bluuebunny/crossref_metadata_2025_split huggingface dataset:
Can chromosomal heterosis inDrosophilabe explained by deleterious recessive genes? Negative results from a dichromosomal population test
Authors: Wilton Alan N. , Joseph Michael G. , Sved John A. 
Published: September 2009

SummaryHigh levels of chromosomal heterosis have previously been detected inDrosophilausing the balancer chromosome equilibration (BE) technique, in which single wild-type chromosomes are introduced into population cages along with a dominant/lethal balancer chromosome. The balancer chromosome is rarely eliminated in such populations, showing that the fitness of chromosome homozygotes must be low by comparison with chromosomal heterozygotes. As with all cases of chromosomal heterosis, the underlying cause could either be deleterious recessives at various loci or generalized overdominance. The experiment of the present paper examines the first of these explanations. Population cages containing just two wild-type chromosomes (dichromosomal populations) were set up and allowed to run for many generations. Single chromosomes were then re-extracted from these populations, and their fitness measured using the BE technique. Our expectation was that the gradual elimination of recessive genes from the dichromosomal populations ought to result in an increase in the fitness of such re-extracted chromosome homozygotes. Yet in two replicated experiments we were unable to demonstrate an; unequivocal increase in fitness. We have estimated the rate of increase of fitness under multiple locus dominance and partial dominance models. The principal unknown parameter in these calculations is the selection intensity per locus,s. The expected increase is approximately proportional tos, and we estimate that values ofsaround 1/64 should be detectable in our experiments. However linkage is expected to reduce the efficiency of the dichromosomal procedure We show by computer simulation that this reduction is by a factor of approximately 2, thus increasing the detectable level ofsto approximately 1/32. Consideration of mutation-selection balance models shows that this is a feasible selection intensity only if dominance is nearly complete. Thus we are unable to rule out the notion that the genes responsible for heterosis are maintained by a simple mutation-selection balance, but the experimental results constrain the parameters of such a model to a narrow range.
Chromosomal localization of the mouse gene coding for vimentin
Authors: Mattei Marie-Genevieve , Lilienbaum Alain , Lin Li Zhen , Mattei Jean-François , Paulin Denise 
Published: September 2009

SummaryThe chromosomal location of the mouse gene coding for vimentin, one of the intermediate filament subunits, was determined by in situ hybridization using specific H3-labelled DNA probes. There is only one copy of the vimentin gene and it is located on chromosome 2 region A2.
Cytogenetic manifestations associated with the reversion, by gene amplification, at the HGPRT locus in V79 Chinese hamster cells
Authors: Di Leonardo A. , Agnese C. , Cavolina P. , Maddalena A. , Sciandrello G. , Randazzo R. 
Published: September 2009

SummarySome HGPRT spontaneous revertants were isolated from a mutant line (E2) of V79 Chinese hamster cells and phenotypically characterized. Dot–Blot hybridization with a32P-Iabelled HGPRT probe revealed an increase in the number of HGPRT sequences in some of these revertants, suggesting the occurrence of gene amplification. Cytogenetic analysis performed in three of these revertants showed a characteristic abnormally banding region (ABR) on the elongated p arm of theXchromosome.In Situhybridization in one revertant (RHE2) showed that the amplified sequences reside on the p+arm of theXchromsome in two different localizations. Because of the very probable clonal origin of the revertant, these features indicate that the amplified sequences might rearrange after their integration into the chromosome.
Interaction of Hairless, Delta, Enhancer of split and Notch genes ofDrosophila melanogasteras expressed in adult morphology
Authors: Siren Mariitta , Portin Petter 
Published: September 2009

SummaryThe interaction of three neurogenic lociviz.Delta, Enhancer of split and Notch, and a related gene, Hairless, ofDrosophila melanogasterwas investigated at the adult morphology level by measuring the effects of the mutations of the three other genes on the expression of the recessive lethal antimorphic Abruptex mutations of the Notch locus. The Abruptex mutations were also coupled incisortranswith facet-glossy or split mutations of the Notch locus. In some of the experiments, the genotype of the fly was homozygous for either facet-glossy or split mutation or their wild type alleles but heterozygous for the Abruptex. Facet-glossy is located in a large intron of the locus, whereas split is located in the same exon as Abruptex. In all compounds studied, Delta suppressed the expression of Abruptex while Hairless and Enhancer of split enhanced it. The interactions of the four genes studied were allele specific, suggesting an interaction at the protein level. The comparison of the results presented in this study on the interaction of the neurogenic genes with other results on the same subject suggests that the interactions are similar in embryonic and imaginal development.
Quantitative genetic variability maintained by mutation-stabilizing selection balance: sampling variation and response to subsequent directional selection
Authors: Keightley Peter D. , Hill William G. 
Published: September 2009

