bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitochondrial DNA heteroplasmy maintained in natural populations ofDrosophila simulansin Réunion
Authors: Matsuura Etsuko T. , Fukuda Haruyo , Chigusa Sadao I. 
Published: September 2009

SummaryMitochondrial DNA (mtDNA) variation inDrosophila simulanswas studied to determine whether the cytoplasmic state of mtDNA heteroplasmy persists in natural populations in Réunion. For this purpose, 172 isofemale lines, newly collected from two local populations, were examined, among which three types of mtDNA (siII,siIII andsiIII′) were found, based on theHpaII restriction pattern. Ten of the lines were heteroplasmic for a combination ofsiII and siIII, as determined by autoradiography. The same type of heteroplasmy had been noted in one of the two local populations 8 years before (Sattaet al.1988). The present results suggest that the heteroplasmic state occurs recurrently in natural populations ofD. simulansin Réunion.
Transposable elements in natural populations with a mixture of selected and neutral insertion sites
Authors: Charlesworth Brian 
Published: September 2009

SummaryThis paper examines models of the population dynamics of transposable elements when chromosomal sites vary with respect to the effect on fitness of mutations caused by element insertions. Element abundance is assumed to be stabilised solely by the joint results of transposition, excision, and selection against insertional mutations. When there are only two classes of site, selected and neutral, it is hard to find parameter values for which numbers of elements are maintained that match the findings from surveys ofDrosophilapopulations, as elements tend to accumulate at high frequencies at the neutral sites. It is similarly hard to produce realistic equilibria with three classes of site (strongly selected, weakly selected, and neutral), when elements can transpose out of the neutral sites. If transposition from neutral sites is impossible, as might be the case for elements inserted into centric heterochromatin, then realistic equilibria can be generated if there is very weak selection against elements inserted into the majority of non-neutral sites. This model predicts a modest over-representation of elements at the neutral sites. It also predicts that elements should be under-represented on the X chromosome compared with the autosomes, but this is not generally found to be the case. It is concluded that selection against insertional mutations is unlikely to be the major factor involved in the containment of element abundance.
Linkage between sperm abnormality level and major urinary protein phenotype in mice
Authors: Styrna Jozefa 
Published: September 2009

SummarySegregation of sperm abnormality level and the pattern of major urinary proteins (MUPs) were investigated in F2 and B1 hybrid males obtained from crosses involving two contrasting inbred strains of mice: CBA/Kw (Mup-1a1a, 3·3% abnormal sperm) and C57BL/Kw (Mup-1b1b, 21·9% abnormal sperm). In the progeny of both crosses mean levels of abnormal spermatozoa were significantly higher for males typed as Mup-1b1b than for heterozygous Mup-1a1b males. Moreover, all F2 hybrid males showing very high percentages of abnormal sperm were Mup-1b1bhomozygotes. Similarly, among B1 males with a high level of deformed spermatozoa, a statistically significant majority were Mup-1b1b genotypes. Our results suggest that at least two genes which influence sperm abnormality level are segregating in these crosses. Both appear to be recessive for high sperm abnormality level, and one shows weak linkage to Mup-1 on chromosome 4.
Thein vivoandin vitrotransmission ratio distortion of one complete and two partialthaplotypes in mice
Authors: Garside William , Ruangvoravat Christine , Dolan Patricia , Hillman Nina 
Published: September 2009

SummaryThe effects of different types of insemination (normal and delayed matings andin vitrofertilization) on the transmission ratio distortion (TRD) of threethaplotypes were determined. Thetw73haplotype which contains all of the loci known to affect TRD is transmitted at equivalent frequencies in normal matings and inin vitrofertilizations (0·84 and 0·85, respectively) but at a significantly lower frequency (0·62) in delayed matings. The distal partialth18haplotype is transmitted at equivalent frequencies in all types of insemination (0·66 to 0·70) while the proximal partialtw18haplotype is transmitted in Mendelian frequencies in normal matings and inin vitroinseminations but at a significantly lower frequency in delayed matings. The results are discussed with reference to the current genetic model for transmission ratio distortion.
An increased level of sperm abnormalities in mice with a partial deletion of the Y chromosome
Authors: Styrna Jozefa , Imai Hirotami T. , Moriwaki Kazuo 
Published: September 2009

