bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of replicated selection for body weight in mice on vertebral shape
Authors: Johnson D. R. , O'Higgins P. , McAndrew T. J. 
Published: September 2009

SummaryThe shapes of T1 and T2 vertebrae from unselected Q strain mice and from strains selected for large and small body size were studied by Fourier analysis in order to ascertain whether shape change was produced by size selection. The vertebrae of large, small and control strains were easily distinguishable, but between replicate groups shape differences were less marked. The main component of shape change was size related, but mice unselected for size also showed a non-size-related shape change.
Differential inhibition of the initiation of DNA replication in stringent and relaxed strains ofEscherichia coli
Authors: Guzman Elena C. , Carrillo Francisco J. , Jimenez-Sanchez Alfonso 
Published: September 2009

SummaryStarvation for isoleucine inhibits chromosome, minichromosome and pBR322 DNA replication in a stringent strain ofE. coli, but does not do so in a relaxed mutant. Starvation for other amino acids inhibits either chromosome and minichromosome replication in both strains. From these results we conclude thatoriCand pBR322 replication are stringently regulated and that isoleucine seems not to be essential for the protein synthesis required at the initiation oforiCreplication. Deprivation of isoleucine in a Rel−strain gives rise to amplification of minichromosome and pBR322 with a better yield of the latter plasmid than that following treatment with chloramphenicol.
Genome evolution in mosquitoes: intraspecific and interspecific variation in repetitive DNA amounts and organization
Authors: Black William C. , Rai Karamjit S. 
Published: September 2009

SummaryDNA reassociation kinetics were used to determine the amounts and organization of repetitive and unique DNA in four mosquito species:Anopheles quadrimaculatus(Say),Culex pipiens(L.),Aedes albopictus(Skuse) andAe. triseriatus(Say). Intraspecific variation in repetitive DNA amounts was examined in two geographic strains ofAe. albopictusfom Calcutta, India and the island of Mauritius. Repetitive and unique sequences inAn. quadrimaculatuswere distributed in a pattern of long period interspersion. Repetitive DNA in all other mosquito species exhibited a pattern of short period interspersion. The amounts of fold-back, middle repetitive, and highly repetitive sequences increased with genome size. The amount of foldback DNA increased at a much slower rate than the middle and highly repetitive sequences. Intraspecific variation in genome size inAe. albopictuswas due primarily to the amounts of highly repetitive DNA. S1 nuclease digestion of repetitive DNA in all species revealed a positive correlation between genome size and the proportion of the repetitive DNA consisting of short repeats. The amounts of long and short repeats increased with genome size but short repeats increased at a higher rate. The repetitive DNA of the Mauritius strain contained approximately 15% more short repeats than the Calcutta strain. These findings suggest that genome evolution in mosquitoes has resulted from changes in both the amounts and organization of repetitive elements.
The detection of mosaics and polyploids in a hereditary mosaic strain of the silk moth, Bombyx mori, using egg colour mutants
Authors: Ebinuma Hiroyasu , Kobayashi Masahiko , Kobayashi Jun , Shimada Toru , Yoshitake Narumi 
Published: September 2009

SummaryTo analyze abnormal fertilization in a hereditary mosaic strain (mo/mo) of Bombyx mori, the percentages of diploidy mosaic, polyploidy mosaic and polyploid eggs in a batch were estimated by using egg colour mutants (pe re). Among 48 890 eggs from crosses of pe + / + re, mo/mo females with pe re/pe re males, 9409 abnormal eggs were obtained; 4472 of them were diploidy mosaics (red-white eggs), 4038 were polyploids (black eggs) and 899 were polyploidy mosaics (566 black-white, 256 black-red and 77 black-white-red eggs). The total number of diploidy mosaic eggs was approximately equal to that of polyploid eggs. A significant correlation was detected between the diploidy mosaic and polyploid egg ratios within a batch. This suggests that diploidy mosaics are produced by double fertilization in which two genetically non-identical egg nuclei are fertilized in turn by a sperm, and polyploids are formed by the fertilization of a diploid, non-disjunctive egg nucleus gamete by a single sperm. Our results also indicated the presence of common factors modifying both mosaic and polyploid frequency. The concordance of the observed ratio of polyploidy mosaic eggs (1·84%) with the expected value (diploidy mosaic ratio × polyploidy ratio × 2 = 1·83%) suggests that the formation of mosaics occurs independently of the formation of polyploids in this abnormal fertilization process. We point out that it is necessary to modify Goldschmidt & Katsuki's general model to explain abnormal fertilization, and we propose several possible models.
P-element-induced mutation and quantitative variation inDrosophila melanogaster: lack of enhanced response to selection in lines derived from dysgenic crosses.
Authors: Torkamanzehi A. , Moran C. , Nicholas F. W. 
Published: September 2009

