental mutants in a homothallic strain ofPhysarum polycephalum
Authors: Wheals A. E. 
Published: September 2009

SUMMARYA derivative line of the homothallic Colonia strain ofPhysarum polycephalumhas been isolated which produces plasmodia with high efficiency within clones of amoebae. Using the synergistic effect of ultraviolet light and caffeine, mutants of this line have been isolated which fail to undergo the developmental transition between haploid amoebae and diploid plasmodia (aptmutants). They are isolated by selecting for amoebae which fail to produce plasmodia within clones. Complementation tests of four mutants have shown that they are mutants of four different loci and they are recessive to wild-type. A further analysis of one mutant reveals that theapt-1locus is unlinked to three other known markers. Crosses of this mutant with heterothallic strains yield progeny which are homothallic indicating that the lesion is not a revertant from a homothallic to a heterothallic mating-type. The use of this system in isolating developmental mutants is discussed.
Sex ratio distortion and semi-sterility in the progeny of irradiatedGlossina morsitans
Authors: Curtis C. F. , Langley P. A. , Mews A. R. , Offori E. D. , Southern D. I. , Bell P. E. 
Published: September 2009

SUMMARYMaleGlossina morsitanswere subjected to various doses of gamma radiation in air or nitrogen and mated to untreated females. The sex ratio of theF1progeny was biased towards males, and this may be explained by the extra vulnerability to dominant lethal induction that the presence of the largeXchromosome gives to female determining sperms. The mean fertility of theF1progeny was subnormal. This was due to the induction of 50 % sterility in a large proportion ofF1individuals. Cytogenetic examination of the progeny of outcrosses ofF1individuals indicated that in most of the semi-steriles there were translocations involving the large autosomes or theYchromosomes. Almost all the normally fertileF1flies gave only cytogenetically normal progeny. TheF1sex-ratio distortion and semi-sterility would provide a ‘bonus’ in the application of the sterile male technique, which would amount to a 15–50% saving in the releases required to achieve a population control target compared with the requirement if theF1was normal.
Reproductive lifespan in irradiated and unirradiated chromosomally XO mice
Authors: Lyon Mary F. , Hawker Susan G. 
Published: September 2009

SUMMARYLifetime reproductive performance was studied in 50 sib-pairs of female mice, one member of each pair chromosomally XX and the other XO. Twenty-five pairs were irradiated with 25 rad X-rays at 10 days of age and 25 were unirradiated. In both the irradiated and control series the XO mice had a significantly shorter reproductive life than the XX ones, but unirradiated XO bred longer than irradiated XX. The median age of unirradiated XO at birth of last litter was 280 days and they had 6·5 ± 0·80 litters, whereas for XX the figures were 420days and 12·6 ± 0·74. The mean litter-size of XO mice was only about 55% and their lifetime productivity 34% of that of their XX sibs. Similarly, the lifetime productivity of irradiated XX females was only 31% of that of unirradiated XX. Histological studies showed that in the unirradiated XO mice reproduction ended through shortage of oocytes, and the resulting secondary ovarian changes were similar to those in irradiated mice. Thus, the differences between human and mouse XO types are to some extent reconciled. Both become sterile through death of oocytes, in humans before puberty and in mice after. This difference may be connected with different times from oogenesis to puberty in the two species.
Multiple gene control of the tRNA aminoacylating system inDrosophila melanogaster
Authors: Rose Raymond W. , Hillman Ralph 
Published: September 2009

SUMMARYThe stimulation ofin vitrotRNA aminoacylation by post-microsomal supernatant enzymes isolated fromAbnormal Abdomen(A53g) adult flies is a function of the residual genome of these flies rather than of the major mutant gene,A53g. Genes controlling this stimulation are located on theXchromosome as well as on the autosomes. These observations are discussed in terms of the phenotypic effect of the major mutant gene in response to changes in protein synthesis which are under the control of modifier genes responsible for aberrant genetic translation mechanisms.