SummaryA model of genetic variation of a quantitative character subject to the simultaneous effects of mutation, selection and drift is investigated. Predictions are obtained for the variance of the genetic variance among independent lines at equilibrium with stabilizing selection. These indicate that the coefficient of variation of the genetic variance among lines is relatively insensitive to the strength of stabilizing selection on the character. The effects on the genetic variance of a change of mode of selection from stabilizing to directional selection are investigated. This is intended to model directional selection of a character in a sample of individuals from a natural or long-established cage population. The pattern of change of variance from directional selection is strongly influenced by the strengths of selection at individual loci in relation to effective population size before and after the change of regime. Patterns of change of variance and selection responses from Monte Carlo simulation are compared to selection responses observed in experiments. These indicate that changes in variance with directional selection are not very different from those due to drift alone in the experiments, and do not necessarily give information on the presence of stabilizing selection or its strength.
Clonal analysis of thelacoperons fromKlebsiellaM5a1 and the Lac plasmid (pRE2) fromKlebsiellaV9A
Authors: Hitchin F. E. , Reeve E. C. R. 
Published: September 2009

SummaryThe chromosomallacregion of the coliform bacteriumKlebsiellaM5al was cloned into the multicopy plasmid pBR322 to give pHE7 and pHE8. pHE8 contains 12·6 kb of M5al DNA, including its completelacoperon, and pHE7 contains 2·5 kb of M5al DNA and includes the completelac Ygene and a small segment oflacZ. The M5al operon has the same gene order as theEscherichia coli lacoperon. Thelacgenes of the Lac plasmid ofKlebsiellaV9A were cloned into pBR322 to give pHE1 and pHE2, of approximately 39 and 43 kb. Both plasmids were unstable in anE. coli RecA- strain, in contrast to the stability of pHE8. Polyacrylamide gel electrophoresis tests suggested that the M5a1 β-galactosidase monomer is about 5% longer, i.e. has about 50 more amino acids, than that of theE. coli Zgene. Tests made on the enzymes coded by thelacoperons of M5a1, anotherKlebsiellastrain (V9A) and its resident Lac plasmid, and several Lac+Enterobacteria, led to the conclusion that onlyEscherichia coliamong the Enterobacteria contains an activelacAgene.
Characterization of third chromosome dominant α-methyl dopa resistant mutants (Tcr) and their interactions withl(2)amdα-methyl dopa hypersensitive alleles inDrosophila melanogaster
Authors: Bishop Clifton P. , Sherald Allen F. , Wright Theodore R. F. 
Published: September 2009

SummaryInDrosophila melanogastertwo alleles at theThird chromosome resistancelocus (Tcr; 3–39·6) were isolated in a screen of EMS mutagenized third chromosomes for dominant resistance to dietary α-methyl dopa, α-MD, a structural analogue of DOPA. Both alleles ofTcrare recessive lethals exhibiting partial complementation. Almost half (48·3%) of theTcr40/Tcr45heterozygotes die as embryos but some survive past adult eclosion. Both the embryonic lethal phenotype and the adult phenotype suggest thatTcris involved in cuticle synthesis.Tcrmutants suppress the lethality of partially complementing alleles at the α-MD hypersensitive locus,l(2)amd. The viability ofTcr40/Tcr45, however, is not increased by the presence of al(2)amdallele. The possibility that theTcrandl(2)amdmutations reveal a catecholamine metabolic pathway involved in cuticle structure is discussed.
RelAmutation and pBR322 plasmid amplification in amino acid-starved cells ofEscherichia coli
Authors: Riethdorf Sabine , Schroeter Andreas , Hecker Michael 
Published: September 2009

