bluuebunny/crossref_metadata_2025 huggingface dataset:
Chromosomal anomalies that cause male sterility in the mouse also reduce ovary size
Authors: Mittwoch Ursula , Mahadevaiah Shantha , Setterfield Leslie A.
Published: September 2009

Two male-sterile chromosome anomalies, the insertion Is(7; 1)40H and the tertiary trisomy, Ts(512)31H, were found to be associated with reduced ovarian volumes in immature females. Together with the reciprocal translocation, T(11; 19)42H, in which this effect was described previously, reduced ovaries have been found in all three male-sterile chromosome anomalies investigated so far, suggesting that ovarian involvement is likely to be common in these conditions. Assuming that the smaller ovarian size reflects a reduction in the number of oocytes, it is suggested that male-sterile chromosome anomalies may exert basically similar deleterious effects on meiotic germ cells in males and females, the difference in outcome being due to cell-physiological differences between spermatocytes and oocytes and to the small number of surviving oocytes required for fertility in females.
Postmeiotic segregation as a source of mosaics in diploid organisms
Authors: Leslie John F. , Watt Ward B.
Published: September 2009

Postmeiotic segregation (PMS) of genetic variants occurs when a DNA heteroduplex formed during meiotic recombination goes undetected by repair enzymes and is transmitted unresolved to the meiotic products. PMS provides an alternative explanation for the origin of mosaics now attributed to half-chromatid mutation. In multicellular diploid eukaryotes, PMS could result in mosaic individuals with unusual migration patterns for proteins studied by gel electrophoresis. If the gonade were mosaic, complex progenies containing as many as six phenotypic classes at a single locus could be produced.
Jumping genes meet abdominal bristles: hybrid dysgenesis-induced quantitative variation inDrosophila melanogaster
Authors: Mackay Trudy F. C.
Published: September 2009

When males from a strain ofDrosophila melanogasterwhich have multiple copies of the P family of transposable elements integrated into their genome (Bingham, Kid well & Rubin, 1982) (‘P’ strains) are crossed to females of strains lacking those elements (‘M’ strains), the F1 progeny manifest a number of aberrant traits known collectively as hybrid dysgenesis (Kidwell, Kidwell & Sved, 1977). Progeny of the reciprocal cross (P♀ × ♂M) are normal. The dysgenic syndrome is characterized by a high degree of genomic instability caused by enhanced transposition of P elements. Since mutations at visible loci and chromosomal rearrangements are frequently observed in dysgenic hybrids, it was hypothesized that this phenomenon could be used to investigate the effects of transposition on quantitative characters; therefore, the progeny of dysgenic and non-dysgenic crosses were artificially selected for high and low abdominal bristle number. The response to selection, phenotypic variation, and realized heritability were all increased in the dysgenic lines, relative to the non-dysgenic control. It is postulated that these features are the result of P element-induced mutations of loci affecting bristle number, and that future work should lead to the identification of these loci, as well as elucidating the role of transposition in population differentiation for metric traits
Hybrid dysgenesis inDrosophila melanogaster: the evolution of mixedPandMpopulations maintained at high temperature
Authors: Kiyasu Phillip K. , Kidwell Margaret G.
Published: September 2009

The ability of hybrid dysgenesisPfactors to survive and multiply under conditions of strong negative sterility selection was studied in mixedPandMlaboratory cultures. Eight populations were initiated with varying proportions ofPandMstrains. Mixed populations and controls were maintained for seventeen generations at 27 °C, a temperature sufficiently high to induce maximum frequencies of sterility in dysgenic hybrids. The two components of dysgenesis,Pfactor activity and cytotype, were monitored every generation for the first ten generations and intermittently thereafter. With one exception, all the mixed populations evolved to thePtype indicating thatPfactors can survive and multiply, despite low initial frequency and strong negative selection against dysgenic hybrids. However, the average level ofPfactor activity attained at equilibrium was considerably lower than that of thePstrain control population maintained under the same conditions. It was also lower than the equilibrium level ofPfactor activity attained in a similar experiment carried out at a lower temperature, suggesting that selection favouredPfactors with weak rather than strong sterility potential.
The angora locus (go) in the mouse: hair morphology, duration of growth cycle and site of action
Authors: Pennycuik Pamela R. , Raphael Kathryn A.
Published: September 2009

All four coat hair types were longer in mice homozygous for angora (go / go) than in wild-type mice ( + / +). This increase in hair length in mutant animals was due to an increase in the duration of the phase of hair growth (anagen VI). When skin recombinants incorporating mutant or wild-type epidermis and dermis were grafted to a nude host, the activity of the mutant was found to be confined to the epidermis.
The population genetics of haplo-diploids and X-linked genes
Authors: Avery P. J.
Published: September 2009

