bluuebunny/crossref_metadata_2025 huggingface dataset:
The phasmid as a tool for plasmid genetics: I. Fine structure of the β-lactamase gene
Authors: Castagnoli Luisa , Cesareni Gianni , Brenner Sydney
Published: September 2009

The reversible integration of a plasmid into a phage genome viaint-mediated recombination permits rapid and facile analysis of plasmid genes. Seventy-six independent mutants in theβ-lactamase(bla) gene have been isolated and genetically mapped. The end points of deletions generated by partial digestion with restriction enzymes have been identified and this, together with the assignment of some nonsense mutations to specific amino acid residues, allows alignment of the genetic map with the DNA sequence.
Sex-determinants and their distribution in various populations ofMusca domesticaL. of Western Europe
Authors: Franco M. G. , Rubini P. G. , Vecchi M.
Published: September 2009

The distribution of sex-determinants in field populations ofMusca domestica domesticaL. was studied in 62 samples of flies collected at 53 sites (animal farms) between 1975 and 1981 in an area stretching North–South from Denmark (+ Iceland) to Sicily.

Karyological observations and genetic analyses demonstrated the existence of three types of population along a latitudinal cline. Populations of Northern Europe were of the standard type (XXfemales andXYmales) with theYchromosome determining sex. Those of Central and Southern Italy from sites below 100 m.a.s.l. (metres above sea level) were autosomal (XXfemales and males), sex in them being determined by autosomal sex-determinants for both femaleness and maleness. In the large intermediate zone the populations were mixed and had several karyotypes in both sexes. In this zone an altitudinal gradient was also observed, with autosomal determinants less common at higher altitudes. Genetic tests showed, in the autosomal and in the mixed populations, the presence of two autosomal male factors:MIII, the most common, on autosome III andMII, on autosome II.

The gradient in sex determinants found in flies of Western Europe appears to be a dynamic phenomenon of relatively recent origin. Both climatic influence and selective pressure with insecticides have probably contributed towards the micro-evolution of populations with different sex-determinants in the houseflies of the area studied.
Genetics and origin of a Drosophila melanogaster population recently introduced to the Seychelles
Authors: David J. R. , Capy P.
Published: September 2009

During an extensive survey of drosophilid fauna in 1977, D. melanogaster was not collected in the Seychelles. However, a population was found in 1981 in Victoria city, suggesting a recent introduction of this species. With respect to allozyme frequencies or ethanol tolerance, this population is almost identical to European ones and very different from those living under a similar equatorial climate on the African continent. The frequencies of rare biochemical alleles perhaps suggested that this population was founded by a small number of flies, less than ten inseminated females. For various biometrical traits, the situation was not so clear: according to the trait considered, Seychellian flies are either intermediate between European and African populations or closer to the latter. These data suggest that a few flies, recently introduced from a temperate (European?) country, built up a big population which is now on the way to adapting itself to new tropical conditions. Such an involuntary experiment should afford a unique opportunity to distinguish the respective roles of drift and adaptation in the evolution of D. melanogaster geographic races.
Metaphase I centromere co-orientation in interchange heterozygotes of pearl millet
Authors: Koduru Prasad R. K.
Published: September 2009

Using interchanges T(1, 3) and T(3, 6) ofPennisetum americanumorientation types of the interchange multiple at MI were studied in different genetic backgrounds. Orientation types alternate 1 and alternate 2, in addition to adjacent 1, adjacent 2 and indefinite could be identified for both the interchanges. The relative frequencies of various orientation types were influenced by a change in the genetic background.

For these interchanges, homologous centromeres do not seem to play a predominant role in the co-orientation of interchange multiple. The non-homologous co-orientation types were more subjected to genetic regulation than the homologous co-orientations.
Abuffspore colour mutant inSordaria brevicollisshowing high-frequency conversion
Authors: Macdonald Mary V. , Whitehouse Harold L. K.
Published: September 2009

A mutant, YS17, at thebuffspore colour locus inSordaria brevicollis, when crossed with wild type, gives rise to aberrant asci with a frequency over 10 times that of otherbuffmutants. Over 98% of the aberrant asci have 6 wild type and 2 mutant spores. From tests with anotherbuffmutant it is concluded that loss of the mutant spore colour when YS17 shows conversion to wild type is associated with loss of the high frequency conversion, and that both characters are caused by the same mutation. A methionine-requiring mutant (met-1) has been obtained that maps 5 units to the left ofbuff, and this, together with the nicotinamide-requiring mutant (nic-1) 2 units to the right, has provided flanking markers forbuffthat can be scored with complete reliability. Crosses between YS17 and 28 otherbuffmutants have revealed close linkage to three of them which map to its right on the basis of flanking marker behaviour, all the others mapping to its left. The frequency of postmeiotic segregation at the sites ofbuffmutants near to the site of YS17 is greatly increased in the presence of YS17, and occurs in the chromatid showing conversion to wild type at YS17.

From these and other results, obtained largely by ascus analysis, the following conclusions have been drawn.

(1) The YS17 mutation is probably acting as a recognition site for an endonuclease that initiates recombination, with the result that the frequency of heteroduplex DNA within thebuffgene is much increased.

