bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetics of the lac-PTS system ofKlebsiella
Authors: Hall Barry G. , Imai Ko , Romano Charles P.
Published: September 2009

The isolation of a temperature sensitivepts Imutant which fails to utilize lactose provides strong evidence thatKlebsiellastrain CT-1 utilizes lactose via a phosphoenolpyruvate dependent lactose-phosphotransferase system (PTS-lac). We designate this lactose utilization systemeluforevolved lactose utilization. Analysis of a series ofLac−mutants identifies two genes,eluAandeluB, whose function is required for lactose utilization by this pathway. The functions specified by these genes are not known, but neither locus specifies the hydrolytic enzyme phospho-β-galactosidase. A mutant of CT-1, strain RPD-2, exhibits a half-maximal growth rate at a lactose concentration 40 fold lower than that of strain CT-1; and it has aKmfor lactose uptake that is 40 fold lower than that of strain CT-1. That mutation defines the locuseluC, which is assumed to specify the enzyme Il(lac) of the PTS-lactose system. From the observations that (i) cellobiose induces the phospho-β-galactosidase enzyme, (ii) pregrowth in cellobiose dramatically reduces the growth lag when cells are shifted into lactose minimal medium, (iii)eluBmutants exhibit a growth lag when shifted into cellobiose minimal medium, and (iv) lactose induces a phospho-β-glucosidase enzyme; we speculate that the phospho-β-glucosidase enzyme is the same enzyme as the phospho-β-glucosidase that normally functions in cellobiose metabolism. We conclude that the original mutation that allowed CT-1 to utilize lactose was a regulatory mutation that permitted inducible expression of theeluCgene.
X-chromosome activity in female mouse embryos heterozygous forPgk-1and Searle's translocation, T(X; 16) 16H
Authors: McMahon A. , Monk M.
Published: September 2009

To investigate whether the preferential expression of genes on the translocatedXchromosome in female mice carrying theX-autosome translocation T(X; 16)16H (Searle's translocation) is due to non-random inactivation or to cell selection, we examined tissues of mouse embryos heterozygous for the X-linked gene coding for phosphoglycerate kinase (Pgk-1). From the cross T16HPgk-lb/+Pgk-lb♀ × +Pgk-la/Y♂, embryos expressing both isozymic forms of PGK-1 in the epiblast, and only the maternally inheritedPgk-lballele in extra-embryonic tissues, were assumed to be chromosomally balanced, heterozygous female embryos carrying the Searle's translocation (like the mother). The normalXchromosome in this cross carries a high-expressionXceclocus. At 6 days post-coitum (p.c.) both isozymes were equally expressed in the epiblast as expected if bothXchromosomes are active, but by 7 days p.c. the PGK-1B contribution was significantly less than 50%, suggesting thatXinactivation has occurred with a bias towards inactivation of the translocatedXchromosome carrying the lower-expressionXceallele. By 8 days p.c. the situation was the reverse, with aPgk-lbcontribution of significantly more than 50%, and by 12½ days p.c. noPgk-laexpression could be detected. We interpret the dramatic change in isozy me expression between 7 and 8 days p.c. as indicating rapid selection against cells that had inactivated the translocated 16Xchromosome. Two 7-day p.c. embryos unexpectedly showed equal expression of bothPgk-1alleles in both embryonic and extra-embryonic tissues; these were presumably chromosomally unbalanced embryos which had inherited from the mother both an active translocated 16Xchromosome carryingPgk-lband an active normalXchromosome carryingPgk-la.
Post-settlement viability in the American oyster (Crassostrea virginica): an overdominant phenotype
Authors: Zouros E. , Singh Shiva M. , Foltz David W. , Mallet André L.
Published: September 2009

The degree of heterozygosity as determined by electrophoretic analysis of three or four polymorphic loci correlates positively with survival in age groups of the American oyster (Crassostrea virginica) collected as spat from two different natural populations. The phenomenon is shown to operate in ages from 2 weeks (post-settlement) to 3 years and appears to be general in populations of marine molluscs. The most likely explanation for this result is that heterozygosity improves survival through its effect on growth (heterozygotes grow faster). The effects of individual loci on viability are independent of each other. A direct involvement of the enzyme polymorphisms is the most probable genetic interpretation of the data, but associative overdominance cannot be excluded.
Cytological location and lethal interactions of three Minute loci in chromosome 3 ofDrosophila melanogaster
Authors: del Prado Jaime Moscoso , Ripoll Pedro
Published: September 2009

Using seven newly induced duplications, three Minute loci have been located cytologically:M(3)hS 37in 65F10–11; 66A (a new Minute locus),M(3)iin 67C, andM(3)hyin 68F; 69F.M(3)hS 37andM(3)hywere previously thought to be allelic because they do not complement for lethality. The finding of Minute mutations with additive or synergistic rather than epistatic interactions makes us suspect that some other Minute mutations have been erroneously called allelic. The involvement of Minute loci in more than one biochemical pathway is discussed in view of the existence of synergistic interactions and of Minute loci without known mutant alleles.
Genetic variation in β-adrenergic receptors in mice: A magnesium effect determined by a single gene
Authors: Markovac Jasna , Erickson Robert P.
Published: September 2009