From the available electrophoretic data, it is clear that haplodiploid insects have a much lower level of genetic variability than diploid insects, a difference that is only partially explained by the social structure of some haplodiploid species. The data comparingX-linked genes and autosomal genes in the same species is much more sparse and little can be inferred from it. This data is compared with theoretical analyses ofX-linked genes and genes in haplodiploids. (The theoretical population genetics ofX-linked genes and genes in haplodiploids are identical.)X-linked genes under directional selection will be lost or fixed more quickly than autosomal genes as selection acts more directly onX-linked genes and the effective population size is smaller. However, deleterious disease genes, maintained by mutation pressure, will give higher disease incidences atX-linked loci and hence rare mutants are easier to detect atX-linked loci. Considering the forces which can maintain balanced polymorphisms, there are much stronger restrictions on the fitness parameters atX-linked loci than at autosomal loci if genetic variability is to be maintained, and thus fewer polymorphic loci are to be expected on theX-chromosome and in haplodiploids. However, the mutation-random drift hypothesis also leads to the expectation of lower heterozygosity due to the decrease in effective population size. Thus the theoretical results fit in with the data but it is still subject to argument whether selection or mutation-random drift are maintaining most of the genetic variability atX-linked genes and genes in haplodiploids.
A simple method for increasing the response to artificial selection
Authors: Toro Miguel Angel , Nieto Blanca Maria
Published: September 2009

Selection theory usually assumes an equally probable contribution of each selected individual to a large ‘gene pool’ from which the individuals to be measured in the next generation are sampled. With unequal contributions it is possible to find several sets of values for N (the number of selected individuals) and fi (probability of contribution of the ith individual) such that the same selection intensity is attained. It is suggested that the set of values producing minimum genetic drift should be chosen in order to increase the long-term response without any reduction in the short-term advance.
Adaptation to environmental heterogeneity in populations ofDrosophila melanogaster
Authors: Verdonck Margriet V.
Published: September 2009

For 29 generations, populations ofDrosophila melanogasterwere offered one favourable (standard) and one suboptimal (salt-supplemented) medium, either singly or simultaneously. Egg-to-adult viability, fecundity and choice of oviposition medium were measured at regular intervals on both resources up to 17 generations after initiation of the salt treatment. Except for a decrease in viability on salt medium in the single-resource populations (SRPs) maintained on the optimal medium, these fitness components remained unchanged. Estimation of a more inclusive measure of fitness, productivity, obtained at generations 27–29, revealed that: (1) the SRPs maintained on salt medium were more adapted to salt medium; (2) the mixed-resource populations (MRPs) were intermediate in their adaptation to salt medium between either type of single-resource population. These results support Levins' model of optimal strategy for populations living in a coarse-grained environment when the fitness set is convex. Family selection for increased and decreased resistance to salt in the medium, carried out for the viability component at generations nine and 19, showed that: (1) genetic variation with respect to this component was present in all populations; (2) the SRPs maintained on salt medium had responded to the salt treatment by eliminating sensitive genotypes; (3) in the first selection experiment, the MRPs had a greater amount of additive genetic variance with respect to viability than either type of SRP; in the second experiment, this difference was not significant, but it was in the predicted direction. The latter finding provides some evidence in favour of the hypothesis repeatedly presented in the literature that environmental heterogeneity could promote the maintenance of genetic variability in populations.
Interspecific mitochondrial DNA transfer and the colonization of Scandinavia by mice
Authors: Gyllensten Ulf , Wilson Allan C.
Published: September 2009

Restriction enzymes were used to search for genetic variability at 162 cleavage sites in mitochondrial DNA (mtDNA) purified from 22 mice caught at seven Swedish localities. Although all of these mice bear the nuclear genes ofMus musculus, they bear the mtDNA ofM. domesticusexclusively. Yet, some of the Swedish localities are 750 km away from the hybrid zone between these two species. Furthermore, only one type of mtDNA was found at the seven Swedish localities; this type was found before at an eighth locality in Sweden as well as in Jutland north of the hybrid zone. The apparent lack of mtDNA divergence in the mouse population of Sweden contrasts with the extensive divergence usually found within other geographic areas in Europe, Africa and North America. Electrophoretic analysis of proteins encoded by nuclear genes indicates that the Swedish mice have lower average heterozygosity than Danish and Central European populations ofmusculusmice. These findings lead us to suggest that the source of the commensal mouse population in Sweden was a small propagule that originated from a population situated only a few kilometres to the east of the point at which the hybrid zone on the European mainland meets the Baltic Sea, namely on East Holstein. Such a founder event may have been associated with the spread of farming from north Germany into Sweden about 4000 years ago.
A test for the role of natural selection in the stabilization of transposable element copy number in a population ofDrosophila melanogaster
Authors: Montgomery Elizabeth , Charlesworth Brian , Langley Charles H.
Published: September 2009

The numbers of members of three families ofcopia-like elements were counted on twentyX, 2nd and 3rd chromosomes collected from a natural population ofDrosophila melanogaster. Theoretical predictions were computed for two models of copy number stabilization: (1) element frequencies are regulated by a simple genetic process such as copy number dependent transposition or excision, independent of chromosomal location; (2) elements are eliminated by natural selection against mutational effects of their insertion into the chromosome. Since insertions into theXcan be expected to suffer more selection than autosomal insertions, due to expression of mutant phenotypes in the hemizygous state, hypothesis 2, called the disproportional model, predicts that the proportion of elements on theXwill be smaller than the proportion of the genome contributed by theX, while hypothesis 1, called the equiproportional model, predicts that this proportionality will be unaffected. Two of the elements,297androo, showed no evidence for deficiency ofX-linked elements, but the data for a third element,412, were consistent with the prediction based on the selective model.

