bluuebunny/crossref_metadata_2025 huggingface dataset:
cDNA sequence and chromosomal localization of the mouse parvalbumin gene,Pva
Authors: Zühlke Ch. , Schöffl F. , Jockusch H. , Simon D. , Guénet J.-L.
Published: September 2009

In the homozygous condition, the mutationadr(arrested development of righting response) of the mouse causes a myotonia and a drastic reduction of the Ca2+-binding protein parvalbumin (PV) in fast muscles. Using a rat PV probe, a mouse cDNA clone was isolated from a λgt11 wild-type fast-muscle library and its nucleotide sequence was determined. The protein coding and the 3′ non-translated regions of the mouse gene show extensive homology with the rat PV gene. The result of Southern blot hybridization is consistent with a single copy gene for parvalbumin. Restriction fragment length polymorphisms (RFLPs) betweenMus musculus domesticus(e.g. C57BL/6) andMus spretus(SPE) were detected with the enzymesEcoRI,PstI, andSstI. The restriction fragment patterns of DNA samples from 65 individual offspring of (C57BL/6 × SPE)F1 × C57BL/6 backcrosses were tested with the PV probe and matched, for linkage detection, to pre-existing patterns established with various RFLP probes on the same samples. A co-distribution of PV-RFLPs withPvt-1 andMlvi-2, which had been localized on chromosome 15, was detected. Thus, the structural gene for PV, designatedPva, maps to chromosome 15 of the mouse whereas theadrmutation shows no linkage with markers on this chromosome. Gene locus homology between chromsome 15 of the mouse and chromosome 22 of man (which carries the human PV gene) is discussed.
A study of ten families of transposable elements onXchromosomes from a population ofDrosophila melanogaster
Authors: Charlesworth Brian , Lapid Angela
Published: September 2009

Data were collected on the distribution of ten families of transposable elements among fourteenXchromosomes isolated from a natural population ofDrosophila melanogaster, by means ofin situhybridization to polytene chromosomes. It was found that, with the exception ofroo, the copy number per chromosome followed a Poisson distribution. There was no evidence for linkage disequilibrium, either within or between families. Some pairs of families of elements were correlated with respect to the identity of the sites that were occupied in the sample, although there was no evidence for a correlation with respect to the sites at which elements attained relatively high frequencies. Elements appeared to be distributed randomly along the distal part of theXchromosome. There was, however, a strong tendency for elements to accumulate at the base of the chromosome. Element frequencies per chromosome band were generally low, except at the base of the chromosome where bands in subdivisions 19E and 20A sometimes had high frequencies of occupation. These results are discussed in the light of models of the population dynamics of transposable elements. It is concluded that they provide strong evidence for the operation of a force or forces opposing transpositional increase in copy number. The accumulation of elements at the base of the chromosome is consistent with the idea that unequal exchange between elements at non-homologous sites is such a force, although other possibilities cannot be excluded at present. The data suggest that the rate of transposition per element per generation is of the order of 10−4, for the elements included in this study.
P-element transposase induces male recombination inDrosophila melanogaster
Authors: McCarron Margaret Y. , Duttaroy Atanu , Doughty Glenn A. , Chovnick Arthur
Published: September 2009

Male recombination in P–M dysgenic crosses has been viewed as a reflection ofP-element transposase interacting withPelements. However, recent studies suggest that the transposase may catalyse double-stranded breaks in chromosomal DNA. We have, therefore, introducedP(Δ2–3ry+) (99B), a single non-mobileP-element transposase source, into the long-standing laboratory trueMstrains of a flanking lethal crossover selective system, thus facilitating the examination of rare male recombination events as an assay for transposase activity. We find that the rate of male recombination in the presence of this non-mobilePelement is greater than twenty times the background rate of male recombination in the control examined prior to introduction of the transposase source.
Acrosin activity in spermatozoa from sterilet6/tw32and fertile control mice
Authors: Mittal Ram Devi , Wileman Geraldine , Hillman Nina
Published: September 2009

Spermatozoa from sterilet6/tw32and control fertile + / +,T/tw32,T/t6mice were compared for their abilities to hydrolyse protein matrices and for their levels of acrosin activity. The data show that the immature and mature gametes from both the experimental and control males hydrolyse protein matrices. The quantitative acrosin assays show, however, that the mature gametes from the intercomplement males have significantly less total acrosin activity than any of the control groups of gametes. These findings suggest that this reduced acrosin activity is an additional phenotypic expression of the intercomplement genotype which results in male sterility.
Origin of rare Ha-ras alleles: relationship of VTR length to a 5′ polymorphic Xho I site
Authors: Baxter Glenn D. , Hayward Nicholas K. , Collins Russell J. , Lavin Martin F.
Published: September 2009

Amongst the four common Ha-ras alleles in both controls and cancer patients, we detected the presence of a polymorphic Xho I site associated specifically with the 6·6 and 7·7 kb Bam HI fragments but absent from the 7·1 and 8·2 kb alleles, as recently reported by others. We have extended this study and report here, the consistent appearance of this Xho I site in unusual alleles close in size to the two common alleles of 6·6 and 7·7 kb, in control lymphoblastoid DNA samples in a variety of tumor DNAs. Unusual alleles grouped around the 7·1 and 8·2 kb common alleles on the other hand, did not possess the Xho I site. The consistent presence of the Xho I site polymorphism, in the unusual Ha-ras alleles surrounding the 6·6 and 7·7 kb common alleles and its absence in alleles around the 7·1 and 8·2 kb common alleles, suggests that the unusual ones are derived from the corresponding common alleles to which they are closest in size.
Hybrid dysgenesis-induced response to selection inDrosophila melanogaster
Authors: Pignatelli Patricia M. , Mackay Trudy F. C.
Published: September 2009

