bluuebunny/crossref_metadata_2025_split huggingface dataset:
The correlation of rare alleles with heterozygosity: determination of the correlation for the neutral models
Authors: Eanes Walter F. , Koehn Richard K. 
Published: September 2009

SUMMARYWe have shown in an earlier paper that there is routinely a large correlation between the heterozygosity of common (P> 0·05) alleles and the number of rare (P≤ 0·05) alleles at allozyme loci inDrosophila. We postulated that this correlation might be due to a high rate of intragenic recombination. While these correlations are large enough to be significantly different from zero, their relation to the mean correlations expected under the neutrality models is unknown. This paper reports the findings of a computer analysis determining the correlation for neutral allele pools as specified by the infinite-allele and charge-state models.In the analysis, mean correlations for a range ofNeμ values and sample sizes of 100 and 1000 genes varied from a high of 0·284 to a low of – 0·780. For the particular values ofNeμ relating to the heterozygosity ofDrosophilaallozymes in natural populations, tests of the empirical correlations to the means expected under the neutral models are made. Most empirical correlations are significantly different from the mean correlations under the neutrality models.
Genetic distance between the Australian Merino and the Poll Dorset Sheep
Authors: Manwell Clyde , Ann Baker C. M. 
Published: September 2009

SUMMARYMerinos (189) and Poll Dorsets (106) were compared for genetic variation at 30 loci for blood proteins. ‘Malic enzyme’ and NADH diaphorase I polymorphism occur in Merinos but not in Poll Dorsets, whereas both breeds are polymorphic for haemoglobin, erythrocyte X-protein, serum esterase, catalase and transferrin, although the breeds differ in the presence or absence of certain rare transferrin variants. Poll Dorsets but not Merinos have genetic variation of erythrocyte pyruvate kinase at low gene frequencies; Merinos but not Poll Dorsets have genetic variation of two erythrocyte Gly-Leu peptidases, glucosephosphate isomerase, superoxide dismutase, and NADH diaphorase II, all at low gene frequencies (P< 0·05).Using Masatoshi Nei's (1972, 1976) standard genetic distance, over all 30 loci, to calculate the time of divergence of the two breeds, we obtainedt= 69700 years – whereas sheep are believed to have been domesticated by man for not more than 11000 years, and ancestors of the British breeds and of the Merino have probably not been separated for more than 2000 years. Several possible explanations for this discrepancy are discussed, including the accuracy of the coefficient of codon change (α), changes in population size and structure, selection, and additional hybridization in the ancestry of the Merino.
Information on the nature oft-haplotypes from the interaction of mutant haplotypes in male fertility and segregation ratio
Authors: Lyon Mary F. , Mason Irene 
Published: September 2009

SUMMARYThet-haplotypet6interacts with brachyury,T, to produce taillessness, and exhibits lethality, male sterility and high male segregation ratio. Mutant haplotypes derived fromt6which have lost the lethality also lose the sterility. We here report that two mutants which have retained the lethality have also retained the sterility and suggest that the two properties of lethality and sterility are due to a factor or region of thet-haplotype located close to the locus oftf. Althought6has a high male segregation ratio, mutants derived from it may have low or normal ratios. In trans heterozygotes of two mutant haplotypes the ratios tended to be equalized, whereas in cis heterozygotes a high ratio liket6was obtained, at least in one case. On this evidence the low-ratio geneLowis reinterpreted as a mutantt-haplotype and designatedtlow. It is suggested that abnormal ratio is due to anA-factor or region located between the loci ofTandtf, so thatt6carries T-, A- and LS-factors which can exist separately and retain their properties.t6may extend less proximally than other naturalt-haplotypes, which in general may involve changes in interstitial heterochromatin.
Evidence from chimaeras for the pattern of proliferation of epidermis in the mouse
Authors: Green Margaret C. , Durham Dianne , Mayer Thomas C. , Hoppe Peter C. 
Published: September 2009

