bluuebunny/crossref_metadata_2025 huggingface dataset:
Rec-mediated recombinational activity of two adjacent Chi elements in bacteriophage lambda
Authors: Yagil Ezra , Shtromas Inna
Published: September 2009

Chi is a sequence of eight nucleotide pairs which stimulaterecBC-mediated recombination (Smith, 1983a, b). The effect of two linked Chis onrecBC-mediated recombination was tested in bacteriophage lambda. It was noticed that the Chi element located on the right side of the phage chromosome is epistatic on the other Chi. These findings support a model proposed by Stahlet al.(1983) which suggests that the recombination machinery moves unidirectionaly in the phage chromosome from right to left. The results also suggest that in the presence of more than one Chi only the rightmost one stimulates recombination.
Evidence on the nature and complexity of the mechanism of chiasma maintenance in maize
Authors: Maguire Marjorie P.
Published: September 2009

Inferences on the mechanism of chiasma maintenance can be drawn from study of the distribution and frequency of chiasma-like associations between bridges and fragments and between normal chromatids and fragments in meiotic material heterozygous for paracentric inversions. These bridges and fragments are the result of crossing over within the inverted region so that differing predictions for the associations are generated by the various models for chiasma maintenance mechanism. Results of such a study in material heterozygous for a large paracentric inversion in the long arm of chromosome 1 in maize are reported here. Findings are generally consistent with predictions of the ‘generalized sister chromatid cohesiveness model’, but are markedly at odds with the ‘binder only at specific crossover sites model’, and with the ‘late effective doubling of telomeres model’. Some of the results do not conform quantitatively to predictions of the ‘generalized sister chromatid cohesiveness model’ for a linear relationship between potential extent of sister chromatid cohesiveness and frequency of maintained association, suggesting additional complexity.
Parental influences on X chromosome expression
Authors: Forrester Lesley M. , Ansell J. D.
Published: September 2009

Using mice that were mosaics for both Xce and phosphoglycerate kinase (Pgk-1) alleles, we have established that the parental source of the Xce gene may affect the probability with which the X chromosome carrying it will remain active. This effect was seen in one allelic combination of Xce but not in another. The relationship between these effects and other phenomena of maternal ‘imprinting’ is discussed.
Polymorphism of lactate dehydrogenase B subunit in rat erythrocytes
Authors: Stolc V.
Published: September 2009

Lactate dehydrogenase regulator geneLdr-1controls the amount of the lactate dehydrogenase A subunit in rat serum and the amount of lactate dehydrogenase B subunit in rat erythrocytes because no recombinant rats were found among 295 pups produced in the BDIV × (ACI × BDIV)F1 and (ACI × DI) Fl × DI backcrosses. Two alleles regulate the high (Ldr-1a) and low (Ldr-1b) activity enzyme. TheLdr-1is not linked to hooded coat pattern or glyoxalase-1. Sex andLdr-1assorted independently; hence the gene is autosomal.
A new spontaneous mutation at the tufted locus within a mousethaplotype
Authors: Silver Lee M. , Cisek Lois , Jackson Catherine , Lukralle Deborah
Published: September 2009

We report here the occurrence of a new spontaneous mutation at the tufted locus present within the crossover-suppressed region of the completethaplotypefwLub1This new tufted allele shows complete expressivity of the tufted phenotype without any apparent effect on viability or reproduction. The presence of a tufted mutation within athaplotype that is cytologically marked by a Robertsonian translocation is particularly useful in genetic experiments aimed at understanding the structure and function ofthaplotypes.
Transcriptional organization of the Tra2 region controlling conjugational transfer of the narrow host rangePseudomonas aeruginosaplasmid R91–5
Authors: Moore R. J. , Krishnapillai V.
Published: September 2009

The transcriptional organization of the Tra2 region controlling conjugation by the narrow host range plasmid R91–5 ofPseudomonas aeruginosahas been determined. This region of 15·2 kilobase pairs of DNA encodes ten cistrons and specifies the synthesis and functionality of sex pili. The order of the cistrons was previously shown to betraW, (S, Z),U, (V, R),Q, T, Y, X(those within parentheses could not be ordered with respect to each other). The organization was determined by complementation tests for the restoration of plasmid transfer between transposon Tn7or Tn501induced insertion mutants and point mutants representative of the ten cistrons. Polarity mutations induced by Tn7permitted the identification of three operons. CistronstraW, Z, S, U, V, RandQformed a large operon with transcription postulated to be in that order. The second consisted oftra Tandtra Yalso in that order and the third consisted of only one cistron,traX. Polarity was not observed with Tn501insertions as they still permitted full expression of cistrons distal to the site of insertion with respect to the proposed promoter. Despite the unexpected behaviour of this transposon it nevertheless led to the identification of two previously unidentified cistrons,traOandtraPbeing betweentraZandSandtraRandV, respectively.
The genetic control of triosephosphate isomerase of hexaploid wheat and other Triticeae species
Authors: Pietro Michael E. , Hart Gary E.
Published: September 2009

