bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selection for a threshold character in Drosophila I. An analysis of the phenotypic variance on the underlying scale
Authors: Latter B. D. H. 
Published: September 2009

The short-term response to artificial selection in a wild-type population for increased scutellar bristle number, has been interpreted in terms of two alternative threshold models. Both models have been shown to give a satisfactory transformation of the scale of measurement, in that the underlying variable shows an effectively linear response in terms of the accumulated selection differential, and the pheno-typic variance on the underlying scale remains virtually unchanged over a period of generations sufficient to increase the incidence of extra-bristles to almost 100%.A genetic analysis based on the bivariate model, which to a large extent takes account of the location of the supernumerary bristles, has shown the phenotypic variance on the underlying scale to have the following composition: the additive genetic variance is 27·2 ± 0·9% of the total, and the developmental error or ‘chance’ variance accounts for a further 63·8 ± 2·6%, so that the remaining 9·0 ± 2·7% of the variance must be due to environmental differences among individuals and to non-additive genetic effects.The relative magnitudes of these parameters are remarkably similar to those observed for two quasi-continuous variables in the same population, viz. abdominal and sternopleural hair number. In view of the ease with which scutellar bristles may be scored, the character can therefore serve as an extremely useful model character for quantitative genetic experiments.
Complementation in balanced heterokaryons and heterozygous diploids ofAspergillus nidulans
Authors: Roberts C. F. 
Published: September 2009

1. Two total and five leaky sorbitol mutants isolated inAspergillus nidulansby defective growth on the sugar are all recessive. The mutants are closely linked, they appear to represent three linked genes spanned by a deletion.2. Mutants which complement in heterozygous diploids do not complement in balanced heterokaryons. Failure to complement is a property of the mutants and not the result of a nutritional interaction or an unfavourable nuclear ratio in the heterokaryons.3. Sorbitol is oxidized by an inducible enzyme system in the wild-type. There are at least two enzymes concerned in the oxidative assimilation of sorbitol, an initial oxidative enzyme, which is defective in the leaky mutants, and a later enzyme defective in the total mutants. There may also be a second non-oxidative pathway for sorbitol metabolism.4. In diploids complementary pairs of mutants oxidized sorbitol at 75% the rate of the wild-type but non-complementary mutants did not oxidize the sugar. In balanced heterokaryons none of the pairs of mutants oxidized the substrate. It is concluded that failure ofinter-genic complementation in the heterokaryons is the result of a failure of either enzyme formation or enzyme function. Models to account for differences in enzyme formation in heterokaryons and diploids are suggested.
Egg albumen polymorphisms in the fowl: The ovalbumin locus
Authors: Lush I. E. 
Published: September 2009

1. Ovalbumin was shown, by starch gel electrophoresis, to exist in two genetically different forms, A and B. It was suggested that these are determined by two alleles at one locus, namedOv.2. Ovalbumin of each genetic type is electrophoretically heterogeneous. Dephos-phorylation of each type with human prostatic phosphatase and calf intestinal phosphatase removed some of the heterogeneity, but some remained.3. The genetic difference was shown not to reside in the fragment released from ovalbumin by the proteolytic enzyme subtilisin.4. The genetic difference was evident in the ovalbumin present in the fluid contained in right oviduct cysts.
Episomic suppression of phenotype inSalmonella
Authors: Smith-Keary P. F. , Dawson G. W. P. 
Published: September 2009

1. An auxotroph ofSalmonella typhimurium, pro-401, was isolated in a strain that was unstable at thesu-leuAlocus. The auxotrophy ofpro-401is probably due to the attachment of a controlling episome to the proline region of the genome where it suppresses gene expression.2. The controlling episome frequently transposes over short distances so that all clones consist of cells, mixed for the site at which the controlling episome is attached; homologous transductions yield prototrophs.3. The controlling episome can transpose to a different complementation group; homologous transductions yield abortive transductants; syntrophism occurs between cells that are ‘mutant’ in different complementation groups to give reversions consisting entirely of auxotrophic cells which are called auxotrophic reversions.4. The controlling episome transposes over very short distances and never to beyond the limits of this proline region of the genome; no wild-type reversions were found.5. The controlling episome can be located at relatively distant proline sites in different clones; prototrophs from transductions between clones that are separated by many subculturings can be 100 times more frequent than from homologous transductions.6. The controlling episome has its frequency of transposition to different complementation groups increased by UV; irradiation increases the frequency of auxotrophic reversions.7. The controlling episome continues to transpose in stored cells.8. The pattern of reversions ofpro-401is different in these studies from its pattern two years previously. This is discussed.
A gene conferring actidione resistance and abnormal morphology onPhysarum polycephalumplasmodia
Authors: Dee Jennifer , Poulter Russell T. M. 
Published: September 2009