Genetic variation in the amount of binding of dihydroalprenolol (a potent antagonist) to hepatocyte β-adrenergic receptors has been observed among inbred strains of mice. This variation is attributed to a differential effect of magnesium on the receptors between the high and low binding strains. Evidence for a single gene controlling the magnesium effect on dihydroalprenolol binding to β-adrenergic receptors was found using recombinant inbred lines between the high and low strains. We suggest the provisional gene symbolBadm.
Quantitative genetic variation in the skeleton of the mouse: I. Variation between inbred strains
Authors: Lovell D. P. , Johnson F. M.
Published: September 2009

A series of six bones from samples of mice from eleven inbred strains and one F1hybrid were measured using a simple apparatus. The bones examined were the mandible, os coxae, femur, tibia–fibula, scapula and humerus. Considerable variation in the shape of each bone was found and successful discrimination between the strains was obtained. Correct strain classification ranged from 87% for the scapula to 98% for the os coxae. Gross abnormalities and quantitative variants were identified.

As the pattern of discrimination is different for each bone, the use of other bones in addition to the mandible may improve resolution in the identification and quality control of mouse stocks. The objective and precise identification of abnormal and variant bones suggests that the method may be useful for population studies and for the detection of induced skeletal abnormalities in toxicological investigations.
The genetic control of hexokinase isozymes in wheat
Authors: Ainsworth C. C.
Published: September 2009

In extracts of mature wheat grains, 13 hexokinase isozymes were distinguished by IEF. The genes controlling the production of five isozymes were located on chromosome arms 1BS, 1DS and 3BS by nullisomic analysis. The three loci, part of two homoeoallelic series (Hk-1andHk-2) are designatedHk-B1,Hk-D1andHk-B2respectively. Analysis of chromosome 1D short-arm terminal deletions indicated theHk-D1locus to be located proximally to the glucose phosphate isomerase locus,Gpi-D1on the shortarm. Three variant HK phenotypes were distinguished amongst 55 hexaploid wheats examined. Analysis of seven Chinese Spring/Agropyron elongatumchromosome addition lines showed thatAg. elongatumisozymes were expressed in the wheat background in additions IV and V.
Clear plaque mutation sites linked to theimmIregion of the Salmonella phage P22
Authors: Prell Hermann H. , Auer Johanna M. , Soška Jiri
Published: September 2009

A complete genetic map has been established for the P22 clear plaque forming mutationscir4-l,cir5-l andcir6-l. These are located within or closely linked to theimmIregion of P22 and represent a new class of clear plaque forming mutants located outside and rather distant from the immC region. They were mapped with respect to the markersmnt, vyand ant of theimmIregion and to genes16and9which span it. The threecirmutations complement each other and – with one possible exception – thecl,c2andc3mutations of theimmCregion. P22cir6-l – like P22cir5-l (Harveyet al.1981) – is suppressed by theant−am19 allele, whereas P22cir4-l is not. The results are discussed in terms of the regulation of earlyantexpression.
Daughterless X Sxr/Y Sxr mice
Authors: McLaren Anne , Burgoyne Paul S.
Published: September 2009

McLaren & Monk (1982) and Cattanach et al. (1982) reported that T(X; 16)16H/X Sxr mice, in which the X chromosome bearing Sxr is the inactivated X chromosome, can develop as fertile females. By mating such females to X/Y Sxr males it has been possible to produce mice homozygous for Sxr. Two X Sxr / Y Sxr males were identified which together fathered 141 sons and 1 daughter. The single daughter proved to be XO, indicating a non-disjunctional event with neither paternal sex chromosome being transmitted. It is concluded that X Sxr / Y Sxr mice are viable and fertile, and that all their progeny, provided they receive a paternal sex chromosome, develop as males.
Activity differences between acid phosphatase allozyme variants ofDrosophila virilis: Differences in intracellular localization of allozymes
Authors: Narise Sumiko
Published: September 2009

Three acid phosphatase allozyme strains (Acph-1, Acph-2 and Acph-4) ofDrosophila virilisshow large differences of enzyme activity when examined by means of starch gel electrophoretic technique, Acph-4 strain showing approximately four times the activity of Acph-1 and twice that of Acph-2, as reported previously (Narise, 1976). Crude extract difference between Acph-4 and Acph-1 strains is less than twofold and this compared with larger differences in supernatants. Cell fractionation and density gradient centrifugation demonstrated that the acid phosphatase resides mainly in lysosomes and becomes soluble in part during preparation without structural damage to lysosomes. The solubility of the allozymes from lysosomes was variable among the three strains. ACPH4allozyme was released in the highest degree. However, the release-rate of other lyso-somalenzymes, such as α-glucosidase, β-galactosidase and β-glucuronidase was similar among these strains. These results suggest that the strain variation in ability of the allozymes to be incorporated into lysosomes is due to the allozymes themselves, not due to alteration in the lysosomes.
The genetics of hormone-induced cyclic AMP production and PhospholipidN-methylation in inbred strains of mice
Authors: Markovac Jasna , Erickson Robert P.
Published: September 2009

Genetic variation in hormone-sensitive cyclic AMP production was investigated among inbred strains of mice. Significant strain differences were observed in β-adrenergic- and glucagon-stimulated adenylate cyclase activity. Comparable differences were also found in membrane methyl-transferase I activity in these strains. Our results of studies using F1progeny of high and low strains suggest a dominance of high MT I activity over low MT I activity. Investigation of recombinant inbred lines between the high and low strains indicates that MT I activity is regulated by at least two major genes;H-2-congenic lines of several inbred strains were then used to identify an association between hormone-stimulated MT I activity and the mouse major histocompatibility complex.
Genome organization of thePseudomonas aeruginosanarrow host range plasmid R91–5 determined by deletion and cloning analysis
Authors: Moore R. J. , Krishnapillai V.
Published: September 2009