The zymogram phenotypes of triosephosphate isomerase (TPI) were determined for a large number of aneuploid derivatives of Triticum aestivum cv. ‘Chinese Spring’ and for six wheat-alien species chromosome addition series. Examination of the available compensating nullisomic-tetrasomic and homoeologous groups 3 and 5 ditelosomic lines of Chinese Spring disclosed that T. aestivum possesses two systems of dimeric TPI isozymes, designated TPI-1 and TPI-2. The genes TPI-A1, TPI-B1 and TPI-D1 were located in Chinese Spring chromosome arms 3Ap, 3Bp and 3Dp, respectively and the genes TPI-A2, TPI-B2 and TPI-D2 in chromosome arms 5Aq, 5Bq and 5Dq, respectively. TPI-1 genes were also located in Hordeum vulgare cv. Betzes chromosome 3H, T. longissimum chromosome G, Elytrigia elongata chromosome 3E, and Secale cereale cvs. Imperial and Dakold chromosome 3R. TPI-2 genes were found in Betzes chromosome 5H, T. umbellulatum chromosome 5U, T. longissimum chromosome F, and Imperial and Dakold chromosome 5R. These gene locations provide evidence of homoeology between the alien chromosomes in which the genes are located and the chromosomes of homoeologous groups 3 and 5 of Chinese Spring, respectively. Evidence was obtained for the presence of a TPI-R2 gene in each of the T. aestivum cv. Kharkov -S. cereale cv. Dakold chromosome addition lines studied suggesting that this gene is present in the wheat genome in each member of this addition series.
Introgression of extranuclear genomes in finite populations: nucleo-cytoplasmic incompatibility
Authors: Takahata Naoyuki
Published: September 2009

A ‘two locus two allele’ model is developed with special reference to the introgression of extranuclear genomes between two species of finite size. The model assumes that one locus, coded by a nuclear genome, causes the reproductive barrier while the other locus, coded by an extranuclear genome, causes nucleo-cytoplasmic incompatibility in particular genotypes. To fully study this model, simulations are conducted, and a diffusion equation is derived when introgression or extranuclear gene flow occurs in one direction. It is shown that although selection against the nuclear genome can reduce the levels of extranuclear gene flow and retard the introgression process, the dynamics are very similar to those without such selection. In contrast, the nucleo-cytoplasmic incompatibility directly affects the dynamics of introgressing extranuclear genomes: in large populations the ability of incompatibility to overcome extranuclear gene flow is conspicuous, but in small populations it is overshadowed by random sampling drift. Paternal leakage of extranuclear genomes, if present, is of evolutionary importance only when the male's migration rate is much larger than the female's. When the sizes of two populations are unequal, the introgression is most likely to occur from the larger population to the smaller one in the absence of mating preferences of backcross progeny. Recent observations on interspecific mitochondrial transfer in various species do not support the ubiquitousness of nucleo-cytoplasmic incompatibility as an efficient reproductive barrier.
Glucose-6-phosphate dehydrogenase expression in heterozygous kangaroo embryos and extra-embryonic membranes
Authors: Johnston P. G. , Robinson E. S.
Published: September 2009

The electrophoretic expression of the X-linked enzyme glucose-6-phosphate dehydrogenase was examined in heterozygous Macropus robustus embryos and their extra-embryonic membranes. The amnion and allantois, like the somatic tissues of the embryo proper, showed paternal X inactivation while the avascular and vascular yolk sac cells showed evidence of activity of both maternal and paternal alleles.
Recombination between thet6complex and linked loci in the house mouse
Authors: Nadeau Joseph H. , Phillips Sandra J. , Egorov Igor K.
Published: September 2009

Recombination between thet6complex, three allozyme-encoding loci, two antigen-encoding loci, and four molecular markers was studied. The allozyme-encoding loci were complement component-3 (C-3), kidney catalase (Ce-2), and glyoxalase-1 (Glo-1); the antigen-encoding loci were theH-2Class I genesH-2KandH-2D; the four molecular markers wereTu66, an α-globin pseudogene (Hba-4ps), an unidentifiedH-2Class I gene, and theH-2ClassIIgene I-Aβ. The latter six loci were used as markers for thetcomplex. Recombination was detected betweenGlo-1,Ce-2andC-3, but not between the markers for thetcomplexTu66,Hba-4ps, and theH-2loci. These data indicate thatCe-2andC-3are located outside thet6complex, while the latter are located within. These data also indicate that the telomeric boundary of thet6complex is located betweenH-2andCe-2. Recently published studies have shown that complete gametic disequilibrium exists between thetcomplex and loci located centromeric to theH-2-Ce-2interval, while disequilibrium was not detected between loci located telomeric to this interval. Loci included within the region of recombination suppression are also those in disequilibrium with thetcomplex. As a result, recombination suppression probably resulting from chromosomal rearrangements associated with thetcomplex appears to be a sufficient explanation for the gametic disequilibrium observed between certain loci and thetcomplex.
Covariance between direct and maternal genetic effects in mice, with a model of persistent environmental influences
Authors: Riska Bruce , Rutledge J. J. , Atchley William R.
Published: September 2009