(2) The recombination initiated at YS17 is asymmetric (or at least pre-dominantly so), with the YS17 site acting as a recipient of a nucleotide chain from the other parent, not a donor to it.

(3) The frequency of crossing over associated with conversion at YS17 is variable: about 30% in crosses with most of thebuffmutants, about half this value in crosses with wild type, and almost zero in crosses with closely-linkedbuffmutants.

(4) In about one third of the crossover asci in crosses between YS17 and otherbuffmutants the crossover is not adjacent to the site of YS17 but separated from it by the site of the allele, which shows normal 4:4 segregation.

(5) It seems necessary to revive the idea of more than one recombination event in proximity, a non-crossover conversion event sometimes leading to a second event – a crossover – in the vicinity. It is tentatively suggested that both might be controlled by a single enzyme aggregate.
Nutritional regulation of antennal/leg homoeotic mutants inDrosophila melanogaster
Authors: Jowett Trevor , Sang James H.
Published: September 2009

The expression of the antennal homoeotic mutant,Nasobemia, is shown to be strongly dependent on nutrition. Dietary deficiencies in any of the following: thiamine, calcium pantothenate, nicotinic acid or RNA, cause acuringof the homoeotic defect. It is demonstrated that the effects of thiamine and pantothenate are through limiting acetyl-CoA synthesis and that fatty acids are required for high penetrance of theNsgene. Similar nutritional effects are described for otherAntennapediaandaristapediaalleles. The period of sensitivity to nutritional changes is defined forNsand compared with the period of temperature sensitivity. These results suggest the hypothesis that the homoeotic mutationsAntennapediaandaristapediashare some common metabolic requirements which involve synthesis of acetyl-CoA.
A world-wide survey of genetic variation in the yellow fever mosquito,Aedes aegypti
Authors: Tabachnick Walter J. , Powell Jeffrey R.
Published: September 2009

Thirty-four populations ofAedes aegyptirepresenting the world-wide distribution of the species, were analysed for genetic variation at 19–22 isozyme loci. The species has an average expected heterozygosity of 0·129±0·045 based on 19 loci analysed in every population. Based on this genetic information, two major groups can be defined: the dark, often sylvan, African subspeciesformosusand the light domestic subspeciesaegyptiin Africa and the New World. Asian populations do not fall easily into either group. These results are related to models which have been proposed for the evolution of this species. AlthoughA. aegyptiwas introduced into the New Worldc. 350 years ago and has recently recolonized many areas following eradication programmes, no signs of founder effects are evident in this region. Asian populations, on the other hand, do show a significantly lower level of genetic variation compared to other populations. This may be related to the time of introduction ofA. aegyptiinto Asia and historical absence of yellow fever on the Asian continent.
The genetics ofSleek: a possible regulatory mutation of thetabby-crinkled-downlesssyndrome
Authors: Crocker Mark , Cattanach Bruce M.
Published: September 2009

A new mutation,Sleek, similar in appearance to mutations at theTa, cranddlloci, has been investigated. It is inherited as an autosomal dominant and maps very close todlon chromosome 13. Allelism withdlseems probable sinceSleekinteracts withdlbut not withcr. The unusual occurrence of dominant and recessive alleles at the same locus which produce a similar mutant phenotype suggests that the locus might either code for a multimeric protein or a regulatory product.
The production of heterozygous diploids and haploidization analysis inAspergillus amstelodami
Authors: Bertoldi M. de , Caten C. E.
Published: September 2009

The steps in the parasexual cycle required for genetic analysis by mitotic haploidization were readily accomplished inAspergillus amstelodami. Balanced heterokaryons were synthesized between strains carrying complementary auxotrophic mutations and heterozygous-diploid colonies were recovered from these heterokaryons at frequencies between 1 × 10−6and 5 × 10−6among conidia plated. When grown in the presence ofp-fluorophenylalanine or benomyl, heterozygous-diploid strains produced discrete haploid segregants. Examination of the segregation of 12 mutations among haploid segregants from ten diploids indicated that these genes were located in six linkage groups, thereby increasing the number of linkage groups recognized in this species. This haploidization analysis provided a clear distinction between linked and unlinked genes and continuation of this approach should reveal the chromosome number ofA. amstelodami. Linkage at meiosis was detected between only one of five pairs of mitotically linked genes tested, emphasising the value of mitotic-haploidization analysis for assigning markers to linkage groups.A. amstelodamiis amenable to both mitotic and meiotic genetic analysis and further studies should permit extensive comparisons of the genetic and biochemical organization of this species with that ofA. nidulans.
Some sampling properties of selectively neutral alleles
Authors: Chakraborty Ranajit , Fuerst Paul A.
Published: September 2009

Some sampling properties related with the mean and variance of the number of alleles and single locus heterozygosity are derived to study the effect of variations in mutation rate of selectively neutral alleles. The correlation between single locus heterozygosity and the number of alleles is also derived. Monte Carlo simulation is conducted to examine the effect of stepwise mutations. The relevance of these results in estimating the population parameter, 4Neν, is discussed in connexion with neutralist-selectionist controversy over the maintenance of genetic variability in natural populations.
Dominance modification in a fluctuating environment
Authors: Charlesworth Brian , Charlesworth Deborah
Published: September 2009