SummaryDysgenic and non-dysgenic base populations were made by reciprocal crossing of Harwich (P) and Canton-S (M) strains. From each cross, two up and two down selection lines were established, with selection on abdominal bristle number for ten generations. The intensity of selection was 10 out of 50 individuals from each sex. Mean bristle number, phenotypic variation and heritabilities were compared between dysgenic and non-dysgenic populations under selection. Except for an anomalous non-dysgenic downline in which a mutation of large effect occurred, all lines showed similar responses to selection. These results contrast with the results reported by Mackay (1984, 1985) in which substantial increases were obtained for response to selection, phenotypic variation and heritability in the dysgenic compared to non-dysgenic lines. There are some indications that the higher response in our aberrant non-dysgenic downline is the result of transposition. Possible explanations for the occurrence of transposition and dysgenesis in the lines derived from nondysgenic crosses are discussed.
Heterogeneity in the Sxr (sex-reversal) locus of the mouse as revealed by synthetic probes
Authors: Epplen Jörg T. , Studer Roland , McLaren Anne 
Published: September 2009

SummaryThe sex-reversal mutation, Sxr and a variant form, Sxr′ have been established on the inbred C57BL/6Mcl background by repeated backcrossing to form the CB and CB′ strains, respectively. DNAs of normal XY, XX Sxr and XX Sxr′ as well as XY Sxr and XY Sxr′ carrier male mice have been digested with the restriction enzymes Hae III and Hinf I and electrophoresed. The DNAs show many common but also differing hybridization bands with synthetic oligonucleotide probes. In XY Sxr (and XY Sxr′) carrier males, the hybridization patterns of normal XY and those of XX Sxr (and XX Sxr′) males are simply superimposed. Individual differing bands can be categorized by their differential hybridization behaviour to the (GATA)4, (GACA)4, (GATA)2 GACA (GATA)2 and (GATA)3 (GACA)2 probes. In general, the hybridization patterns are regularly inherited. In addition to the predominant pattern in each strain, one additional XX Sxr and one additional XX Sxr′ hybridization pattern was observed: the additional pattern in the CB strain was transmitted (via variant XY Sxr carriers) while the secondary XX Sxr′ pattern in the CB′ strain could only be observed once. Thus ‘DNA finger printing’ with oligonucleotide probes can successfully be used to discriminate the DNAs of normal Y chromosomes, XX Sxr and XX Sxr′ variants as well as XY Sxr and XY Sxr′ carrier mice. Implications of the comparatively high unequal recombination rate involving the murine Y chromosome are discussed, as well as possible mechanisms.
Xcegenotype has no impact on the effect of imprinting onX-chromosome expression in the mouse yolk sac endoderm
Authors: Bücher Theodor , Linke Ingrid M. , Dünnwald Manfred , West John D. , Cattanach Bruce M. 
Published: September 2009

SummaryThe effect of theXce(x-chromosome controlling element) genotype on the randomness ofX-chromosome inactivation in the mouse was studied by monitoring the expression of theX-linked locuspgk-1. The main aim was to test whether theXcegenotype modified the preferential expression of the maternally derivedX-chromosome in the yolk sac endoderm. Quantitative electrophoresis of phosphoglycerate kinase (PGK-1) was used to studyPgk-1expression in the foetus, yolk sac mesoderm and yolk sac endoderm at 13½ dayspost coitum. TheXcea/Xcecgenotype caused non-randomX-chromosome expression in the foetus and yolk sac mesoderm. However, there was no evidence that theXcegenotype moderates the preferential expression of the maternally derivedX-chromosome in the yolk sac endoderm, as reported by Rastan & Cattanach (1983).
Screening of guinea pig strains for electrophoretic isoenzyme polymorphisms
Authors: Csaikl F. 
Published: September 2009