Covariance between direct and maternal genetic effects on body weight in random-bred ICR mice at 2 through 10 weeks of age was estimated from cross-fostering experiments. The covariance contributes only a few percent of phenotypic variance at 2 weeks, but increases to 10–15% at later ages. Nearly all estimates are positive. We suggest that genes active during later parts of growth affect maternal performance more than those active during early growth, causing increased covariance at later ages. A model of combined genetic and persistent environmental effects on maternal performance is presented. Persistent effects of genetic or environmental variation in recent ancestors can influence covariance between relatives and response to selection.
Polymorphism from environmental heterogeneity: models are only robust if the heterozygote is close in fitness to the favoured homozygote in each environment
Authors: Hoekstra Rolf F. , Bijlsma R. , Dolman A. J.
Published: September 2009

The lack of robustness of models of the maintenance of polymorphism in a heterogeneous environment which has been pointed out by Maynard Smith & Hoekstra (1980), applies also to models based on habitat selection, on temporal variation and on density-regulated selection. Only if (partial) dominance ‘switches’ between environments such that the fitness of the heterozygote is always close to the favoured homozygote, is there reasonable robustness. This is true for all models considered. It is argued that there are good reasons for supposing that the favourable allele at a locus may show dominance, although the experimental evidence is still scanty.
Glu-B2, a storage protein locus controlling the D group of LMW glutenin subunits in bread wheat (Triticum aestivum)
Authors: Jackson Elizabeth A. , Holt Linda M. , Payne Peter I.
Published: September 2009

Genes controlling the synthesis of the D group of low-molecular-weight (LMW) subunits of glutenin occur on the short arms of chromosomes 1B and 1 D. Their position on chromosome 1 B, relative to the storage protein lociGlu-B1(long arm) andGli-B1(short arm), was estimated by analysing the backcross-one progeny of two different crosses. To estimate recombination between the D subunit genes andGli-B1, half grains were analysed by two-dimensional electrophoresis. TheGli-B1locus contains genes for the B group of LMW glutenin subunits, γ-gliadins and ω-gliadins although only the latter were made use of in this study to distinguish the parental alleles. Additionally, the complementary half grains were analysed by sodium dodecyl sulphate, polyacrylamide-gel electrophoresis to estimate recombination betweenGli-B1andGlu B1, coding for high-molecular-weight (HMW) glutenin subunits. The D subunit genes occur at a new locus, provisionally defined asGlu-B2, which lies in betweenGlu-B1andGli-B1, 17 cM from the former and 22 cM from the latter. On the basis of previous mapping data involvingGli-B1, it was concluded that the D subunit genes occur close to the nucleolar organizing region and probably on the short-arm satellite, likeGli-B1.
Extension of the Haldane-Muller principle of mutation load with application for estimating a possible range of relative evolution rate
Authors: Ishii Kazushige , Matsuda Hirotsugu
Published: September 2009

The Haldane-Muller principle of mutation load is generalized so as to be applicable to both cases of strong and very weak selection with any time variation. It is proved that in an infinite asexual haploid population, theaverageMalthusian parameterm¯of a population, the evolution rate ν, and the total mutation rate μ satisfy the relation ∂m¯/∂/∂μ = ν/μ−1, so long as each Malthusian parameter is independent of μ. A similar result is also true in a diploid population under genie selection. It is discussed how the above relation gives a restriction on the possible range of values of relative evolution rate ν/μ.
Gene diversity in finite populations
Authors: Takahata Naoyuki
Published: September 2009

DNA sequence comparison among homologous genes sampled at random from one or two populations allows one to estimate the ultimate amount of genetic variation maintained in a population and to construct the gene genealogy within and between populations. Moreover, if we use the finding of the molecular clock (Zuckerkandl & Pauling, 1965), it is also possible to estimate the divergence time of populations examined. Such an estimated divergence time is, however, intricately affected by samples and stochastic forces occurring in the course of evolution.
Segregation and pairing of compound fifth-chromosomes inLucilia cuprinamales
Authors: Foster G. G. , Maddern R. H.
Published: September 2009

Variability in fertility in compound chromosome (CC) strains ofLucilia cuprina(Wiedemann) is directly correlated with the segregation properties of the CCs in those strains. In compound fifth-chromosomes, high fertility (up to 50% ) is associated with high frequencies of segregation of the left element (C(5L)) from the right element (C(5R)) in males, while low fertility (up to 25%) is associated with random assortment of the CCs in males. Regular segregation ofC(5L) andC(5R) chromosomes in males is associated with particularC(5L) elements, which contain cytologically visible duplications of5Rchromatin. These duplications may contain a site which is normally involved in the pairing of the fifth chromosomes in males.

In females the CCs segregate from one another with a frequency of 89%. None of theC(5R) elements studied affected segregation in males, and neitherC(5L) norC(5R) elements had any demonstrable effect on segregation in females. Transmission of certain CC elements through one or both sexes is significantly lower than expected. This could have a variety of causes, such as meiotic drive, inviability associated with position effects, or homozygosis of deleterious mutations on homologous CC arms during meiotic crossing over in females. The CC strains released during a field trial of genetic control contained both high-fertility and low-fertilityC(5L) chromosomes. Both types of CC were subsequently recovered from individuals which had overwintered in the field. Over a period of several generations following this recolonization one particular high-fertilityC(5L) chromosome increased in frequency to near-fixation, despite the presence in this chromosome of deleterious mutations.
Genetic studies of three sibling species ofDrosophilawith relationship to theories of speciation
Authors: Coyne Jerry A.
Published: September 2009