This paper examines the suggestion of Gale & Mackay (1979) that dominance modification will be slower in an environment with fluctuating selection coefficients than in a constant environment. The case of statistical independence between successive environments is studied. It is shown that there is an effect in the suggested direction, but that it is quantitatively slight with biologically plausible values for the parameters involved. It therefore seems unlikely that the phenomena noted by Charlesworth (1979) can be explained in these terms.
The plasmid system ofEscherichia colistrain UR12644: Identification and molecular characteristics of transposons involved in the generation of endogenous R-plasmids
Authors: Schöffl F. , Pühler A.
Published: September 2009

Two spontaneously formed R-plasmids (pFS401 and pFS402) originating from the multiple drug-resistantEscherichia colistrain UR12644 were found to carry transposable drug-resistance elements. Incompatibility between these two plasmids was used to select for transposition. An ampicillin transposon (Tn1781) residing on pFS401 and a tetracycline transposon (Tn1771) present on pFS402 were independently translocated to the endogenous RTF-plasmid pFS2. Molecular weight determinations of pFS2::Tn1781(Ap) and pFS2::Tn1771(Tc) revealed a value of 2·9 Mdal for Tn1781 and 7·1 Mdal for Tn1771. The arrangement of 3PstI and 1BamHI restriction endonuclease sites was found to be characteristic for the ampicillin transposon whereas the restriction map of Tn1771 features a nearly symmetrical location of 3EcoRI cleavage sites, two of them close to the termini and one in the middle of the transposon. A model is presented suggesting the existence of repetitive DNA-segments at these positions which represent the structural preconditions for the genetic properties of Tn1771. The role of a cryptic plasmid involved in the generation of the endogenous R-plasmids pFS401 and pFS402 is discussed.
Are geographic populations equivalent to genetic populations in biennial species? A study usingVerbascum virgatum(Scrophulariaceae)
Authors: Wells Harrington , Wells Patrick H.
Published: September 2009

Geographic populations are not necessarily equivalent to genetic populations. Electrophoretic isozyme analysis shows that in the biennial,Verbascum virgatum, not only is spatial distribution a factor creating isolated populations, but time also is an isolating mechanism. Thus, in the biennial situation there is a possibility that selection can be rejected as the probable cause of variation, much as can random drift in cases involving spatial distributions. The magnitudeof difference infrequency of alleles between the odd and even year colonies studied was too large to be explained by random drift in populations of the size and short duration of those we observed. Similarly, it is unlikely that random fluctuations in selection intensity on one age class would produce a difference as large as that observed. It is possible, however, that variation was introduced (mutation or founder) when the population was much smaller and that the difference was trapped at a relatively high level when the population rapidly increased in size. Simulations and algebraic theory do not refute this idea. They also show that colony differentiation can occur with migration rates considerably greater than previously predicted.
The effect of migration and recombination on the equilibrium structure of populations subject to a common symmetric selection regime
Authors: Campbell R. B.
Published: September 2009

The effect of migration and recombination on the equilibrium structure of populations subject to a common symmetric selection regime in all habitats is studied. Attention is restricted to a class of symmetric polymorphic equilibria which have been studied in two-deme systems by Bazykin (1972) and Karlin & McGregor (1972) for one locus and by Christiansen & Feldman (1975) for two loci. With increased migration and recombination the heterozygosity increases unless it is already at the maximum level. Although the populaton system as a whole is always at linkage equilibrium, the magnitude of linkage disequilibrium in the individual demes may either increase or decrease with more migration and recombination. In general, the less the migration and the less the recombination between interacting loci, the greater the possibilities of polymorphic equilibria.
R68.45, a plasmid with chromosome mobilizing ability (Cma) carries a tandem duplication
Authors: Rieβ G. , Holloway B. W. , Pühler A.
Published: September 2009

Plasmids R68 and R68.45 were transferred fromPseudomonas aeruginosatoEscherichia coliby conjugation. R68.45 was able to mobilize theE. colichromosome from different origins at a frequency of about lO−6/donor cell. With R68, no transfer of chromosomal genes could be detected. Plasmid R68.45 differs from its parent R68 only by an additional DNA segment, 2120 bp long, located close to the kanamycin resistance gene. By restriction enzyme analysis it was shown that the additional DNA segment of R68.45 is a duplication of a pre-existing DNA region of R68. The duplicated region is characterized by the following sequence of restriction sites: A–310 bp–SmaI–70 bp–PstI–795 bp–PstI–15 bp–KpnI–540 bp–HpaI–370 bp–B.

The endpoints A and B of the duplicated region were determined by a heteroduplex experiment betweenHindIII linearized molecules of R68 and R68.45. It is proposed that this duplication found in R68.45 is responsible for its chromosome mobilizing ability.
Artificial selection with differing population structures
Authors: Rathie K. A. , Nicholas F. W.
Published: September 2009

The effect of subdivision of a population on response to artificial directional selection for abdominal bristle number inDrosophila melanogasterwas compared using large, replicated lines. Three different population structures were compared: (i) selection in an Undivided, large population with 50 pairs of parents (treatment U); (ii) selection in each of 10 sublines which were reconstituted every 6th generation by Crossing after Culling the 5 lowest sublines (treatment CC); and (iii) selection in each of 10 sublines which were reconstituted every 6th generation by Crossing after Retaining all 10 sublines (treatment CR). At the end of three cycles of selection and crossing, neither CR nor CC was superior to U; sublining did not increase response to selection. These results agree with the predictions arising from an entirely additive model and provide no evidence for the presence of epistasis.