SummaryPlasmid pBR322 is amplified following amino-acid limitation inEscherichia coli relAhosts. InrelA+hosts there was no significant amplification or a much smaller one. Plasmid amplification is due to therelAmutation; when therelA+allele is transferred into therelAmutant CP79 this strain no longer amplifies plasmid DNA during amino acid starvation. It is concluded that ppGpp is a negative effector of plasmid replication. Amplification is temperature dependent, being maximal at 32 °C and negligible at 37 °C.
Wsp-1, a set of genes controlling water-soluble proteins in wheat and related species
Authors: Liu C. J. , Chao S. , Gale M. D. 
Published: September 2009

SummaryThree water-soluble wheat endosperm proteins of the wheat variety Chinese Spring have been shown, by isoelectric focusing, to be the products of genes located on the long arms of chromosomes 7A, 7B and 7D. In the absence of any evidence of function these genes have been assigned the temporary symbol, Wsp-1.Considerable intervarietal variation was found among a sample of 44 hexaploid wheat varieties. Five alleles at Wsp-A1, three at Wsp-B1 and two at Wsp-D1 were identified. Intrachromosomal mapping showed that Wsp-B1 is located distally on the long arm of chromosome 7B.Alien homoeoloci were identified on chromosomes 7Hch of Hordeum chilense, 7H of H. vulgare, 7E of Agropyron elongatum, 7S1 of Aegilops sharonensis and 7V of Dasypyrum villosum. Some other loci encoding WSPs found in wheat and some alien species are also briefly described.
Genomic imprinting: normal complementation of murine chromosome 16
Authors: Berger Christoph N. , Epstein Charles J. 
Published: September 2009

SummaryParental imprinting effects for chromosome 16 were investigated using disomic animals which were obtained by mating (Rb32Lub × Rb2H) F1 mice. Two allelic forms of the enzyme CuZn-superoxide dismutase, Sod-1a and Sod-1c, were` used to identify maternally or paternally disomic animals. Both types of disomic animals were found with the expected frequencies and did not visibly differ from one another or from non-disomic animals. These results indicate that the genomic imprinting mechanism either does not act on chromosome 16, or, if it does, does not do so in a manner which affects normal development.
Localization of P elements, copy number regulation, and cytotype determination inDrosophila melanogaster
Authors: Biémont C. , Ronsseray S. , Anxolabéhère D. , Izaabel H. , Gautier C. 
Published: September 2009

SummarySeventeen highly-inbred lines ofDrosophila melanogasterextracted from an M′ strain (in the P/M system of hybrid dysgenesis) were studied for their cytotype and the number and chromosomal location of complete and defective P elements. While most lines were of M cytotype, three presented a P cytotype (the condition that represses P-element activity) and one was intermediate between M and P. All lines were found to possess K.P elements and only eight to bear full-sized P elements. Only the lines with full-sized P elements showed detectable changes in their P-insertion pattern over generations; their rates of gain and of loss of P-element sites were equal to 0·12 and 0·09 per genome, per generation, respectively. There was no correlation between these two rates within lines, suggesting independent transpositions and excisions in the inbred genomes. The results of both Southern blot analysis andin situhybridization of probes made from left and right sides of the P element strongly suggested the presence of a putative complete P element in region 1A of the X chromosome in the three lines with a P cytotype; the absence of P copy in this 1A region in lines with an M cytotype, favours the hypothesis that the P element inserted in 1A could play a major role in the P-cytotype determination. Insertion of a defective 2 kb P element was also observed in region 93F in 9 of the 13 M lines. The regulation of the P-element copy number in our lines appeared not to be associated with the ratio of full-length and defective P elements.
Direct and correlated responses to artificial selection on lipid and glycogen contents inDrosophila melanogaster
Authors: Clark Andrew G. , Szumski Frances M. , Bell Karen A. , Keith Lisa Esterling , Houtz Sharyn , Merriwether D. Andrew 
Published: September 2009