SUMMARYPlasmodia ofP. polycephalumhomozygous and heterozygous for a mutation (act) which confers resistance to actidione on the haploid amoebal stage have been tested for resistance to actidione in liquid semidefined medium. Growth of homozygous resistant (act/act) plasmodia determined by protein or pigment assay was inhibited less by actidione than growth of homozygous-sensitive or heterozygous plasmodia. The mutant (act) is therefore recessive but, contrary to a previous report, confers resistance on homozygous plasmodia. The same mutation affects the morphology of homozygous (act/act) plasmodia on agar medium, causing slow growth, fragmentation and excessive sliminess.
Repression of induction by u.v. of λ phage byexrAmutations inEscherichia coli
Authors: Donch John , Greenberg Joseph , Green Michael H. L. 
Published: September 2009

SUMMARYThe effect of ultraviolet radiation (u.v.) onλlysogens ofexrAstrains ofEscherichia coliwas studied.exrAstrains could be lysogenized with, as well as support the vegetative reproduction of, λ. However, though spontaneous induction of λ occurred inexrA(λ) strain at 10% the frequency ofexrA+(λ) strain,exrA(λ) strains were not induced by u.v. Because λ was not induced inexrA(λ) strains, lysogens of these strains were no more sensitive to u.v. than were non-lysogens.The heat-inducible mutant λhcI857could be induced inexrAstrains at elevated temperatures. Furthermore, u.v. irradiation ofexrA(λhcI857) strain did not prevent the heat induction of this λ mutant. TheexrAmutation appeared to interfere only with the inactivation of λ repressor by u.v.Among theexrAstrains studied was strainBs1(exr A uvrB). Whereas the λ lysogen of strain Bsl could not be induced by u.v. and was no more sensitive to u.v. than its non-lysogen, theexrA+uvrB(λ) derivative of strain Bsl could be induced by u.v. and was more sensitive to u.v. than its non-lysogen.
Selection in experimental populations ofDrosophila pseudoobscurawith different initial frequencies of chromosomal variants
Authors: Watanabe T. , Anderson W. W. , Dobzhansky Th. , Pavlovsky O. 
Published: September 2009

SUMMARYEight experimental populations ofDrosophila pseudoobscurawere made in laboratory population cages. All were polymorphic for ST, AR, CH, and PP gene arrangements in their third chromosomes, and all the chromosomes were of the same geographic origin. The initial frequencies of the gene arrangements were, however, different in the different populations. Natural selection has caused frequency changes in all the populations, from which we have attempted to infer the adaptive values of the different karyotypes. There was no evidence that the adaptive values were different in the populations begun from different initial frequencies of the inversions, although our ability to demonstrate such differences is severely limited. The selection process in these populations has been complex, and the simple model of constant adaptive values does not fit.
The nature of the leucine requirement of the barley mutant Xan-b61
Authors: Land J. B. , Norton G. 
Published: September 2009

SUMMARYContrary to previous reports, evidence has been presented which indicates that Xan-b61, a Xantha mutant of barley, does not have an auxotrophic requirement for leucine. It has been shown that this mutant, when grown under appropriate conditions in the absence of leucine, will synthesize leucine and will continue to grow for an extended period of time.
Genetic fine structure of the albino (al) region ofNeurospora crassa
Authors: Subden R. E. , Threlkeld S. F. H. 
Published: September 2009