Drosophila melanogaster,D. simulansandD. mauritianaare closely related species, the first two cosmopolitan and the last restricted to the oceanic island of Mauritius.D. simulansandD. mauritianaare the most closely related pair, with the latter species probably resulting from a founder event. The relatedness of the three species and their ability to hybridize allow tests of recent theories of speciation. Genetic analysis of two characters differing betweenD. simulansandD. mauritiana(sex comb tooth number and testis colour) show that the differences are due to at least five and three loci respectively. Behavioural tests further demonstrate that sex combs are probably used by males at a crucial step in mating, and that the differences between the two species may be related to differences in their mating ability. These genetic studies and previous work indicate that differences among these species are polygenic and not (as proposed by recent theories) attributable to only one or two loci of large effect. Further studies of interspecific hybrids show that genetic divergence leading to developmental anomalies is more advanced in the older species pairD. simulans/D. melanogaeterthan in the younger pairD. simulans/D. mauritiana. This supports the neo-Darwinian contention that reproductive isolation is one step in a continuous process of genetic change among isolated populations, and does not support current theories that such change occurs only during the evolution of reproductive isolation. Finally, investigations of the degree of gonadal atrophy and its sensitivity to temperature inD. simulans/D. mauritianahybrids fail to support recent speculations that phenomena similar to hybrid dysgenesis (which causes such atrophy inD. melanogaster) play a role in speciation.
Origin and diversity of mutants controlled by theUqtransposable element system in maize
Authors: Pereira Andy , Peterson Peter A.
Published: September 2009

Three transposable element mutations, displaying an unstable pheno-type at theAlocus, were isolated from lines exhibiting Aberrant Ratio behaviour that originated from maize plants treated with plant RNA viruses. Each of these three unstable mutants is shown to belong to theUq-ruqtransposable element system. The two new mutants, along with the previously describeda-ruqmutant, are nonautonomous in mutability control in that the control of mutability is governed by the segregatingUqregulatory element. By following the distribution of differentUqelements segregating in independently derived genetic lines and utilizing tests of allelism and linkage, certain lineages ofUq-element-containing lines are revealed.
Clonal relationships among naturally occurring nicotinamide-requiringSalmonella typhimurium
Authors: Barker Ruth M. , Yousuf A. A.
Published: September 2009

Salmonella typhimuriumstrains of biotype 25x have been shown in transductional cross experiments to be clonal in the Nad character. The ancestral bacterium, probably of biotype 25a, mutated to a requirement for nicotinamide and subsequently diversified in phage type and secondary biotype characters. Such a sequence of events indicates interconversion among phage types 6, 16, 46, 49, 73, 76 and 135. Strains in biotypes 1x, 9ix, 17x, 17dx, 19dx and 25hix yielded Nad+recombinants in interbiotype crosses, suggesting that each originated as an independent mutant line.
Genetic differences between substrains of the inbred mouse strain 101 and designation of a new strain 102
Authors: West John D. , Lyon Mary F. , Peters Josephine , Selby Paul B.
Published: September 2009

Genetic polymorphisms revealed two distinct substrains of the inbred strain 101. One group included substrains 101*/Rl, 101/H and 101/HOxe; the other group comprised 101/El and 101/Sl. The two groups differed at 5 of the 8 genetic loci tested. The accompanying paper (Evans, Burtenshaw & Adler, 1985) shows that the two groups also differ for several chromosome polymorphisms. We suggest that genetic contamination occurred during the derivation of 101/El from 101/Rl and was already present in 101/El when 101/Sl was produced from this substrain. We further propose that these substrains be renamed 102/El and 102/Sl respectively.
Genetic analysis of the right (3′) end of the rosy locus inDrosophila melanogaster
Authors: Clark S. H. , Hilliker A. J. , Chovnick A.
Published: September 2009

Prior reports from this laboratory have described the experimental basis for our understanding of the rosy locus (ry: 3–52·0) ofDrosophila melanogasteras a bipartite genetic entity consisting of a structural element that codes for the xanthine dehydrogenase (XDH) peptide and a contiguouscis-acting control element immediately to the left of the structural element. Although the left end (5′) of the structural element has been well defined, the right boundary (3′) has been given only casual treatment in our prior reports. In our recent studies of rosy locus expression we have been concerned with the production and identification of mutations in the non-structural regions immediately flanking the structural element. An improved definition of the right end of the structural element is essential to this analysis. In addition to producing a better definition of the right boundary of the structural element, this study produced several phenotypically novel mutations. These mutations were classified initially ascontrol element mutations, but upon analysis were found to map within the rosy structural element.Noevidence was obtained for the existence of a control element contiguous with the right end of the structural element.
Induction of recessive lethal mutations in theT/t–H-2region of the mouse genome by a point mutagen
Authors: Shedlovsky Alexandra , Guenet Jean-Louis , Johnson Lawrence L. , Dove William F.
Published: September 2009

TheT/t–H-2region on mouse chromosome 17 is known from complex natural variants (‘t-haplotypes’) to contain numerous genes, including some affecting the immune system and the development of the embryo. Rapid progress in the isolation of recombinant DNA clones for this 50 megabasepair region is generating the material for its complete molecular anatomy. A crucial step in revealing the biological functions controlled by the region is to obtain mutants in which genes are inactivated individually. We have used a pair of inbred mouse strains and a series of classical breeding schemes that permit the detection of recessive lethal and detrimental mutations in theT/t–H-2region.