SummaryA large outbred population ofDrosophila melanogasterwas subjected to artificial selection on lipid and glycogen storage. In three separate experiments, two replicates underwent sib selection for both increased and decreased storage. In the first study, flies were selected on the basis of total triacylglycerol for ten generations. This experiment resulted in no significant direct response, but there was a significant change in total body weight, underscoring the importance of concern for the allometric relationship between body weight and lipid content. In the second study, selection was performed for 15 generations on the percentage of body composition that was triacylglycerol. A significant direct response was obtained, and the two replicates revealed heritability estimates of 0·40 and 0·43. The third study selected glycogen content for 15 generations, and produced a significant response with heritabilities of 0·25 and 0·31. A series of 12 biochemical and enzyme kinetic traits was examined at five generation intervals in all experiments, and a number of correlated responses were detected. The results are interpreted with respect to the evolutionary constraints on energy storage evolution and the genetic basis of the allometric relationship between body weight and fat content.
Chromosomal fragment responsible for genetic mosaicism in larval body marking of the silkworm,Bombyx mori
Authors: Fujiwara Haruhiko , Ninaki Osamu , Kobayashi Masahiko , Kusuda Jun , Maekawa Hideaki 
Published: September 2009

SummarySeveral genetic mosaics for larval body marking of the silkworm,Bombyx mori, have been induced by X-ray irradiation. It is hypothesized that the occasional loss of chromosomal fragments carrying the genes for body marking during development may give rise to this type of mosaicism. Using pulsed field gel electrophoresis (PFGE), we find that a DNA molecule of about 2·5 megabases (Mb) is present in one type of mosaic (mottled striped strains pSm788 and pSm872), and not in any other strain. This DNA fragment hybridizes strongly with some chorion genes which are less than 6·9 cM away from thepslocus, and hence it corresponds to a chromosomal fragment containing genes for both striped marking (ps) and the chorion. In the non-mottled psstrain, the phenotype before X-ray irradiation, no band was detected either on a PFGE gel or after hybridization with the chorion probe. These results suggest that the mottled psstrains carry short chromosome fragments which are lost differentially during cell divisions.
Gene mapping and cross-resistance in cyclodiene insecticide-resistant Drosophila melanogaster (Mg.).
Authors: Ffrench-Constant R. H. , Roush R. T. 
Published: September 2009

SummaryResistance to the cyclodiene insecticide dieldrin maps to a single gene (Rdl) on the left arm of chromosome III in Drosophila melanogaster (Meigen). The gene was further mapped by the use of chromosomal deficiencies to a single letter sub-region, 66F, on the polytene chromosome. The cross-resistance spectrum of a backcrossed strain lacking elevated mixed function oxidase activity, a common resistance mechanism, was examined. Levels of resistance similar to those found in other insects were found to dieldrin, aldrin, endrin, lindane, and picrotoxinin. Strong similarity of this single major gene with that found in other cyclodiene resistant insects is suggested by its cross-resistance spectrum and chromosomal location, via homology with other Diptera. The significance of major genes in insecticide resistance is discussed.
Tich: a mutant causing disproportional growth in the mouse
Authors: Archer James R. , Archer Victoria A. , Festing Michael F. W. , Ghiraldini Mirian A. 
Published: September 2009

SummaryA spontaneous mutation ‘tich’ (gene symbol tch) appeared as a recessive mutation in inbred mice of strain A. TL. Homozygotes are rather dumpy mice of approximately normal weight but with short limbs and tail. Skeletal measurements on backcross siblings show that the mandible bones are almost normal but long bones and some parts of the pelvic and pectoral girdles are short. Although tich resembles brachypodism phenotypically it is not linked to agouti, and does not match the description of any other skeletal mutation. There was some evidence for weak linkage with albinism on chromosome 7. The mutation has reappeared amongst the A. TL mice of a UK commercial breeder and may have been accepted as the norm for A. TL amongst some European users of this mouse.
Tpi-1andGapdare linked very closely on mouse chromosome 6
Authors: Pretsch Walter , Neuhäuser-Klaus Angelika , Merkle Siegbert 
Published: September 2009

SummaryMutations in the structural genes for triosephosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase activity in the mouse, selected after mutagen treatment, were used to estimate the map distance between the two loci. It is shown thatTpi-1 andGapdare closely linked on chromosome 6, with a recombination frequency of 0·1±0·1%.
The effect of H-2 region and genetic background on hormone-induced ovulation rate, puberty, and follicular number in mice
Authors: Spearow J. L. , Erickson R. P. , Edwards T. , Herbon L. 
Published: September 2009