InDrosophila melanogaster, theP−MandI−Rsystems of hybrid dysgenesis are associated with high rates of transposition ofPandIelements, respectively, in the germlines of dysgenic hybrids formed by crossing females of strains without active elements to males of strains containing them. Transposition rates are not markedly accelerated in the reciprocal, nondysgenic hybrids. Previous attempts to evaluate the extent to which hybrid dysgenesis-mediatedPtransposition contributes to mutational variance for quantitative characters by comparing the responses to selection ofP−Mdysgenic and nondysgenic hybrids have given variable results. This experimental design has been extended to include an additional quantitative trait and theI−Rhybrid dysgenesis system. The selection responses of lines founded from both dysgenic and nondysgenic crosses showed features that would be expected from the increase in frequency of initially rare genes with major effects on the selected traits. These results differ from those of previous experiments which showed additional selection response only in lines started from dysgenic crosses, and can be explained by the occasional occurrence of large effect transposable element-induced polygenic mutations in both dysgenic and nondysgenic selection lines. High rates of transposition in populations founded from nondysgenic crosses may account for the apparently contradictory results of the earlier selection experiments, and an explanation is proposed for its occurrence.
Relationship between chromosome content and nuclear diameter in early spermatids ofDrosophila melanogaster
Authors: González Cayetano , Casal José , Ripoll Pedro
Published: September 2009

We have studied, using light microscopy, the relationship between chromosome content and nuclear diameter in early spermatids of males carrying different combinations of wild-type and compound chromosomes inDrosophila melanogaster. By using these genotypes we have been able to observe spermatid nuclei bearing various numbers of chromosomes ranging from only one sex chromosome and no major autosomes to almost twice the normal chromosome complement. We have found that variations in the chromosome content are accompanied by increasing the variance in early spermatid nuclear diameter; the more gametic classes produced, the higher the variance of nuclear diameters. These results indicate that measuring nuclear diameters in early spermatids represents a useful way to estimate the levels of meiotic non-disjunction and thereby to improve the characterization of lethal or male sterile mutants in which analysis of meiotic chrosome non-disjunction cannot be achieved by conventional genetic methods.
Gene dosage effects on transmission ratio distortion and fertility in mice that carrythaplotypes
Authors: Silver Lee M.
Published: September 2009

Completethaplotypes can be transmitted at distorted ratios from heterozygous +/tmale mice as a consequence oft-specific alleles at a series oft complex distorterloci (Tcd-1tthroughTcd-4t) and at complex responderlocus. Partialthaplotypes that lack theTcd-2tallele cannot be transmitted at the very high ratios characteristic of completethaplotypes. The breeding studies reported here tested the possibility that the absence ofTcd-2tcould be compensated for by the presence of double doses of otherTcdtalleles. The results indicate that a double dose ofTcd-4talone will not work, but that a double dose of bothTcd-1tandTcd-4tcan promote a very high transmission ratio in the absence ofTcd-2t. These results suggest that the extent to which transmission ratios are distorted is dependent upon the absolute level of expression of the individualTcdgenes. Further studies of genotypic effects on transmission ratio distortion, as well as fertility, lead to the suggestion of a fiftht complex distorter(Tcd-5) locus withinthaplotypes.
A population genetical model for sequence evolution under multiple types of mutation
Authors: Iizuka Masaru
Published: September 2009

DNA sequencing and restriction mapping provide us with information on DNA sequence evolution within populations, from which the phylogenetic relationships among the sequences can be inferred. Mutations such as base substitutions, deletions, insertions and transposable element insertions can be identified in each sequence. Theoretical study of this type of sequence evolution has been initiated recently. In this paper, population genetical models for sequence evolution under multiple types of mutation are developed. Models of infinite population size with neutral mutation, infinite population size with deleterious mutation and finite population size with neutral mutation are considered.
An XXY mouse, the result of a rearrangement between one X and a Y chromosome
Authors: Evans Edward P. , Breckon George , Peters Josephine
Published: September 2009

A male mouse with irregular white spotting, typical of piebald, s, arose during an experiment designed to search for mutations induced in spermatogonial cells by ethylnitrosourea (ENU). On being examined cytologically it was found to carry 40 chromosomes but was effectively XXY since one of the two X chromosomes present was distally fused to a Y chromosome. In common with the previously described XXY mice, all of which carried 41 chromosomes, the mouse was sterile with a total absence of germ cells. Because of this, it was not possible to determine if the white spotting was inherited. The spotting could not be related to any observable abnormality of chromosomes known to carry spotting genes, nor could it be linked in any way with the X and Y fusion. It was concluded from the cytological considerations and the time interval (6 months) that had elapsed between mutagen treatment and birth of the offspring, that whereas the spotting was probably the result of ENU damage in a spermatogonial stem cell, the XY fusion was probably a later and spontaneous event.
Meiotic imbalance in laboratory-produced hybrid males of Chorthippus parallelus parallelus and Chorthippus parallelus erythropus
Authors: Bella J. L. , Hewitt G. M. , Gosálvez J.
Published: September 2009

