bluuebunny/crossref_metadata_2025_split huggingface dataset:
The inheritance in wheat of crossability with rye
Authors: Riley Ralph , Chapman Victor 
Published: September 2009

1. By the use of intervarietal chromosome substitution lines, the poor crossability with rye (S. cereale, 2n = 14) of the wheat (T. aestivum, 2n = 42) variety Hope was shown to be determined by chromosomes 5A and 5B. The genes Kr1 and Kr2, which are responsbile for poor crossability (Lein, 1943), are probably located on chromosomes 5B and 5A respectively.2. Crossability is actively inhibited by the dominant alleles, Kr1 and Kr2, of Hope and is apparently not enhanced by the recessive alleles, kr1 and kr2, of the readily crossable variety Chinese Spring.3. The inhibition of crossability with rye conferred evolutionary and agricultural advantage upon wheat by preventing the production of sterile wheat-rye hybrids which could be regarded as weeds generated from within the crop.
A genetic study of primary and secondary reversions of sometryptophanAauxotrophs ofSalmonella typhimurium
Authors: Riyasaty S. , Dawson G. W. P. 
Published: September 2009

1. The linkage order of fourtryAmutants ofS. typhimurium, andcysB-12, is:Attempts to plot the position oftryA-50were unsuccessful.2. Some of the reversions oftryA-8,tryA-47,tryA-56andtryA-50were analysed genetically;tryA-52does not revert. All four auxotrophs gave reversions that were phenotypically and genetically indistinguishable from that expected by back-mutation of the original mutant site.3. BothtryA-8andtryA-50produced reversions that grew as wild-type but were due to unlinked suppressor mutations. Some of these were super-suppressors in that they suppressed bothtryA-8andtryB-4; others suppressed many site mutants in thetryAgene but did not suppresstryB-4.4. All the slow-growing reversions oftryA-8,tryA-50andtryA-56, and a minority of the semi-fast reversions oftryA-8, were due to unlinked suppressors.5. All the slow-growing reversions oftryA-47, the semi-fast reversions oftryA-56and the majority of the semi-fast reversions oftryA-8were due to genetic changes that were inseparable, in very extensive experiments, from their original mutant site.6. Slow-growing reversions oftryA-47produced faster growing mutants. Some of these were due to mutation in unlinked modifying genes and in others the genetic change was within thetryAgene. Nine of the latter had the genetic change just to the left of the47Ssite; in one the change was inseparable from the47Ssite. None had this further change to the right of the47Ssite. These further changes, in the absence of the47Ssite, gave prototrophic phenotypes; they are inter-site suppressors.
Four new linkage groups inCoprinus lagopus
Authors: Moore David 
Published: September 2009

1. By means of tetrad analysis three vitamin-requiring mutants have been established as markers of centromeres distinct from those of the two known chromosomes.2. Mutants existing in stock were tested for linkage with these centromere markers, and four previously unknown linkage groups with independent centromeres thereby established and accurately mapped.3. Corrections were made to the maps of existing linkage groups. TheAlocus (Group I) was shown to be approximately four times as distant from its centromere as hitherto supposed (at least in most crosses); and several markers of Group II were mapped for the first time.
On the induction of a recombination-deficient mutant ofEscherichia coliK-12
Authors: Ben-Gurion Renana 
Published: September 2009

A lysogenic, recombination-deficient bacterial mutant (rec−) can be induced to produce λind−C587 by a temperature shift, although it does not produce phage after u.v. irradiation when lysogenic for wild λ. When this mutant (rec−) was made colicinogenic for colicins E2 and I, colicin production was found not to be inducible.Superinfection of irradiated lysogenicrec−(λ) bacteria, at doses of irradiation that did not reduce their capacity to produce phage λ, was not productive. It seems therefore that a certain product(s) that usually arises following u.v. irradiation inrec+cells, and triggers the induction of lysogenic and colicinogenic cells by causing loss of immunity or repression, is not produced in therec−mutant. However, immunity is lost and the prophage is induced after a temperature shift inrec−cells which are lysogenic for λind−C857.
Polarized exclusion of bacteriophage T2 in crosses with T4
Authors: De Groot B. 
Published: September 2009

