bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental genetics of leaf formation inLolium3. Inheritance of a developmental complex
Authors: Edwards K. J. R. 
Published: September 2009

SUMMARYUsing four lines derived from a single base population ofLolium perenneby selection for large leaf size (LL), small leaf size (SL), fast rate of leaf appearance (FR), and slow rate of leaf appearance (SR), the inheritance of a number of related characters specifying various aspects of leaf development was studied.F1andF2generations were produced for all possible crosses between these four lines.The genetic differences between the selection lines were largely additive for all characters studied and entirely so for rate of leaf appearance, duration of elongation of a single leaf and for the time interval between the maturation of leaf 3 and the unfolding of the next youngest leaf on the same side of the apex, leaf 5. The non-additive variances noted in rate of total leaf area formation, individual leaf size and its components length and width, and in the rate of leaf elongation, were associated with a tendency towards heterosis in these characters. This was quite marked in some crosses and tended to be larger for the more complex characters, rate of total leaf area formation and leaf size, suggesting that the heterosis was, to a considerable extent, due to interactions between genes controlling component characters.The data confirmed the earlier finding that the negative correlated selection response between leaf size and rate of leaf appearance was due to a basic association between the maturation of a leaf and the unfolding (onset of rapid elongation) of the next youngest leaf on the same side of the apex. Thus an increase in rate of leaf appearance reduces the duration of elongation of a leaf and this in turn will reduce leaf length. However, the basic association, which seems to be controlled by vascular development of the young leaf, is not entirely invariate.
The influence of theylocus on DDT resistance in the mosquitoAedes aegyptiL
Authors: Wood R. J. 
Published: September 2009

SUMMARYThe influence of the linkage group II locusyon DDT resistance inAedes aegyptihas been studied in crosses between the Trinidadresistant strain and QS susceptible strain. Theylocus influences DDT resistance in bothR/RandR/+ larvae. The effect ofymay be interpreted as reducing the penetrance ofR(RDDT1), which is also located on linkage group II.y+is partially dominant and incompletely penetrant in its resistance-enhancing role (although in its pleiotropic effect on larval colour it is dominant and fully penetrant). Penetrance ofy+is influenced by an environmental factor, probably associated with the larval diet.The effect ofyon resistance is evaluated in relation to other genetic influences on the expression ofRDDT1.The significance of polymorphism at theylocus is discussed.
Characteristics ofE. coliK12 strains carrying both an F prime and an R factor
Authors: Willetts N. S. , Finnegan D. J. 
Published: September 2009

SUMMARYThe interrelationship between an F prime and an F-like or I-like R factor was studied inEscherichia coliK 12 strains carrying both. The donorability of such strains suggested that these plasmids were transferred independently by their own transfer systems. Plaque formation by several male- and female-specific phage was tested; the inhibition by Flacof several female-specific phage was not affected by an F-like R factor. Neither did an R factor affect the incompatibility between Flacand Fhis. However, the surface exclusion characteristic of Flacwas lost in the presence of an F-like R factor. This is probably closely related to the simultaneous loss of donorability, the F-pilus, and the f+antigen: all may be the result of the inhibition by an R product of the formation or activity of a single F product.
Genetics of nitrate reductase inUstilago maydis
Authors: Lewis C. M. , Fincham J. R. S. 
Published: September 2009

SUMMARYMutants ofUstilago maydishave been isolated both, deficient and derepressed for nitrate reduction. Those deficient in enzyme fall into six groups, one of which is the structural gene. Enzyme which has proved to be more labile than that of wild-type has been isolated from a temperature-sensitive mutant at this locus. All the mutants in the structural gene have xanthine dehydrogenase activity and the situation closely parallels that ofAspergillus nidulans.The derepressed mutants fall into four complementation groups and all are partially derepressed in that they are further inducible by nitrate. Full derepression can be conferred by induction of a second mutation. In one analysed case the second reinforcing mutation proved to be pheno-typically similar to the first one when separated from it.
Development of associative overdominance through linkage disequilibrium in finite populations
Authors: Ohta Tomoko , Kimura Motoo 
Published: September 2009