The grasshopper Chorthippus parallelus has two quite distinct subspecies, which meet along the Pyrenees forming a hybrid zone. Using silver staining we show that on the French side Cp. parallelus has three nucleolar organizer regions, on the L2, L3 and X chromosomes, while on the Spanish side Cp. erythropus has only two NORs, on the L2 and L3. Laboratory F1 hybrid males show reciprocal differences in the expression of NORs. When a Cp. erythropus is female parent the male progeny show four active NORs in mitotic cells and two silver precipitates in meiotic cells, as expected. But when a Cp. parallelus female donates the X with a NOR, her male offspring have a variable disrupted nucleolar expression. Some NORs are not expressed and extra sites of cryptic rDNA are revealed. Meiosis is more disturbed in this latter F1 cross with higher levels of polyploidy, but both Fls show around 90% spermatid abnormality. Such variation in rDNA expression is also found in individuals collected from the hybrid zone, and the role of this disturbance in affecting fitness is discussed.
Selection in different environments: effects on environmental sensitivity (reaction norm) and on mean performance
Authors: Falconer D. S.
Published: September 2009

To simplify the description of selection in two environments the terms ‘ antagonistic’ and ‘synergistic’ are used. Selection upwards in a bad environment or downwards in a good environment is antagonistic, the selection and the environment acting in opposite directions on the character. Synergistic selection is the reverse, upwards in a good environment or downwards in a bad, selection and environment acting in the same direction. Published experiments are reviewed to see how well they agree with two expectations. First, Jinks & Connolly (1973) showed that antagonistic selection reduces environmental sensitivity and synergistic selection increases it. The experiments reviewed showed many exceptions to this rule, but they all showed that sensitivity was less after antagonistic than after synergistic selection. This is shown to be simply the consequence of correlated responses being less than direct responses. Second, I suggested (Falconer, 1989) that antagonistic selection might be the best way to improve the mean performance in the two environments. In the experiments reviewed, antagonistic selection was significantly better than synergistic for changing the mean, but it is now shown that there is no theoretical justification for this expectation; if one type of selection is better in one direction the other ought to be better in the other direction.

Expressions are given for the changes of mean performance and of sensitivity resulting from selection in one or other environment; these changes can be predicted from the parameters of the base population. In the experiments reviewed, an increase of mean performance accounted for 49% or more of the upward response. Equations are presented which allow the variance of mean performance, the variance of sensitivity, and the covariance of mean with sensitivity to be derived from parameters estimated in an unselected population, namely the variances in the two environments and the corresponding covariance. The variance of sensitivity that might be ascribed to scale effects is deduced. Directional selection in a single macro-environment is synergistic with respect to the micro-environmental differences, and is expected to increase environmental sensitivity and consequently to increase environmental variance. Stabilizing selection is antagonistic selection in both directions at the same time, and so is expected to decrease environmental variance.
Frequency of the transposable elementUqin Iowa stiff stalk synthetic maize populations
Authors: Lamkey Kendall R. , Petérson Peter A. , Hallauer Arnel R.
Published: September 2009

TheUqtransposable element is one of two transposable elements consistently found in maize (Zea maysL.) populations. Populations developed from two independent recurrent selection programs initiated in the Iowa Stiff Stalk Synthetic (BSSS) maize population were tested for the frequency ofUqtransposable elements to determine howUqfrequency has changed with cycles of recurrent selection. In the first programme, 13 cycles of half-sib and S2progeny recurrent selection [BSSS(S)C13] have been completed and 10 of the 13 cycles were assayed for activeUqelements. In the second programme, 11 cycles of reciprocal recurrent selection [BSSS(R)C11] have been completed and five of the 11 cycles were assayed for activeUqelements. The frequency ofUqwas different for the two recurrent-selection programmes. The percentage of plants containing activeUqelements increased from 19% (BSSS) to 91% [BSSS(S)C13] at a linear rate after 13 cycles of half-sib and S2progeny recurrent selection, whereas the percentage of plants containing activeUqelements decreased from 19% (BSSS) to 0% [BSSS(R)C11] after 11 cycles of reciprocal recurrent selection, with extinction of theUqelement occurring between the fifth and sixth cycles of selection. Our data suggest that the increase in frequency ofUqwith half-sib and S2progeny recurrent selection was predominantly due to random genetic drift coupled with a selective advantage possibly associated with a region of the genome linked toUq. Neither replicative transposition or chromosome assortment and segregation can be invoked to explain the change in frequency ofUqin these populations. The extinction ofUqafter reciprocal recurrent selection was best explained by random genetic drift.
Production of X0 clones in XX females ofDrosophila
Authors: Bachiller Daniel , Sánchez Lucas
Published: September 2009