By physical and genetic analysis of deletion mutants of the narrow host range IncP-10P. aeruginosaconjugative plasmid R91–5 it has been shown that the phenotypes related to its transfer, namely the inhibition of the replication of the phage G101, entry exclusion and the fertility inhibition of the wide host range plasmid R18 map at kilobase coordinates 19·7–20·7, 18·5–19·7, 28·8–30·15 and/or 34·9–36·15, respectively. These locations have been confirmed by cloning restriction enzyme generated DNA fragments of R91–5 into a small broad host range, multicopy non-conjugative plasmid.
Observed relationships between protein heterozygosity and protein genetic distance and comparisons with neutral expectations
Authors: Ward R. D. , Skibinski D. O. F.
Published: September 2009

Relationships between protein genetic distance (D) and protein heterozygosity (H) were studied using allele frequency data for 42 proteins derived from multilocus electrophoretic surveys of genetic variation in over 200 invertebrate and over 300 vertebrate species.D¯andH¯values for the different proteins (mostly enzymes) were calculated, and large and significant correlations betweenD¯andH¯were found in comparisons of both intraspecific and interspecific populations. Empirical relationships betweenD¯andH¯were compared with neutral expectations under the stepwise model of neutral mutation with the assumption that populations are in equilibrium with respect to the effects of mutation and genetic drift.

At low divergence levels, a linear relationship ofD¯onH¯was observed, but at high levels of divergenceDtended towards an asymptote at highH¯. The results at high divergence cannot be explained using the approximate relationshipD=2ut(whereu= mutation rate,t= time). However, computer simulations of neutral models showed that changes of this nature in the relationship betweenD¯andH¯were to be expected as divergence increases, the equationD=2utbeing a poor approximation at highDWe therefore conclude that the observed relationships betweenD¯andH¯are, in fact, compatible with equilibrium neutral theory.
A gamma ray-induced non-excitable membrane mutant inParamecium caudatum: a behavioral and genetic analysis
Authors: Takahashi Mihoko , Haga Nobuyuki , Hennessey Todd , Hinrichsen Robert D. , Hara Ritsuo
Published: September 2009

A new CNR (caudatumnon-reversal) mutant ofParamecium caudatumwas isolated after gamma ray mutagenesis. This CNR lacks not only the transient inward Ca2+current but also the sustained Ca2+current. It was shown to complement the three known CNR mutants ofP. caudatum(cnrA, cnrBandcnrC) by crossbreeding analyses. Thus, this new mutant belongs to a 4th CNR locus, designatedcnrD. The defect ofcnrDcan be partially rescued by microinjection of cytoplasm from any of the three CNR mutants or the three Pawns (pwA, pwBandpwC) inP. tetraurelia. Since the three CNR genes have been shown to be different from the three Pawn genes by cytoplasmic complementation test (Hagaet al.1983), this result suggests thatcnrDis the 7th non-excitable mutant inParamecium. Thus, there are at least seven genes controlling Ca2+channel function inParamecium.
Male mating success and fertility inDrosophila melanogaster
Authors: Partridge Linda , Mackay Trudy F. C. , Aitken Susan
Published: September 2009

The male mating ability and male fertility of 40 third chromosome homozygote lines has been measured. There was significant between-line differentiation for both characters, and comparison with a heterozygous stock indicated inbreeding depression and hence dominance variation for them. The characters showed significant positive correlation both with each other and with other fitness components and total fitness, as measured by Mackay (1985). This pattern of large positive correlations between fitness components is not expected to occur in outbred populations.
Chromosome differences between substrains of the inbred 101 mouse strain
Authors: Evans E. P. , Burtenshaw M. D. , Adler Ilse-Dore
Published: September 2009

A centromeric heterochromatin (Hc) comparison of two substrains of the mouse inbred strain 101 with another two, revealed differences in at least two and possibly in up to six chromosome pairs. The differences could have arisen by the inclusion of chromosomes from the inbred strain C3H/He.
Structural genes for phosphatases inAspergillus nidulans
Authors: Caddick Mark X. , Arst Herbert N.
Published: September 2009

Although the fungusAspergillus nidulanshas a multiplicity of phosphatases and of genes where mutations affect one or more phosphatases, we have succeeded in identifying structural genes for three phosphatases as well as one other gene which might encode a fourth. Using both conditional and non-conditional mutations,palD has been shown to be the structural gene for a phosphate-repressible alkaline phosphatase,palG to be the structural gene for a non-repressible alkaline phosphatase which apparently exists in two electrophoretically distinct forms (but whose rates of thermal inactivation are apparently very similar) andpacA to be the structural gene for both intracellular and secreted forms of a phosphate-repressible acid phosphatase. Colony staining techniques for the enzymes specified bypalD andpacA have been described previously but we have now shown that the enzyme specified bypalG can be detected by staining toluene-permeabilized colonies. Mutations inpacG lead to loss of non-repressible acid phosphatase as judged by colony staining and electrophoretic patterns but their effects on assays of activity in cell-free extracts are only marginal. Under phosphate-limited, but not phosphate-starved or phosphate-sufficient, conditions,pacG−mutations also affect the regulation of other, phosphate-repressible phosphatases. None of these phosphatases, alone or in combination, plays an essential role.
Two-dimensional Gel Analysis of Proteins from Mouse Fetuses with Trisomy 19 after DEAE-Sepharose Chromatography
Authors: Reichert Gerd H.
Published: September 2009