SUMMARYAssociative overdominance arises at an intrinsically neutral locus through its non-random association with overdominant loci. In finite populations, even if fitness is additive between loci, non-random association will be created by random genetic drift.The magnitude of such associative overdominance is roughly proportional to the sum ofbetween the neutral and the surrounding over-dominant loci, whereis the squared standard linkage deviation, defined between any two loci by the relationin whichpand 1 –pare frequencies of allelesA1andA2in the first locus,qand 1 –qare frequencies of allelesB1andB2in the second locus, andDis the coefficient of linkage disequilibrium. A theory was developed based on diffusion models which enables us to obtain formulae forunder various conditions, and Monte Carlo experiments were performed to check the validity of those formulae.It was shown that ifA1andA2are strongly overdominant whileB1andB2are selectively neutral, we have approximatelyprovided that 4Nec≫ 1, whereNeis the effective population size andcis the recombination fraction between the two loci. This approximation formula is also valid between two strongly overdominant as well as weakly overdominant loci, if 4Nec≫ 1.The significance of associative overdominance for the maintenance of genetic variability in natural populations was discussed, and it was shown thatNes′, that is, the product between effective population size and the coefficient of associative overdominance, remanis constant with varyingNe, if the total segregational (overdominant) load is kept constant.The amount of linkage disequilibrium expected due to random drift in experimental populations was also discussed, and it was shown thatin the first generation, if it is produced by extractingnchromosomes from a large parental population in whichD= 0.
Change of host range in a resistance factor
Authors: Anderson E. S. , Threlfall E. J. 
Published: September 2009

SUMMARYAn R factor for ampicillin and streptomycin resistance (AS) was identified inSalmonella enteritidis. The AS factor transferred freely toEscherichia coliK12, but only two of 260 K12(AS) clones from this cross would transfer AS toS. typhimurium, although all lines tested transferred it toS. enteritidisand K12. A study of one of the two exceptional lines“ revealed that it also transferred AS toS. paratyphiB,S. thompsonandS. anatum. The R factor maintained its transferability when cycled between these serotypes and K12. Transfer toS. enteritidis, however, resulted in loss of the ability of AS to transfer to the heterologous serotypes, that is, it apparently became host specific forS. enteritidis. S. paratyphiB andS. anatumalso imposed host specificity on AS, butS. typhimuriumandS. thompsondid not. The R factor would always enterS. enteritidis, whatever its previous salmonella host but, once it had done so, it became specific forS. enteritidis. AS could always transfer to K12, which did not seem to modify its host range. These phenomena are most easily explained by analogy with host-controlled modification of phage. Their possible significance in relation to apparent host specificity of R factors is discussed.
A test of the functional significance of the quantity of mitochondria in the spermatozoa of mice
Authors: Woolley D. M. 
Published: September 2009

SUMMARYFollowing an experiment in which mice had been selected for the length of the mitochondrial section (midpiece) of their sperm tails, an attempt has been made to determine experimentally the adaptive significance of this character; this was by the artificial insemination of mixtures of selected and unselected (control) spermatozoa, and the subsequent disclosure of their competitive fertilizing ability in the paternity of the offspring. After the birth of nearly 500 offspring, there was no indication that the control cells were—by this criterion—functionally superior. From the discrepancy between the pairs of males sampled, however, it is possible that other biological or technical factors have been important.
Selection for the length of the spermatozoan midpiece in the mouse
Authors: Woolley D. M. 
Published: September 2009

SUMMARYA subcellular dimension, the length of the spermatozoan midpiece, has been the subject of a two-way selection programme in mice. After thirteen generations of within-family selection the divergence between the selected lines amounted to 5·4 phenotypic standard deviations. The realized heritability was found to be 0·76 ± 0·02, dominance and commonenvironmental effects being apparently very small. The reality of the selection response was verified in measurements on live spermatozoa. Other measurements have shown that the change in the length of the midpiece has been independent of its width, and has occurred without a proportionate change in the length of the main-piece of the flagellum. An electron microscope study has shown that the selection has, in fact, brought about changes in the quantity of mitochondrial material in the sperm cells.
Genetic variation in the eel II. Transferrins, haemoglobins and esterases in the eastern North Atlantic. Possible interpretations of phenotypic frequency differences
Authors: Pantelouris E. M. , Arnason A. , Tesch F. W. 
Published: September 2009

SUMMARYComparison, by electrophoretic methods, of eel samples from Iceland, Scotland and Germany confirmed previous reports of uniformity in haemoglobin types. When liver esterases were examined, significant differences in the frequencies of phenotypes in the ‘fast’ zone of the electropherogram were found between samples from Germany and samples from Iceland and Scotland. The frequencies of transferrin phenotypes in Icelandic and Scottish eels differed significantly from those of French and American eels.It follows that regional differences in gene frequencies probably exist within the speciesAnguilla anguilla. The implications for the ‘atlantic eel problem’ are briefly discussed.
A new class of slow-growing non-perithecial mutants ofAspergillus nidulans
Authors: Houghton J. A. 
Published: September 2009

SUMMARYTwenty-four mutants ofAspergillus nidulanswere isolated which grew more slowly than normal on glucose as sole source of carbon and were unable to utilize intermediates of the tricarboxylic acid cycle. By complementation tests they were divided into five groups, each group representing a different cistron and the cistrons were assigned to linkage groups by mitotic analysis. The mutant loci have been designatedsgp-1 tosgp-5 respectively. Three mutants have been mapped by meiotic analysis.
A variegated position effect inAspergillus nidulans
Authors: Clutterbuck A. J. 
Published: September 2009