SummaryTwo congenic lines of mice, one with a partial deletion of the Y chromosome, differ in the percentage of spermatozoa with abnormal heads: B10.BR/SgSn males give 22·6%; and B10.BR-Ydel/Ms males give 64·2%; abnormal sperm. The F1s resulting from crosses of B10.BR/SgSn males with females of five common inbred strains exhibited significantly lower levels of abnormal sperm than the parental strains, as opposed to F1 hybrids sired by B10.BR-Ydel/Ms mutant males, where very high levels of abnormal spermatozoa were found. About 30%; of abnormal spermatozoa, produced by males with deletion on the Y chromosome, were characterized by a flat acrosomal cap. This class of abnormality was never observed in non-mutant males, suggesting a mutant-specific defect. These results demonstrate the important role of the Y chromosome in spermatogenesis.
Genetic and molecular analysis of repression in the P–M system of hybrid dysgenesis inDrosophila melanogaster
Authors: Heath Ellen M. , Simmons Michael J. 
Published: September 2009

SummaryTwelve inbred lines derived from an M′ strain ofDrosophila melanogasterwere used to study the repression of P-element-mediated hybrid dysgenesis. Initial assessments indicated that the lines differed in the ability to repress gonadal dysgenesis, and that this ability was highly correlated with the ability to represssnwhypermutability. Later assessments indicated that most of the lines with low or intermediate repression potential evolved to a state of higher repression potential; however, Southern analyses failed to reveal significant changes in the array of genomic P elements that could account for this evolution. In addition, none of the lines possessed the incomplete P element known as KP, which has been proposed to explain repression in someD. melanogasterstrains. One of the lines maintained intermediate repression potential throughout the period of study (52 generations), indicating that the intermediate condition was not intrinsically unstable. Genetic analyses demonstrated that in some of the lines, repression potential was influenced by factors that were inherited maternally through at least two generations; however, these factors were not as influential as those in a classic P cytotype strain. Additional tests with a dysgenesis-inducing X chromosome calledT-5indicated that repression itself was mediated by a combination of maternal effects and paternally inherited factors that were expressed after fertilization. These tests also suggested that in some circumstances, the P transposase, or its message, might be transmitted through the maternal cytoplasm.
Genetic and molecular analyses ofvgal: a spontaneous and unstable mutation at thevestigiallocus inDrosophila melanogaster
Authors: Bazin Claude , Lemeunier Françoise , Periquet Georges , Silber Joël 
Published: September 2009

SummaryWe describe herein, a new unstable mutant of thevestigiallocus, isolated from a French natural population. From this mutantvestigialalmost(vgal) wild-type flies (vgal+) and extremevgphenotypes (vge) arose spontaneously without genomic shock. The occurrence ofvgal+orvgealleles depends mostly on the breeding temperature;vgal+revertants arose principally at low temperature (21 °C) andvgeat 28 °C. These events occur mainly in the male germ line and the phenomenon appears to be premeiotic. Our results within situhybridization experiments and Southern blots show that thevgalmutation is due to a 2 kb DNA insertion, which is a deletedhoboelement. Genetic and molecular analyses show that two distinct events may underly the wild-type revertants. One is the excision of the residenthoboelement, the other a further deletion (about 300 bp in the example characterized herein). Thevgemutation is probably due to a deletion ofvestigialsequences flanking thehoboinsertion.
Muscle opacity(mo), a new mutant gene inXenopus laevis, linked to therustylocus
Authors: Droin Anne 
Published: September 2009

SummaryA new developmental mutant is described inXenopus laevis(Amphibia, Anura):muscle opacity(mo). Homozygotes die at larval stage 48. The underlying defect, visible at stage 47, is a degeneration of cephalic musculature. Themogene is linked to therustylocus, with a map distance of 6·1%.
The synergistic effect of X-rays and deficiencies in DNA repair in P-M hybrid dysgenesis inDrosophila melanogaster
Authors: Margulies Lola , Griffith Carole S. 
Published: September 2009