Four crosses were made between bacteriophages T4 and partially non-excludable T2exr+4. Each cross was designed as a four-factor cross: in total seven pairs of homologous genes were used as markers, extending over half the circular map from the locus for adsorption specificity (h+) along the map segment for the early functions to osmotic-shock sensitivity (o).The frequencies of T2 markers recovered in the progeny show polarized exclusion: the frequencies are low forh+2at the beginning of the map segment for the early functions and increasing too+2. Recombination of T2exr+4is restricted for all loci concerned and the recombinational events are probably non-reciprocal. Restriction of sequential replication from a fixed starting point is proposed to explain polarized exclusion of T2 genes. Non-homology is dicussed in relation to restricted recombination.
Homoeologous pairing of a chromosome from Agropyron elongatum with those of Triticum aestivum and Aegilops speltoides
Authors: Johnson Roy , Kimber Gordon 
Published: September 2009

1. Complex hybrids were produced having twenty-nine chromosomes, consisting of one telocentric and twenty complete chromosomes of T. aestivum (2n = 6x = 42), seven complete chromosomes of Ae. speltoides (2n = 2x = 14) and one telocentric chromosome derived from A. elongatum (2n = 10x = 70). The presence of the Ae. speltoides genome permitted pairing between homoeologous chromosomes at meiosis and the behaviour of the two telocentric chromosomes was observed.2. The A. elongatum chromosome was seen to pair with chromosomes homoeologous to those of group 6. There was no evidence that it paired with chromosomes of any other group.3. When the A. elongatum telocentric and those of 6A and 6D occurred in the same configuration it was evident that the telocentrics 6A and 6D were for corresponding chromosome arms, and the A. elongatum telocentric for the opposite arm.4. The average rate of pairing was much lower for the A. elongatum telocentric than for wheat telocentrics. Previous studies had indicated very good genetic compensation of the A. elongatum chromosome for chromosomes 6A and 6D. It was therefore indicated that genetic equivalence and pairing affinity were not closely related in this case. Some implications of this are discussed.
A partial deletion map of the galactose operon inE. coliK12
Authors: Davison John , Frame Robin , Bishop John 
Published: September 2009

We have isolated a number of λdgHFT lysates which carry proximal fragments of the galactose operon. Most of these have been shown to be different, and each terminates in either the kinase or transferase cistron. They divide the kinase cistron genetically into seven blocks of mutants, and the transferase into eight.When a λdgis used to transduce a bacterium which carries a mutation in a cistron which is intact in the λdgthe transduction frequency is high in the presence of λ-helper. This is attributed to integration of the transducing fragment at the λ-attachment site and complementation between the two operons in the heterogenote. When the same λdgtransduces a mutation lying in the cistron in which the λdgterminates, so that recombination within the galactose operon is obligatory, the transduction frequency is 10 to 1000 times less.In such cases there is a general increase in transduction frequency between distal mutations (i.e. those lying near the termination of the deletion) and proximal mutations, but the relationship does not hold for many individual pairs of mutants, probably due to physiological differences between the bacterial strains.
A study on simultaneous conversions in linked genes inAscobolus immersus
Authors: Paszewski Andrzej 
Published: September 2009

White-spored mutants ofA. immersuswere used in experiments carried out to study the relationship between conversions occurring simultaneously in linked genes, and to check whether conversion occurs at random in the two chromatids of a chromosome.Conversions in two loosely linked loci were shown to be independent of each other and randomly distributed between sister chromatids. On the other hand, conversions in two closely linked loci showed a high correlation of occurrence.
On the relationship between heterochromatization and variegation inDrosophila, with special reference to temperature sensitive periods
Authors: Hartmann-Goldstein Ingeborg J. 
Published: September 2009