The experiments reported here are aimed at determining whether mutations deleting the function of theSex-lethal(Sxl) gene are able to suppress the lethality of X0 clones, induced in females after the time when the state of activity ofSxlis irreversibly fixed by the ratio of the number of X chromosomes to sets of autosomes (X: A). This analysis was carried out by comparing the frequency of induced male clones (X0 constitution) inSxlfLS/ + andSxl+/Sxl+females, following irradiation at blastoderm and larval stages. The genotype used in these experiments, however, could also give rise to 2X; 2A cells homozygous forSxlfLS, and such cells would also differentiate male structures. To minimize this possibility, we have constructed a genotype made up of a ring and a rod X chromosome. In such ring-rod females the production of 2X; 2A clones homozygous forSxlfLSis a rather rare event, if possible at all. X0 male clones were produced in both types of females following irradiation at blastoderm stage, while X0 male clones were only observed inSxlfLS/ + females when irradiation took place at larval stage. In this latter case, the only X0 male clones were those that contained theSxlfLSmutation. These results support the idea of Sánchez & Nöthiger (1983) that the X: A signal irreversibly sets the state of activity ofSxlat blastoderm stage, and in addition show that X0 clones generated after that time are viable if they contain aSxl−mutation. These results are compatible with the idea ofSxlbeing the only gene that responds to the X:A signal.
Meiotic drive of t haplotypes: chromosome segregation in mice with tertiary trisomy
Authors: Agulnik Alexander I. , Agulnik Sergei I. , Ruvinsky Anatoly O.
Published: September 2009

The properties of the t haplotypes, specific mutant states of the proximal region of chromosomes 17 in the house mouse, are of continuing interest. One such property is increased transmission of the t haplotype by heterozygous t/ + males to offspring. Using the reciprocal translocation T(16; 17)43H we have constructed males with tertiary trisomy of chromosome 17 (+ T43/+ +/Rb7 + ) carrying the Robertsonian translocation Rb(16.17)7Bnr. Only the progeny of these males which had inherited either T43/ + or Rb7 from their male parent were viable. The segregation patterns in the offspring of t-bearing trisomics were analysed on days 16–18 of embryonic development. It was found that, when the t12 haplotype is in the normal acrocentric (♂♂ + + T43/ + t12 + /Rb7 + +), its presence in the gamete + t12 + / + + T43 does not produce meiotic drive. However, when t6 is in Rb7, meiotic drive was observed: 80% of offspring carried the t haplotype. It is concluded that the meiotic drive is probably inhibited by the presence of a normal homologue of chromosome 17 in the same sperm. Possible mechanisms for the t haplotype effect are discussed.
Partial complementation by murinethaplotypes: deficit of males amongt6/tw5double heterozygotes and correlation with transmission-ratio distortion
Authors: King Thomas R.
Published: September 2009

To evaluate whether sex reversal contributes to sex-ratio imbalance amongt6/tw5double heterozygotes, the cross performed by K. B. Bechtol (Genetical Research39, 1982, 79–84),T/t6×T/tw5, was repeated. Significantly more normal-tailed (t6/tw5) females than males were recovered. By contrast, sex ratios were normal among tailless progeny resulting from this cross and among all classes produced by control crosses. Hybridization of a Y-specific DNA probe with genomic DNA from phenotypic females revealed no XY, sex-reversed males. On the genetic backgrounds that generated only moderate transmission distortion oftw5(81–85%), the overall viability of the doubly heterozygous progeny was only 50% and the sex-ratio skew among this class was strong. However, on a genetic background that displayed extremetw5transmission (99%), embryonic viability was more than 80% and the sex-ratio imbalance was weak.
Biochemical and genetic characterization of esterase-27 (ES-27), the major plasma cholinesterase of the house mouse (Mus musculus)
Authors: von Deimling O. H. , Gaa A.
Published: September 2009

Esterase-27A (ES-27A) was characterized in strain A/WySnA by a cascade of seven bands seen after disc electrophoresis of serum and subsequent staining for esterase. ES-27A catalyses the hydrolysis of thiocholine butyrate and is strongly inhibited by 100 μm tetraisopropyl pyrophosphamide (isoOMPA). Hence, the enzyme was concluded to be a cholinesterase EC 3.1.1.8. A heat-labile form termed ES-27B was represented by strain AKR/Han. From a three-point cross (AKR/Han, A/Wy) and a five-point cross (AKR/Han, SEG/1), the gene order on chromosome 3 was concluded to be centromere–Car-2–Es-26–Es-27–Amy-1–Adh-1.
Genetics of morphological differences and hybrid sterility betweenDrosophila sechelliaand its relatives
Authors: Coyne Jerry A. , Rux John , David Jean R.
Published: September 2009

We conducted classical genetic analysis of the difference in male genitalia and hybrid sterility between the island-dwelling sibling speciesDrosophila sechelliaandD. mauritiana. At least two loci (one on each autosome) are responsible for the genital difference, with the X chromosome having no significant effect. In contrast, male hybrid sterility is caused by at least four gene loci distributed among all major chromosomes, with those on the X chromosome having the largest effect.

We also show that the large difference in ovariole number betweenD. sechelliaand its mainland relativeD. simulansis due to at least two gene substitutions, one on each major autosome. The X and the left arm of the second chromosome, however, have no significant effect on the character. This implies that the evolution of reduced ovariole number involved relatively few gene substitutions.