A comparison of 50-pair lines (U) with several 5-pair lines was made over 31 generations. For the 50-pair lines, there was close agreement between response predicted from the base population (usingih2σp) and observed response throughout all 31 generations of selection. Although the best of the 5-pair lines exceeded the 50-pair lines in the early generations, average response to directional selection in the 5-pair lines soon fell behind that predicted fromih2σp, and soon reached a plateau.
A third gene affecting GABA transaminase levels inAspergillans nidulus
Authors: Bailey Christopher R. , Arst Herbert N. , Penfold Hugh A.
Published: September 2009

Mutations in thegatB gene as well as mutations in the putative structural genegatA and the positive acting regulatory geneintA can affect γ-amino-n-butyrate (GABA) transaminase (EC 2.6.1.19) levels in the ascomycete fungusAspergillus nidulans. Partial or complete loss of function mutations ingatA,gatB andssuA, which specifies succinic semialdehyde dehydrogenase, can lead to accumulation of ω-amino acids resulting in pseudo-constitutivity and elevated expression of (retained) activities underintA control. These regulatory effects underlie selective methods forgatB−,ssuA−and leakygatA−mutations. However, all threegatB−alleles which have been selected lead only to partial loss of GABA transaminase activity as judged by bothin vivoandin vitrocriteria. It has not been established whether the leakiness of these threegatB−mutations is an allele-specific or a locus-specific effect and whether or not the GABA transaminase present ingatB−strains differs from the wild type enzyme. Thus the role of thegatB product remains to be elucidated. ThegatB gene is not closely linked to any other gene involved in ω-amino metabolism or related pathways.
Linkage disequilibrium between amino acid sites in immunoglobulin genes and other multigene families
Authors: Ohta Tomoko
Published: September 2009

Linkage disequilibrium between segregating amino acid sites in repeated genes which form a multigene family was investigated by using the population genetics theory. The degree of non-random association of amino acids is measured by the disequilibrium coefficient which is determined by the balance among various forces; unequal and equal crossing-over, mutation, random genetic drift and recombination which takes place between the two sites in question. Another measure of disequilibrium, ‘standardized identity excess’, represents excess probability of simultaneous identity at the two sites over that expected from random association of amino acids. Sequence data of variable region of immunoglobulins provide most interesting example of multigene family to apply the theory. Statistical analyses on identity excess for various groups and subgroups of variable region sequences of immunoglobulins suggest that a multigene family such as human κ or mouse κ gene family consists of several subfamilies between which recombination is limited. The analyses also indicate that the recombination may take place between any gene members in one subfamily.
twPa−1,twPa−2,twPa−3: three newt-haplotypes in the mouse
Authors: Guenet Jean-Louis , Condamine Hubert , Gaillard Jean , Jacob François
Published: September 2009

twPa−1is a new lethalt-haplotype isolated in the South of France. Homozygous embryos die at the time of implantation or shortly there-after following general disorganization.twPa−1complements all previously knownt-haplotypes and has thus to be considered as the first representant of a new complementation group.twPa−2andtwPa−3are viable, male sterile haplotypes, buttwPa−2is low transmitter.
Pattern mosaicism for behaviour controlled by theyellowlocus inDrosophila melanogaster
Authors: Burnet B. , Wilson R.
Published: September 2009

Someyellowalleles which show full expression of the mutant phenotype have behavioural defects, including reduced locomotor activity and a low level of male competitive mating success. Otheryellowalleles produce pattern mosaics in which some cuticular structures areyellowand others wild type within the same individual. The pattern mosaic expression of these alleles extends to behaviour. Mosaicism in respect of the different pleiotropic effects reveals something about the possible mode of action of this locus on behaviour.
Adaptive value of PGM polymorphism in laboratory populations ofDrosophila melanogaster
Authors: Carfagna M. , Fucci L. , Gaudio L. , Pontecorvo G. , Rubino R.
Published: September 2009

Experiments have been performed to show that PGM polymorphism for the two common electrophoretic allozymes, PGMAand PGMB, inDrosophila melanogasterhas adaptive value. Firstly, the allele frequencies converge to the same equilibrium value in six experimental populations. Secondly, density-dependent selection operates. Thirdly, the relative fitness of the three genotypes varies in modified culture media. PGM polymorphism is maintained by frequency-dependent selection and heterotic selection: the first mechanism operates to reach equilibrium frequency, the second cooperates to maintain it. The experiments performed with modified culture media favour the view that the two allozymes have different affinities for two components which are present in the nutritional environment. These components may be either substrates or other factors involved in the reaction catalyzed by PGM.
Search for ribosomal mutants inPodospora anserina: genetic analysis of cold-sensitive mutants
Authors: Picard-Bennoun Marguerite , Coze Denise Le
Published: September 2009