These results indicate that simple selection against mutational effects of insertions of transposable elements is not generally adequate to account for their distribution within populations. We argue that a mechanism such as recombination between elements at different chromosomal sites, leading to rearrangements with highly deleterious, dominant effects could play a role in stabilizing copy number. This process would lead to a higher abundance of elements in genomic regions with restricted crossing over. We present some data indicating such an effect, and discuss possible interpretations.
Susceptibility to phenytoin-induced cleft lip with or without cleft palate: many genes are involved
Authors: Karolyi I. Jill , Liu Sharon , Erickson Robert P.
Published: September 2009

In a search for genetic differences in susceptibility to cleft lip with or without cleft palate [CL(P)], congenic and recombinant inbred strains of mice were treated with phenytoin or control injections. Of six loci tested, five were found to affect susceptibility to phenytoin-induced and/or sporadic CL(P): (1) the major histocompatibility locus,H-2; (2) the locus controlling β2-microglobulin,B2m; (3) a locus controlling β-glucuronidase,Gus; (4) the locus controllingN-acetyl transferase,Nat; and (5) the locus for brown pigmentation,b. B2mandGusonly affected the sporadic incidence of CL(P), while theblocus only affected phenytoin-induced incidence of CL(P). Three of these loci are also known to affect glucocorticoid-induced isolated cleft palate (CP), but different alleles of the loci are involved. Phenytoin did not affect levels of adenosine 3′,5′-cyclic monophosphate (cAMP) in palates and tongues of day 15 fetuses. A comparison of glucocorticoid receptor parameters with the incidence of phenytoin-induced CL(P) found no correlation.
Five of the nine genetically defined regions of mousethaplotypes are involved in transmission ratio distortion
Authors: Silver Lee M. , Remis David
Published: September 2009

Mousethaplotypes have been divided into nine subregions that are each defined by one or more molecular markers. In previous studies, three of these subregions were shown to contain ‘distorter loci’ that interact to effect the transmission-ratio distortion phenotype characteristic of all completethaplotypes. To determine which of the remaining six subregions also play a role in this phenotype, we analysed the accumulated data on transmission ratio distortion from males that carried one of 26 different combinations of two partialthaplotypes. We have obtained evidence for the association of two additional subregions with distorter loci. First, we present further evidence for the existence of a previously postulated distorter locus,Tcd-3, and describe its mapping to the T66C subregion. Secondly, we describe the identification of a new distorter locus,Tcd-4, in association with the subregion defined by the structural gene for theTCP-1 protein. Further studies indicate that two doses of theTcd-4locus are equivalent in effect to a single dose each ofTcd-4and a second distorter locus,Tcd-1. This result suggests that different distorter locus products could have a common mode of action.
A new regulatory gene in the histidine decarboxylase gene complex determines the responsiveness of the mouse kidney enzyme to testosterone
Authors: Middleton Richard J. , Martin S. A. M. , Bulfield Grahame
Published: September 2009

The level of histidine decarboxylase in mouse kidney normally differs between the sexes with females higher than males. In a strain derived from feral Danish mice (DAN), however, both males and females have the same, high, HDC activity due to the males being insensitive to repression by testosterone. Genetic analysis indicates that this insensitivity is caused by a variant allele of a new gene in the histidine decarboxylase gene complex,Hdc-a; theHdc-aballele in C57BL/10 confers high sensitivity to testosterone whereas theHdc-awallele in the DAN strain confers low sensitivity. In addition, the DAN strain has a novel haplotype for the other three known elements of [Hdc]: the alleleHdc-sdof the structural gene, theHdc-cdallele of the gene determining enzyme concentration, and the oestrogen-inducible alleleHdc-eb.
The general relationship between average effect and average excess
Authors: Templeton Alan R.
Published: September 2009

The average effect and average excess both measure the phenotypic effects of gametes in a population. A matrix notation is introduced that provides a general analytical solution for the average effects at a single locus with k alleles that can be solved for any population regardless of its genotype frequencies. This same notation also provides an easy way of deriving and generalizing to k alleles the well-known relationships between average effects and average excesses that exist under random-mating and regular deviations from Hardy–Weinberg equilibrium due to inbreeding.
Genetic localization of a regulatory site necessary for the production of the glue protein P5 inDrosophila melanogaster
Authors: Hoshizaki Deborah K. , Dlott Bonnie M. , Joslyn Geoffrey L. , Beckendorf Steven K.
Published: September 2009

The glue proteins are products of a developmentally regulated gene family. These genes are transcriptionally active during the third larval instar and code for the major protein products of salivary glands. The activity of several of the genes can be visualized as intermoult puffs in the polytene salivary gland chromosomes. The amount of one of these proteins, P5, varies widely among wild-type strains. We have used biochemical and genetic methods to investigate the source of this variation. The results ofin vitrotranslation of salivary gland RNA suggest that the variation occurs pretranslationally. Genetic mapping experiments showed that sites on several chromosomes can modulate the amount of P5, but that one site on the third chromosome determines the absence and presence of this protein. We have mapped this glue protein gene, calledGP5, to the interval betweenbx(3–58·8) and sr (3–62·0) which also includes the intermoult puff at 90BC. We discuss the relationship between P5 and the glue protein geneSgs-5which is also located at 90BC.
Transposition of the I element andcopiain a natural population ofDrosophila melanogaster
Authors: Leigh Brown Andrew J. , Moss Julie E.
Published: September 2009

