bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

SUMMARYThe 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

SUMMARYDuring 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

SUMMARYUsing 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

SUMMARYA 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

SUMMARYThe 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

SUMMARYThirty-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

SUMMARYA 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

SUMMARYThe 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

SUMMARYSome 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

SUMMARYThis 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

SUMMARYTwo 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

SUMMARYGeographic 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

SUMMARYThe 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

SUMMARYPlasmids 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

SUMMARYThe 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

SUMMARYMutations 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

SUMMARYLinkage 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

SUMMARYtwPa−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

SUMMARYSomeyellowalleles 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

SUMMARYExperiments 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.