SummarySeven strains of guinea pig (Cavia porcellus) with different degrees of inbreeding were investigated for genetic variability by starch gel electrophoresis. Variants for six out of 31 loci (Gpd-1, Aat-1, Ak-2, Pgm-1, Ada and Gpi) are reported. The data suggest that the strains all come from a small founding population and therefore are genetically more homogenous than the visible characteristics imply. Differences between isoenzyme data and other genetic characters are described and possible underlying genetic mechanisms are discussed.
Is offspring—midparent regression affected by assortative mating of parents?
Authors: Gimelfarb A. 
Published: September 2009

SummaryAn analysis based on a model that is different from the traditional Fisher's model for quantitative characters under assortative mating reveals that the genotypic offspring–midparent regression can be affected by assortative mating of parents. It is demonstrated that the prediction that mating parents assortatively introduces only a negligible bias in the estimated coefficient of linear offspring-midparent regression is limited to Fisher's model and cannot be generalized.
Biased conversion as the primary function of recombination
Authors: Bengtsson B. O. 
Published: September 2009

SummaryRecombination is hard to understand in darwinian terms when the process is identified with the production of crossover chromosomes. As an alternative explanation I propose instead that biased conversion is the primary function of meiotic recombination. In particular I show that a conversion process directed against the most common type of genetic damage can substantially reduce the mutational load, even if the conversion force is weak and if the conversion process occasionally creates new mutations.
Biochemical variation in purebred and crossbred strains of domestic rabbits (Oryctolagus cuniculusL.)
Authors: Hartl G. B. , Höger H. 
Published: September 2009

SummaryGenetic variation in 40 domestic rabbits (Oryctolagus cuniculus) from eight different strains was investigated by horizontal starch gel electrophoresis. Twenty nine enzyme systems were examined in different tissues, 10 isoenzymes were found to be polymorphic. Indices of genetic variation show values comparable to those found in most other mammalian species. Thus the unusually high values reported previously by other authors may be due to a limited and not randomly chosen set of enzymes studied.
DK/Lm: A Strain of Laboratory Mouse with an Unusual Expression of the Lethal Yellow (Ay) Phenotype
Authors: Lamoreux M. Lynn , Galbraith Donald B. 
Published: September 2009

SummaryDK/Lm is a new inbred mouse strain with over 20 generations of brother–sister mating. The genotype of the DK/Lm mouse at the black-brown locus isb/band heterozygosity at the agouti locus (Ay/a) is maintained. DK/Lm-Ay/amice become sable in phenotype at the first moult, whereas C57BL/6J-Ay/amice do not. The sable phenotype is defined as that of a mouse whose basic colour is yellow (phaeomelanic) but whose dorsal aspect is more or less darkened by the presence of nonyellow (eumelanic) pigment. At about 6 months of age the DK/Lm mouse gradually reverts to yellow in phenotype.Mice of the two strains are compared. Observations are discussed and related to hypotheses regarding gene action at theaandeloci. The new strain is a useful experimental model for study of the relationship between gene action at the agouti locus and the important pleiotropic effects influenced by this locus.
A different level ofX-chromosomal transcription in an In(1)BM2(reinverted) strain and in its hyperploid derivatives resolves anX-coded regulatory activity for dosage compensation inDrosophila
Authors: Mukherjee A. S. , Ghosh Mita 
Published: September 2009

SummaryThe transcriptional competence of theX-chromosome of a mutant strain ofDrosophila melanogaster, [in(1)BM2(reinverted)], and of hyperploid derivatives with different additional segments of theX-chromosome has been examined. The singleXin the mutant male shows twice as much puffiness and RNA synthesis as does that in the normal male, revealing a level ofX-coded activity in addition to the normal male and female levels. Feulgen cytophotometry reveals no duplication of DNA content in the mutantX. When duplication for the segments 1A-3E, 9A-20F, 11A-20F and 16A-20F of theX-chromosome are combined in the male with the mutant chromosome, the super-hyperactivity of the mutantXis completely abolished. In combination with theBs.Yduplication, which contains 16A7-B2, the two-fold activity is also completely suppressed.The mutant chromosome can appear in three discrete manifestations, namely, highly flabby, intermittently flabby and normal, suggesting a leaky nature of the mutant. The effect is also temperature-sensitive. Our results suggest that there may be a modulator gene complex (M+) in the 16A7-B2 region as well as regulators elsewhere on theX, which in combination influence the hyperactivity of the maleXinDrosophila. We suggest that the In(1)BM2(reinverted) chromosome carries a hypomorphic mutation of M+(Mm). The results presented here and earlier data on variousX-chromosomal and autosomal hyperploids are discussed in the light of a model for dosage compensation inDrosophila.
Transposable element-induced fitness mutations inDrosophila melanogaster
Authors: Mackay Trudy F. C. 
Published: September 2009