Twenty-four cold-sensitive (prototrophic) mutants were isolated after UV mutagenesis of protoplasts of the fungusPodospora anserina. Genetic analysis of these mutants was performed in order to detect those among them which were most likely to be impaired in translational fidelity. The 24 mutations belonged to 24 different genes. One half of the mutants were pleiotropic and displayed an altered phenotype: growth rate at the permissive temperature, germination of the spores, fertility and/or sporulation. Nine mutants differed from wild-type in their resistance levels to cycloheximide, trichodermin and/or paromomycin. Several mutations were linked to known ribosomal loci. Two mutations behaved like informational antisuppressors: one is allelic to the previously describedAs3gene and the other one defines a new antisuppressor gene,AS6.
Genetics of lycopene cyclization and substrate transfer in β-carotene biosynthesis inPhycomyces
Authors: Torres-Martínez S. , Murillo F. J. , Cerdá-Olmedo E.
Published: September 2009

The mutations which block lycopene cyclization and those which stop substrate transfer along the carotene pathway are very closely linked inPhycomyces. Simultaneous blocking of both processes commonly results from single exposures to mutagens; and both blockings may be simultaneously removed after a second exposure. The frequencies of different kinds of mutants after treatments with the mutagensN-methyl-N′-nitro-N-nitrosoguanidine and ICR-170, their reversion patterns, and recombination analyses indicate that lycopene cyclization and substrate transfer are governed by separate segments of a single bifunctional gene.
Use of isozymes as chromosome markers in the isolation and characterization of wheat-barley chromosome addition lines
Authors: Hart Gary E. , Islam A. K. M. R. , Shepherd K. W.
Published: September 2009

The alcohol dehydrogenase (ADH), glutamic oxaloacetic transaminase (GOT), aminopeptidase (AMP), endopeptidase (EP), and esterase (EST) zymogram phenotypes of Chinese Spring wheat, Betzes barley, Chinese Spring-Betzes heptaploids, and a number of presumptive Betzes chromosome additions to Chinese Spring were determined. It was found that four disomic chromosome addition lines could be distinguished from one another and from the other three possible lines on the basis of the zymogram phenotypes of these isozymes.

The structural geneAdh-H1was located in Betzes chromosome 4, the genesGot-H2andAmp-H1in chromosome 6, and the geneEp-H1in chromosome 1. These gene locations provide evidence of homoeology between Betzes chromosomes 4, 6, and 1 and the Chinese Spring chromosomes of homoeologous groups 4, 6, and 7, respectively.
The genetic component in coronary heart disease – a review
Authors: Robertson Forbes W.
Published: September 2009

The importance of atherosclerosis in public health has generated a vast literature relating to epidemiology of the disease, clinical descriptions of symptoms and records of variation of serum concentration of cholesterol, triglyceride or lipo-protein fractions in normal or affected persons. Such evidence has led to a number of hypotheses as to the origins of the disease, and although rival theories may be espoused with fervour or may fluctuate in popularity, a familial predisposition to coronary disease is a recurring theme. In this brief review, which does not aim to be exhaustive and is not concerned with hypertension, we shall focus attention on the more important aspects and attempt to set the conflicting evidence in perspective.
Retarded development of females, a case of maternal inheritance in a moth, Ephestia kuehniella
Authors: Traut Walther
Published: September 2009

Retarded development of females (Symbol: Rf) has arisen spontaneously as a new trait in a chromosome mutant strain, which has an autosome fused to the original W chromosome. Female imagines with this trait emerge 1–3 weeks later than the males, due to retarded larval development. The proportion of female imagines is low. Rf is maternally inherited, it is neither expressed in nor transmitted through males. The evidence suggests that it is a dominant or epistatic factor on the autosomal part of the W chromosome-autosome fusion.
Autosomal genetic maps of the Australian Sheep Blowfly,Lucilia cuprina dorsalisR.-D. (Diptera: Calliphoridae), and possible correlations with the linkage maps ofMusca domesticaL. andDrosophila melanogaster(Mg.)
Authors: Foster G. G. , Whitten M. J. , Konovalov C. , Arnold J. T. A. , Maffi G.
Published: September 2009

Linkage data and revised maps for 52 autosomal loci inL. cuprinaare presented. Examination of the linkage relationships of biochemically and morphologically similar mutations inL. cuprina, Musca domesticaL. andDrosophila melanogaster(Mg) suggests that the major linkage groups have survived largely intact during the evolution of the higher Diptera.
Does ‘affinity’ hold the key to fertility in the female mule?
Authors: Chandley Ann C.
Published: September 2009

Michie's hypothesis of ‘affinity’ is invoked to explain how fertility might theoretically be achieved in a female mule or hinny. Chromosomally balanced haploid gametes could be produced in these inter-specific hybrids by movement of centromeres of similar ancestry to opposite poles at anaphase I of meiosis. Male hybrids could probably never be fertile on account of the low numbers of spermatozoa produced; females, on the other hand, might occasionally achieve fertility by the ovulation of a chromosomally balanced egg.
Selfing mutants from heterothallic strains ofPhysarum polycephalum
Authors: Honey N. K. , Poulter R. T. M. , Winter P. J.
Published: September 2009