SummaryX-rays and deficiencies in DNA repair had a synergistic effect on genetic damage associated with P-element mobility inDrosophila melanogaster. These interactions, using sterility and fecundity as endpoints, were tested in dysgenic males deficient in either excision or post-replication DNA repair. Three sublines of the Harwich P strain were used for the construction of hybrid males. These sublines differ in P-induction ability based on gonadal dysgenesis sterility (GD) andsnwmutability tests, in P-element insertion site pattern, and in the types of defective P-elements, such as KP elements, they possess. A lower degree of gonadal dysgenesis was correlated with the presence of KP elements. GD sterility andsnwmutability were not always correlated. Dysgenic hybrids originating from the standard reference subline, Harwichwhite, were much more sensitive to the post-replication repair than the excision repair defect. In contrast, sterility of hybrids derived from the weak subline was least affected by, and that of hybrids of the strongest subline was most affected by either DNA repair deficiency. The exacerbation by X-rays of the effects of DNA repair deficiencies on genetic damage indicates that both repair mechanisms are required for processing DNA lesions induced by the combined effect of P activity and ionizing radiation.
Linkage of loci associated with two pigment mutations on mouse chromosome 13
Authors: Holcombe Randall F. , Stephenson Dennis A. , Zweidler Alfred , Stewart Ruby M. , Chapman Verne M. , Seidman J. G. 
Published: September 2009

SummaryProgeny from one intra- and two inter-specific backcrosses between divergent strains of mice were typed to map multiple markers in relation to two pigment mutations on mouse chromosome 13, beige (bg) and pearl (pe). Both recessive mutants on a C57BL/6J background were crossed separately with laboratory strain PAC (M. domesticus) and the partially inbredM. musculusstock PWK. The intra- and inter-specific F1hybrids were backcrossed to the C57BL/6J parental strain and DNA was prepared from progeny. Restriction fragment length polymorphisms were used to follow the segregation of alleles in the backcross offspring at loci identified with molecular probes. The linkage analysis defines the association between thebgandpeloci and the loci for the T-cell receptor γ-chain gene (Tcrg), the spermatocyte specific histone gene (Hist 1), the prolactin gene (Prl), the Friend murine leukaemia virus integration site 1 (Fim-1), the murine Hanukuh Factor gene (Muhf/Ctla-3) and the dihydrofolate reductase gene (Dhfr). This data confirms results of prior chromosomal mapping studies utilizingbgas an anchor locus, and provides previously unreported information defining the localization of the prolactin gene on mouse chromosome 13. The relationship of multiple loci in relation topeis similarly defined. These results may help facilitate localization of the genes responsible for two human syndromes homologous withbgandpe, Chediak–Higashi syndrome and Hermansky–Pudlak syndrome.
Growth hormone and insulin-like growth factor-I measurements in high growth (hg) mice
Authors: Medrano J. F. , Pomp D. , Sharrow L. , Bradford G. E. , Downs T. R. , Frohman L. A. 
Published: September 2009

SummaryEffects of a recessive gene causing high growth (hg) were studied on two major components of the growth axis in mice. Plasma and pituitary levels of growth hormone and plasma levels of insulin-like growth factor I (IGF-I) were measured in three lines homozygous forhg, each compared with a control line of alike genetic background but wild type for thehglocus (Hg). Line Gh (hghg) and line GH (HgHg) are from a line which had undergone long-term selection for high postweaning weight gain; line Ch (hghg) and line CH (HgHg) were extracted from the second backcross of Gh to C57BL/6J; line L54 (hghg) was from the sixth backcross to C57BL/6J (B6) (HgHg). Pituitary GH levels and plasma IGF-I levels were measured in both sexes at 3, 4·5, 6 and 9 wk of age. Plasma growth hormone was measured in 8- to 12-wk-old males at hourly intervals from 08.00 to 17.00. Body weight in lines homozygous forhgat 6 and 9 wk of age was 10–30% greater than in control lines. The ontogeny of this increased growth depended on genetic background. Pituitary growth hormone content was 52% lower in the twohghglines measured (lines Ch and Gh) than in control lines at 4·5, 6 and 9 wk. Plasma growth hormone levels were also much lower inhgmice, with values only 20–30% of those in their respective controls,hglines showed consistently low plasma growth hormone levels throughout the 9 hr sampling period, while control lines expressed the characteristic pulsatile hormone secretion. In contrast, plasma IGF-I levels were greater in line Ch (hghg) than in line CH (HgHg) at 3, 4·5 and 9 wk, and were also greater in line Gh (hghg)vs. line GH (HgHg) at 6 wk of age. The results suggest that the growth enhancing effect of thehggene occurs through an IGF-I-mediated process. In addition, the genetic background itself is also a factor in the phenotypic expression of the gene.
Genetic analysis of a switch in cell specificity of P lysozyme expression inmolossinusmice
Authors: Cortopassi Gino A. , Wilson Allan C. 
Published: September 2009