In order to increase our understanding of the evolutionary dynamics of transposable genetic elements we have studied the chromosal location of copies of 2 element families in 20 X chromosomes extracted from a natural population ofDrosophila melanogasterfrom Spain. The I element was localized at a total of 64 chromosomal sites andcopiaat 45 sites in this sample with a mean copy number of 3·2 and 2·3 elements/chromosome respectively. Both elements were highly variable in location, with no site reaching a higher frequency than 4/20 in either case. Comparisons with other data sets suggest that insertion frequencies can be used to detect population structuring.
Evolution of genetic variability in a spatially heterogeneous environment: effects of genotype–environment interaction
Authors: Via Sara , Lande Russell
Published: September 2009

Classical population genetic models show that disruptive selection in a spatially variable environment can maintain genetic variation. We present quantitative genetic models for the effects of disruptive selection between environments on the genetic covariance structure of a polygenic trait. Our models suggest that disruptive selection usually does not alter the equilibrium genetic variance, although transient changes are predicted. We view a quantitative character as a set ofcharacter states, each expressed in one environment. The genetic correlation between character states expressed in different environments strongly affects the evolution of the genetic variability. (1) If the genetic correlation between character states is not ± 1, then the mean phenotype expressed in each environment will eventually attain the optimum value for that environment; this is the evolution of phenotypic plasticity (Via & Lande, 1985). At the joint phenotypic optimum, there is no disruptive selection between environments and thus no increase in the equilibrium genetic variability over that maintained by a balance between mutation and stabilizing selection within each environment. (2) If, however, the genetic correlation between character states is ± 1, the mean phenotype will not evolve to the joint phenotypic optimum and a persistent force of disruptive selection between environments will increase the equilibrium genetic variance. (3) Numerical analyses of the dynamic equations indicate that the mean phenotype can usually be perturbed several phenotypic standard deviations from the optimum without producing transient changes of more than a few per cent in the genetic variances or correlations. It may thus be reasonable to assume a roughly constant covariance structure during phenotypic evolution unless genetic correlations among character states are extremely high or populations are frequently perturbed. (4) Transient changes in the genetic correlations between character states resulting from disruptive selection act to constrain the evolution of the mean phenotype rather than to facilitate it.
Genetic analysis of a large autosomal region inCaenorhabditis elegansby the use of a free duplication
Authors: Howell A. M. , Gilmour S. G. , Mancebo R. A. , Rose A. M.
Published: September 2009

In this paper we describe the use of a free duplication,sDp2(I;f), for the recovery, maintenance, and analysis of mutations defining essential genes in the left third of Linkage GroupIofCaenorhabditis elegans. The lethals were induced in a strain of genotype (sDp2) + /dpy-5+unc-13/dpy-5 unc-15+, using either 12 mM ethylmethane sulphonate or 1500 r of gamma radiation. Lethal mutations linked to thedpy-5 unc-13chromosome were recognized by the absence of Dpy-5 Unc-13 individuals amongst the self progeny and were maintained by isolating Unc-13 hermaphrodites. These strains – which have two mutant alleles of the essential gene and a wild-type allele on the duplication – are balanced, since crossing-over does not occur betweensDp2and the normal homologues. Using this sytem we have recovered 58 EMS-induced mutations. These have been characterized with regard to map position and complementation. Twenty-nine of the EMS-induced mutations lie to the left ofdpy-5and define 20 complementation groups; 3 were inseparable fromdpy-5and define 3 complementation groups; 21 were to the right and define 17 complementation groups. Among a set of 29 gamma radiation-induced lethal mutations, 17 appear to be single gene mutations or are very small deletions. We estimate that we have identified from one-sixth to one-half of the essential genes in thesDp2region.
Inheritance of seasonal cycles in Chrysoperla (Insecta: Neuroptera)
Authors: Tauber Catherine A. , Tauber Maurice J.
Published: September 2009

Two separate, but interacting, genetic systems underlie the variation in seasonal cycles among members of the Chrysoperla carnea species-complex. The two systems are expressed as all-or-none reproductive responses to photoperiod and prey (i.e. short-day/long-day requirement for reproduction versus long-day reproduction and prey requirement for reproduction versus reproduction without prey). In each case the alternative to reproduction is reproductive diapause. The photoperiodic responses are determined by alleles at two unlinked autosomal loci. The expression of dominance by the alleles at these loci varies among geographical populations. The genes that determine the photoperiodic responses also act as suppressors of the genes that govern responsiveness to prey. An autosomal, polygenic system, with a threshold for the expression of diapause, determines responsiveness to prey. The two genetic systems are important to seasonal diversification and speciation within the C. carnea species-complex.
Transposable element-induced polygenic mutations inDrosophila melanogaster
Authors: Mackay Trudy F. C.
Published: September 2009