In this initial phase of our study, 280 gametes mutagenized in the male germ line by ethylnitrosourea (ENU) have yielded eleven independent pre-natal recessive lethal mutations. Four have been mapped againstTmutations and have been shown to complement one another in all pairwise combinations.
Persistence of an alcohol dehydrogenase thermostable variant in a natural population ofDrosophila melanogaster
Authors: Hernández M. , Padrón G. , Cabrera V. M.
Published: September 2009

A temporal survey of the alcohol dehydrogenase locus in a natural population ofDrosophila melanogasterfrom the Canary Islands has revealed the existence of an electrophoretic Fast thermostable variant, mapped within 0.8 units of the structuralAdhlocus, and which persists over a 6-year period with a frequency ranging from 0.8 to 0.5%.
Recombination and the evolution of satellite DNA
Authors: Stephan Wolfgang
Published: September 2009

In eukaryotic chromosomes, large blocks of satellite DNA are associated with regions of reduced meiotic recombination. No function of highly repeated, tandemly arranged DNA sequences has been identified so far at the cellular level, though the structural properties of satellite DNA are relatively well known. In studying the joint action of meiotic recombination, genetic drift and natural selection on the copy number of a family of highly repeated DNA (HRDNA), this paper looks at the structure–function debate for satellite DNA from the standpoint of molecular population genetics. It is shown that (i) HRDNA accumulates most probably in regions of near zero crossing over (heterochromatin), and that (ii), due to random genetic drift the effect of unequal crossover on copy numbers is stronger, the smaller the population size. As a consequence, highly repeated sequences are likely to persist longest (over evolutionary times) in small populations. The results are based on a fairly general class of models of unequal crossing over and natural selection which have been treated both analytically and by computer simulation.
Induction of new mutations in a mouset-haplotype using ethylnitrosourea mutagenesis
Authors: Justice Monica J. , Bode Vernon C.
Published: September 2009

N-ethyl-N-nitrosourea (ENU) was used to induce mutations within thetw5-haplotype of the mouse to make possible a further study of gene arrangement int-mutants and to provide potential landmarks for cloning and sequence studies in the region. Two independent mutants were isolated for each of three loci in thet-region, brachyury (T), quaking (qk), and tufted (tf). The newTktalleles produce tailless mice when atctmutation is present intrans. The newqkktalleles are recessive and homozygous lethal. They are viable, male fertile, and cause seizures and quaking when paired with theqkmutation which previously defined the locus. Thetfktmutations are recessive and phenotypically similar to the mutant alleles available in non-tchromosomes. The mutations were induced in thetw5-haplotype at an average per locus frequency of 1 in 1500. Their isolation demonstrates the power of this technique for obtaining the specific mouse mutants that are needed to genetically dissect a complex mammalian system.
Selection for growth on normal and reduced protein diets in mice: I. Direct and correlated responses for growth
Authors: Nielsen B. Vivi Hunnicke , Andersen Søren
Published: September 2009

Mice were selected for growth from 3 to 9 weeks of age on a normal protein diet (N) containing 19·3% protein and a reduced protein diet (R) containing 5·1% protein. On each diet there were 3 high (H), 3 low (L) and 3 unselected control (C) lines. After 6 generations of selection, half of the mice in each line were tested on each diet. Responses were obtained when selecting for both increased and decreased growth on both diets. The realized heritabilities from within-family selection were 33 and 26% for the divergences on the normal and reduced protein diets, respectively. Consistent genotype-environment interactions were found when all lines were tested on both diets in generation 7. Performance on each protein level was best improved by selection on that protein level. Further, the correlated response was significantly less than the direct response when selecting on both diets. The estimates of the genetic correlation between growth on the two protein levels were low,rN= 0·16 from selection on the normal protein diet andrR= 0·51 from selection on the reduced protein diet. Selection resulted in a change in environmental sensitivity in the lines, dependent on the diet and direction of selection. The average of the divergences on the two diets was not dependent on the selection environment.
Heterogeneity of human haptoglobin α chains detected by two-dimensional gel electrophoresis
Authors: John Huw A. , Purdom Ian F.
Published: September 2009

The protein spots representing the haptoglobin α1F, α1Sand α2chains in two-dimensional gels of human plasma samples representative of the six common haptoglobin phenotypes were identified by comparing their position with those of purified haptoglobin and distinguished from other spots in the vicinity by comparison with plasma with undetectably low levels of haptoglobin. Silver staining indicated that the α1Fchain was represented by one spot in subtypes 1F-1F, 1F-1S and 1F-2, the α1Schain by three spots in subtypes 1S-1S, 1F-1S and 1S-2 and the α2chain by six spots in 1F-2, 1S-2 and 2–2
Non-random inactivation of theX-chromosome in interspecific hybrid voles
Authors: Zakian S. M. , Kulbakina N. A. , Meyer M. N. , Semenova L. A. , Bochkarev M. N. , Radjabli S. I. , Serov O. L.
Published: September 2009