SUMMARYThe recessive mutant gene downless (dl) causes abnormal texture of the coat and absence of hair on the tail. Thedllocus had previously been shown to act in the epidermis and not in the dermis. To obtain evidence on the pattern of proliferation of epidermis, downless ↔ normal chimaeras were produced by embryo aggregation, and the pattern of normal and mutant hair in the coat was examined. The chimaeras showed a pattern of narrow transverse stripes of normal and abnormal hair. This pattern was similar to that found in mice chimaeric for alleles at the agouti locus known to act in the dermis. This evidence supports the conclusion that the pattern of cell proliferation is similar in dermis and epidermis, and is compatible with the hypothesis that both tissues proliferate by lateral coherent clonal growth from a randomly mixed array of longitudinally arranged cells.
Inheritance of reaction to halothane anaesthesia in pigs
Authors: Smith C. , Bampton P. R. 
Published: September 2009

SUMMARYThe inheritance of reaction to halothane anaesthesia (so-called malignant hyperthermia syndrome) in pigs was studied in a series of 61 litters by 18 sires from an F3–F4 Pietrain–Hampshire crossbred population. A single locus two allele model allowing for reactors from all three genotypes, was fitted by maximum likelihood. It was concluded that the reaction is due to a single autosomal recessive gene with a frequency of 0·46 (0·44–0·48) and penetrance of 0·95 (0·92–0·98) in this stock.
Dislodgement and thymineless elimination of N-group plasmids
Authors: Pinney R. J. , Jacob A. E. , Hedges R. W. , Smith J. T. 
Published: September 2009

SUMMARYThymineless strains ofEscherichia coliC600 were constructred harbouring both an R factor of the N incompatibility group (R46 or R447b) and a compatible plasmid (Plac-of the A-C group or the Iα plasmid R62), which contained a segment of N group DNA. Selection was made for the transferred plasmid and dislodgement phenomena were manifest either as loss of an entire plasmid or as deletions of a region of plasmid DNA. Even after the two R factors had become established as separate replicons, the N group R factor but not the other plasmid exhibited instability.Thymine starvation of strain C600thy(R447b/R62) increased the elimination rate of the N group plasmid R447b but no elimination of R62 was observed. However, thymine starvation of strain C600thy(R46/Plac-) not only increased the rate of elimination of R46 but also increased the rate of loss of Plac-. There was no detectable increase in nuclease activity in unstarved R46/Plac-strains and it is concluded that dislodgement of R46 from these strains is not due to induction of the nuclease that has been proposed to be responsible for the elimination of N group plasmids during thymine starvation.Two variants of Plac-were isolated. These did not dislodge R46 from unstarved R46/Plac-strains and were not lost during thymine starvation even though thymineless elimination of R46 occurred at normal frequency.
Resistance to p-fluorophenylalanine in diploid/haploid dikaryons: dominance modifier gene explained as a controller of hybrid multimer formation
Authors: Lewis D. , Vakeria Dina 
Published: September 2009

SUMMARYThe gene pfpr-10 in Coprinus confers resistance to p-fluorophenylalanine. The resistance of the heterozygote pfpr-10/pfp8-10 is completely recessive, both in diploids and dikaryons. A dominance modifier Mod+ makes pfpr-10 dominant in a dikaryon but not in a cliploid. It also enhances the degree of resistance in r homozygotes. These results are explained on a hypothetical model based upon a hexameric product of the pfpr-10 gene, with resistance to PFP being proportional to the percentage of homo r hexamers. The Mod+ is presumed to act by keeping the r and s products separate so that hybrid multimers are reduced to a minimum. Critical threshold concentrations of PFP for diploid/haploid dikaryons in 40 different combinations of pfpr and Mod+ genes cover a wide range of gene doses and percentage of homo r multimers. The relationship between the critical threshold concentrations and the calculated percentage of homo r multimers supports the model.
Protein variation in the plaice,Pleuronectes platessaL.
Authors: Ward R. D. , Beardmore J. A. 
Published: September 2009

SUMMARYThirty-nine enzyme loci and seven non-enzymic protein loci have been screened for electrophoretically detectable variation in a population ofPleuronectes platessa, a marine flatfish. The mean heterozygosity per individual is 0·102 ± 0·026, or 0·118 ± 0·030 if the non-enzymic proteins are excluded. The distributions of allele frequencies and single locus heterozygosities are given, and the results discussed with reference to current theories concerning the nature of protein variation.
Derivation of mutantt-haplotypes of the mouse by presumed duplication or deletion
Authors: Lyon Mary F. , Bechtol Kathleen B. 
Published: September 2009