Plasmodial formation in the myxomycetePhysarum polycephalumis controlled by a mating type (mt) locus, with heterothallic amoebae normally being unable to form plasmodia in pure clones. We report the isolation by mutagenesis of selfing mutants from heterothallic strains, and their analysis. Various amoebal strains of different mating types were mutagenized with a range of mutagens, and a number of selfing mutants (designated Het−) were isolated. A specific sensitivity ofmt2amoebae to mutagenesis by NMG was observed. This sensitivity segregated as a single locus closely linked or allelic to themt2locus. When the Het−clones were incubated at 30 °C, selfing was greatly inhibited. This property was used to determine themtspecificities of four Het−clones. The process of plasmodial induction in pure clones ofCLwas also studied using the 30 °C temperature effect.
A variation in mouse kidney pyruvate kinase activity determined by a mutant gene on chromosome 9
Authors: Johnson F. M. , Chasalow Fred , Anderson Gretchen , Macdougal Paul , Hendren R. Wayne , Lewis Susan E.
Published: September 2009

Pyruvate kinase activity was studied in kidney extracts of mice from various sources. One C57BL/6J female among several hundred examined expressed activity approximately one half of the normal level. This animal transmitted the trait, and a single gene responsible for the activity difference was identified and mapped to chromosome 9. Linkage withMod-1anddilutewas established. A spontaneous mutation in the C57BL/6J strain apparently was responsible for the variant pyruvate kinase.
Reversion analysis of [psi−] mutations inSaccharomyces cerevisiae
Authors: Lund P. M. , Cox B. S.
Published: September 2009

Mutants of [psi] a cytoplasmically inherited factor in the yeastSaccharomyces cerevisiaewere isolated after treatment with a variety of agents including conventional mutagens and a number of compounds which cause loss of [psi] at high frequencies, namely methanol, KCl, dimethyl sulphoxide and guanidine hydrochloride. In [psi−] mutants the suppressorSUQ5does not suppress ochre mutations such asade.2.1.

Reversion analysis of the [psi−] mutants revealed three classes: (1) a class of agents producing [psi−] mutations which could readily revert to [psi+] (methanol, KCl and dimethyl sulphoxide belong to this class), (2) those which could not be shown to revert (GuHCl) and (3) the conventional mutagens which produced both revertible and apparently non-revertible [psi−] mutations. We conclude that GuHCl causes a deletion or loss of the [psi] factor. Methanol may cause an alteration of ‘state’ for example, of a promoter, and KCl may be selecting or inducing low copy number variants of [psi+] strains. It is possible that DMSO may be involved in regulation of [psi].
Relationship between the parental origin of theXchromosomes, embryonic cell lineage andXchromosome expression in mice
Authors: Papaioannou Virginia E. , West John D.
Published: September 2009

The electrophoretic variants of theX-chromosome-linked enzyme phosphoglycerate kinase (PGK-1) have been used to investigate the randomness ofXchromosome expression in the fetus and various extra-embryonic membranes of the mouse conceptus. The amnion shows essentially random expression of the maternally derivedXchromosome (Xm) and the paternally derivedXchromosome (Xp). The parietal endoderm, however, shows exclusive or preferential expression ofXm. The results support the idea that the randomness ofXchromosome expression is correlated with embryonic cell lineage such thatXmis preferentially (perhaps exclusively) expressed in derivatives of the primitive endoderm and trophectoderm but thatXmandXpare randomly expressed in the derivatives of the primitive ectoderm.

Experiments involving ovary transplants, embryo transfers or crosses with heterozygous mothers confirm previous findings thatXmis preferentially expressed regardless of theXchromosome expressed in the reproductive tract. Additional experiments show that the preferentially expressedXchromosome in the parietal endoderm and visceral yolk sac endoderm of a normalXmXpconceptus is alwaysXmregardless of grand-parental origin ofXmand regardless of whether the mother is a normalXXfemale or anXOfemale.Xpis, however, expressed in these tissues hiXpOfemale conceptuses. It is argued that a form of chromosome imprinting occurs at each generation to markXmandXpas different and that this difference influences the choice of whichXchromosomes are expressed in each cell lineage.
Production of disomic wheat-barley chromosome addition lines usingHordeum bulbosumcrosses
Authors: Islam A. K. M. R. , Shepherd K. W.
Published: September 2009

The possibility of usingHordeum bulbosumCrosses to facilitate production of disomic wheat–barley addition lines from monosomic additions was investigated. Aneuhaploids with 22 chromosomes were obtained in the expected gametic frequencies after crossing monosomic, disomio and monotelo-disomic addition lines, involving four different barley chromosomes, as the female parent with tetraploidH. bulbosum. Thus the added barley chromosomes were not eliminated when preferential elimination of thebulbosumchromosomes took place in the hybrid embryos. Disomic addition lines were obtained after treating the aneuhaploids with colchicine. This method could have wider application in the production of other wheat–alien chromosome disomic addition lines, especially where the transmission frequency of the alien chromosome through the pollen is very low, but its use will depend on the wheat parent being crossarle withH. bulbosumand the alien chromosome being retained during the elimination ofbulbosumchromosomes.
Variation in activity and thermostability of alcohol dehydrogenase inDrosophila melanogaster
Authors: McKay J.
Published: September 2009