SUMMARYBy crossing a pair of albino strains each with a different adjacent nutritional marker and then crossing the same pair of albino markers with the nutritional markers transposed it was possible to order a series ofalmutants with a resolution approaching that available for nutritional markers. A genetic map with approximated distances is provided demonstrating a grouping of mutant sites for a range of discrete carotenoidless phenotypes.
A search for temperature-sensitive mutants ofUstilago maydisblocked in DNA synthesis
Authors: Unrau P. , Holliday R. 
Published: September 2009

SUMMARYOver 400 temperature-sensitive mutants ofUstilago maydishave been tested for DNA synthesis at the restrictive temperature of 32°C by measuring14C adenine incorporation into DNA and RNA. Five mutants were defective in DNA synthesis but none was completely blocked. One mutant,tsd-1, which is unlinked to the others, forms long uninucleate filaments at 32°C which die exponentially after 4h temperature treatment. The phenotype is comparable to that of thymine-starved bacteria, but it is possible that rather than being specifically defective in DNA synthesis the mutant is blocked in nuclear division.
Genetic and phenotypic relationships between ovulation rate and body weight in the mouse
Authors: Land R. B. 
Published: September 2009

SUMMARYThe genetic and phenotypic regressions and correlations between ovulation rate and body weight were examined in a random bred strain (Q) of laboratory mice during the course of three experiments. These experiments were (1) a sib analysis; (2) selection for natural and induced primiparous ovulation rate; and (3) replicated selection for 6-week weight. The following results were obtained:(a) The genetic correlations between body weight and natural and induced ovulation rate were positive, and approximately equal to 0·4 and 0·6 respectively.(b) The genetic regressions of natural and of induced ovulation rate on body weight were approximately 0·4 and 0·9 eggs per gram respectively.(c) The genetic regressions of body weight on natural and on induced ovulation rate were approximately 0·5 and 0·25 g per egg respectively.(d) The phenotypic correlation between natural ovulation rate and body weight was approximately 0·4 and the corresponding regression of ovulation rate on body weight approximately 0·4 eggs per gram.(e) The phenotypic correlation between induced ovulation rate and body weight declined from 0·4 at 6 weeks of age to zero at the time of scoring, the corresponding regressions of ovulation rate on body weight declining from 0·1 eggs per gram to zero.It was concluded that natural ovulation rate itself, and both its components (FSH activity and ovarian sensitivity) are positively genetically correlated with body weight. Furthermore, the observation that large mice shed at least as many eggs as small ones in response to the same dose of PMS showed that the response was more closely related to the absolute dose than to the resultant concentration.
Controlling elements in the mouse X-chromosome
Authors: Cattanach B. M. , Perez J. N. , Pollard C. E. 
Published: September 2009

SUMMARYThe frequency and nature of the changes in ‘state’ of the mouse X-chromosome controlling element (inactivation centre) have been investigated on an inbred background. The results indicate with near-certainty that meiotic crossing over is the responsible mechanism and that the frequency of recombination between theT(1; X)Ctbreakpoint and the locus of the controlling element is approximately 3%. Maize-type ‘changes in state’ may occur under other experimental conditions. The data do not distinguish on which side of the autosomal insertion the element lies but when combined with observations of other investigators suggest that the location must be on theMo-Taside and very close toTa.
The effect of individual rye chromosomes on the amino acid content of wheat grains
Authors: Riley Ralph , Ewart J. A. D. 
Published: September 2009

SUMMARYAt the present time attempts are being made to improve the nutritional value of wheat by increasing the content of certain essential amino acids, particularly lysine, in the proteins of the grain. Rye grain has a considerably higher lysine content than that of wheat. Consequently in the present work studies were made of the amino acid contents of the grains of the wheat variety Holdfast, the rye variety King II, the Triticale derived from these parental varieties and the seven lines in which, in turn, each pair of chromosomes of King II are separately added to Holdfast.Rye chromosome I increased the lysine content of wheat by 8·7% and associated changes in the proportions of other amino acids suggest that this increase is meaningful. Rye chromosome I is in homoeologous group 5 and other reports have indicated a relationship between changed lysine content and another character determined by chromosomes of this group. Consequently there is a suggestion that group 5 chromosomes may be of particular significance in the determination of lysine content in wheat grains. Confirmation of this would lead to a more rational approach to breeding for higher lysine content.
A gene triplet in the mouse
Authors: Searle A. G. , Truslove Gillian M. 
Published: September 2009