SummaryP element mutagenesis was used to contaminate M strain second chromosomes with P elements. The contaminated lines were compared to uncontaminated control lines for homozygous and heterozygous fitness and its components. Mean homozygous fitness, viability and fertility of chromosome lines contaminated with P elements is decreased relative to the uncontaminated control lines by, respectively, 55, 28 and 40%. Variance among contaminated homozygous lines of total fitness increases by a factor of 1·5, variance of viability by a factor of 5·9, and variance of fertility by a factor of 1·9, compared to variance of these traits among the population of uncontaminated homozygous chromosomes. Estimates of P-element-induced mutational variance among second chromosome lines for homozygous fitness, viability and fertility are, respectively, 2 × 10−2, 5 × 10−2and 2 × 10−2. This magnitude of mutational effect is equivalent, in terms of incidence of induced recessive lethal chromosomes and D:L ratio, to a dose of approximately 1·0–2·5 × 10−3m EMS. The distributions of fitness traits among M-derived second chromosome homozygous lines contaminated with P elements are remarkably similar in many regards to distributions of fitness and viability of chromosomal homozygotes derived from naturalDrosophilapopulations. It is possible that a proportion of the fitness variation previously observed (reviewed by Simmons & Crow, 1977) following homozygosis of wild chromosomes was not present in the natural populations, but was generated by P-element transposition during the chromosome extraction procedure. P-element-induced fitness mutations appear to be completely recessive. Implications for models of evolution of transposable elements are discussed.
High levels of fitness modifiers induced by hybrid dysgenesis inDrosophila melanogaster
Authors: Fitzpatrick Benjamin J. , Sved John A. 
Published: September 2009

SummaryWild-type chromosomes ofD. melanogastermutagenized by passage through a single generation of hybrid dysgenesis have been compared against identical chromosomes passed through a reciprocal, non-dysgenic cross. Fitness of the chromosome in homozygous condition has been examined in population cages using the technique of balancer chromosome equilibration. The results indicate that amongst chromosomes with no lethal or visible mutation, more than 50% have suffered a measurable decline in fitness. The magnitude of this decline is estimated to be in the range 10–20%.
Heterosis among lines of mice selected for body weight: 3. Thermoregulation
Authors: Lynch Carol Becker , Roberts R. C. , Hill W. G. 
Published: September 2009

SummaryCrosses were made among 18 lines of mice, six previously selected for large 6-week weight, six for small 6-week weight, and six unselected controls, comprising a complete diallel cross among sizes and a partial diallel cross among replicate lines within sizes, and all purebred matings. Across all groups large size was associated with lower weight-specific food consumption and brown adipose tissue, and increased nest-building. Overall the crosses had lower weight-specific food consumption, and increased nest-building, body temperature, and brown adipose tissue than the purebreds. In general, heterosis in crosses between lines of different size, especially those involving large lines, tended to exceed that in crosses between lines of the same size.
Growth, efficiency and body composition of mice selected for post-weaning weight gain onad libitumor restricted feeding
Authors: Hetzel D. J. S. , Nicholas F. W. 
Published: September 2009