The activity and thermostability of alcohol dehydrogenase (ADH) from 247 strains ofDrosophila melanogasterwere studied by spectrophotometric assay. The strains, in which second chromosomes had been made homozygous in a standard genetic background, were derived from five natural populations from diverse geographical and ecological sites. Evidence is presented that the majority of variation in ADH activity is attributable to the presence, in all five populations, of two electromorphs of the enzyme. However, some variation does exist between strains carrying the same electromorph, to some extent associated with variation hi body weight. Two strains showed atypical ADH activities. Variation in ADH thermostability was almost wholly attributable to the presence of two electromorphs; only two strains had enzymes with thermostabilities atypical of their electromorph. In the four strains with abnormal ADH properties the locus (loci) responsible map in the region of theAdhlocus. Therelatively low level of heterogeneity within electrophoretic classes at this locus is discussed in view of recent findings at other enzyme loci inDrosophila.
The transposons Tn501(Hg) and Tn1721(Tc) are related
Authors: Altenbuchner J. , Choi C.-L. , Grinsted J. , Schmitt R. , Richmond M. H.
Published: September 2009

Internal sequences of Tn501(Hg) and Tn721(Tc) have been compared by hybridization. In spite of the difference in the resistance they code for, there is extensive homology between the two elements. This homology resides in the transposon-coded genes that are necessary for transposition and indicates that the elements are closely related.
GPI expression in female germ cells of the mouse
Authors: McLaren Anne , Buehr Mia
Published: September 2009

The genetically determined oocyte-specific expression of glucose-phosphate isomerase activity in the mouse is first apparent at 6 to 7 days after birth, and occurs in XO as well as in XX oocytes. The regulator locus that controls oocyte-specific expression shows the same linkage relations as the structural gene, suggesting that both form part of a Gpi-1 gene complex.
Mobilization of the non-conjugative IncQ plasmid RSF1010
Authors: Willetts Neil , Crowther Carol
Published: September 2009

The broad host-range non-conjugative IncQ plasmid RSF1010 was mobilised with 100% efficiency in membrane filter matings, both inE. coliK12 andP. aeruginosaPAO, by broad host-range conjugative IncP plasmids. No homology between RSF1010 and an IncP plasmid could be detected. InE. coli, IncIα and IncX plasmids, but not IncF, IncN or IncW plasmids, were also relatively efficient at mobilising RSF1010, while inP. aeruginosa, R91–5 (IncP-10) was highly efficient, but pMG5 (IncP-2) and FP2 (IncP-8) were very inefficient. IncP plasmids also mobilised several plasmids derived from RSF1010 for use as in vectors inin vitrorecombination experiments very efficiently, and pSC101 quite efficiently: this reduces the level of biological containment possible with these plasmids.
X chromosome activity in female germ cells of mice heterozygous for Searle's translocation T(X;16)16H
Authors: Johnston P. G.
Published: September 2009

The expression of X-linked phosphoglycerate kinase (PGK-1) in germ cells from embryos heterozygous for both PGK-1 and Searle's translocation T(X; 16) 16H was examined to investigate X chromosome activity during oogenesis. ThePgk-lballele on the translocated X chromosome was the only allele active in somatic cells of all embryos and in germ cells from 12·5 d.p.c. embryos. However, an additional faint band representingPgk-laactivity was observed in germ cells from older embryos (13·5–18·5 d.p.c.) and neonates (1–2 d.p.p.). It is concluded that there is a period when only one X chromosome is active in early female germ cells and that reactivation of the inactive X chromosome takes place just prior to meiotic prophase.
The growth of mice selected for large and small size in relation to food intake and the efficiency of conversion
Authors: Roberts R. C.
Published: September 2009

Mice selected for large size show increases in both food intake and efficiency, and small mice show decreases in both. This is true whether the comparisons are made at the same age or at the same weight. Food intake and efficiency contributed more or less equally to the responses to selection for growth. Mice seem to regulate their food intake to a certain level of energy. On suspension of a period of food restriction, mice ate the same amount as others of the same strain that had not been restricted, and which were bigger. At the same time, they converted it more efficiently than the mice which had been full-fed throughout, because of a linear negative association between efficiency and body weight. Thus, following restriction, mice eat as much as bigger mice of the same age, and convert it as efficiently as younger mice of the same weight. The product of these two effects gives rise to rapid (compensatory) growth.
The control of body size in mouse chimaeras
Authors: Falconer D. S. , Gauld I. K. , Roberts R. C. , Williams D. A.
Published: September 2009

Aggregation chimaeras were made from embryos of strains of mice selected for large and small body size and of unselected controls. The strains were combined in pairs marked by albino coat colour and by allo-zyme variants at the Gpi-1 locus. The proportion of cells derived from each component was scored visually in the coat melanocytes and by electrophoresis in ten other organs or tissues (blood, liver, lung, spleen, spinal cord, brain, pituitary, kidney, adrenal and testis). The object was to find out how body weight is related to cell proportions in the body as a whole and in the separate organs. Individuals varied widely in their mean cell proportions but there were significant differences between organs within individuals. Body weight was linearly related to the mean cell proportions which accounted for most, or possibly all, of the chimaeric variance of body weight. No one of the organs studied could be identified as being solely responsible for growth control, or as having a predominant influence on growth. The weights of some organs were probably influenced to a small extent by their own cell proportions independently of the individual's mean, but the differences of body weight were too great to be accounted for by the summation of localized effects on organs. The mean cell proportion, averaged over individuals, was close to 50%, proving that there was no tendency for cells from the larger component to outgrow those from the smaller. It is concluded that growth control must be systemic, but it was not possible to decide whether the systemic effect comes from some particular organ not studied, or is in some undefined way the consequence of the cell proportions in the body as a whole. There was some evidence, though it was inconclusive, that chimaeras show ‘heterosis’ for body weight.
A gene (Neu-1) on chromosome 17 of the mouse affects acid α-glucosidase and codes for neuraminidase
Authors: Peters Josephine , Swallow Dallas M. , Andrews Sandra J. , Evans Lorraine
Published: September 2009