Expression ofX-linked genes for G6PD and GALA in interspecific hybrids betweenMicrotus arvalis, M. subarvalisandM. kirgisorumvoles was studied. Quantitative predominance of the enzyme activities ofM. arvalisover G6PD activity ofM. subarvalisand the GALA activity ofM. kirgisorumin the female hybrids was shown. The definitive patterns of these enzyme activities was found on day 6·5 of embryonic development. Non-random inactivation ofX-chromosomes derived fromM. subarvalisandM. kirgisorumin the interspecific hybrids withM. arvalisis supposed to be the cause of the phenomenon observed. A hypothesis is proposed that there is a connection between the presence of large heterochromatin regions in theX-chromosomes derived fromM. subarvalisorM. kirgisorumand the preferential inactivation of these in female hybrids withM. arvalis.
Additive variance and average effect with partial selfing
Authors: Wright A. J.
Published: September 2009

The covariance of an ancestor and the average of its descendants in generationt(CPt)is formulated for a breeding system which is a mixture of selfing and outcrossing. This covariance is partitioned into least squares additive (σA. At) and non-additive (σD. Dt) components summed over individual loci, and the combined inbreeding effects of all loci (H′), such thatCPt= σA. At+ (s/2)t[σD. Do+H′]. For themth locus the covariancemσA. At= 2(1 +F)Σipiα(0)iα(t)i, in whichpiis the frequency of theith allele whose additive effect (α(t)) depends on the generation for which it is defined. For distant descendants α(∞)is equal to half of the derivative of the population mean with respect to the frequency of the allele. The covarianceCP∞= σA. A∞thus relates directly to permanent selection response measured in the equilibrium population, any additional responses observed in earlier generations being due to temporary disturbances in population genotypic structure. It is only for these distant descendants that the least squares additive component has any direct interpretation in terms of selection response. The definitions of α(0)and α(∞), lead to two distinct definitions of the average effect of an allele substitution for a model with two alleles (Fisher, 1941), and to a clarification of their significance for this breeding system.
Y-chromosomal DNA polymorphism in mouse inbred strains
Authors: Nishioka Yutaka
Published: September 2009

Mice are the most widely used experimental mammals, and many inbred strains are available. However, except for the relatively recent strains derived from known wild populations, the relationships between wild and laboratory mice are not well understood. Based on the Y-chromosomal restriction fragmentlength polymorphism, seventeen inbred strains were classified into two groups: strains with theMus musculus musculustype Y chromosome and those with theM. m. domesticustype Y chromosome. We extended the survey to an additional twenty-two inbred strains. TheM. m. musculustype Y chromosome was found in AEJ/GnLe, AAU/SsJ, BDP/J, BXSB/MpJ, DA/HuSn, HTG/GoSfSn, I/LnJ, LP/J, NZW/LacJ, RIIIS/J, SB/Le, SEA/GnJ, SF/CamEi, SK/CamEi, SM/J, WB/ReJ, WC/ReJ and YBR/Ei, while theM. m. domesticustype Y chromosome was present in BUB/BnJ, MA/MyJ, PL/J and ST/bJ.
Temporal stability of P–M cytotype polymorphism in a natural population ofDrosophila melanogaster
Authors: Izaabel Hassan , Ronsseray Stephane , Anxolabéhère Dominique
Published: September 2009

The P–M system of hybrid dysgenesis inDrosophila melanogasteris a syndrome of genetic abnormalities which appears in the progeny of crosses between strains different with regard to their possession of ‘P’ transposable elements. Cytotype is an extrachromosomal property which regulates the mobility of the P element. We report here data showing that a cytotype polymorphism previously observed in a natural population from North-Africa is stable over a period of 5 years. A potentially high rate of mutation is associated with this cytotype polymorphism. Explanations of the appearance of a cytotype polymorphism are proposed and the consequences for the genetic load induced by transposable elements are discussed.
Hybrid dysgenesis in natural populations ofDrosophila melanogasterin Japan. II. Strains which cannot induceP-Mdysgenesis may completely suppress functionalPelement activity
Authors: Hagiwara Nobuko , Nakamura Etsuko , Matsuura Etsuko T. , Chigusa Sadao I.
Published: September 2009

Many inbred and isofemale lines derived from wild populations ofDrosophila melanogasterwere tested for gonadal dysgenic sterility, male recombination andsnwsecondary mutation. Among them, we have found strains whose dysgenic offspring show negligible sterility, and undetectable male recombination andsnwmutation. They can be considered to be neutral strains in the strict sense. Such neutral strains appear to carry only defectivePelements in their genomes. Taking the observations of Karess & Rubin (1984) into account, it is suggested that some defectivePelements retain the function necessary forPcytotype. Cytotype determination mechanisms are discussed.
Nucleotide sequence analysis of class II genes borne by mousetchromosomes
Authors: Golubić M. , Budimir O. , Schoepfer R. , Kasahara M. , Mayer W. E. , Figueroa F. , Klein J.
Published: September 2009