Isoelectrofocusing two-dimensional polyacrylamide gel electrophoresis (IEF-2D-PAGE) offers the opportunity to detect typical alterations in the protein pattern of trisomic mouse foetuses at a given time of development. The fractionation of the cell lysate by differential centrifugation into various subcellular components (nuclei, membranes, polyribosomes, cytoplasmic proteins) and fractionation of the proteins through DEAE-Sepharose chromatography allows detection of protein differences.

It is possible to detect eight differences in the protein patterns between trisomy 19 (Ts 19) mouse foetuses and euploid mouse fetuses at day 15. Five of these differences are quantitative in nature, three are qualitative. One of these proteins is synthesized in Ts 19 foetuses at a higher level than in euploid mouse fetuses (primary gene dosage effect). The other seven proteins are reduced or not present in trisomic foetuses (consequences of primary gene dosage effects).

The molecular mass of the individual proteins ranges from 13 to 41 kDa.
Mating competition in artificial populations ofDrosophila melanogasterpolymorphic forebony: II. A test for minority male mating advantage
Authors: Søndergaard Leif
Published: September 2009

Mating competition experiments withD. melanogasterwere performed in light and darkness under conditions mimicking those under which artificial populations show a stable polymorphism for theebonygene (e). In both light and darkness a minority male mating advantage was found fore/ + males in competition with wild-type males, but in light only when ebony was in the majority. Homozygous wild-type males showed minority advantage only in light and ebony males only in darkness.
Heritable variation and heterozygosity under a balance between mutations and stabilizing selection
Authors: Slatkin Montgomery
Published: September 2009

A model of the balance between mutations and stabilizing selection affecting a quantitative character is developed and analysed. This model is essentially a discretized version of the continuum-of-alleles models analysed previously by Kimura, Lande, Turelli and others, and is formally similar to the stepwise mutation models used to interpret electrophoretic data. The complete model cannot be solved even for a haploid species, but there are useful approximations for most parameter values of interest. The ‘house-of-cards’ approximation can be used when selection is strong relative to mutation, and a normal approximation can be used when selection is relatively weak. For intermediate levels of selection a new ‘five-allele’ approximation provides accurate results over a wide range of parameter values. The house-of-cards and five-allele approximations applied to recessive alleles in a diploid population show that, for a given mutation rate, a somewhat larger genetic variance is maintained at equilibrium than in a comparable model of additive alleles. Under directional selection, the increase in genetic variance is largest for alleles of large effect and is much smaller for alleles of intermediate or small effect. At an equilibrium under stabilizing selection, homozygotes would tend to have a higher average fitness than heterozygotes when each mutation has a relatively large effect (the house-of-cards approximation), with the reverse if each mutation has a small effect (the normal approximation).
Correlation of compound autosome segregation and sex-chromosome disjunction in femaleLucilia cuprina(Wied.) (Diptera: Calliphoridae)
Authors: Foster G. G. , Maddern R. H.
Published: September 2009

InLucilia cuprina(Wiedemann) females, non-segregation of compound fifth-chromosomes is correlated with non-disjunction of theXchromosomes. Approximately two-thirds of eggs which inherit both maternal compound elements are nullo-X, suggesting that meiotic pairing betweenXchromosomes and compound autosomes has occurred. There was no evidence for pairing of the compounds and theXorYchromosome in males. A limited amount of data suggests that high non-segregation frequencies may occur in the offspring of putativeX/X/XandX/Ofemales. These results suggest the existence of non-homologous (distributive) pairing inL. cuprinafemales.
Autosomal assignment of OTC in marsupials and monotremes: implications for the evolution of sex chromosomes
Authors: Sinclair Andrew H. , Wrigley Jacyln M. , Graves Jennifer A. Marshall
Published: September 2009

The OTC gene coding for ornithine transcarbamylase is sex linked and subject toXinactivation in humans and mice. We have used a rat cDNA probe to localize OTC byin situhybridization in marsupials and monotremes. The gene maps to an autosomal site in two distantly related marsupial species and in one monotreme (the platypus); the first demonstration that a geneX-linked in one mammalian species may be autosomal in another. Since the conservation of the mammalianXis thought to be a consequence of its isolation by the inactivation mechanism, we propose that an autosomal or pseudoautosomal segment containing OTC has been recruited into the inactivated region of theXrather recently in eutherian evolution while it remained autosomal, or was translocated to an autosome, in metatherian and prototherian mammals.
An allele at the triose phosphate isomerase,Tpi-1locus on chromosome 6 recovered from feral mice
Authors: Bulfield Grahame , Ball Simon T. , Peters Josephine
Published: September 2009