SUMMARYThe genetic properties of some new mutantt-haplotypes derived from the naturally occurring haplotypet6have been investigated. Several mutant haplotypes gave taillessness with brachyury,T, were viable when homozygous, and when in compound witht6, and all these expressedtfand appeared to have arisen by meiotic crossing-over betweenTandtfin the region of crossover-suppression oft6. The haplotypeth17arose by crossing-over in a stock oft6carrying the translocation T(1; 17) 190Ca, in which the translocation break in chromosome 17 is within the crossover-suppressing region; henceth17could not be separated from T190. It was of the complementary crossover type in that it did not interact withT, and was lethal in compound witht6; its male segregation ratio was normal with heterogeneity. A further haplotype,th20, expressedtf, gave taillessness withT, and was lethal when homozygous and in compound witht6. The expression oftfwas attributed to a deletion, which also covered the loci of the nearby lethals knobbly,Kb, andtw5.th20showed weak complementation oftw5. The haplotypeth7had previously been interpreted as carrying a duplication; it was shown that this duplication was semi-lethal when homozygous. it is suggested that lethal mutantt-haplotypes commonly arise by duplication or deletion but such structural changes are not necessarily at the end of the haplotype, and need not arise by unequal meiotic crossing-over.
On the gene conversion model as a mechanism for maintenance of homogeneity in systems with multiple genomes
Authors: Ohta Tomoko 
Published: September 2009

SUMMARYThe gene conversion model reported by Birky & Skavaril (1976) has been analytically studied by using the theory of diffusion models of Kimura (1964) in population genetics. It has been shown that the fate of new mutations in systems with multiple genomes may be satisfactorily treated by the diffusion model.
Optimum selection intensities in artificial selection programmes: an experimental evaluation
Authors: Frankham R. 
Published: September 2009

SUMMARYAn experimental evaluation of Robertson's (1970) theory concerning optimum intensities of selection for selection of varying durations has been carried out using published results from a long term selection study inDrosophila. Agreement of predicted rankings of treatments with expectations was excellent for low values oft/T(generations/total number scored) but poor for larger values oft/T. This was due to the 20% selection intensity treatments responding worse than expected and the 40% treatments relatively better than expected. Several possible reasons for the discrepancies exist but the most likely explanation is considered to be the greater reduction in effective population size due to selection in treatments with more intense selection.
Genetic analysis of larval feeding behaviour inDrosophila melanogaster: II. Growth relations and competition between selected lines
Authors: Burnet Barrie , Sewell David , Bos Marten 
Published: September 2009

SUMMARYGrowth relations of lines selected for fast or slow larval feeding rate have been compared with those in the genetically heterogeneous control base population from which they were derived. Larvae of the slow strain have reduced growth rate and reach their critical weight for pupation later than unselected larvae. Larvae of the fast strain attain their critical weight at the same time as the unselected control larvae, suggesting that growth rate in the precritical period of development is already maximized in the base population and cannot be improved by increasing food intake. This constraint does not apply to the fixed period of post-critical growth however, since fast feeding larvae give rise to larger adult flies than the controls.Larval feeding rate is affected by genes located on all three major chromosomes. The small fourth chromosome has negligible effect. Selection for slow feeding rate has led to an increase in the frequency of recessive genes affecting the character. High scores of larvae selected for fast feeding rate depend upon interactions between non-homologous selected chromosomes which individually have little effect. Larval feeding rate in the control unselected population appears to be buffered, firstly by epistatic interactions against the effects of chromosomes tending to promote ‘supra-optimal’ feeding rate and, secondly, by dominance against chromosomes promoting a lowering of feeding rate.Under conditions of scramble type competition between the selected lines for limited resources, fast feeding larvae have a higher survival rate, and complete their period of larval development earlier to give larger adult flies than their slow feeding competitors. The contribution of larval feeding rate to competitive ability at different levels is discussed, and it is suggested that the effects of change in this behavioural character may be far reaching.
Response to selection for increased pupa weight inTribolium castaneumas related to population structure
Authors: Katz Alan J. , Enfield Franklin D. 
Published: September 2009