Using a strain ofD. melanogastercarrying an X-4 translocation, comparison between groups of individuals cultured at 14°, 19° and 25°C. showed good correlation between heterochromatization, variegation in malpighian tubules andNotch. All these phenomena are enhanced by low temperatures. Correlation was less good within each temperature group, and considerable variability was observed between individuals within the group, and between nuclei from one individual.Experiments involving a temperature change during the embryonic period indicate that (1) heterochromatization is especially temperature-sensitive during the early embryonic period but may be increased by low temperature later, (2) larval malpighian tubules are sensitive to temperature only during the early embryonic stage, and (3)Nis influenced by temperature during early embryonic life and also during the larval period.Our observations, in conjunction with those of other workers, could be explained as follows: exposure of individuals to low temperature at a time when a specific system is beginning to differentiate will cause the processes concerned to be blocked in some cells. At least during the early embryonic stages this appears to involve heterochromatization of the relevant locus. Once the processes are established which will lead to the formation of a character, further heterochromatization has no effect on the phenotype. Temperature may affect pupal or adult phenotype in this way or by a direct action on the metabolic processes of cells.Further experiments showed: (1) the greatest temperature-sensitivity of all three phenomena within the first 6 hours of embryonic life; (2) striking fluctuations of the effect of temperature, especially within the early embryonic period; (3) close correspondence between all three phenomena in time of response to temperature. Some alternative interpretations are considered.
The initiation and development of the hair follicle population in tabby mice
Authors: Claxton J. H. 
Published: September 2009

Hair follicle initiation and development was examined in tabby mutants and compared with a previous study of this sequence in normal mice. Initiation commenced at about the 17th embryonic day and continued for 1 and possibly 2 days after birth. Although central primary follicle initiation was of shorter than normal duration, it was more rapid, with the result that the central primaries achieved a greater maximum density, and their total numbers were greater in tabby than in normal mice.In general structural terms, follicle group development proceeded normally except that no secondary follicles appeared, and for this reason, the mature grouping pattern of follicles was comparatively simple. Central primary follicles, the first to be initiated, were evenly spaced in the skin but the later association of lateral primaries with them was unusually close, and the resulting groups of primary follicles were relatively more compact in the mutants than they were in normal mice.No simple explanation in terms of the altered timing of follicle initiation or the reduced complexity of the follicle group could be given for the abnormalities of the tabby coat.Selection for high and low numbers of secondary vibrissae in tabby mice produced some correlated changes in the maincoat follicle population, but there was no apparent alteration to the time of onset of initiation. Evidently selection did not simply modify the effects of theTagene.
Genetic studies on mutations in species A and B of theAnopheles gambiaecomplex
Authors: Mason G. F. 
Published: September 2009

1. A number of mutants affecting changes in the pigment of larval and adultAn. gambiaeare reported.2. Two other pigment characters are also described. One of these, diamond, is probably inherited as a single factor.3. Two of the mutants are sex-linked and the experimental results showAn. gambiaeto have aDrosophilaform of sex-linkage.4. The sex-linked white-eye mutant is shown to be epistatic to the gene for collar and the characters diamond and red stripe.5. Attention is drawn to the difference in sex-linkage betweenAn. gambiae, andC. pipiensandAe. aegyptiwhich may indicate different methods of sex-determination.
The recognition of an alien chromosome segment translocated to a wheat chromosome
Authors: Kimber G. 
Published: September 2009

1. Chromosome 6B of T. aestivum, to which a small segment of an Ae. umbellulata chromosome had been translocated, was examined both by interference microscopy and in stained preparations.2. In the stained preparation a constriction was observed in the long arm of chromosome 6B and also a terminal knob that was also observed on chromosome A of Ae. umbellulata.3. These features were also observed by interference microscopy and in addition the portion of the chromosome 6B of Transfer distal to the constriction had different phase-retarding properties.4. It is concluded that the part of chromosome 6B distal to the constriction is the part of Ae. umbellulata chromosome A which carries the gene for the leaf-rust resistance of that species and of the wheat variety into which it was translocated.
Genetic studies inEudorina
Authors: Mishra Nawin C. , Threlkeld S. F. H. 
Published: September 2009

