bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Summary(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.
Evidence for random distribution of sequence variants inTenebrio molitorsatellite DNA
Authors: Plohl Miroslav , Borˇstnik Branko , Lucijanić-Justić Vlatka , Ugarković ÐurÐica 
Published: September 2009

SummaryTenebrio molitorsatellite DNA has been analysed in order to study sequential organization of tandemly repeated monomers, i.e. to see whether different monomer variants are distributed randomly over the whole satellite, or clustered locally. Analysed sequence variants are products of single base substitutions in a consensus satellite sequence, producing additional restriction sites. The ladder of satellite multimers obtained after digestion with restriction enzymes was compared with theoretical calculations and revealed the distribution pattern of particular monomer variants within the satellite. A defined higher order repeating structure, indicating the existence of satellite subfamilies, could not be observed. Our results show that some sequence variants are very abundant, being present in nearly 50 % of the monomers, while others are very rare (0-1 % of monomers). However, the distribution of either very frequent, or very rare sequence variants inT. molitorsatellite DNA is always random. Monomer variants are randomly distributed in the total satellite DNA and thus spread across all chromosomes, indicating a relatively high rate of sequence homogenization among different chromosomes. Such a distribution of monomer variants represents a transient stage in the process of sequence homogenization, indicating the high rate of spreading in comparison with the rate of sequence variant amplification.
Distribution and structure of cloned P elements from theDrosophila melanogasterP strain π2
Authors: O'Hare Kevin , Driver Alan , McGrath Stephen , Johnson-Schiltz Dena M. 
Published: September 2009

SummaryP transposable elements ofDrosophila melanogastercloned from the strong P strain π2have been analysed. The structures and chromosomal locations of 26 of the 30–50 elements estimated to be present in π2 have been determined. At one location two elements are inserted 100 base pairs (bp) apart, and in a second location two elements are only separated by the 8 bp duplicated upon P-element insertion. In addition to 2.9 kilobasepair (kbp) elements, elements with 14 different internal deletions from 1.3 to 2.3 kbp in size have been isolated. There are 7 copies of the 2–9 kbp element, 2 copies each of 5 internally deleted elements and a single copy of 9 internally deleted elements. One of the elements found twice is the KP element, which may play a role in the regulation of hybrid dysgenesis in strains which contain many copies of this element. Apart from internal deletions the elements are extremely homogeneous in DNA sequence, with only 2 single base polymorphisms detected twice each in over 16 kbp of P-element sequence. Although transpositions are infrequent in an inbred P cytotype strain such as π2, the distribution of these cloned elements indicates that when the genomic library was made, the strain was polymorphic with respect to element location. The distribution and structures of the element are discussed with respect to models for regulation of P-element transposition.
Polymorphisms distinguishing different mouse species andthaplotypes
Authors: Horiuchi Yoshihito , Agulnik Alexander , Figueroa Felipe , Tichy Herbert , Klein Jan 
Published: September 2009

SummaryThree anonymous chromosome 17 DNA markers,D17Tu36,D17Tu43, and D17Le66B, differentiate between house mouse species and/or betweentchromosomes. TheD17Tu36probe, which maps near theFulocus and to theIn(17)4ontchromosomes, identifies at least 15 haplotypes, each haplotype characterized by a particular combination of DNA fragments obtained after digestion with theTaqI restriction endonuclease. Ten of these haplotypes occur inMus domesticus, while the remaining five occur inM. musculus. In each of these two species, one haplotype is borne bytchromosomes while the other haplotypes are present on non-r chromosomes. TheD17Tu43probe, which maps near theD17Leh122locus and to theIn(17)3ontchromosomes, also identifies at least 15 haplotypes inTaqI DNA digests, of which nine occur in M. domesticus and six inM. musculus. One of the nineM. domesticushaplotypes is borne bytchromosomes, the other haplotypes are borne by non-f chromosomes; two of the sixM. musculushaplotypes are borne bytchromosomes and the remaining four by non-f chromosomes. Some of theD17Tu43haplotypes are widely distributed in a given species, while others appear to be population-specific. Exceptions to species-specificity are found only in a few mice captured near theM. domesticus-M. musculushybrid zone or in t chromosomes that appear to be of hybrid origin. TheD17Leh66Bprobe, which maps to theIn(17)2, distinguishes three haplotypes ofM. domesticus-dznved t chromosomes and one haplotype ofM. musculus-derivzd t chromosomes. Because of these characteristics, the three markers are well suited for the study of mouse population genetics in general and of t chromosome population genetics in particular. A preliminary survey of wildM. domesticusandM. musculuspopulations has not uncovered any evidence of widespread introgression of genes from one species to the other; possible minorintrogressions were found only in the vicinity of the hybrid zone. Typing of inbred strains has revealed the contribution of onlyM. domesticusDNA to the chromosome 17 of the laboratory mouse.
Dominant hemimelia andEn-1on mouse chromosome 1 are not allelic
Authors: Higgins Maureen , Hill Robert E. , West John D. 
Published: September 2009