An animal with low erythrocyte triose phosphate isomerase (TPI) activity was found amongst mice trapped on a farm in Leicestershire. The low TPI activity was caused by the segregation of a single co-dominant gene which also affected theKmfor glyceraldehyde-3-phosphate and heat stability of the enzyme. We designate the geneTpi-1, the structural locus for TPI, with theaallele in the common inbred strains and theballele derived from the wild-caught mouse.Tpi-1was known to be on chromosome 6 by somatic cell techniques and, as shown in a preliminary report (Peters & Bulfield, 1984), we have confirmed and extended this finding using three chromosome-6 marker genes giving the order:Sig-28-Lc-11-Miwh-16-Tpi-1.
Estimating the recombination parameter of a finite population model without selection
Authors: Hudson Richard R.
Published: September 2009

An estimator is proposed for the parameter C = 4Nc. where N is the population size andcis the recombination rate. The estimator is appropriate for use with sequence or restriction site data from random samples from within populations. Properties of the estimator are investigated for an infinite-sites neutral model using Monte Carlo simulations. The median and mode of the distribution of the estimator are close to the true value for all parameter values examined, but large data sets are required to obtain reliable estimates.
The murine cataractogenic mutation, Cat Fraser, segregates independently of the gamma crystallin genes
Authors: Rupert Jim L. , Kuliszewki Maciek , Tsui Lap-Chee , Breitman Martin L. , Gold Reynold J. M.
Published: September 2009

The murine mutation, Cat Fraser (CatFr), causes dominantly inherited ocular cataracts. Lenses of adult mice bearing this mutation contain reduced amounts of all seven γ-crystallin proteins and their corresponding transcripts. Levels of other lens proteins and transcripts appear normal and no extra-ocular effects of the mutation have been observed. The selective effect of this mutation on the γ-crystallins is consistent with the possibility that the site at which it occurs is involved in the coordinated regulation of the family of genes which encodes them. We have shown that several restriction fragment length polymorphisms in the γ-crystallin genes segregate independently of the CatFr mutation. Therefore, despite its selective effect on the expression of the γ-crystallin genes, the mutation is not linked to them. This observation rules out the possibility that the mutation is in a cis-acting regulatory site.
Three ENU-induced alleles of the murine quaking locus are recessive embryonic lethal mutations
Authors: Justice Monica J. , Bode Vernon C.
Published: September 2009

The quaking (qk) locus on mouse chromosome 17 has been defined by a single viable quaking allele. Three new alleles of quaking were selected after ENU mutagenesis by their failure to complement the quaking phenotype. Theqkk2allele was induced on wild-type chromatin and theqkkt1andqkkt4alleles were induced ont-chromatin. Each is a recessive embryonic lethal mutation. They fail to complement each other and are not complemented by the deletion,TtOrl. Homozygotes and hemizygotes die at 8–9·5 days gestation, but not at a single precise time. Because the classical quaking mutation complements the lethality of these new alleles, but they fail to complement its quaking phenotype (myelination defect), we conclude that the quaking+function is required for embryonic survival as well as for myelination.
Identification of two genes controlling kasugamycin resistance in the filamentous fungusPodospora anserina
Authors: Kieu-Ngoc An , Coppin-Raynal Evelyne
Published: September 2009

We have investigated the effect of the ribosome-targeted antibiotic kasugamycin (ksg) inPodospora anserina. While ksg inhibits both growth and sporulation, it has a stronger inhibitory effect on the sporulation process. It was previously reported that sporulation ofPodosporacould be impaired when ribosomes translate with a too high accuracy, and since ksg was demonstrated to increase the ribosomal accuracy inE. coli, we wondered whether it would act similarly inPodospora. As a first approach we have isolated two mutations at different loci,Ks1andKs2, that increase the resistance to ksg at the level of both growth and sporulation. InterestinglyKs1−1also confers a decreased resistance to paromomycin, which is a mistranslation inducer. Characterization ofKs1−1andKs2−1mutants suggests that they could be ribosomal mutants.
Geographical variation in house-fly (Musca domesticaL.) sex determinants within the British Isles
Authors: Denholm I. , Franco M. G. , Rubini P. G. , Vecchi M.
Published: September 2009

Genetic and cytological analyses of house-flies collected from 12 pig-breeding farms throughout the British Isles demonstrated that the non-standard sex determination mechanism prevailing in South-East England, involving a dominant female determinant (F) and virtual homozygosity for a male determinant on theXchromosome (Xm, both males and females morphologicallyXX), was not typical of the country as a whole. Instead there was a gradual decrease in the frequency of F,Xmand a rarer male determinantMIII, and a concomitant increase in the standard male determiningYchromosome, on moving north, east and west of this region. Only the Scottish and probably the Irish populations were fully standard (XXfemalesXYmales), although one from the East Anglian coast in which non-standard determinants were rare was predominantly of this type. Populations from intermediate areas possessed complex multifactorial mechanisms in whichY, FXmandMIII coexisted. It is hypothesized that this radial cline in sex determinants, like the latitudinal cline known from mainland Europe, represents a transient polymorphism caused by the recent and continuing invasion of non-standard determinants into originally standard populations. The cause(s) of this apparently rapid evolutionary change, however, remain unclear.
Genetic analysis of theY-chromosome of the mouse: evidence for two loci affecting androgen metabolism
Authors: Jutley Jaswant K. , Stewart Alistair D.
Published: September 2009