These results extend previous findings that morphological differences betweenDrosophilaspecies are caused by genes distributed among all chromosomes, while hybrid sterility and inviability are due primarily to X-linked genes. Because strong X-effects on male sterility have been found in all three pairwise hybridizations amongD. simulans, D. sechelliaandD. mauritiana, these effects must have evolved at least twice independently.
Isolation and characterization of a cDNA clone corresponding to the mouse t-complex gene Tcp-1x
Authors: Dudley Keith , Shanahan Francis , Burtenshaw M. , Evans E. P. , Ruddy S. , Lyon M. F.
Published: September 2009

The mouse t complex on chromosome 17 is known to harbour many genes which have an important role in spermatogenesis. One of these, Tcp-1 has been cloned and shown to code for a protein probably essential for acrosome formation. During the isolation of a cDNA for Tcp-1 two other homologous sequences were recognized and described as Tcp-1x and Tcp-1y. In this paper we describe the isolation of a cDNA which has been shown by in situ hybridization to correspond to the Tcp-1x gene. Sequence analysis has confirmed that a 140 bp region of homology between Tcp-1 and Tcp-1x lies in the 3′ portion of both genes. Northern blotting has revealed that the Tcp-1x gene is expressed abundantly in liver where two transcripts are detectable and hybrid selection shows that the gene codes for a 37 kDa protein. A search of the DNA databases has failed to find any significant homology between Tcp-1x and any other sequences apart from Tcp-1.
The apparent selection on neutral marker loci in partially inbreeding populations
Authors: Charlesworth D.
Published: September 2009

Deterministic computer calculations were used to investigate the effects on the fitnesses of genotypes at neutral loci that are caused by associations with several linked or unlinked selected loci, in partially self fertilizing populations. Both mutation to partially recessive alleles and heterozygote advantage at the selected loci were studied. In the heterozygote advantage models, either arbitrary linkage between all loci was modelled, with a single neutral locus, or many unlinked selected and neutral loci were modelled. Large apparent overdominance could be generated in all types of model studied. As has previously been suggested, these types of effect can explain the observed associations between fitness and heterozygosity in partially inbreeding populations. There were also apparent fitness differences between the genotypes at the neutral locus among the progeny produced by selfing, especially with linkage between the neutral and selected loci. There is thus no genotype-independent fitness value for these progeny. Marker based methods for estimating the relative fitness of selfed and outcrossed progeny assume equality of these fitnesses, and will therefore be inaccurate (with in most cases a bias towards overestimating the degree of inbreeding depression) when there is linkage between the neutral marker loci and loci determining fitness.
Multilocus models of inbreeding depression with synergistic selection and partial self-fertilization
Authors: Charlesworth B. , Morgan M. T. , Charlesworth D.
Published: September 2009

Mean fitness and inbreeding depression values in multi-locus models of the control of fitness were studied, using both a model of mutation to deleterious alleles, and a model of heterozygote advantage. Synergistic fitness interactions between loci were assumed, to find out if this more biologically plausible model altered the conclusions we obtained previously using a model of multiplicative interactions. Systems of unlinked loci were assumed. We used deterministic computer calculations, and approximations based on normal or Poisson theory. These approximations gave good agreement with the exact results for some regions of the parameter space. In the mutational model, we found that the effect of synergism was to lower the number of mutant alleles per individual, and thus to increase the mean fitness, compared with the multiplicative case. Inbreeding depression, however, was increased. Similar effects on mean fitness and inbreeding depression were found for the case of heterozygote advantage. For that model, the results were qualitatively similar to those previously obtained assuming multiplicativity. With the mutational load model, however, the mean fitness sometimes decreased, and the inbreeding depression increased, at high selfing rates, after declining as the selfing rate increased from zero. We also studied the behaviour of modifier alleles that changed the selfing rate, introduced into equilibrium populations. In general, the results were similar to those with the multiplicative model, but in some cases an ESS selfing rate, with selfing slightly below one, existed. Finally, we derive an approximate expression for the inbreeding depression in completely selfing populations. This depends only on the mutation rate and the dominance coefficient and can therefore be used to obtain estimates of the mutation rate to mildly deleterious alleles for plant species.
Differential susceptibility to a trematode parasite among genotypes of the Mytilus edulis/galloprovincialis complex
Authors: Coustau Christine , Renaud François , Maillard Claude , Pasteur Nicole , Delay Bernard
Published: September 2009

We show that parasitism by the trematode Prosorhynchus squamatus in parental and introgressed Mytilus edulis/galloprovincialis (Bivalvia) mussels occurs in individuals with a predominantly M. edulis genome. This result suggests that the restricted specificity of P. squamatus is dependent on genetic factor(s) present in M. edulis. Because of its strong pathogenic effects (i.e. total castration and possible death), this parasite may be a source of intense selection against M. edulis genomes when they are present in a site. As a consequence, it may favour the geographic extension of the M. galloprovincialis genome. Previous studies have indicated that, in hybrid zones, recombinant genotypes are more susceptible to parasitic infections than either parental genotype. We demonstrate that this is not the case for the M. edulis/M. galloprovincialis system, and that the parental genotype alone determines susceptibility.
Inheritance ofP-element regulation inDrosophila melanogaster
Authors: Raymond John D. , Ojala Todd A. , White Jennifer , Simmons Michael J.
Published: September 2009