SummaryPrevious studies have shown thatEn-1, a homeobox-containing gene, maps close to or at theDhlocus in the mouse. Since homeobox-containing genes are key genes in the control of development the close proximity ofEn-1to the developmentally significant geneDhraised the possibility that theDhmutation represented a mutant allele ofEn-1. A genetic analysis involvingEn-1,Dh, and other chromosome 1 markers (Emv-17,InandPep-3) shows that althoughDhandEn-1are closely linked they are separable by recombination (4/563). The likely gene order and recombination frequencies of these loci are: In (5.2±0.9)Emv-17(1.1±0.4) Dh (0.7±0.4)En-1(3.0±0.7) Pep-3. This shows thatDhis not a mutant allele ofEn-1.
The role of DNA replication and isochores in generating mutation and silent substitution rate variance in mammals
Authors: Walker Adam Eyre 
Published: September 2009

SummaryIt has been suggested that isochores are maintained by mutation biases, and that this leads to variation in the rate of mutation across the genome. A model of DNA replication is presented in which the probabilities of misincorporation and proofreading are affected by the composition and concentration of the free nucleotide pools. The relationship between sequenceG + Ccontent and the mutation rate is investigated. It is found that there is very little variation in the mutation rate between sequences of differentG + Ccontents if the total concentration of the free nucleotides remains constant. However, variation in the mutation rate can be arbitrarily large if some mismatches are proofread and the total concentration of free nucleotides varies. Hence the model suggests that the maintenance of isochores by the replication of DNA in free nucleotide pools of biased composition does not leadper seto mutation rate variance. However, it is possible that changes in composition could be accompanied by changes in concentration, thus generating mutation rate variance. Furthermore, there is the possibility that germ-line selection could lead to alterations in the overall free nucleotide concentration through the cell cycle. These findings are discussed with reference to the variance in mammalian silent substitution rates.
The distribution of transposable elements within and between chromosomes in a population ofDrosophila melanogaster. II. Inferences on the nature of selection against elements
Authors: Charlesworth Brian , Lapid Angela , Canada Darlene 
Published: September 2009

SummaryData were collected on the distribution of nine families of transposable elements among a sample of autosomes isolated from a natural population ofDrosophila melanogaster, by means ofin situhybridization of biotinylated probes to polytene chromosomes. There is no general tendency for elements to accumulate at the tips of chromosomes. Elements tend to be present in excess of random expectation in the euchromatin proximal to the centromeres of the major autosomes, and on chromosome four. There is considerable heterogeneity between different families in the extent of this excess. The overall abundance of element families is inversely related to the extent to which they accumulate proximally. The level of proximal accumulation for the major autosomes is similar to that on the fourth chromosome, but less than that for the X chromosome. There is an overall deficiency of elements in the mid-section of the X compared with the mid-sections of the major autosomes, with considerable heterogeneity between families. The magnitude of this deficiency is positively related to the extent to which elements accumulate proximally. No such deficiency is seen if the proximal regions of the X and autosomes are compared. There is a small and non-significant excess of elements in third chromosomes carrying inversions. There is some between-year heterogeneity in element abundance. The implications of these findings are discussed, and it is concluded that they generally support the hypothesis that transposable element abundance is regulated primarily by the deleterious fitness consequences of meiotic ectopic exchange between elements. If this is the case, such exchange must be very infrequent in the proximal euchromatin, and the elements detected in population surveys of this kind must be inserted into sites where they have negligible mutational effects on fitness.
Aspects of maximum likelihood methods for the mapping of quantitative trait loci in line crosses
Authors: Knott S. A. , Haley C. S. 
Published: September 2009

SummaryMaximum likelihood methods for the mapping of quantitative trait loci (QTL) have been investigated in an F2population using simulated data. The use of adjacent (flanking) marker pairs gave improved power for the detection of QTL over the use of single markers when markers were widely spaced and the QTL effect large. The use of flanking marker loci also always gave moreaccurate and less biassed estimates for the effect and position of the QTL and made the method less sensitive to violations of assumptions, for example non-normality of the distribution. Testing the hypothesis of a linked QTL against that of no QTL is not biassed by the presence of unlinked QTL. This test is more robust and easier to obtain than the comparison of a linked with an unlinked QTL. Fixing the recombination fraction between the markers at an incorrect value in the analyses with flanking markers does not generally bias the test for QTL or estimates of their effect. The presence of multiple linked QTL bias both tests and estimates of effect with interval mapping, leading to inflated values when QTL are in association in the lines crossed and deflated values when they are in dispersion.
Electrofusion of mouse embryos results in uniform tetraploidy and not tetraploid/diploid mosaicism
Authors: James Roberta M. , Kaufman Matthew H. , Webb Sheila , West John D. 
Published: September 2009