SUMMARYThe effectiveness of selection for increased pupa weight inTriboliumwas compared for three different selection systems. In all three systems the same number of breeding individuals was used each generation. Population L was a large random mating population with 24 males and 48 females selected each generation. The C4and C8populations were each divided into 6 subpopulations (lines) consisting of 4 males and 8 fem ales. Each of the three populations was replicated. In C4, selection for pupa weight was within lines for three generations, followed by a generation of among-line selection when the best two out of six lines were selected. These lines were then crossed to produce 6 new subpopulations, and the cycle was repeated. The C8population was handled in exactly the same manner except that seven generations of selection within lines were practised before each generation of among-line selection. Selection response for the 42-generation period was significantly greater in the L population than in either subdivided population. No consistent differences among the selection systems were apparent when evaluating short-term response for the first 12 generations of the experiment. The results were interpreted as indicating that the influence of multiple-peak epistasis was not of major importance for this trait in determining ultimate response to selection when starting from a base population of previously unselected lines and utilizing a within- and among-line selection regime.
Warfarin resistance: a balanced polymorphism in the Norway rat
Authors: Greaves J. H. , Redfern R. , Ayres P. B. , Gill J. E. 
Published: September 2009

SUMMARYThe frequency of monogenic resistance to anticoagulant rodenticides in Rattus norvegicus in an area straddling the England–Wales border was monitored from 1967 until 1975. Rats were trapped on farms and tested in the laboratory by administering a dose of warfarin lethal to susceptibles. The mean incidence of resistance was 44% and did not change significantly, despite the extensive use of anticoagulants by farmers during the 9-year period. In 1975 more refined techniques showed that the frequencies of susceptible (SS) and resistant (RR) homozygotes were significantly below the Hardy–Weinberg expectations and simple estimates of the relative fitness ratios for the RR, RS and SS phenotypes were 0·37, 1·0 and 0·68 respectively. In two relatively isolated valleys, where selection with anticoagulants was minimal, the frequency of resistance decreased significantly from 57% to 39% during 1973–5. The results are consistent with the hypothesis that a balanced polymorphism is being maintained. Selection against susceptible homozygotes by the use of anticoagulant rodenticides, and against the resistant homozygote due to its high susceptibility to a primary deficiency of vitamin K gives the heterozygotes a selective advantage. A number of ecological factors that influence the incidence of the resistance are discussed briefly.
Effect of pre-treatment with 5-bromouracil in an ultraviolet sensitive strain ofNeurospora crassa
Authors: Nemerofsky Arnold 
Published: September 2009

SUMMARY5-Bromouracil was shown to enhance the mutation frequency in an ultraviolet sensitive strain ofNeurospora crassa (uvs-2) that was previously irradiated with ultraviolet light. The design of the experiment eliminated light or dark repair as possible hypotheses to account for the observed enhancement. Since a similar effect was noted at therib-1 locus inN. crassa, which is not a UV-sensitive strain, it appears that the error prone repair mechanism inN. crassamay be related to post-replication repair. This enhancement may be attributed to the interference of 5-bromouracil with post-replication repair. It is also postulated that the maximum increase in the mutation frequency occurs when the greatest number of unrepaired pre-mutational UV lesions are repaired in the presence of 5-bromouracil.
Re-establishment of breeding stocks of mutant and inbred strains of mice from embryos stored at –196 °C for prolonged periods
Authors: Whittingham D. G. , Lyon Mary F. , Glenister P. H. 
Published: September 2009