Five class IIH-2genes borne bytchromosomes were partially sequenced:borne by thetTuw10chromosome of EDY589 (H-2w2);andborne by thetTuw8chromosome of CR0437 (H-2w57), as well asandborne by thetTuw7chromosome of CR0435 (H-2w37). These genes are representatives of the three major groups of alleles found associated withtchromosomes. The sequenced part consisted of almost the entire exon 2 and the entire exon 3 coding for the first and the second domain of the β polypeptide chains, respectively. The sequence was compared with the published sequences ofAβandEβalleles borne, by non-tchromosomes. The comparison revealed that thet-associated alleles are no more similar to one another than they are to the corresponding genes present on non-tchromosomes in laboratory mice. This divergence in the nucleotide sequence among the class II genes is interpreted as evidence that thetcomplex is very old.
Genetic effects on susceptibility to histidine induced teratogenesis in the mouse
Authors: Burns Julie E. , Kacser Henrik
Published: September 2009

In the mouse histidinaemia has a teratogenic effect. Animals subjected to high levels of histidine in utero may develop inner ear and behavioural abnormalities typical of the ‘shaker–waltzer’ syndrome. Selection procedures for abnormalities and relaxation of selection have resulted in two histidinaemic strains: the Cambridge strain in which abnormalities occur in over 80% of animals, and the Edinburgh strain in which the penetrance of abnormal behaviour has declined to about 1%. Breeding experiments suggest that the differences are largely due to differences in the genetic backgrounds which modify foetal susceptibilities to the teratogenic effects of high histidine levels. High susceptibility appears to be dominant over low susceptibility in the present strains. There appears to be no interaction of maternal histidinaemia with the dreher mutation which is considered to induce inner ear malformation as a result of an early neural tube abnormality.
Estimating the proportion of neutral mutants
Authors: Watterson G. A.
Published: September 2009

Kimura used the heterozygosity and the number of low-frequency alleles to estimate that about 14% of mutations are selectively neutral. The method is shown to be subject to biases and to disruption due to bottleneck effects. Let deleterious alleles have selective disadvantage,s, compared with neutral alleles and letNedenote the effective diploid population size. The estimator,, of the proportion of neutral alleles is positively biased if (roughly) 4NeS< 25 or if 4Nes> 200. In the former case, one cannot adequately detect the different influences of deleterious and neutral alleles, whereas in the latter case, deleterious alleles will rarely appear in the sample. These difficulties cause the biases in, and are likely to cause similar biases for any estimation method based solely on allele frequencies. There is substantial sampling variability inin cases of practical interest, when data from 11 loci, or even as many as 31 loci, are pooled. If there has been a recent contraction in population size,will be positively biased, often yielding values greater than 1 or even being infinite. But after a recent expansion in population size, the heterozygosity will not have made as quick an increase andwill be negatively biased. Population expansion alone can producevalues close to those observed by Kimura, even if all alleles are neutral. In an appendix, a new method for simulating samples of neutral and deleterious genes is described.
Erratum
Authors: Caddick Mark X. , Arst Herbert N.
Published: September 2009

Genet. Res., Camb. (1986), 47, pp. 83–91

Structural Genes for Phosphatases in Aspergillus nidulans

A labelling error caused nimD-4 to be substituted for nimQ-20. The nim locus shown in Fig. 3 (p. 88) is nimQ not nimD. The genotypes of strains given in the legend to Fig. 3 should read nimQ-20 in place of nimD-4.
The organization and composition of the ribosomal RNA gene non-transcribed spacer ofD. busckiiis unique among the drosophilids
Authors: Slavicek James M. , Krider Hallie M.
Published: September 2009

Several ribosomal RNA (rRNA) genes fromD. busckiiwere cloned and characterized. The prominent repeat classes have lengths of 12·8 and 13·6 kb and lack 28S introns. rRNA genes were cloned containing 28S insertions which exhibit heterogeneity in size and sequence. The non-transcribed spacer (NTS) contains two regions composed of different repeated sequences that exhibit pronounced instability in HB 101. NTS region II, centrally located within the NTS, contains predominately 11 or 16HincII generated 160 bp repeats. NTS region III, next to the 18S gene, contains repeats that are variable in number, and are either heterogeneous in length or are dispersed within unique sequences. The organization and composition of the rRNA gene NTS ofD. busckiiis different in comparison to the NTSs of other drosophilids. In addition, the pronounced instability of two different NTS regions is unique in comparison to all other cloned rRNA genes.
A new allele of the testosterone-responsive gene,Hdc-a, in the histidine decarboxylase gene complex of the mouse
Authors: Middleton Richard J. , Williamson Kathleen , Bulfield Grahame
Published: September 2009

In C57BL/10 and the majority of other strains of mice, females have about 20-fold higher kidney histidine decarboxylase levels than males; in DBA/2 mice, however, HDC in females is only 3- to 4-fold higher than males. The low ratio HDC phenotype of DBA/2 animals is due to decreased sensitivity of the HDC gene complex to repression by testosterone in males. From conventional crosses and by the use of the BXD recombinant inbred lines we conclude that the C57BL/ 10: DBA/2 difference, in testosterone sensitivity of HDC, is due to an allelic difference in the regulatory geneHdc-aof the HDC gene complex, [Hdc], on chromosome 2; DBA/2 contains a third allele of this gene,Hdc-ad.
Molecular characterization of a radiation-induced reverse mutation at the dilute locus in the mouse
Authors: Favor Jack , Strauss P. Günter , Erfle Volker
Published: September 2009