SummarySome previous attempts to produce tetraploids experimentally have resulted in a proportion of treated embryos becoming 2n/4n mosaics at a frequency which may be as high as 20%, when using cytochalasin B as a fusigenic stimulus and cytogenetic techniques to identify putative tetraploid embryos. To investigate the possible occurrence of 4n/2n mosaicism, tetraploid embryos were produced by electrofusion, a process which allows adjacent blastomeres at the 2-cell stage to fuse following exposure to electric field pulses. Embryos used for electrofusion were hemizygous for a transgene consisting of approximately 1000 copies of the mouse β-globin gene. Afterin situhybridization, one hybridization signal is expected per diploid genome. Tetraploid cells in 7·5-, 8·5-, 9·5- and 10·5-day-old conceptuses were distinguished from diploid cells by performingin situhybridization on histological sections. The frequency of nuclei with two hybridization signals in the ‘hemizygous’ tetraploid embryos was compared to diploid embryos which were either hemizygous or homozygous for the β-globin transgene. Comparison of the frequency of nuclei with two hybridization signals between tissues of ‘hemizygous’ tetraploid conceptuses and homozygous diploid conceptuses showed no significant difference, which implies that the tissues in the tetraploid conceptuses were uniformly tetraploid. No evidence was found to suggest that electrofusion results in 2n/4n mosaicism.
Studies of linkage in populations. X. Altitude and autosomal gene arrangements inDrosophila robusta
Authors: Levitan Max , Scheffer Sonja J. 
Published: September 2009

SummaryData are presented concerning the gene arrangements in the second and third chromosomes ofDrosophila robustain eight altitudinal transects. A consistent change is the increase in the arrangement 2L-3, particularly in the linkage combination2L-3.2R, with increasing altitude. The reciprocal decrease with increasing altitude affects several different 2-left arrangements, most consistently 2L-1. The arrangements of 2-right show no significant variation with altitude, and those of 3-right do so only in a few samples of the two northern transects studied, none in any of the southern ones. These results confirm previous evidence for the significant role of the arrangements of the left arm of the second chromosome in the adaptations of this species to altitude and suggest further that interactions of linked arrangements are involved in these adaptations. The data also indicate that the factors responsible for the altitudinal adaptations of this species are in many cases not the same ones that are responsible for variations in its gene arrangements with latitude.
Mitochondrial DNA analysis of introgression between adjacent taxa of rock-wallabies,Petrogalespecies (Marsupialia: Macropodidae)
Authors: Bee C. A. , Close R. L. 
Published: September 2009

SummarySimple, inexpensive techniques were used to analyse the mtDNA of nine chromosomally distinct populations ofPetrogale. Eight of these populations occur in sequence along the Great Dividing Range of eastern Australia; six have been described as species. Diagnostic mtDNA morphs were found throughout the latitudinal ranges of four of the described species. A fifth morph spanned the ranges of two described species and three additional taxa which have been designated chromosome races. These five mtDNA morphs, and others with local distributions, were used to assess interactions between the taxa. Limited introgression was indicated across the chromosomal boundaries ofP. penicillata/P. herbertiandP. inornata/P. assimilis; atypical mtDNA morphs were found within theP. herbertiandP. inornatachromosomal distributions. No introgression was detected betweenP. herbertiandP. inornata, whose distributions are separated by the Fitzroy River. Nor was there evidence of recent contact betweenP. assimilis,P. herbertiandP. purpureicollis, despite the late occupancy of parts of the intervening area by unidentifiedPetrogale. These data, considered in the light of information obtained from previous studies on chromosomes, allozymes and parasites, have contributed to the decision to consider all the eastern representatives of thelateralis-penicillatagroup ofPetrogaleas being specifically distinct from each other.
The role of growth hormone in lines of mice divergently selected on body weight
Authors: Hastings Ian M. , Bootland Lorna H. , Hill William G. 
Published: September 2009

SummaryAn understanding of the physiological and genetic changes which determine the response to selection is critical for both evolutionary theory and to assess the application of new molecular techniques to commercial animal breeding. We investigated an aspect of physiology, growth hormone (GH) metabolism, which mighta priorihave been expected to play a large part in the response of mouse lines selected for high or low body weight. Disruption of endogenous GH or addition of exogenous GH had similar proportionate effects on body weight in both lines of mice (although differences in body composition arose) suggesting that neither the production of GH nor receptor sensitivity to GH had been altered as a result of selection. This supports a ‘pleiotropic model’ of the response to selection: that many genes with diverse metabolic roles all contribute to the divergent phenotype. This result has significant commercial implications as it suggests that artificial selection, transgenic technology and environmental manipulation may be synergistic rather than antagonistic strategies.
Spontaneous mutation for a quantitative trait inDrosophila melanogaster. I. Response to artificial selection
Authors: López María A. , López-Fanjul Carlos 
Published: September 2009