Male mice from congenic lines carryY-chromosomes derived from two pairs of inbred strains (CBA/FaCamSt and C57BL/FaSt; PHL/St and PHL-YH/St) on various genetic backgrounds were compared. Serum testosterone levels, and the response of target organs in castrated animals to graded doses of exogenous testerone propionate were measured. These comparisons produced evidence for twoY-chromosomal loci influencing androgen metabolism. One of these affects serum testosterone levels, with variant alleles on theY-chromosomes derived from the PHL and PHL-YH strains. The other locus influences the response to testosterone of target organs, most significantly seminal vesicle, and variant alleles are found in the CBA and C57 strains. The effects of both loci are modulated by the genetic background. The relationship of these loci to otherY-chromosomal loci in the mouse is briefly discussed.
A quantitative genetic analysis of fitness and its components inDrosophila melanogaster
Authors: Mackay Trudy F. C.
Published: September 2009

Forty-one third chromosomes extracted from a natural population ofDrosophila melanogasterwere assessed for net fitness and for the quantitative characters viability, net fertility, female productivity, male weight, abdominal bristle number, and sternopleural bristle number. Net homozygous and heterozygous fitness of the third chromosomes was estimated by competition against a marked balancer third chromosome. Average fitness of the homozygous lines relative to wild-type heterozygotes was 0·13, indicating substantial inbreeding depression for net fitness. All significant correlations of quantitative characters with fitness and with each other were high and positive. Homozygous fitness is strongly correlated with net fertility, viability, and female productivity, moderately associated with male weight, and not significantly associated with bristle traits. The combination of metric traits which best predicts homozygous fitness is the simple multiple of viability and female productivity. Heterozygous fitness is not correlated with homozygous fitness; furthermore, the relative contribution of metric traits to fitness in a heterozygous population is likely to be different from that deduced from homozygous lines. These observations are consistent with a model of genetic variation for fitness in natural populations caused by segregation of rare deleterious recessive alleles.
Effect of multiple copies ofrpoBCon the rate of RNA synthesis inEscherichia coli
Authors: Guzman Elena C. , Jimenez-Sanchez Alfonso
Published: September 2009

The cloning of therpoBandrpoCgenes in a high copy number vector inE. coliincreased the amount of the encoded gene products, the β and β′ subunits of RNA polymerase. However, this unexpectedly caused a 30–50% decrease in RNA synthetic activity which alternatively induced a reduction of growth rate and enlargement of cell size, and decreased the DNA replication time. The results can be explained by autogenous regulation of the RNA polymerase genes by the ββ′ subunits. A relation between the decrease in number of transcription units and the observed higher rate of movement of DNA replication forks is discussed.
Genetic divergence between transposable elements
Authors: Charlesworth Brian
Published: September 2009

The probabilities of genetic identity between different members of the same family of transposable elements in a randomly mating host population are determined, under the assumption of statistical equilibrium between neutral mutations, random genetic drift, transposition and unbiased gene conversion. The method allows for variation in numbers of copies of the element between individuals within the host population, and for dependence of the probability of identity between a pair of elements on the frequencies of elements at the sites from which they were drawn. It is shown that, for the range of parameters under which the approximations used are valid, the effects of gene conversion on identity probabilities are relatively small, as are the effects of copy number variation and variation between sites in element frequencies.
Transcription of rDNA insertions in bobbed mutants ofDrosophila melanogaster
Authors: Terracol Régine
Published: September 2009

InDrosophila melanogastera large number of the genes coding for 18S and 28S rRNA are interrupted in the 28S region by insertions of two types. Ribosomal insertion transcripts were compared in wild-type and bobbed strains. We found that the level of insertion transcripts increased in bobbed mutants after deletion of 50% of INS−genes, and inversely decreased in revertants when more than 50% of wild-type levels. Among type II insertion transcripts we found a predominant 3·5 kb RNA, precisely of the most frequent insertion size. No primary insertion transcript has been found, although it could be undetected if very fast splicing leads to mature 28S occurs.
Absence of Y-chromosome introgression across the hybrid zone between Mus musculus domesticus and Mus musculus musculus
Authors: Vanlerberghe F. , Dod B. , Boursot P. , Bellis M. , Bonhomme F.
Published: September 2009

A cloned Y-specific sequence (Bishop et al. 1985) was used as a diagnostic probe to distinguish between Mus musculus domesticus and Mus musculus musculusY-chromosomes. Analysis of the RFLPs obtained with genomic DNA isolated from wild mice caught along the contact zone between M. m. domesticus and M. m. musculus in Bulgaria and Denmark showed that the Y-chromosome flow between the two semi-species is very limited. The degree of Y-chromosome penetration was compared with that of seven diagnostic autosomal loci and the mitochondrial DNA. Breeding experiments showed that the lack of Y-chromosome introgression from one semispecies to the other was not due to a major hybrid breakdown. The results suggest that the disruption of differentiated co-adapted gene systems could play a role in limiting Y-introgression.
Map position of dysgenetic lens (dyl) locus on chromosome 4 in the mouse
Authors: Sanyal S. , van Nie R. , de Moes J. , Hawkins R. K.
Published: September 2009

The autosomal recessive gene, dysgenetic lens (dyl) in the mouse has been mapped on chromosome 4. Two- and three-point crosses involving b (brown) and Mup-1 (Major urinary protein-1) indicate the following gene order: dyl–b–Mup-1. The approximate distance between dyl and b is 12 and between dyl and Mup-1 is 20 cM.
The range of amino acids whose limitation activates general amino-acid control inNeurospora crassa
Authors: Barthelmess Ilse B. , Kolanus Johanna
Published: September 2009