A formal genetic analysis of the heterothallic, colonial green algaEudorina eleganshas been described. Wild-type strains were found to be sensitive to different drugs when grown on minimal agar containing very low concentrations of these drugs. Mutant strains resistant to high concentrations of drugs have been isolated. These aremsr-500(resistant to 500 μg/ml of DL-methionine-DL-sulfoximine),ery-r-100(resistant to 100 μg/ml of erythromycin) andsr-100(resistant to 100 μg/ml of streptomycin). The wild-type phenotypes sensitive to these drugs have been designated asmss-500,ery-s-100andss-100respectively. Thesr-100also showed cross-resistance to other antibiotics belonging to the streptomycin group.On genetic analysis, themsr-500andery-s-100were found to be inherited in a Mendelian way. These alleles are not linked to each other or to the mating type locus. The inheritance of mating type was found to be due to a single gene difference.The inheritance ofss-100/sr-100was found to be non-chromosomal and was characteristically uniparental, always transmitted through the female parent. The evidence for the non-chromosomal gene (NC genes) controllingsr-100/ss-100phenotypes in this organism has been derived from the exceptional zygotes in which the male parent apparently transmits streptomycin resistance to the progeny. Although ultraviolet or gamma-radiation resulted in normal survival curves of the exposed cells, no mutant deficient in any nutritional requirement was isolated.
Inhibition of mitochondrial synthesis in yeast by erythromycin: cytoplasmic and nuclear factors controlling resistance
Authors: Thomas D. Y. , Wilkie D. 
Published: September 2009

Erythromycin-resistant mutants were separated into two categories showing Mendelian and non-Mendelian inheritance of resistance respectively. The cytoplasmic factor was located in the mitochondrion based on the fact that the loss of the mitochondrial genetic unit associated with the petite mutation (the ρ factor, assumed to be the mitochondrial DNA) resulted in a corresponding permanent loss of resistance. Conversely, the petite mutation in gene resistant mutants had no effect on the inheritance of resistance.Analysis of vegetative and sexual progeny of isolated zygotes from a number of crosses between resistant and sensitive strains indicated that different mitochondrial types, both sensitive and resistant, co-exist in the yeast cell and are distributed at random among daughter cells under non-selective conditions. Only resistant mitochondria are in evidence if zygotes are put down to proliferate on medium containing the antibiotic.Resistant strains were tested for retention of resistance following anaerobic culture (known to cause disruption of mitochondria). The cytoplasmic mutants retained their resistance but two gene-resistant mutants tested both lost their resistance. It was suggested in the latter case that resistance is dependent on the existence of intact mitochondrial membrane (possibly inner membrane). In the former mutants the mechanism of resistance may be the alteration of one or other of the components of the protein-synthesizing system of the organelle.
The effects of nutritional deficiencies on themaroon-likematernal effect in Drosophila
Authors: Chovnick A. , Sang J. H. 
Published: September 2009

1. Themaroon-likematernal effect, present whenma-lflies are bred from non-mutant mothers, is not found among the late emergents from normal cultures. The hypothesis that this is due to a deficiency of some nutrient(s) in old cultures is tested by growing larvae on defined, germ-free media with the nutrients reduced one at a time.2. Omission of lecithin (but not reduction of casein, sucrose, RNA or cholesterol) decreases the percentage of maternally affected emergents, in proportion to the lowering of the lecithin supply. This is not a consequence of choline deficiency but of the shortage of fatty acids. Oleic, palmitic and linoleic acids can substitute for lecithin, when adequate choline is provided.3. Pantothenic acid, nicotinic acid, thiamine and biotin deficiencies (but not reduced pyridoxine, riboflavine or folic acid) also lower the proportion of maternally affected flies. There is an interaction between pantothenic acid and lecithin, but not between lecithin and the other effective vitamin deficiencies.4. Addition of the excretory product hypoxanthine to the complete diet significantly lowers the proportion of maternally affected emergents, but equivalent amounts of uric acid, or of guanylic acid, do not. It is argued that the quantitive relationships make it improbable that accumulation of excretory products play any great part in the disappearance of the maternal effect, whereas it is more likely that nutritional deficiencies do.5.ma-llarvae grown on low lecithin have the same complement of xanthine dehydrogenase as those reared on normal lecithin. The lecithin effect is therefore assumed to operate by affecting the pattern of pteridine synthesis. Phenylalanine, which would also be expected to alter this pattern, modifies the maternal effect similarly.
The production and characteristics of diploids inUstilago violacea
Authors: Day A. W. , Jones J. K. 
Published: September 2009