SUMMARYIn mutants at the ‘bristle’ locus ofAspergillus nidulansthe conidiophore remains as a stiff hypha rather than developing a vesicle, sterigmata and conidia. ThebrlA12 allele of this locus has a variegated phenotype, and genetic analysis has shown that this is associated with a translocation which has a breakpoint in the map interval adjacent to thebristlelocus.The mutant phenotype is partially repaired on high-salt medium at low pH, and can also be repaired by suppressors, one of which has been mapped at a locus unlinked tobrlA12.The mutant provides proof that variegation is due to instability of gene expression and not to mutability sincebrlA12 is genetically stable and can be propagated from either conidia or sterile conidiophores, the structures formed at the two extremes of variegation, and the resulting colonies in both cases are identical to the original strain.It has been shown by mitotic recombination that the translocation associated with the variegated mutant is a ‘simple translocation’ in which the distal half of linkage group VIII is attached to the end of linkage group III. This terminal attachment site does not appear to be damaged in any genetically detectable way.
The tolerance of aneuploidy in yeast
Authors: Parry Elizabeth M. , Cox B. S. 
Published: September 2009

SUMMARYSingle ascospore cultures from triploids were screened as a potential source of disomic tester stocks for the purpose of genetical mapping of chromosomes in yeast. A high tolerance of aneuploidy was found, and strains disomic for only one chromosome were rare. There was a high occurrence of strains disomic at specific chromosomes and in certain multiple combinations of disomic chromosomes.
Genetic effects of acridines onPseudomonas aeruginosa
Authors: Stanisich Vilma , Holloway B. W. 
Published: September 2009

Mutants ofPseudomonas aeruginosamale strains with altered mating properties have been obtained through treatment with nitrogen half mustards. The response varied with the type of male strain. A mutant of the infectious male PTO 13 was obtained which acts as a female strain and has apparently lost the FP sex factor. A mutant of the non-infectious strain 2 male mates not only with strain 1 females, but shows a thousand-fold increase in its ability to mate with strain 2 males, when it can act as either donor or recipient in conjugation. Derivatives of strain 1 males were obtained which had reduced recombinant forming ability.While acriflavine is ineffective in producing such mutants, and has not been shown to cure male strains of their sex factor inP. aeruginosa, it is very effective in inhibiting infectious transfer of FP from FP+to FP−strains. Furthermore, it markedly inhibits recombinant formation in 1 FP−× 1 FP+crosses, and this latter effect is thought to be due to the inhibition of chromosome transfer by the male parent. In view of the almost complete lack of effect of AF on the normal growth ofP. aeruginosait is likely that the control of chromosome replication during vegetative cell division is different from the occurring during conjugation and that the FP factor is involved in this control during conjugation.
The inheritance of the killer character in yeast
Authors: Somers J. M. , Bevan E. A. 
Published: September 2009

1. First- and second-generation crosses between killer, neutral and sensitive strains of yeast have been carried out in all combinations.2. The results of this analysis indicated that the killer character is under the control of two types of cytoplasmic genetic determinant. One type, (k), determines killing, and the other, (n), neutrality. The absence, (o), of both types of determinants confers the sensitive phenotype.3. That both types of cytoplasmic determinant require the same dominant nuclear allele, M, for their maintenance has been indicated in two ways. First, both types are lost when the nuclear genotype is changed from M to m. Secondly, cells of genotype m(k) or m(n), which have been shown to occur among the first formed cells arising from spores of Mm(k) and Mm(n) diploids respectively, are unable to maintain their cytoplasmic determinants. On the other hand, spore cultures of M(k) and M(n) genotype derived from these same diploide continue to maintain the determinants.4. Thus genotype of killer cells is M(k), of neutrals M(n), and of sensitivities either M(o) or m(o).5. Cells maintaining both types of cytoplasmic determinant (i.e. of genotype M(k)(n) or M−(k)(n)) have been obtained by appropriate crosses, and shown to be of killer phenotype.6. Alternative hypotheses to account for the results of this genetic analysis have been discussed.
Cytogenetical study in Spalax leucodon Nordm. in Moldavia (Rumania)
Authors: Raicu Petre , Duma Doina 
Published: September 2009