The ability to repress P-element-induced gonadal dysgenesis was studied in 14 wild-type strains ofD. melanogasterderived from populations in the central and eastern United States. Females from each of these strains had a high ability to repress gonadal dysgenesis in their daughters. Reciprocal hybrids produced by crossing each of the wild-type strains with an M strain demonstrated that repression ability was determined by a complex mixture of chromosomal and cytoplasmic factors. Cytoplasmic transmission of repression ability was observed in all 14 strains and chromosomal transmission was observed in 12 of them. Genomic Southern blots indicated that four of the strains possessed a particular type of P element, called KP, which has been proposed to account for the chromosomal transmission of repression ability. However, in this study several of the strains that lacked KP elements exhibited as much chromosomal transmission of repression ability as the strains that had KP elements, suggesting that other kinds of P elements may be involved.
Fertility and viability at theSodlocus inDrosophila melanogaster: non-additive and asymmetric selection
Authors: Milosevic Mirjana , Moya Andrés , Ayala Francisco J.
Published: September 2009

Experiments were designed to test inDrosophila melanogasterthe effect of mating type at theSodlocus on fertility and viability. The experiments show that fertility is neither additive (or multiplicative) nor symmetric, i.e. that the fertility of a mating type cannot be predicted from the average fertility of the two genotypes involved in the mating. There is no significant male x female interaction with respect or progeny viability; but the interaction is significant for productivity, i.e. when fertility and viability are jointly taken into account. There is overdominance with respect to female fertility, but not with respect to male fertility or to viability. There also is alloprocoptic selection with respect to fertility and with respect to productivity, i.e. matings between like homozygotes are less fertile and productive than matings between dissimilar homozygotes. Selection at theSodlocus yields stable polymorphic equilibria, with the frequency of theFallele predicted atP= 0·641 or 0·695, respectively for low and high larval density.
Restriction enzyme banding in Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)
Authors: Hartley S. E.
Published: September 2009

Fixed metaphase chromosomes of brown trout and Atlantic salmon were digested with various restriction enzymes and stained with Giemsa. C band-like patterns were produced in both species by Alu I, Dde I, Hae III and Mbo I. Alu I revealed extra chromosome bands in brown trout which allowed identification of additional chromosome pairs, while the other three enzymes produced patterns identical to C banding. In the Atlantic salmon Dde I revealed telomeric bands at all telomeres in addition to the conventional C bands and all four enzymes had differential effects on the nucleolar organizer-associated heterochromatin. The relevance of these findings to chromosome identification and constitutive heterochromatin organization in salmonid fishes is discussed.
Genome size in Tribolium flour-beetles: inter- and intraspecific variation
Authors: Alvarez-Fuster Asunción , Juan Carlos , Petitpierre Eduard
Published: September 2009

Eight species of Tribolium and the related species Alphitobius diaperinus have been microdensitometrically analysed by measuring the nuclear content (1C value) of their Feuigenstained spermatids. The range of mean genome sizes goes from 0·157 pg in T. audax to 0·388 pg in T. brevicornis, including five significantly different groups of values. Also, in ail but one species of Tribolium significant intraspecific heterogeneity of genome size was found. The resemblances in genome size are not generally correlated with genetic homologies among species, but there is a highly significant correlation between genome size and spermatid size.
hobotransposable elements inDrosophila melanogasterandD. simulans
Authors: Boussy I. A. , Daniels S. B.
Published: September 2009

Genomic patterns of occurrence of the transposable elementhoboare polymorphic in the sibling speciesDrosophila melanogasterandD. simulans. Most tested strains of both species have apparently complete (3·0 kb) and smallerhoboelements (H lines), but in both species some strains completely lack such canonicalhoboelements (E lines). The occurrence of H and E lines inD. simulansas well as inD. melanogasterimplies that an hypothesis of recent introduction in the latter species is inadequate to explain the phylogenetic occurrence ofhobo. Particular internally deleted elements, the approximately 1·5 kbTh1andTh2elements, are abundant in many lines ofD. melanogaster, and an analogous 1·1 kb internally deleted element,h del sim, is abundant in most lines ofD. simulans. Besides the canonicalhobosequences, both species (and their sibling speciesD. sechelliaandD. mauritiana) have manyhobo-hybridizing sequences per genome that do not appear to be closely related to the canonicalhobosequence.
AXenopus laeviscreatine kinase isozyme (CK-III/III) expressed preferentially in larval striated muscle: cDNA sequence, developmental expression and subcellular immunolocalization
Authors: Robert Jacques , Barandun Benjamin , Kobel Hans Rudolf
Published: September 2009

A cDNA containing the nearly complete coding sequence of CK-III subunit ofX. laeviswas isolated, sequenced and further identified by comparing the tissue distribution of CK-III/III isozyme with that of its messenger. Comparison of CK-III deduced amino acid sequence with other CK sequences published reveals its close homology to M-CK subunits. Results using both cDNA probes and monoclonal antibodies specific for CK-III subunits indicate that the appearance and the accumulation of CK-III occur in parallel with myoblast differentiation. Moreover, subcellular immuno-histolocalization shows that CK-III/III isozyme is especially concentrated on larval myofibres at the level of A-bands.
Sandy: a new mouse model for platelet storage pool deficiency
Authors: Swank Richard T. , Sweet Hope O. , Davisson Muriel T. , Reddington Madonna , Novak Edward K.
Published: September 2009