Several amino-acid synthetic enzymes, belonging to arginie, glutamine, leucine, lysine and phenylalanine biosynthesis, respectively, were investigated under conditions of reduced availability of any one of 16 out of the 20 amino acids represented in proteins. The enzymes showed simultaneous derepression under each condition, albeit to different degrees. Derepression was abolished and the remaining basal enzyme levels reduced by mutations at thecpc-1locus which governs general amino-acid control inNeurospora. Glutamine synthetase was shown to be undercpc-1and additional controls. The evidence emphasizes the global nature of general amino-acid control.
Search for differences amongthaplotypes in distorter and responder genes
Authors: Lyon Mary F.
Published: September 2009

Transmission ratio distortion due to the mousetcomplex is thought to be due to harmful effects oftrans-acting distorter genes acting on a responder, with thetcomplex form of the responder being relatively resistant to this harmful action of the distorters. Previous work had indicated that naturally occurringthaplotypes differed in their responders or in distorters lying near the responder, with the result that animals doubly heterozygous for two responder-carrying haplotypes transmitted these haplotypes unequally. In the present workthaplotypes could be divided into three types on the basis of their transmission when doubly heterozygous with the responder-carrying partial haplotypetlowH. The majority,t0,t6,tw1,tw2andtw73, were transmitted equally withtlowH, a second group, includingtw5and two haplotypes derived from it, were transmitted less frequently thantlowH, and the single member of a third group,t32, was transmitted in excess oftlowHThis last result suggests that the underlying differences are in the responder itself, rather than in the distorters. Search for differences amongthaplotypes in distorters produced some equivocal results possibly resulting from effects of genetic background. In particular, results of others suggesting presence of a fourth distorter,Tcd-4, were not confirmed.
The induction of tail malformations in trisomy 16 mouse fetuses heterozygous for thecurly tailrecessive gene
Authors: Crolla John Anthony , Lakeman Sarah Katrine , Seller Mary J.
Published: September 2009

The mouse mutantcurly tailis thought to be inherited as an autosomal recessive (ct/ct) with incomplete penetrance so that approximately 60% ofct/ctindividuals exhibit thecurly tail(CT) phenotype. By outcrossingct/ctwith mouse stock carrying specific heterozygous combinations of Robertsonian (Rb) chromosomes, trisomy 16 (Ts16) and Ts19 mouse fetuses (and their chromosomally balanced littermates) were derived which were heterozygous for thectgene. All of the Ts16 (ct/Rb;Rb) fetuses, studied between days 14–19 gestation had tail malformations, 86% of which were tail flexion defects (TFD) apparently very similar to thecurly tailphenotype. Neither Ts19 nor any of the chromosomally balanced (ct/Rb) littermates from both experimental crosses showed any type of tail or other spinal malformation. At the 27–29 somite stage of development, Ts16 (ct/Rb;Rb) fetuses did not show any significant delay in the closure of the posterior neuropore (PNP) compared with their littermate controls, suggesting that the tail malformation observed in Ts16 (ct/Rb;Rb) occur as a result of mechanisms which differ significantly from those thought to be responsible to causing thecurly tailmalformation.
Non-random chromosomal distribution ofAc-like sequences in inbred maize
Authors: Johns Mitrick A. , Fuerstenberg Susan I. , Hennelly Cheryl A.
Published: September 2009

We have searched for evidence of historical transpositions ofAc-like sequences in four standard maize lines using the recombinant-inbred mapping technique. Thirty restriction fragments were mapped usingEcoR I,EcoR V, andHindIII. The four inbreds contained 24 fragments which mapped to independent sites within each line; the other 6 fragments probably represented multiple mappings of the same element. Possible allelism between lines reduced this number to a minimum of 15 different sites containingAc-like elements. The distribution of these sequences does not fit the expected Poisson distribution; instead, an unusually large number of these elements were found on chromosome 4. The other sequences were scattered randomly throughout the genome. With few exceptions, each line had sequences in different locations; however, the overall distribution ofAc-like sequences was similar for all lines. The non-random distribution ofAc-like sequences suggests that they have undergone a limited number of transpositions in maize; the distribution is incompatible with either complete immobility or frequent transposition.
Genetic analysis of polymorphic proteins of the human malaria parasitePlasmodium falciparum
Authors: Fenton Brian , Walliker David
Published: September 2009

Five polymorphic proteins, detected by two-dimensional electrophoresis, were analysed in the parents and progeny of a cross between two clones of the malaria parasitePlasmodium falciparum. The information obtained showed that different forms of each protein were determined by allelic variants of each respective gene. One protein was identified as the parasite enzyme adenosine deaminase. Recombinant parasites were produced at a higher than expected frequency.
Spontaneous induction of an homologous Robertsonian translocation, Rb(11.11) in a murine embryonic stem cell line
Authors: Crolla John Anthony , Brown David , Whittingham David G.
Published: September 2009

Karyotype analysis of a series of established mouse embryonic stem cell (MESC) lines showed that the majority were aneuploid by the 7th and 9th passage and that all lines contained a single Robertsonian (Rb) translocation chromosome with a symmetrical, homologous, arm composition Rb(11.11). Although the chromosomal imbalance makes these MESC lines unsuitable for genetic manipulation in vitro and hence for subsequent production of transgenic animals, the spontaneous occurrence and stable retention of the homologous Rb(11.11) as the only metacentric chromosome in an otherwise all acrocentric karyotype, provides potentially useful cell lines for gene assignment and recombinant DNA studies.
Mariner, Mosand associated aberrant traits inDrosophila mauritiana
Authors: Jacobson James W.
Published: September 2009