1. Forty-nine auxotrophic mutants were isolated after irradiation with ultraviolet light. The biochemical requirements were identified and the response to possible precursors tested in some of them.2. Diploid colonies were synthesized from compatible, auxotrophic haploid strains on an artificial medium by an adaptation of the balanced heterokaryon technique. Selection of diploid cells was especially convenient as the dikaryon cannot grow on such media, and is therefore only a transitory stage under these cultural conditions. Diploid cells were different in shape and size from haploids, and gave rise to colonies which could be distinguished by eye from haploids. The way in which diploid colonies arose from fusions between haploid cells was followed by microscopic observation. When known numbers of fused haploid cells were plated on minimal medium, diploid colonies occurred at a frequency of 3 × 10−4.3. Diploid cells, heterozygous for mating-type alleles, were incompatible with either haploid mating-type (i.e. neutral).4. Diploid cells could infect the host plant as a pure culture (i.e. they are solopathogenic).5. Meiotic and mitotic segregation of the large-celled strains was used to confirm diploidy. Spontaneous mitotic segregation was very rare. Mitotic crossing-over was induced at a high frequency by irradiation of diploid cells with ultraviolet light. A convenient technique for induced haploidization was devised usingp-fluoro-phenylalanine. Preliminary evidence using this technique indicates a haploid chromosome number of at least seven.6. It is considered thatU. violaceahas many advantages as an organism for genetical research, especially for analysis of the parasexual cycle.
Chromosomal and extrachromosomal transmission of cellular melanization in the Freckled phenotype in Drosophila melanogaster
Authors: Barigozzi C. , Gorla M. Sari 
Published: September 2009

Freckled (Frd) is a dominant mutant of D. melanogaster, lethal in double dose, which manifests itself by melanization in the adult stage, while nothing can be noticed in the larva and/or in the pupa. Its localization has been determined at nearly 102 of the second chromosome.Among the offspring from backcrosses involving Frd, some individuals that do not carry the Frd gene exhibit a weak Frd manifestation in the adult stage, or a stronger one, mostly lethal, in the larval or pupal stage. Weak Frd, indicated as [Frd], is transmitted indefinitely without any recognizable linkage with the chromosomes, although its frequency is influenced by the 1st and, probably, by the 3rd chromosome. No matroclinous transmission has been found. It is concluded that [Frd] is probably controlled by an extrachromosomal entity, not located in the cytoplasm. The possible relationships between Frd and [Frd] are discussed.
Demonstration of different mutational sites controlling rhamnose fermentation in FIRN and non-FIRN rha−strains ofSalmonella typhimurium: an essay in bacterial archaeology
Authors: Morgenroth A. , Duguid J. P. 
Published: September 2009

Observations of mutation and phage-mediated transduction of rhamnose-fermentation properties were made on two groups of wild-type rhamnose-non-fermenting (rha−) strains ofSalmonella typhimuriumisolated in several different countries. The ‘FIRN’ group included twenty-three strains in the biotypes 15, 16, 17 and 18, and the ‘non-FIRN rha−’ group included fourteen strains in a new biotype, provisionally designated 19 X d. The two groups showed different patterns of mutational behaviour and the pattern was uniform for the different strains in each group. Non-FIRN rha−strains gave rise directly to colonies of rha+mutant bacteria in platings on rhamnose minimal media. FIRN strains were unable to do this, but produced rha+bacteria by two successive mutations, the first of which yielded weakly fermenting (rhaw) bacteria capable of fermenting rhamnose in peptone water, but not of utilizing it for growth on minimal medium.Rha+recombinant bacteria were produced in transductional crosses between any one FIRN strain and any one non-FIRN rha−strain, but not in any cross between one FIRN strain and another FIRN strain or between one non-FIRN rha−strain and another non-FIRN rha−strain. These findings suggest that although the sites of the rha−mutations are different between the FIRN and non-FIRN rha−groups, they are located at identical sites on the chromosome in all strains in either group. It is concluded that all FIRN strains have probably descended from a single ancestral strain which underwent mutations at two sites in the rhamnose region of the chromosome and that all non-FIRN rha−strains have descended from a single ancestral bacterium which underwent a mutation at a third site in the rhamnose region.