SummaryAn electrophoretic survey of concentrations of lysozymes M and P was carried out with seven species in the house mouse group (spretus, hortulanus, abbotti, musculus, castaneus, domesticusandmolossinus). In most species M is the predominant lysozyme in all tissues tested, except the small intestine, where P predominates if present. In inbred strains ofmolossinusmice P is more abundant than M in all tissues tested. The phenotypes of high expression of P lysozyme and low expression of M lysozyme in peritoneal and alveolar macrophages were examined genetically. Results of interspecific crosses and backcrosses todomesticusmice support the model that the phenotypes are caused by mutation(s) tightly linked to the lysozyme locus. Alleles at the regulatory loci show additive inheritance.
Two new X-autosome Robertsonian translocations in the mouse: I. Meiotic chromosome segregation in male hemizygotes and female heterozygotes
Authors: Tease Charles , Fisher Graham 
Published: September 2009

SummaryTwo new X-autosome Robertsonian (Rb) translocations, Rb(X.9)6H and Rb(X.12)7H, were found during the course of breeding the Rb(X.2)2Ad rearrangement at Harwell. The influence of these new Rbs on meiotic chromosome segregation was investigated in hemizygous males and heterozygous females and compared to that of Rb(X. 2)2Ad. Screening of metaphase II spermatocytes gave incidences of sex chromosome aneuploidy of 9·2% in Rb(X. 2)6H/Y and 9·6% in Rb(X.9)2Ad/Y males; no metaphase II cells were present in the testes of the Rb(X. 12)7H/Y males examined and no males with this karyotype have so far proved fertile. In breeding tests, 5% of the progeny of Rb(X.2)2Ad/Y males were sex chromosome aneuploids compared to 10% of the Rb(X. 9)6H/Y offspring. The difference was not significant, however. Cytogenetic analyses of metaphase II stage oocytes showed elevated rates of hyperhaploidy (n+ l) in Rb heterozygous females over chromosomally normal mice: 4·2% for Rb(X.2)2Ad/+; 2·1% for Rb(X.9)6H/+; 2·2% for Rb(X.12)7H/+ and 1·1% for normal females. There was, however, no statistically significant difference in the rates of hyperhaploidy between the three different Rb types, nor overall between Rb/ + and normal females. Karyotypic analyses of liveborn offspring of Rb heterozygous females revealed low incidences of X0 animals but no other type of sex chromosome aneuploidy. Intercrosses of heterozygous females and hemizygous males yielded 5·5% aneuploidy for Rb(X.2)2Ad and 5·4% for Rb(X.9)6H. In heterozygous females, there was evidence from the metaphase II and breeding test data for all three rearrangements, of preferential segregation of the Rb metacentric to the polar body resulting in a deficiency of cells and progeny carrying a translocation chromosome.
Strategies for increasing fixation probabilities of recessive mutations
Authors: Caballero A. , Keightley P. D. , Hill W. G. 
Published: September 2009

SummaryFixation probabilities and mean times to fixation of new mutant alleles in an isogenic population having an effect on a quantitative trait under truncation selection were computed using stochastic simulation. A variety of population structures and breeding systems were studied in order to find an optimal design for maximizing the fixation probability for recessive genes without impairing that for non-recessives or delaying times to fixation. Circular mating or cycles with repeated generations of close inbreeding alternating with combination of the families proved to be very inefficient. The most successful scheme found, considering fixation probabilities and times to fixation jointly, was to practise individual selection and mate full sibs whenever possible, otherwise mate at random. The benefit was directly proportional to the number of full-sib matings performed, which, in turn, almost exclusively depended on the number of selected individuals with very little effect of selection intensity or magnitude of gene effects. Fixation rates could be well approximated by diffusion methods. When selection was practised in only one sex and, therefore, the proportion of full-sib matings could be varied from zero to one, maximizing the amount of full-sib mating was found to maximize fixation probability, at least for single mutants.
A method for detecting effect of beneficial mutations in natural populations ofDrosophila melanogaster
Authors: Koga A. , Kusakabe S. , Tajima F. , Takano T. , Harada K. , Mukai T. 
Published: September 2009