Sandy (sdy) is a mouse mutant with diluted pigmentation which recently arose in the DBA/2J strain. Genetic tests indicate it is caused by an autosomal recessive mutation on mouse Chromosome 13 near thecrandXtgenetic loci. This mutation is different genetically and hematologically from previously described mouse pigment mutations with storage pool deficiency (SPD). The sandy mutant has diluted pigmentation in both eyes and fur, is fully viable and has prolonged bleeding times. Platelet serotonin levels are extremely low although ATP dependent acidification activity of platelet organelles appears normal. Also, platelet dense granules are extremely reduced in number when analysed by electron microscopy of unfixed platelets. Platelets have abnormal uptake and flashing of the fluorescent dye mepacrine. Secretion of lysosomal enzymes from kidney and from thrombin-stimulated platelets is depressed 2- and 3-fold, and ceroid pigment is present in kidney. Sandy platelets have a reduced rate of aggregation induced by collagen. The sandy mutant has an unusually severe dense granule defect and thus may be an appropriate model for cases of human Hermansky-Pudlak syndrome with similarly extreme types of SPD. It represents the tenth example of a mouse mutant with simultaneous defects in melanosomes, lysosomes and/or platelet dense granules.
Further evidence for the importance of parental source of the Xce allele in X chromosome inactivation
Authors: Fowlis Deborah J. , Ansell John D. , Micklem H. Spedding
Published: September 2009

Using mice that were mosaics for bothXceand phosphoglycerate kinase (Pgk-1) alleles, we present further evidence that the parental source of the X chromosome may affect the probability of that X chromosome remaining active. The reciprocal cross differences in PGK-1 activity described here are intermediate between those published previously for other alleles ofXce.
Geographical patterns of gene frequencies in Italian populations ofOrnithogalum montanum(Liliaceae)
Authors: Pigliucci Massimo , Barbujani Guido
Published: September 2009

Geographic variation was studied at 15 electrophoretic loci (40 alleles) in Italian populations ofOrnithogalum montanumCyr. ex Ten. (Liliaceae). Homogeneity of allele frequencies was assessed byGtests; gene-frequency patterns were described by spatial autocorrelation statistics; matrices of genetic and environmental distance were compared through a series of Mantel's tests, and the zones of highest overall gene-frequency change per unit distance (steep multi-locus clines, or genetic boundaries) were identified. Nineteen allele frequencies appear heterogeneously distributed, but only 3 of them show significant spatial structure. Only 2 allele frequencies are correlated with 1 environmental parameter. Large genetic differences are observed between spatially close populations. These findings support a model of differentiation in which the genetic relationships between isolates do not depend on their spatial distances, but reflect mainly population subdivision and restricted gene flow.
Heterochromatin as a factor affecting X-inactivation in interspecific female vole hybrids (Microtidae, Rodentia)
Authors: Zakian Suren M. , Nesterova Tatyana B. , Cheryaukene Olga V. , Bochkarev Michail N.
Published: September 2009

Female interspecific vole hybrids were examined for the expression of the G6PD and GALA genes on the X chromosomes. When one of the parents was a species with a heterochromatin block on the X, and the other parent was M. arvalis, without a heterochromatin block on the X, preferential expression of the genes of the M. arvalis X was consistently observed. When both parental species had heterochromatin on the X, the parental forms of G6PD and GALA were in about equal proportions in the hybrid females. The results of the cytological identification of the active and inactive X on the metaphase spreads in the hybrid females are in agreement with the biochemical results. It is suggested that the observed phenomenon may be due to a nonrandom inactivation of the X chromosome containing a heterochromatin block in crosses involving M. arvalis and by a random inactivation in those with both parents having heterochromatin blocks on the X chromosomes. These results support our previous suggestion that heterochromatin has an effect on X inactivation in female interspecific vole hybrids.
The Aedes aegypti genome: complexity and organization
Authors: Warren Ann M. , Crampton Julian M.
Published: September 2009

We describe the use of DNA reassociation kinetics to determine the total genome size and complexity together with the individual complexity and copy number of the single copy, middle repetitive and highly repeated DNA fractions of cell line and larval DNA from the mosquito, Aedes aegypti. The genome of Ae. aegypti is both large and complex, being one third the size of the human genome, and exhibits a short period interspersed repeat pattern. The implications of patterns of sequence arrangement and genome complexities for experiments aimed at isolating specific classes of DNA sequences, such as mobile genetic elements, are discussed.
The liver/erythrocyte pyruvate kinase gene complex [Pk-1] in the mouse: regulatory gene mutations
Authors: Fitton Lesley A. , Davidson Morag , Moore Karen J. , Charles Daniel J. , Pretsch Walter , Elston Robert C. , Bulfield Graham
Published: September 2009

Nine enzyme activity variants and one charge variant of liver/erythrocyte pyruvate kinase have been found amongst laboratory and wild mice. Four of the enzyme activity variants were previously reported to be caused by allelic differences in the structural gene,Pk-ls. Analysis of two putative regulatory gene mutations is now reported, both of which map at, or close to, the structural gene on chromosome 3. One of these mutations, in the inbred strain SWR, is tissue specific, affecting enzyme concentration in the liver but not the erythrocyte the other, which arose in a mutation experiment, doubles the enzyme concentration in both tissues. The organization and the nomenclature in the [Pk-1] gene complex are discussed and are compared with the organization of other comprehensively analysed gene complexes in the mouse.
Multiple amylase genes inDrosophila ananassaeand related species
Authors: Da Lage J.-L. , Lemeunier F. , Cariou M.-L. , David J. R.
Published: September 2009