The karyotype of Spalax leucodon (2n = 56) from Moldavia (Rumania) shows 27 pairs of autosomes: two metacentrics, three submetacentrics, eight suhtelocentrics and 14 acrocentrics. The X chromosomes are the longest subtelocentrics and the Y chromosome is a submetacentric of medium size. In metaphase I we have found a partial homology between the short arm of the X and the Y chromosome.The population of S. leucodon from Moldavia shows considerable differences of karyotype as compared with other populations of the same species from the south of Europe. This species presents a high degree of chromosomal polymorphism in different populations.
A comparison of two methods for predicting changes in the distribution of gene frequency when selection is applied repeatedly to a finite population
Authors: Pike Derek J. 
Published: September 2009

Robertson (1960) used probability transition matrices to estimate changes in gene frequency when sampling and selection are applied to a finite population. Curnow & Baker (1968) used Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population to develop an iterative procedure for studying the effects of repeated cycles of selection and regeneration. To do this they assumed a beta distribution for the unfixed gene frequencies at each generation.These two methods are discussed and a result used in Kojima's paper is proved. A number of sets of calculations are carried out using both methods and the results are compared to assess the accuracy of Curnow & Baker's method in relation to Robertson's approach.It is found that the one real fault in the Curnow-Baker method is its tendency to fix too high a proportion of the genes, particularly when the initial gene frequency is near to a fixation point. This fault is largely overcome when more individuals are selected. For selection of eight or more individuals the Curnow-Baker method is very accurate and appreciably faster than the transition matrix method.
The rate of selection advance for non-additive loci
Authors: Hill W. G. 
Published: September 2009

Expected changes in the gene frequency and the population mean for a quantitative trait are described for selection in a population of sizeNat a single locus where the favoured allele has initial frequencyq0and selective values. Models of additive and completely dominant gene action are compared. Results are generally expressed as the half-life of the total change relative toN.If the favoured allele is additive or recessive the half-life of the gene frequency and mean of the trait are usually reduced whenq0orNsis increased. However, if the dominant allele is favoured the half-life of gene frequency is still generally reduced asNsis increased, but has a minimum at low or intermediate values ofq0. Since inbreeding depression and selection oppose each other when the dominant allele is favoured the response in the mean of the quantitative trait may change in direction during selection.
Kappa, mu and the metagon hypothesis inParamecium aurelia
Authors: Byrne Barbara J. 
Published: September 2009

1. The loss of mu 540, mu 138, and kappa 51 following the loss of the dominant genes required for their maintenance was studied. With mu 540 and mu 138 the loss usually occurred within 4–7 cell generations, but occasional cells with mu were found as late as generation 12 with mu 540 and generation 17 with mu 138. Kappa 51 was lost between 5 and 60 fissions in different clones. The variability in time of loss remains unexplained.2. No trail of inheritance of resistance to specific kappa killing comparable to the trail of inheritance reported for mu 540 by Gibson & Beale (1962) was found.3. No loss of kappa 51, mu 540, mu 138, or mu 130 was found following treatment of paramecia with RNase.4.Didinium nasutumwas shown to be able to acquire and maintain kappa 51 when it could not possibly have acquired any RNase-sensitive metagons from paramecia.5. These results show that the metagon hypothesis cannot be accepted without a number ofad hocand at present untestable assumptions.
Nucleic acid content and Chromosome morphology in Chrysanthemum
Authors: Dowrick G. J. , El Bayoumi A. S. 
Published: September 2009

1. The DNA contents of twenty-eight different species and forms of Chrysanthemum have been measured by photometry. It is shown that there are large differences in DNA content between some species with identical chromosome numbers.2. The DNA contents of natural polyploids are frequently not those expected when comparison is made with diploid forms of the same species. The DNA contents of induced polyploids are those expected.3. Chromosome length and volume are positively correlated with DNA content.4. The relationship between chromosome number, chromosome size, DNA content and gene number is considered, and it is suggested that the differences in DNA content may result from the presence of differing amounts of genetically inactive DNA in the chromosomes.
Gene-environment interactions of theeyelessmutant inDrosophila melanogaster
Authors: Hunt David M. , Burnet Barrie 
Published: September 2009

A method is described for quantifying the phenotypic expression ofeyelessusing gauged estimates of the mean and standard deviation of the distribution of facet numbers.Gene-environment interactions of foureyelessallelesey,ey2ey4andeyKare compared in different genetic backgrounds and on a standardized Pacific background. The original strains differ in mean phenotypic value and in direction of response to variations in the ribonucleic acid content of the larval culture medium, whereas the four Pacific strains are more concordant. Consequently these differences are in part attributable to modifier genes present in the different genetic backgrounds of the original strains. Modifier genes also influence the periods in development at whicheyelessis sensitive to nutritional treatments.On the standardized Pacific background deficiencies of cholesterol cause an increase, whereas deficiencies of RNA or thiamine cause a decrease in the expressvity of all foureyelessalleles, but non-identity of their interaction profiles over an array of different suboptimal environments suggest that they may form a group of heteroalleles.