P-element mutagenesis was used to contaminate M-strain second chromosomes with P elements. The effect of P-element transposition on abdominal and sternopleural bristle scores and on female productivity was deduced by comparing the distributions of these quantitative traits among the contaminated second-chromosome lines with a control population of M-strain second-chromosome lines free of P elements. Estimates of P-element-induced mutational variance,Vm, for these characters are very high, and mutational ‘heritabilities’ (Vm/Ve, the ratio of mutational variance to environmental variance) are of the same order as heritabilities of these traits from natural populations. P-element-induced mutational variance of abdominal bristle score is roughly two orders of magnitude greater than spontaneous and X-ray-inducedVm/Vefor this trait.
Dubious maternal inheritance of mitochondrial DNA inD. simulansand evolution ofD. mauritiana
Authors: Satta Yoko , Toyohara Nobue , Ohtaka Chiaki , Tatsuno Yumi , Watanabe Takao K. , Matsuura Etsuko T. , Chigusa Sadao I. , Takahata Naoyuki
Published: September 2009

Within-line heterogeneity has been found in the mitochondrial DNA (mtDNA) in two isofemale lines ofD. simulans. The co-existing types, S and M, were typical of the mtDNA inD. simulansand inD. mauritiana, respectively, their nucleotide divergence per site beingca.2·1%. Segregation analysis confirmed that some individuals in these lines were heteroplasmic and suggested incomplete maternal inheritance of mtDNA inDrosophila. Examination of other lines ofD. simulansrevealed that the M type ofD. mauritianaoccurs at 71% in Réunion, 38% in Madagascar and 0% in Kenya. This finding and interspecific sequence comparisons of both M types indicate thatD. mauritianadiverged fromD. simulansprobably less than 240000 years ago.
Identification of a variant growth hormone haplotype in mice selected for high body weight
Authors: Salmon R. Keith , Berg Roy T. , Yeh Francis C. , Hodgetts Ross B.
Published: September 2009

Restriction site analysis revealed a variant growth hormone gene haplotype fixed within growth-selected mice (High line-3; HL-3) exhibiting growth rates 1·5 times greater than those of unselected Foundation population (FP-3) mice. Relative to the FP-3 haplotype, the HL-3 haplotype exhibited restriction fragment length polymorphisms for each of seven different restriction enzymes. Three of the polymorphic sites lie within 1·1 kb of the 5′ end of the structural gene; a fourth polymorphism exists within the structural gene. The HL-3 haplotype was also fixed within an additional three growth-selected lines (including a replicate of HL-3). This identification of an association, between the natural variant of a growth regulating gene and a growth-related phenotype, is the prototype of experiments that could lead to the isolation of variant genes which enhance livestock production characters.
Recessive mutation in a standard recombinant-inbred line of mice affects seminal vesicle shape
Authors: Shukri N. M. , Grew F. , Shire J. G. M.
Published: September 2009

A recessive autosomal mutation has been found in the CXBI/ByEss recombinant-inbred line but in neither of the parental strains, C57BL/6ByEss and BALB/cByEss. Its presence in the CXBI/ByJax and CXBI/ByLac sublines suggests an origin early in inbreeding. The locus, seminal vesicle shape (svs), appears to be linked to the albino locus on chromosome 7. The homozygote has seminal vesicles with a smooth tubular external appearance. In segregating crosses homozygotes had slightly lighter seminal vesicles but the weights of other androgen target organs were not reduced. Exogenous testosterone increased the size of the seminal vesicles but did not alter their shape. The mutation did not affect the pattern of proteins on SDS–acrylamide gel electrophoresis, which did differ between the parental strains. The locus affecting a 27000 Da protein has provisionally been assigned the symbolsvp-4.
The Ontogeny of γ-crystallin mRNAs in CatFraser Mice
Authors: Kuliszewski Maciej , Rupert Jim , Gold R.
Published: September 2009

Mice which are either homozygous or heterozygous for the CatFraser mutation have ocular cataracts accompanied by selective reduction of the γ-crystallins, a homologous family of proteins present in the lens and encoded by a family of tightly linked genes. We measured the concentrations of four different mRNAs, each encoding a different γ-crystallin, in the lenses of homozygous CatFraser mice and in normal controls at various stages of development by preparing Northern blots from lens RNA, probing with RNAs complementary to each of the four messages and densitometry of the bands thus generated. The results show that, for each of these messages, the ontogenetic patterns observed in normal mice are retained in the mutant, but at much lower concentrations.
Drosophilagenescutandminiatureare associated with the susceptibility to infection bySerratia marcescens
Authors: Flyg Casper , Boman Hans G.
Published: September 2009