An electrophoretically detectable variant of acid α-glucosidase has been found in SM/J mice. This variant is attributable to excess sialylation of the enzyme and is determined by a gene, alpha-glucosidase processing,Aglp, on chromosome 17. In addition, as also reported by Potier, Lu Shun Yan & Womack (1979), SM/J mice are relatively deficient in neuraminidase and it appears that the low level of this enzyme in SM/J is determined by an autosomal codominant gene, neuraminidase-1,Neu-1. Preliminary data indicate thatNeu-1is also on chromosome 17. It seems probable that the several processing genesApl, AglpandMap-2which are all closely linked on chromosome 17 are one and the same, a geneNeu-1coding for neuraminidase.
Relationship between allozyme heterozygosity and rates of divergence
Authors: Skibinski D. O. F. , Ward R. D.
Published: September 2009

The relationship between locus variability and genetic identity is analysed in pooled data from a collection ofDrosophilaand vertebrate allozyme surveys. For vertebrates the analysis provides evidence that loci with high expected heterozygosity diverge at a faster rate than loci with low heterozygosity in comparisons involving pairs of populations and pairs of species. This relationship is not observed in comparisons ofDrosophilaspecies pairs.
The genetics of tasting in mice. I. Sucrose octaacetate
Authors: Lush Ian E.
Published: September 2009

Thirty-one inbred strains were tested for their reaction to drinking water which contained a low concentration (10−4 M) of sucrose octaacetate (SOA). One strain, SWR, showed a strong aversion to drinking the SOA solution. The other thirty strains, and two samples of wild-derived mice, tended to prefer the SOA solution to untreated drinking water. The pheno-typic difference between SWR and the other strains was shown to be determined by an autosomal gene. The allele present in SWR is dominant. The gene is not closely linked to jerker (je), pearl (pe) or waved-2 (wa-2).
Transcription inX-chromosomal segmental aneuploids ofDrosophila melanogasterand regulation of dosage compensation
Authors: Prasad Jayashree , Duttagupta Ashish K. , Mukherjee A. S.
Published: September 2009

Transcription ofXchromosomal DNA has been examined autoradio-graphically in various 1X2Aand 2X2Anormal larvae and 1X2A(+Xfr) and 2X2A(+Xfr) segmental aneuploid larvae of speciesDrosophila melanogaster. The segmental aneuploids contained duplications for the segment 9A–11A and 15D–ISA of theXchromosome. Results show that in the aneuploid male containing 9A–11A duplicaton both the homologous segments involved in the aneuploidy are autonomously hyperactive; their combined activity, measured byX/Agrain ratio, is found to be nearly 70% more than the activity in normal male and about 100% more than that in diplo-Xfemale. In the aneuploid female, containing the aneuploid segment 15D–18A and having three doses of the segment of theXchromosome, the activity was over 100% more than the diplo-Xactivity. The per gene dose activity for the two segments in the aneuploid male and female, respectively, is also significantly higher than their male and female counterparts. The possible role of lack of contiguity of the genetic segments and an intra-nuclear variation has been ruled out by appropriate analysis. We, therefore, interpret these findings to be due to an autonomous expression of theXlinked compensatory genes, resulting from a primary modulation in the organization of the entireXchromosome. The autosomal signal then renders the individual genetic locus hyperactive.
A structural gene (Tcp-1) within the mouse t complex is separable from effects on tail length and lethality but may be associated with effects on spermatogenesis
Authors: Silver Lee M.
Published: September 2009

The Tcp-1 gene is located within the t complex and codes for a major testicular cell protein called p63/6.9. All wild-type chromosomes carry the Tcp-1b allele which codes for a basic form of this protein, while all complete t haplotypes carry the Tcp-1a allele which codes for an acidic form of this protein. It is not clear whether the Tcp-1 gene is associated with phenotypic effects of t haplotypes on embryogenesis and/or spermatogenesis, since the genetic basis for these effects is extremely complex. The elegant analysis of Lyon & Mason (1977) has allowed the identification and separation of a family of genetic factors which interact to produce the observed phenotypes associated with various combinations of t haplotypes. The data summarized in this report indicate that the Tcp-1a locus is separable from all of the identified t haplotype factors except for one; a complete correlation has been obtained between Tcp-1a and a proximal t haplotype factor which is involved in effects on transmission ratio distortion. Two other novel points emerge from this analysis. First, it appears that the tail interaction factor and the proximal sperm factors represent distinct genetic loci. Second, the accumulated data lead to the proposal that the TOrl chromosome carries a short segment of t haplotype chromatin containing Tcp-1a and proximal sperm factors involved in transmission ratio distortion and sterility.