SummaryWe have examined the effects of major histocompatibility (H-2) haplotypes and genetic background (all loci other than the H-2 region) on hormone-induced ovulation rate in congenic strains of mice. In comparison with the H-2a haplotype, the H-2b haplotype increased hormone-induced ovulation rate 92% on the A/J (A) genetic background. However, H-2 haplotype did not affect hormone-induced ovulation rate on the C57BL/10J (C57) genetic background. The H-2b-linked gene(s) increased hormone-induced ovulation rate on the A/J genetic background largely by (1) enhancing the maturation of follicles in response to pregnant mare's serum gonadotrophin (PMSG) and (2) altering the stages of follicular development which can be induced to ovulate in response to human chorionic gonadotrophin (hCG). The observed effects of H-2 on hormone-induced ovulation rate were not explained by differences in the timing of puberty, the number of follicles present in untreated females, or the incidence of follicular atresia. The effect of genetic background on hormone-induced ovulation rate was much greater than was the effect of the H-2 region. We found that hormone-induced ovulation rate was five- to six-fold higher on the C57 genetic background than on the A genetic background. The C57 genetic background increased hormone-induced ovulation rate by (1) enhancing the induction of follicular maturation in response to gonadotropins and (2) by reducing the incidence of follicular atresia.
Mixed model analysis of a selection experiment for food intake in mice
Authors: Meyer K. , Hill W. G. 
Published: September 2009

SummaryData from 23 generations of mice selected for increased and reduced appetite were analysed by Restricted Maximum Likelihood fitting an animal model with litters as additional random effects. Traits considered were food intake between 4 and 6 weeks of age adjusted for 4-week body weight (AFI), the selection criterion, and body weight at 6 weeks (6WW). Selection was carried out within families. A high and a low selection line and a control were maintained in each of three replicates. Analyses were performed for each replicate separately taking subsets of the data spanning different numbers of generations. Overall estimates of heritabilities were 0·15 for AFI, which agreed well with realized heritability estimates, and 0·42 for 6WW. The litter variance, expressed as a proportion of the phenotypic variance, was 0·21 for both traits, yielding intraclass correlations of full-sibs of 0·29 and 0·42, respectively. Similar results were obtained for variances of each trait using univariate and multivariate analyses. From the latter, estimates of correlations between the two traits were 0·46 for additive genetic, −0·19 for litter and 0·31 for residual effects, resulting in a phenotypic correlation of 0·23. Analyses of data from generations 2–7, 8–13 and 14–23 separately showed a marked decrease in genetic variance and heritability in later generations for both traits. Heritabilities of AFI, for instance were 0·24, 0·10 and 0·07, respectively. These changes could not be attributed to the effects of inbreeding or of selection in an infinitesimal model and suggested that some change in variance due to change in gene frequency had occurred during the course of the experiment.
The coalescent process in models with selection, recombination and geographic subdivision
Authors: Kaplan Norman , Hudson Richard R. , Iizuka Masaru 
Published: September 2009

SummaryA population genetic model with a single locus at which balancing selection acts and many linked loci at which neutral mutations can occur is analysed using the coalescent approach. The model incorporates geographic subdivision with migration, as well as mutation, recombination, and genetic drift of neutral variation. It is found that geographic subdivision can affect genetic variation even with high rates of migration, providing that selection is strong enough to maintain different allele frequencies at the selected locus. Published sequence data from the alcohol dehydrogenase locus ofDrosophila melanogasterare found to fit the proposed model slightly better than a similar model without subdivision.
Unequal crossing-over within theBduplication ofDrosophila melanogaster: a molecular analysis
Authors: Tsubota Stuart I. 
Published: September 2009

SummaryTheBmutation is associated with a tandem duplication of 16A1–16A7. It is unstable, mutating to wild type and to a more extreme form at a frequency of one in 1000 to 3000. The reversion to wild type is associated with the loss of one copy of the duplication, whereas the mutation to extremeBis associated with a triplication of the region. The instability ofBhas been attributed to unequal crossing-over between the two copies of the duplication. Recent molecular data show that there is a transposable element,B104, between the two copies of the duplication and support the hypothesis that this element generated the duplicationviaa recombination event. These data suggest that unequal crossing-over within the duplication may not be the cause of the instability ofB. Instead, the instability may be caused by a recombination event involving theB104element. This issue was addressed using probes for the DNA on either side of theB104element at theBbreakpoint. All of the data indicate that theB104element is not involved in the instability ofBand support the original unequal crossing-over model.