A mutant strain ofDrosophila melanogasterwith five markers on theX-chromosome was found to be more sensitive than the wild type when infected with an insect-pathogenic strain ofSerratia marcescens. Two of the five mutations in this fly strain,cutandminiature, were found to be responsible for this sensitivity. A double-mutant, with bothcutandminiature, was as sensitive toSerratiainfection as was the original sensitiveDrosophilastrain with all five mutations. Recombinant flies with other alleles ofcutandminiaturewere also sensitive. A revertant ofcutwas found to be less sensitive than the parental flies. Our insect pathogenic strain ofSerratiaproduces several proteases and a chitinase. A bacterial mutant, lacking proteases and chitinase, was found to be less virulent than wild-type bacteria. When pupal shells from resistant andcut-miniatureflies were incubated with a mixture of protease and chitinase there was a release ofN-acetyl glucosamine, and 50% more material was liberated from pupal shells of sensitive flies. Sensitive flies reared on sucrose infected withSerratiashowed bacteria in their hemolymph earlier than wild-type flies. We conclude thatDrosophilagenes forcutandminiatureare associated with the sensitivity toSerratiainfection, presumably because the gut peritrophic membrane is more susceptible to bacterial proteases and chitinase.
The functions of the phage T4 immunity and spackle genes in genetic exclusion
Authors: Obringer John W.
Published: September 2009

Genetic exclusion is the ability of a primary infecting phage to prevent a secondary infecting phage from contributing its genetic information to the progeny. The molecular mechanism of the phenomenon is not well understood. The two genes in phage T4 mainly responsible for genetic exclusion are the immunity (imm) gene and the spackle (sp) gene. Evidence is presented that the imm gp enables the host exonuclease V to degrade superinfecting phage DNA. This appears to be accomplished by the imm gp altering gp 2/64, the presumed pilot protein, which protects the 5′ end(s) of the phage DNA. Exonuclease III is also involved in genetic exclusion but its action does not appear to depend upon theimmorspgene products. Gp sp appears to interfere with the lysozyme activity of gp 5, a component of the central base plug, postulated to aid in tail tube penetration during the injection process. A molecular model of genetic exclusion is proposed. Genesimmandspare part of a cluster of genes which also includes42, beta-glucosyltransferase, anduvsX. The genes of this cluster encode proteins apparently adapted for competition and defence at the DNA level. These genes may encode fundamental adaptive strategies found throughout nature.
Influence of parental strains on the germination ofPhycomyces blakesleeanuszygospores
Authors: Sarabia María José F. , Eslava Arturo P. , Alvarez María Isabel
Published: September 2009

Phycomyces blakesleeanuswild-type NRRL1555( − ), the standard strain, when crossed with UBC21( + ), another wild type, gives zygospores that germinate in 50–60 days. By backcrossing to UBC21 and selecting for shorter dormancy we have isolated a ( − ) strain, A803, and a ( + ) strain A804, which when crossed give zygospores that germinate in 32 days, the shortest dormancy period found inPhycomyces.The same result was obtained when A803 was crossed with UBC21. Zygospore dormancy decreased as the parental strains became more isogenic with UBC21, but the number of zygospores giving germsporangia with viable germspores also decreased to zero in the third backcross. The existence of germspore-killer alleles in the strain UBC21 is postulated. The strains of shortest dormancy can be used as helper strains (Orejaset al.1985) in sexual crosses. Tetrad analysis of the cross NRRL1554 × S102, a two-factor cross, showed 90% of reciprocal ditypes plus tetratypes in the progeny, indicating that the ( + ) wild-type strain NRRL1554, when crossed with the standard strain, gives regular meiosis and, contrary to current beliefs, may be used inPhycomycesgenetic analysis.
Organ-specific variability and inheritance of maize proteins revealed by two-dimensional electrophoresis
Authors: Leonardi A. , Damerval C. , de Vienne D.
Published: September 2009

Using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), the genetic variation of proteins was investigated in three organs (mesocotyl, sheath and blade of second leaf) from two maize lines and their hybrids. Nine hundred and eighty-six spots were numbered over the three organs. One hundred and fifty-five polypeptides were found to be genetically variable, due to allelic polymorphism of structural genes and/or to polymorphism of any genetic elements controlling protein amounts. Of these 155 variants 12% clearly showed complete dominance effects in the hybrid patterns, which could reveal dominance effects in the regulation of the protein biosynthesis. Comparison of the three organs showed that (i) the level of variability between lines depended upon the organ, since it varied from 7·5% for the blade to 12·6% for the mesocotyl and 13·2% for the sheath; (ii) 68 polypeptides displayed different kinds of variation in different organs and (iii) in all cases but one the dominant inheritance was organ-specific.
Sex reversal in a wild population of Talpa occidentalis (Insectivora, mammalia)
Authors: Jiménez R. , Burgos M. , Caballero L. , De La Guardia R. Díaz
Published: September 2009

Two sex-reversed males and eight intersexes have been found in a natural population of the mole species Talpa occidentalis. All individuals of karyotype 34,XY were normal males, while the 34,XX karyotype was found in normal females, intersexes and sex-reversed males. Small testes were present in XX males, and ovotestes in intersexes. Intersexes showed male antigen levels higher than for females and lower than for males (including XX males), as judged by cytotoxicity tests. The X chromosome of sex-reversed males and intersexes and the Y chromosome of males appeared morphologically normal.
Length of the chromosomal segment marked by galactose-1-phosphate uridyl transferase and soluble aconitase and conserved since divergence of lineages leading to mouse and man
Authors: Nadeau Joseph H.
Published: September 2009