SUMMARYMice heterozygous for rump-white (Rw) have white hair in lumbo-sacral and caudal regions, although the tail-tip is sometimes pigmented. The homozygote is lethal in utero. No recombination has been found between Rw and the very closely linked spotting genes patch (Ph) and the viable allele of W (Wv). The compounds between these genes are all viable and fertile, although individual homozygotes are either lethal (Ph, Rw) or sterile and anaemic (Wv). It is concluded that they are non-allelic, but form a gene triplet. Close linkage between a cluster of dominant spotting genes and an angora gene in mouse and rabbit provide evidence for homology of part of linkage group II in the rabbit and part of linkage group XVII in the mouse.
Cell number in early embryos from strains of mice selected for large and small body size
Authors: Bowman Patricia , McLaren Anne 
Published: September 2009

SUMMARYEmbryos were recovered 3½ days post coitum from females of three replicate large- and small-selected Q-strain lines, together with their unselected control lines. Selection had been carried out by D.S. Falconer, resulting in large and small lines which differed two-fold in adult body weight. Females of the large lines yielded significantly more embryos than those of the other lines. Embryo cell number showed significant heterogeneity among replicates, but was similar in large, small and unselected lines. The data are not consistent with the hypothesis that the divergence in adult body weight is due to a uniform difference in rate of cell division throughout development.
Association of genetic polymorphisms with embryonic mortality in the chicken: II. The B blood-group system and the pure and crossbred progeny of two populations
Authors: Gilmour D. G. , Morton J. R. 
Published: September 2009

SUMMARYWe have studied the association of the ten possibleBblood-group genotypes with mortality during incubation in the 1966 generation of two relatively noninbred populations of Light Sussex chickens. These were related substrains 6D and 6F derived in the 1964 generation by equal division of strain 6, which we had previously studied in its 1962 generation. TheBblood-group genotypes of zygotes but not of dams were associated with marked mortality differences in 6F, while in 6D almost no differences were found. Comparisons of the findings in 6D and 6F with the results previously published for the ancestor strain 6, after adjustment for overall between-population differences, showed marked changes between 6 and 6F in the mortalities associated with the five most frequent genotypes. In four of these, the mortalities in 6D were about half way between those in 6 and 6F. Taken together, these results provide evidence that the selective pressures on theBlocus from differential embryonic mortality vary from generation to generation and even between populations differing apparently only slightly in environment and genetic composition.In progeny of crosses between females from 6D and 6F with males from 5D and 5F respectively, the latter being two related Rhode Island Red/New Hampshire substrains, embryonic mortality was much lower than in the pure matings within 6D and 6F, and only a few associations withBblood-group genotypes of zygotes were found.The results are discussed in relation to the general lack of association of polyallelic polymorphisms with aspects of fitness reported by other workers; and the importance is stressed of studying associations of genotypes rather than genes or serological factors.
DNA feeding and directed mutagenesis in Drosophila melanogaster
Authors: Chopra V. L. 
Published: September 2009

SUMMARYThe mutagenic effects of feeding calf-thymus DNA to larvae of Drosophila melanogaster have been studied on second chromosome recessive lethals, sex-linked dominant and recessive visibles and dominant autosomal visible mutations. While a positional specificity of DNA-induced lethals has been confirmed, no evidence has been obtained for a preponderance of visible mutations or for a specificity of phenotype among the visibles.
Some new mutants of the Large Milkweed BugOncopeltus fasciatusDall
Authors: Lawrence Peter A. 
Published: September 2009

SUMMARYThree new autosomal mutants of the milkweed bug,Oncopeltus, obtained by treatment with ethylmethane sulphonate, are described and compared with the two other previously known variants. Preliminary data are given on the results of testcrosses and of chromatographic analysis of some pteridene pigments.
Small, inherited differences in blood glucose levels in mice
Authors: Charlesworth Deborah 
Published: September 2009