SummaryDivergent selection for abdominal bristle number was carried out for 47 generations, starting from a completely homozygous population ofDrosophila melanogaster. All lines were selected with the same proportion (20%) but at two different numbers of selected parents of each sex (5 or 25). A significant response to selection was obtained in 25 lines (out of 40). In most cases, it could be wholly attributed to a single mutation of relatively large effect (> 0·3 phenotypic standard deviations). A total number of 30 mutations were detected. In agreement with theory, larger responses in each direction were achieved by those lines selected at greater effective population sizes. A large fraction of mutations were lethals (10/30). Thus, the observed divergence between lines of the same effective size selected in opposite directions was smaller than expected under neutrality. The ratio of new mutational variance to environmental variance was estimated to be(0·52±0·09)×10−3.
Genetic structure and differentiation inMetrosideros polymorpha(Myrtaceae) along altitudinal gradients in Maui, Hawaii
Authors: Aradhya K. M. , Mueller-Dombois D. , Ranker T. A. 
Published: September 2009

SummaryThe level and distribution of genetic variability within and amongMetrosideros polymorphapopulations along altitudinal gradients on the island of Maui, Hawaii were examined to assess the extent of genetic differentiation. Sixteen loci encoding 11 enzymes were scored in 17 populations along the NE wet slope of Mt. Haleakala and Kipahulu Valley in East Maui and six populations along the Puu Kukui trail in West Maui. On average, 50% of the loci were polymorphic within populations with an overall mean of 2·15 alleles per locus. The observed heterozygosities for different populations were moderate (0·108–0·220) and conformed to panmixia except for one of the mid-elevation populations. The distribution of allozyme variation indicates that very little differentiation has occurred along altitudinal gradients. Approximately 90% of the total variation resides within populations in East Maui while 95% was found within West Maui populations. The mean populational pair-wise genetic identities (Nei's I) ranged from 0·909 to 0·998. The UPGMA cluster analysis on genetic identity matrices and PCA on allele frequencies revealed marginal altitudinal differentiation. Twenty one alleles out of a total 63 showed statistically significant correlations with environmental variables.
Mapping and characterization ofP-element-induced mutations at quantitative trait loci inDrosophila melanogaster
Authors: Lai Chaoqiang , Mackay Trudy F. C. 
Published: September 2009

SummaryXchromosomes derived from crosses of inbred P and MDrosophila melanogasterstrains that had extreme effects on abdominal and/or sternopleural bristle number in males, were further analyzed to determine their effects in females and to map the loci at which the mutations occurred. Seven lines that had on average 3.9 fewer sternopleural bristles than wildtype in males had average homozygous sternopleural bristle effects of −2·2. The bristle effects were partially recessive, with an average degree of dominance of −0·60. Physical mapping of the sternopleural bristle effects of these lines placed them all at approximately 24·7 cM. These mutations are apparently allelic on the basis of a complementation test, and deficiency mapping indicates they occur within chromosomal bands 8A4; 8C6.In situhybridization analysis of the sites ofPelement insertions of these lines suggests that mutations probably resulted from excision ofPelements at 8C on the original inbred P strain chromosome. Two additional lines, NDC(19) and DP(146), had reduced numbers of sternopleural and abdominal bristles. NDC(19) males had 9·7 fewer abdominal and 8·6 fewer sternopleural bristles than wildtype. The corresponding homozygous abdominal and sternopleural bristle number effects were −5·8 and −3·8, respectively; with the abdominal bristle effect completely recessive and the sternopleural bristle effect nearly additive. DP(146) males had 6·2 fewer abdominal and 4·1 fewer sternopleural bristles than wildtype, with homozygous abdominal bristle effects of −4·3 and sternopleural bristle effects of −2·0. Abdominal bristle effects of this line were partially recessive whereas the sternopleural bristle effects were additive. Physical mapping showed effects on both bristle traits segregated jointly in these two lines, with the NDC(19) mutation closely linked toyand the DP(146) mutation 0·17 cM from it. Complementation tests and deficiency mapping also indicate the mutations in lines NDC(19) and DP(146) are at closely linked but separate loci within chromosomal bands 1B2; 1B4–6 and 1B4–6; 1B10 respectively, with some epistatic effects.In situhybridization analysis of sites ofPelement insertion suggest that the NDC(19) mutation, which may be ascuteallele, was probably caused by aPelement insertion in the IB region; the DP(146) mutation is also associated with an insertion at IB.