Standard linkage testing crosses and ovarian teratoma mapping were used to estimate the length of the chromosomal segment that is marked by galactose-1-phosphate uridyl transferase and soluble aconitase and that has been conserved since divergence of lineages leading to mouse and man. These experiments were also used to determine whether theRb(4·6)2BnrRobertsonian translocation suppresses recombination on the proximal portion of mouse Chromosome 4. The estimated length of the conserved segment marked by galactose-1-phosphate uridyl transferase and soluble aconitase in mouse and man was estimated to be 24 cM. It was also shown thatRb(4·6)2Bnrstrongly suppressed recombination on the centromeric portion of mouse Chromosome 4.
Evolutionary characterization of a Y chromosomal sequence conserved in the genusMus
Authors: Nishioka Yutaka
Published: September 2009

The extent of accumulation of mouseYchromosomal repetitive sequences generally correlates with the known phylogenetic relationships in the genusMus. However, we describe here aM. musculus Ychromosomal repetitive sequence, designated as ACClfl, whose accumulation patterns among eightMusspecies do not correspond to their phylogenetic relationships. Although male-specific hybridization bands were present in all the species examined, significant accumulation (> 200 copies) in theYchromosomes was found inM. minutoides(subgenusNannomys),M. pahari(subgenusCoelomys) andM. saxicola(subgenusPyromys) as well as in the three closely related speciesM. hortulanus, M. musculusandM. spretusthat belong to the subgenusMus. Unexpectedly, theYchromosomes ofM. caroliandM. cookii(both subgenusMus) had considerably reduced amounts of ACClfl-related sequences. Furthermore, in rats (Rattus norvegicus) the major accumulation sites appear to be autosomal. These observations suggest that caution must be taken in the interpretation of data obtained with repetitive sequences that have evolved quickly.
Codon usage as a reason for unsuccessful search for amber-suppressor mutants inStreptomyces lividans?
Authors: Schmieger Horst , Knerr Ralph , Köberlein Maria
Published: September 2009

An amber mutation was created in the CAT gene of plasmid vector pACYC184 and this modified plasmid was fused with theStreptomycesvector pIJ702 for use as an indicator for the identification ofStreptomycesstrains carrying nonsense suppressor tRNA mutations. The resulting hybrid plasmid pGM1109 was introduced into the chloramphenicol-sensitive mutant M252 ofStreptomyces lividans. Chloramphenicol-resistant colonies were isolated and characterized. None of them was a nonsense suppressor mutant. The failure to obtain such mutants is discussed on the basis of codon usage in streptomycetes.
The genes for two neuromuscular diseases of the mouse, ‘arrested development of righting response’, adr, and ‘myotonia’, mto, are allelic
Authors: Jockusch Harald , Bertram Kordula , Schenk Susanne
Published: September 2009

Two hitherto unmapped recessive autosomal mutations, ‘arrested development of righting response’ (adr) and ‘myotonia’ (mto, now adrmto), were found to be allelic, so that preliminary linkage data on adr and adrmto can now be combined. No linkage was found to the glucose phosphate isomerase (Gpi-1) locus on Chr 7 that marks a region of homology between mouse Chr 7 and human Chr 19, and in man is closely linked to the myotonic dystrophy (DM) gene. The adr gene was expressed on diverse genetic backgrounds including the athymic nude mouse.
The genetics of tasting in mice: V. Glycine and cycloheximide
Authors: Lush Ian E. , Holland Gail
Published: September 2009

Glycine tastes both bitter and sweet to mice but there are differences between strains in their ability to detect each taste. With respect to the bitter taste, fifteen strains were classified as tasters and twelve strains as non-tasters. The difference is due to a single gene, Glb (glycine bitterness). Cycloheximide tastes bitter to all mice at a concentration of 8 μM, but strain differences in sensitivity to the taste of cycloheximide can be detected at lower concentrations. The BXD RI strains can be classified into two groups with respect to sensitivity to cycloheximide. This is probably due to the segregation of two alleles of a single gene, Cyx. A comparison of the distribution in RI strains of alleles of four bitterness-tasting genes shows that the loci are all closely linked and are probably in the order Cyx–Qui–Rua–Glb.
Can segregation distortion influence gametic disequilibrium?
Authors: Hedrick Philip W.
Published: September 2009

There are a number of reports of gametic disequilibrium between alleles causing segregation distortion (e.g.talleles inM. musculusandSDalleles inD. melanogaster) and linked loci. These observations have resulted in the conclusion by some researchers that segregation distortion may cause gametic disequilibrium. In this manuscript I have shown that (1) segregation distortion cannot generate gametic disequilibriumde novoand (2) because segregation distortion results in an excess of heterozygotes, the rate of decay of disequilibrium is faster than if segregation distortion were absent. Other factors, such as mutation or selection, appear to generate the observed disequilibrium, and extremely low recombination appears important in retarding its decay.
Effect of Y chromosome and H-2 complex derived from Japanese wild mouse on sperm morphology
Authors: Suh Dong-Sang , Styrna Jozefa , Moriwaki Kazuo
Published: September 2009