A suite of aberrant genetic traits, including increased mutation rate, sex-limited mutation and distorted transmission ratios, was produced among progeny of genetic crosses between two strains ofDrosophila mauritianawhen a paternally contributedMosexcision factor is placed into a non-Mosgenetic background. In the reciprocal cross, involving maternally contributedMosandMosassociated cytoplasm, the same genetic abnormalities are not observed. Differential effects onmarinerexcision in germ-line versus somatic tissue are apparent. BecauseMosis known to influence the mobility of themarinertransposable element, these traits may be associated withmarinerexcision and/or transposition.
‘Exceptional sons’ fromDrosophila melanogastermothers carrying a balancerXchromosome
Authors: Hutter Pierre
Published: September 2009

This study reports on exceptional males which are obtained by usingDrosophila melanogastermothers carrying the balancersIn(l)FM6 orIn(l)FM7 as one of theirXchromosomes. The phenomenon was first observed in interspecific crosses betweenD. melanogasterfemales and males of its closest relatives which normally produce unisexual female hybrid progeny. Whereas hybrid sons from these crosses die as third instar larvae, the presence of the particularXbalancers in the mother allows a low percentage of sons to survive. Similar sterile males are also observed among non- hybrid flies. Data are presented which suggest that the males thus generated could be hyperploid for part of theirXchromosome as a result of a meiotic event in their mothers or else they could start life as female zygotes and change sex through a mitotic event at an early stage.
Segregation ratios withinSegregation Distorterlines ofDrosophila melanogasterconform to a beta-binomial distribution
Authors: Sharp Cecil B. , Hilliker Arthur J.
Published: September 2009

Segregation Distorter(SD) chromosomes are preferentially recovered fromSD/SD+males due to the dysfunction of sperm bearing theSD+chromosome. The proportion of offspring bearing theSDchromosome is given the symbolk. The nature of the frequency distribution ofkwas examined by comparing observedkdistributions produced by six differentSDchromosomes, each with a different mean, withkdistributions predicted by two different statistical models. The first model was one where thekof all males with a givenSDchromosome were considered to be equal prior to the determination of those gametes which produce viable zygotes. In this model the only source of variation ofkwould be binomial sampling. The results rigorously demonstrated for the first time that the observedkdistributions did not fit the prediction that the only source of variation was binomial sampling. The next model tested was that the prior distribution of segregation ratios conformed to a beta distribution, such that the distribution ofkwould be a beta-binomial distribution. The predicted distributions of this model did not differ significantly from the observed distributions ofkin five of the six cases examined. The sixth case probably failed to fit a beta-binomial distribution due to a major segregating modifier. The demonstration that the prior distribution of segregation ratios ofSDlines can generally be approximated with a beta distribution is crucial for the biometrical analysis of segregation distortion.
Reduction of wild-typeXchromosomes with theYbb−chromosome ofDrosophila melanogaster
Authors: Palumbo Gioacchino , Endow Sharyn A. , Hawley R. Scott
Published: September 2009

TheYbb−chromosome has been previously shown to induce reduction ofXchromosome ribosomal genes inXbb/Ybb−orXbb+/Ybb−flies. These reduction events are presumed to arise as one of the two products of unequal sister chromatid exchanges, which result in both magnified and reduced products. Bobbed reduced chromosomes may also arise as products of other recombinative events such as intrachromatid deletions. In this report we use theYbb−chromosome to reduce the number of ribosomal genes present onXchromosomes from two wild-type stocks under ‘non-magnifying’ conditions. We then show that the bobbed reducedXchromosomes show no detectable difference in their Southern blot rDNA patterns when compared with the parental wild-typeXchromosome. This indicates that reduction events do not preferentially delete certain repeat classes, and supports previous observations that the repeat types present in theD. melanogaster Xchromosome nucleolus organizer are not significantly clustered.
Position and orientation in the metaphase equator of an interchange quadrivalent of Allium triquetrum
Authors: Rickards Geoffrey K.
Published: September 2009

The position and orientation of an interchange quadrivalent in flattened, lateral views of metaphase I were studied in pollen-mother-cells of an interchange heterozygote of Allium triquetrum. The quadrivalent is most often located in marginal rather than central positions in the equator. Moreover, when positioned marginally the quadrivalent is more often than expected found in adjacent orientation, whilst when positioned centrally it is more often than expected found in alternate orientation. Consequently, the frequency of alternate (genetically balanced) orientation in the quadrivalent varies sharply according to whether data are obtained from more marginal or more central positions in the metaphase plate.
Evidence for a nonsense mutation at theniaDlocus ofAspergillus nidulans
Authors: Martinelli S. D. , Roberts T. J. , Sealy-Lewis H. M. , Scazzocchio C.
Published: September 2009

Two mutations at theniaDlocus (structural gene for nitrate reductase apo-protein) are genotypically suppressible. Both mutations result in loss of nitrate reductase enzyme activity and cross reacting material and are non complementing, nonleaky and highly revertible. They have the properties of nonsense mutations. This implies that some of the allele specific suppressors, which act on these and alleles at several other loci, are nonsense suppressors.