SummaryAn experimental method is proposed for detecting the effects of positive natural selection on DNA polymorphisms. Since beneficial mutations are expected to increase in frequency faster than neutral mutations, variants which have reached high frequencies in a relatively short period could be linked to some beneficial mutation.D. melanogasterhas a cosmopolitan polymorphic inversion -In(2L)t- whose age in some local populations has been estimated. Setting the age ofIn(2L)tas the upper limit for the age of variants, we searched for variants whose frequencies were possibly influenced by positive natural selection. We detected a single candidate whose frequency and distribution met the requirements imposed by our method.
A theoretical test of the DNA repair hypothesis for the maintenance of sex in eukaryotes
Authors: Szathmáry Eörs , Kövér Szilvia 
Published: September 2009

SummaryThe DNA repair hypothesis for the maintenance of sex states that recombination is necessary for the repair of double-strand DNA damage. In a closed (mitotic) genetic system crossing-over generates homozygosity. This reduces fitness if deleterious recessive alleles become expressed. Thus, outcrossing is required to restore heterozygosity destroyed by recombination. The repair hypothesis is tested by comparing outcrossing sexuality with a hypothetical parthenogenic strategy (the Prudent Reparator) which destroys as little heterozygosity during repair as possible. In the Prudent Reparator, repair of double-strand DNA damage results in a small amount of homozygosity due to gene conversion only, since this process does not render outside markers homozygous. Diploidy, deleterious recessives, multiplicative fitness and linkage equilibrium in mutation-selection balance are assumed. The average fitness of this population increases, and complementation (i.e. masking of recessives in heterozygous form) decreases with the rate of damage per locus. The equilibrium fitness of the Prudent Reparator can be well above that of the sexual population. A lower complementation ability of parthenogens may not be an impenetrable barrier to their successful establishment if the invader's genome is relatively uncontaminated by mutant alleles: there are always such genotypes in the sexual population. Thus, the Prudent Reparator could solve the problem of repairing damage as well as that of invading an existing outcrossing population. As we do not see this strategy widely adopted instead of sexuality, the repair hypothesis is likely to miss some essential feature of the evolution of sex.
Inbreeding coefficients and coalescence times
Authors: Slatkin Montgomery 
Published: September 2009

SummaryThis paper describes the relationship between probabilities of identity by descent and the distribution of coalescence times. By using the relationship between coalescence times and identity probabilities, it is possible to extend existing results for inbreeding coefficients in regular systems of mating to find the distribution of coalescence times and the mean coalescence times. It is also possible to express Sewall Wright'sFSTas the ratio of average coalescence times of different pairs of genes. That simplifies the analysis of models of subdivided populations because the average coalescence time can be found by computing separately the time it takes for two genes to enter a single subpopulation and time it takes for two genes in the same subpopulation to coalesce. The first time depends only on the migration matrix and the second time depends only on the total number of individuals in the population. This approach is used to findFSTin the finite island model and in one- and two-dimensional stepping-stone models. It is also used to find the rate of approach ofFSTto its equilibrium value. These results are discussed in terms of different measures of genetic distance. It is proposed that, for the purposes of describing the amount of gene flow among local populations, the effective migration rate between pairs of local populations,M^, which is the migration rate that would be estimated for those two populations if they were actually in an island model, provides a simple and useful measure of genetic similarity that can be defined for either allozyme or DNA sequence data.
Nucleic acids in mummified plant seeds: biochemistry and molecular genetics of pre-Columbian maize
Authors: Rollo Franco , Venanzi Franco Maria , Amici Augusto 
Published: September 2009

SummaryNucleic acids fractions were isolated from pre-Columbian maize seeds and characterized using different approaches such as polyacrylamide gel electrophoresis, anti-DNA antibody binding, HPLC fractionation, molecular hybridization with cloned genes, and DNA amplification by the polymerase chain reaction. The nucleic acids were found to be very depolymerized (≤140 base pairs in length) and composed mainly of ribosomal RNA. Despite the very low amount and degree of polymerization of seed DNA, specific maize nuclear Mul, Mu4, Mu8 and, possibly, Mu5 element components could be detected, thanks to the use of amplification systems as short as 90 bp. The results suggest that evaluation of the relative proportions of Mu-type element components and, possibly, other maize genomic components in single mummified kernels, may offer a new key to the study of ancient maize populations.