Segregation of sperm abnormality level and H-2 haplotypes was investigated in F2 hybrid males obtained from reciprocal crosses involving two B10.congenic strains carrying H-2 and the Y chromosome of Japanese wild mice: B10.MOL-OHM (H-2ωm4, 23·1% of sperm abnormalities) and B10.MOL-OKB (H-2ωm8, 11·1% of sperm abnormalities). In both types of crosses mean levels of abnormal spermatozoa were significantly higher for males typed as H-2ωm4/H-2ωm4 than for heterozygous H-2ωm4/H-2ωm8 or homozygous H-2ωm8/H-2ωm8. These results suggest that the gene for high sperm abnormality is linked to H-2 complex of the B10.MOL-OHM strain.
The transmission ratio distortion of theth2-haplotypein vivoandin vitro
Authors: Garside William , Hillman Nina
Published: September 2009

Theth2-haplotype is transmitted at low frequencies (< 0·30)by+ /th2males in normal matings. In the studies described here, the transmission frequency of theth2-haplotype fromRb7 /th2males was determined for normal and delayed matings andin vitroinseminations. The data show the transmission frequency from the twoin vivoinseminations to be less than 0·30 and to be statistically equivalent. However, thein vitrotransmission frequency (0·80) is significantly greater than either of thein vivofrequencies. The results show that the environment in which fertilization occurs affects the transmission frequency of this specifict-haplotype significantly.
Variable evolutionary stability ofYchromosomal repeated sequences in the genusMus
Authors: Platt Timothy H. K. , Dewey Michael J.
Published: September 2009

The study reported here is an examination of the organization and evolution of threeYchromosomal repeated sequences, designated pBC10–0.6, pBC15–1.1, and pBA33–1.8, in five closely related species of the genusMus. The species distributions of major restriction fragment length polymorphisms produced with a panel of restriction enzymes is used to develop the phylogenetic relationships between the five species studied. However, the apparent degree of relatedness among these species varied a great deal with each of the three probes and was also highly dependent on the particular restriction enzyme used. The usefulness for phylogenetic studies of closely associated sequences varying in evolutionary stability is discussed.
The genetics of tasting in mice: VI. Saccharin, acesulfame, dulcin and sucrose
Authors: Lush Ian E.
Published: September 2009

Twenty-six strains of mice were tested for their reaction to four different sweet substances; saccharin, acesulfame, dulcin and sucrose. There was considerable strain variation in the degree to which they found the sweet substances preferable to water. The variation in preference for any one sweet substance is very highly correlated with the variation in preference for the other sweet substances. This is interpreted to mean that there is only one sweetness receptor, although an alternative explanation in terms of variation in psychological motivation is not discounted. The difference between C57BL/6Ty and DBA/2Ty is largely due to a single gene,Sac.
Eight independentLdh-1 mutations of the mouse recovered in mutagenicity experiments: biochemical characteristics and chromosomal localization
Authors: Pretsch Walter
Published: September 2009

Eight mouse mutants with altered charge or activity of lactate dehydrogenase-1 have been detected in offspring derived from mutagen-treated spermatogonia. Using two chromosome-7 marker genes pooled recombination frequencies are estimated asc−14·4±0·8−p−6·9±0·6−Ldh-1.
The liver/erythrocyte pyruvate kinase gene complex [Pk-1] in the mouse: structural gene mutations
Authors: Fitton Lesley A. , Bulfield Grahame
Published: September 2009

Nine enzyme activity variants of liver/erythrocyte pyruvate kinase have been found amongst laboratory and wild mice. Four of these variants have been shown by biochemical and immunological criteria to be mutations of the structural gene,Pk-1s. These four structural gene mutations, and two regulatory gene mutations, define the gene complex, [Pk-1]. One allele of the structural gene,Pk-1sl, found in the inbred strain C57BL, has an unusual phenotype and affects the expression of pyruvate kinase in the liver but not erythrocyte. A possible mechanism for this tissue-specific structural gene mutation is suggested.
Inbreeding depression and the maintenance of deleterious genes by mutation: model of aDrosophilachromosome
Authors: Sved John A. , Wilton Alan N.
Published: September 2009

Inbreeding experiments inDrosophila, particularly those carried out using the ‘balancer equilibration’ technique, have revealed high levels of inbreeding depression. It has been estimated that non-lethal chromosomes have a fitness of 20% or less in homozygous condition compared to chromosome heterozygotes. Deleterious recessive genes are, in principle, capable of explaining such inbreeding depression. In this paper we have asked quantitatively whether the observed high levels are consistent with what is known about numbers of loci and mutation rates. We find that accepted mutation rates are easily high enough, provided that the deleterious genes are fully recessive. Partial dominance, even to the extent of 10% or less, reverses this conclusion. These calculations have been made assuming the multiplicative model. However the arguments are potentially sensitive to certain types of selective interactions, and a model which proposes quadratic gene interaction allows for higher levels of partial dominance. We also test the effect of taking into account a further constraint. Crow and Mukai have argued from estimates of the persistence of new deleterious mutations affecting viability that heterozygotes have a reduction in fitness of around 1–2% per locus, similar to the estimate for lethal genes. Application of this additional constraint would markedly reduce the range of permissible selection coefficients. However we argue that the selective disadvantages in heterozygotes of most mutations affecting fitness are unlikely to be as high as estimated for mutations affecting viability.