The number and organization of amylase genes inDrosophila ananassaewere investigated through classical genetic methods andin situand filter hybridizations. At least four genes may be active inD. ananassae, organized as two independent pairs of closely linked copies on the 2L and 3L chromosomal arms. Several other species of theD. ananassaesubgroup were studied and show the same chromosomal locations, suggesting an ancient duplication event. However, the number ofAmycopies seems to be higher in theD. ananassaemultigene family, and there is a striking intraspecific molecular differentiation.
Chromosomal localisation of the mouse and human peripherin genes
Authors: Moncla Anne , Landon Françoise , Mattei Marie-Genevieve , Portier Marie-Madeleine
Published: September 2009

Using a mouse cDNA probe encoding for the major part of peripherin, a type III intermediate filament protein, we have assigned, byin situhybridization, the mouse and human peripherin genes,Prph, to the E–F region of chromosome 15 and to the q12–q13 region of chromosome 12, respectively. These regions are known as homologous chromosomal segments containing other intermediate filament genes (keratins) and also other genes which could be co-ordinately regulated.
Chromosomal location of a barley malt endopeptidase gene
Authors: Guerin J. R. , Lance R. C. M. , Wallace W.
Published: September 2009

Extracts of disomic wheat-barley addition lines were tested for the presence of a barley malt endopeptidase (MEP-1) by employing isoelectric focusing (IEF) and western blotting. The blots were probed with polyclonal antibodies raised against MEP-1 purified from the endosperms of 5-day-old germinated barley seedlings. The endopeptidase was detected in the Betzes barley cultivar and the addition line containing the full genome of the wheat cultivar Chinese Spring plus a chromosome 3 pair from Betzes barley. The endopeptidase was not expressed in Chinese Spring nor the addition lines containing other Betzes chromosome pairs. The endopeptidase was detected in a ditelosomic addition line containing the long arm of Betzes chromosome 3. We have concluded that the gene coding for MEP-1 (Cep-B) is located on the long arm of Betzes chromosome 3.
The segmentation generuntis needed to activateSex-lethal, a gene that controls sex determination and dosage compensation inDrosophila
Authors: Torres Miguel , Sanchez Lucas
Published: September 2009

InDrosophila, sex is determined by the relative number of X chromosomes to autosomal sets (X: A ratio). The amount of products from several X-linked genes, calledsisterlesselements, is used to indicate toSex-lethalthe relative number of X chromosomes present in the cell. In response to the X: A signal,Sex-lethalis activated in females but remains inactive in males, being responsible for the control of both sex determination and dosage compensation. Here we find that the X-linked segmentation generuntplays a role in this process. Reduced function of runt results in femalespecific lethality and sexual transformation of XX animals that are heterozygous forSxlorsisloss-of-function mutations. These interactions are suppressed bySxlMI, a mutation that constitutively expresses femaleSex-lethalfunctions, and occur at the time when the X: A signal determinesSex-lethalactivity. Moreover, the presence of a loss-of-functionruntmutation masculinizes triploid intersexes. On the other hand,runtduplications cause a reduction in male viability by ectopic activation ofSex-lethal. We conclude thatruntis needed for the initial step ofSex-lethalactivation, but does not have a major role as an X-counting element.
The differential staining pattern of the X chromosome in the embryonic and extraembryonic tissues of postimplantation homozygous tetraploid mouse embryos
Authors: Webb S. , de Vries T. J. , Kaufman M. H.
Published: September 2009

(C57BL × CBA)F1 hybrid female mice were mated with hemizygous Rb(X.2)2Ad males to distinguish the paternal X chromosome. Homozygous tetraploids were produced by blastomere fusion at the 2-cell stage, and 161 of these were transferred to recipients and analysed on the 10th day of gestation. 59 implants contained resorptions and 76 contained either an embryo and/or extraembryonic membranes. 38 (20, XXXX and 18, XXYY) were analysed to investigate their X-inactivation pattern. Embryonic and yolk sac endodermally- and mesodermally-derived samples were analysed by G-banding and by Kanda analysis. In the XX and XY controls, the predicted pattern of X-inactivation was observed, though 12·2% of metaphases in the XX series displayed no X-inactivation. In the XY series the Y chromosome was seen in a high proportion of metaphases.

In the XXXX tetraploids, 8 cell lineages were recognized with regard to their X-inactivation pattern, though most belonged to the following 3 categories: (XmXm)XpXp, Xm(XmXp)Xp and XmXm(XpXp). The other categories were only rarely encountered. In the embryonic and mesodermally-derived tissue the ratio of these groups was close to 1:2:1, whereas in the endodermally-derived tissue it was 1:4·11:4·88, due to preferential paternal X-inactivation. A significant but small proportion of all 3 tissues analysed displayed no evidence of X-inactivation. Indirect evidence suggests that this represents a genuine group because of the high efficiency of the Kanda staining. The presence of the Xm(XmXp)Xp category is consistent with the expectation that X-inactivation occurs randomly in 2 of the 4 X chromosomes present. The presence of small numbers of preparations with no evidence of X-inactivation and other unexpected categories suggests that these are probably selected against during development.