Irradiation has been employed successfully to increase the reverse mutation rate at the agouti and dilute loci in the mouse. The dilute allele has previously been shown to be due to the insertion of an ecotropic-specific murine leukaemia virus in the vicinity of the dilute locus, and its instability to be due to the excision of the proviral sequence (Jenkinset al.1981). Molecular analysis of the recovered radiation-induced revertant at the dilute locus indicated excision of all but approximately 500 bp of the proviral sequence. The proviral sequence remaining in the mouse genome hybridizes to a probe specific for the proviral long terminal repeat (LTR) sequence. Previous characterization of two spontaneous reverse dilute mutations indicated precise proviral excision of all but a single LTR, and suggests homologous recombination between the proviral LTR sequences as the mechanism of proviral excision (Hutchison, Copeland & Jenkins 1984). The present results indicate that radiation and increases the reverse mutation rate at the dilute locus acts by a similar mechanism, and suggest that mutagenic treatment may be employed to produce genetic variants of interest.
Errata
Authors: John Huw A. , Purdom Ian F. , Wright A. J.
Published: September 2009

Genet. Res., Camb. (1987), 50, pp. 17–21

Heterogeneity of human haptoglobin α chains detected by two-dimensional gel electrophoresis

The running title for this article should have been Human plasma haptoglobin α chain heterogeneity

Genet. Res., Camb. (1987), 50, pp. 63–68

Additive variance and average effect with partial selfing

(1) The second line of Table 1 should read
Characterization and mapping of a viable anaemic mutant in the mouse: a new allele,mkvan, at themicrocytic anaemialocus
Authors: Handa Sunil , Ferguson Janet M. , Wallace Margaret E. , Bulfield Grahame
Published: September 2009

A viable anaemic mouse mutant arose in the stock of a mouse fancier and has been characterized haematologically and genetically. Anaemic animals were less viable than normal animals (especially from 0 to 2 weeks of age) and had lower haemoglobin levels, percentage packed-cell volumes, higher red cell counts and lower mean cell volume than normal animals. Peripheral blood films showed a wide range of abnormal cells and extreme microcytosis. Linkage studies showed the mutant to be linked to the chromosome 15 markersNa Caandbt; recombination withCawas 1·37 ± 0·68 % for females and 10·5 ± 7·41 % for males. This position is similar to themicrocytic anaemia, mk, mutant, and crosses between the viable anaemia mutation andmk/mkhomozygotes showed the two to be allelic. Viable anaemia is therefore a second allele at themklocusmkvan; new data give its position on chromosome 15.
Variance components of fitness under stabilizing selection
Authors: Tachida Hidenori , Cockerham C. Clark
Published: September 2009

Variance components of fitness under the stabilizing selection scheme of Wright (1935) for metric characters are calculated, extending his original analysis to the case with any number of alleles and multiple characters assuming additivity of gene effects. They are calculated in terms of the moments of the effects of alleles at individual loci for the metric characters. From these formulas, the variance components of fitness are evaluated at the mutation–selection equilibria predicted by the ‘Gaussian’ approximation (Lande, 1976), which is applicable if the per locus mutation rate is high, and the ‘House of Cards’ approximation (Turelli, 1984), which is applicable if the per locus mutation rate is low. It is found that the additive variance of fitness is small compared to non-additive variance in the ‘Gaussian’ case, whereas the additive variance is larger than non-additive variance in the ‘House of Cards’ case if the number of loci per character and the number of characters affected by each locus are not too large. With the assumption that a significant portion of fitness is due to this type of stabilizing selection, it is suggested that the real parameters are in the range where the ‘House of Cards’ approximation is applicable, since available data on variance components of fitness components in Drosophila show that the additive variance is far larger than the non-additive variance. It is noted that the present method does not discriminate the two approximations if the average values of the metric characters deviate from the optimum values. Other limitations of the present method are also discussed.
The inheritance of non-response to noradrenaline in newborn Scottish Blackface lambs
Authors: Simpson S. P. , Slee J.
Published: September 2009

The normal response to injection of noradrenaline (NA) in newborn lambs is an increase in metabolic rate and rectal temperature, due to the stimulation of non-shivering thermogenesis. In a previous study 6 out of 7 lambs born to a sire previously selected for low resistance to cold failed to show this characteristic response and were termed non-responders. The sire, 2 of his male offspring and 6 sires selected randomly from the flock were mated to several ewes and the response to NA stimulation recorded in 116 newborn lambs. Control sires produced only normal responder lambs whereas the remaining sires all produced both responder and non-responder lambs. The proportion of non-responders was not significantly different from 0·50, which is consistent with a dominant major gene. Analysis of the quantitative traits, peak metabolic rate and peak rectal temperature following NA injection confirms that a major gene is segregating in the study population, but is unable to distinguish between dominant and recessive modes of inheritance. Absence of non-responders in other studies suggests that dominance is more likely. This new genetic resource could aid our understanding of brown adipose tissue metabolism and the effect of catecholamines on metabolic pathways.
A vector for studying plasmid stability functions in Streptomyces
Authors: Kendall Kevin , Cullum John
Published: September 2009

We constructed a cloning vector (pMT603) based on the low copy number plasmid SCP2*. pMT6O3 is unstable because it lacks the SCP2* stability region and carries the selectable marker thiostrepton-resistance and a tyrosinase gene which results in melanin production. This allows easy testing of plasmid stability and we demonstrated its usefulness by cloning a plasmid stability function.