Blood glucose levels of mice from five strains were measured. The results showed that each strain was different from the others for genes affecting blood glucose level, although the strain differences were small.Within strains, the chief sources of variation were sex differences, differences between mice from different litters of the same mother, and between mice assayed in different months. Repeatability of measurements on individual mice was low. Genetic analysis, even by biometrical techniques, was not possible because the small genetic effects were obscured by variation due to other causes.
The effect of homozygous deletions upon heterozygote formation in bacteriophage T4D
Authors: Kvelland Ingerid 
Published: September 2009

Experiments were designed to investigate the effect of homozygous deletions upon the frequency and the average length of heterozygous regions in bacteriophage T4D. A long deletion,rdf41, which covers at least the wholerII region, was found to increase the heterozygosity forr48, while no increase was observed when a short deletion was employed. The long deletion was found to increase the average length ofamber-HETs by a length approximately the size of therII region.A drastic reduction in average HET length was found in FUDR crosses homozygous for the long deletionrdf41, indicating that the type of HET that does increase in FUDR is very short.In the cross with no deletion in either parent, premature lysis HETs were found to be much longer than normal lysis HETs. Assuming that redundancy HETs are long compared to heteroduplex HETs this result indicates that redundancy HETs are made earlier in the latent period than heteroduplex HETs. A fluctuation in HET frequencies was found for different markers, especially in FUDR.About half of all HETs, both in normal crosses and in FUDR crosses, was found to be parental for outside markers.In non-FUDR crosses, polarized segregation was shown by 12 out of 27 multi-marker HETs after normal lysis and 5 out of 22 multi-marker HETs after premature lysis. In FUDR crosses, 24 out of 77 multi-marker HETs showed polarity.
Sexual and parasexual analysis ofUstilago violacea
Authors: Day A. W. , Jones J. K. 
Published: September 2009

Forty-two mutants of the anther smut fungusUstilago violaceawere mapped by means of complementation tests, mitotic haploidization, and meiotic segregation. Spontaneous mitotic haploidization was very rare, but haploids were induced at a high frequency usingp–fluorophenylalanine (PFP). Haploid segregants appeared as fast-growing, spherical colonies (papillae) which grew away from the diploid growth on PFP medium. Thirty-three markers, classified by complementation tests into 21 genes, were mapped by mitotic haploidization in 10–12 linkage groups. There were no discrepancies in the linkage data, and all the markers could be assigned unequivocally to linkage groups. Although about 250 diploids were analysed, there were no segregants in which mitotic crossing-over and mitotic haploidization appeared to have occurred simultaneously.Thirteen of the 33 markers, in six or seven genes, were expressed infrequently (0–5%) in the papillae produced on PFP medium. These markers, which behaved unusually and were designated missing-markers, were found to be on two chromosomes which tended to remain disomic on PFP medium. Thus 8–10 chromosomes haploidize readily on PFP medium, whereas two other chromosomes are resistant to the effects of PFP and remain disomic. Meiotic segregation was investigated in crosses of genetically marked haploid stocks and also hi diploids, using the host plant. Some of the results enabled preliminary maps to be made of three linkage groups. The results from meiotic segregation were fully compatible with those from mitotic haploidization and the complementation tests.The genetical evidence for a haploid chromosome number of at least 10–12 is in conflict with the observations of several cytologists thatn= 2 in this species.
Methionine suppressors inAspergillus nidulans: their genetics and behaviour in heterokaryons and diploids
Authors: Ayling P. D. 
Published: September 2009

Nine methionine mutants ofAspergillus nidulans(six new mutants plus three isolated previously) were examined; five responded to homocysteine, none responded to cystathionine or cysteine.Ten revertants of one of the mutants,methB3, blocked before homocysteine, were shown to be due to suppressor mutations. The suppressors were divided into six genes on the basis of complementation tests and recombination data. Mutants of two of the genes were semi-dominant in the heterokaryon but recessive in the diploid. Experiments in which conidial ratios in the heterokaryons were determined suggested that semi-dominance of these suppressors is due to a shift in nuclear ratios in the heterokaryon in favour of the suppressor nuclei.Some of the suppressors were tested for suppression of two other methionine loci; they acted onmethG1blocked before homocysteine, but not onmethH2blocked after homocysteine, although four out of 13 crosses tested gave ambiguous results.