SUMMARYBreeding stocks were re-established from embryos of various mutant and inbred strains of mice after prolonged storage in liquid nitrogen at the 8-cell stage even with strains where only a proportion of the progeny were of the desired type, i.e. in the ModPand XO strains. Gonadotrophin treatment failed to produce superovulation consistently in any of the strains tested. Although the initial survival of embryos after thawing and culture to the morula and blastocyst stage was highest for embryos from XO mothers (61%), these embryos suffered the heaviest early postimplantation loss after transfer (61%). The proportion of embryos, originally frozen, developing into foetuses and offspring was variable (13% HT, 14% PT, 20% ModP, 14% XO, 21% CBA and CBA-T6) and lower than previously reported for hybrid 3H1 embryos (20–30%). The sex ratio of the liveborn young was within the normal expected limits except for the Modpstrain, where it differed significantly from the exected 2♂:1♀ ratio. The proportion of young of the desired type from the frozen embryos of Modpand XO females was less than expected (17 and 3% respectively). In all cases a normal breeding stock was reestablished whose performance was within normal limits for each strain. Even without further improvements in embryo collection and the freezing techniqueper se, the storage of embryos in liquid nitrogen is an extremely economic way of preserving mouse genetic stocks.
Enrichment and screening of heat-sensitive mutants ofPhysarum polycephalum
Authors: Sudbery Peter , Haugli Kari , Haugli Finn 
Published: September 2009

SUMMARYA new method for the isolation of temperature-sensitive mutants ofPhysarum polycephalumis described. It involves enrichment and prescreening of mutagenized amoebae followed by screening at both the plasmodial and amoebal stage. A total of 74 temperature-sensitive strains were recovered of which 26 were temperature-sensitive only as plasmodia, 35 only as amoebae and 13 in both stages. After a shift to the nonpermissive temperature, DNA and protein synthesis were followed in temperature-sensitive plasmodia to discover if the lesion affected functions of the nuclear cycle.
Meiotic recombination in a duplication strain ofAspergillus nidulans
Authors: Van de Vate C. , Jansen G. J. O. 
Published: September 2009

SUMMARYThe (I; II) duplication strain ofAspergillus nidulanscontains a terminal segment of chromosome I twice, one copy being in the normal position, and the other one translocated to a tip of chromosome II. We show that in selfed cleistothecia (homozygous for the duplication) crossing-over between the two segments of the duplication followed by the appropriate disjunction and distribution of the meiotic chromosomes, results in segregation of recessive markers in the duplication. Alternative segregation mechanisms like the deletion mechanism responsible for mitotic non-conformity, cannot explain the observations. The average segregation frequency of the markeryA2 is 11%. Using the mathematical model outlined in the Appendix to this paper, we estimated the recombination frequency between the translocation breakpoint and theyAlocus from the segregation frequency. The essential feature of the model is the computation of the probabilities of combinations of different tetrad types in quadrivalents. Application of the model leads to the qualitative conclusion that the meiotic recombination frequency within the duplication is increased over the normal level. Elsewhere in the genome the frequencies are either unchanged or decreased. Also in crosses heterozygous for the duplication, an increase by at least a factor of two is found. As judged from the appearance of certain recombinant classes, the quadrivalent frequency in homozygous and heterozygous crosses is 2/3 (random pairing) or slightly higher. The increased recombination is attributed to the same lesions that are responsible for the occurrence of deletions in duplication strains ofA. nidulans.
The expression of the gene asebia in the laboratory mouse: I. Epidermis and dermis
Authors: Josefowicz Wendy J. , Hardy Margaret H. 
Published: September 2009

SUMMARYMice homozygous for the asebia mutation (ab/ab), which have defective sebaceous glands, display abnormalities in several other aspects of the integument. Histological sections showed that hyperplasia of the cellular layers and the stratum corneum of the epidermis is apparent at birth and increases markedly with age. Enlarged intercellular spaces are also noted in the epidermis. The thicker dermal layer of the asebic mice is characterized by increased vascularity, increased cellularity and the abnormal morphology of a large proportion of the ‘fibroblast’ population. Electron microscopy demonstrated the many abnormalities in the dermal fibroblasts as well as large amounts of cellular debris in the surrounding matrix. Collagen and elastin show alterations at the light microscopic and ultrastructural levels. Many features of the asebic dermis resemble those found with mild inflammation and with the lysosomal storage diseases. Changes in the dermis of asebic foetuses were noted prior to epidermal alterations and may mediate the latter.
Sufficient conditions for polymorphism with cyclical selection in a subdivided population
Authors: Hoekstra Rolf F. 
Published: September 2009

SUMMARYThe combined effect of multi-niche selection and cyclical selection is studied in a deterministic model. Sufficient conditions for protected polymorphism are derived for diploid populations with and without dominance and for haploid populations. These conditions appear to be broader than in the cases of only multi-niche selection or only cyclical selection.