SummaryAfter seven generations of selection, a line of mice selected for post-weaning (21–42 days) weight gain on full feeding (SF) showed significant increases of 49% in weight gain, 31% in efficiency and 14% in food intake, when compared with its control on full feeding between 21 and 42 days. After day 42, SF mice continued to eat more food and were 28% heavier than control mice at 91 days. Because SF mice were heavier than control mice at almost all ages, they were fatter on an age basis. There was, however, no change in the rate of deposition of fat, protein and ash relative to body weight. On restricted feeding between 21 and 42 days, SF mice showed a non-significant increase in weight gain, and hence in efficiency, of 12%. They deposited more fat than control mice during the feeding period but there was no significant difference when comparisons were made on a weight basis.A contemporary line of mice selected for post-weaning (21–42 days) weight gain on restricted feeding (SR) had significant increases of 12% in weight gain, 17% in efficiency but no significant change in food intake, when compared with its control on full feeding between 21 and 42 days. SR mice were the same weight as control mice at all ages except day 21, when they were significantly lighter due to direct genetic effects rather than maternal effects. SR mice had a lower (P<0·10) rate of fat deposition per unit body weight and became less fat relative to their control as body weight increased. The rate of deposition of other components was not altered by selection. On restricted feeding, SR had a significant increase in weight gain, and hence in efficiency, of 37%. Changes in body composition were similar to those on full feeding.It was concluded that the use of a restricted feeding regime had enabled the exploitation of heritable variation in the partitioning of energy for growth. This variation was independent of genetic variation for appetite and body weight.Overall performance at each level of feeding was best improved by selection on that feeding level. The realized genetic correlation between post-weaning weight gain on full and restricted feeding was estimated to be 0·28 ± 0·08, indicating a very different genetic basis for the same character in the two feeding environments.
Actual number of alleles contained in a multigene family
Authors: Ohta Tomoko 
Published: September 2009

SummaryBy using a simple model of gene conversion, the actual number of alleles contained in a multigene family was theoretically studied. It was shown that the Ewens' sampling theory is applicable to predict the actual number in a gene family of a genome. However, the actual number of the gene family forming the total population becomes larger or smaller than the predicted value by the sampling theory, depending upon the relative magnitude of the rates of two homogenization processes, i.e. intra-genome and in the population.
Models of long-term artificial selection in finite population with recurrent mutation
Authors: Hill William G. , Rasbash Jonathan 
Published: September 2009

SummaryThe effects of mutation on mean and variance of response to selection for quantitative traits are investigated. The mutants are assumed to be unlinked, to be additive, and to have their effects symmetrically distributed about zero, with absolute values of effects having a gamma distribution. It is shown that the ratio of expected cumulative response to generation t from mutants, , and expected response over one generation from one generation of mutants, , is a function of t/N, where t is generations and N is effective population size. Similarly, , is a function of t/N, where is the increment in genetic variance from one generation of mutants. The mean and standard deviation of response from mutations relative to that from initial variation in the population, in the first generation, are functions of . Evaluation of these formulae for a range of parameters quantifies the important role that population size can play in response to long-term selection.
Selection for oviposition preference inDrosophila melanogaster
Authors: Bird Stephen R. , Semeonoff Robert 
Published: September 2009

SummaryPopulations ofDrosophila melanogasterwere subjected to selection for differing oviposition preference under allopatric and sympatric conditions. Flies were presented with the choice of a potato-based medium and a medium containing sugar and killed yeast on which to lay their eggs. Some gene flow was possible under sympatric conditions. In the allopatric lines selection was successful in rapidly generating an increased preference for sugar, and in the sympatric lines divergent oviposition preferences were generated in two cases out of four. A significant degree of reproductive isolation between one pair of allopatric lines was generated after eighteen months of selection.
A theoretical analysis of linkage disequilibrium produced by genetic drift inDrosophilapopulations
Authors: Montchamp-Moreau Catherine , Katz Mariano 
Published: September 2009

SummaryWe analyse the progression of linkage disequilibrium produced by random genetic drift in populations subject to cyclical fluctuations in size. Our model is applied to natural populations ofDrosophilawhich show an annual demographic cycle of bottleneck (finite size) and demographic burst (size supposed to be infinite). In these populations, linkage disequilibrium stabilizes in such a way that, at equilibrium, the expected square of the correlation of gene frequenciesE(r2) shows a stable cycle from year to year. If two loci are tightly linked,E(r2) barely varies during the annual cycle. Its values remain close to the value expected in a population of the same but constant effective size. If two loci are loosely linked, fluctuations inE(r2) are large. The maximum value, reached at the end of the bottleneck, is 10 to 100 times greater than the value obtained at the end of the burst. Our results show that the interpretation of observed linkage disequilibrium, by means of statistical tests, requires an accurate knowledge of population demography.