bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental sequence of chromosome number in a cytologically unstable Rubus hybrid
Authors: Haskell G. , Tun N. N.
Published: September 2009

1. Serial cytological observations were made on one abnormal seedling from the thornless segregants of the F2 progeny from crossing two tetraploid (2n = 28) Rubus species. The number of root-tip chromosomes was found to vary between 9 and 46 per cell, with the mode always at 35. The wide variation in chromosome number decreased with time, until there was almost stability at 2n = 35. A vegetative (stipule) cell was 2n = 39. The numbers lower than 35 were not due to terminal fusion.

2. Evidence from the number of satellites per cell suggests that not always were the same chromosomes being eliminated, although there is a general increase in satellite number with increased numbers of chromosomes per cell.

3. There was a correlation between the chromosome numbers and corresponding cell sizes within the aneuploid series. This may be associated with the incremental change of DNA following the addition or subtraction of individual chromosomes, which are highly similar in Rubus.

4. The cause of the instability was not definitely established. Its initiation is probably attributable to the egg mother cell, as Rubus pollen reacts sensitively to chromosome unbalance. No abnormalities were observed in the mitoses, and virus infection was not responsible for the instability.

5. Chromosome number instability of this plant is discussed in relation to other examples from the same and different genera: it is suggested that the changes in chromosome number known in various Rubi may have arisen somatically.
Genetical studies on the skeleton of the mouse XXVII. The Development of oligosyndactylism
Authors: Grüneberg Hans
Published: September 2009

The complex anatomy of the adult limb skeleton of Os/+ mice is attributable to a reduction of the preaxial margin of the foot plates. This is detectable, in the fore limbs, in the 11-day stage, i.e. before condensations of mesenchyme have taken place. The involvement of the skeleton is thus secondary to an earlier defect in the foot plates. The cause of the latter has not been discovered.
A further examination of the relative efficiency of three methods of selection for genetic gains under less-restricted conditions
Authors: Young S. S. Y.
Published: September 2009

The relative efficiency of three methods of selection (index, independent culling levels and tandem) is compared in terms of genetic gains in economic units. The comparison covers cases where variances, heritabilities and economic weights are unequal, while the case of two correlated characters is also examined. Various factors may influence the relative efficiency, including selection intensity, the number of traits under selection, the relative importance of those traits (in terms of a factor λ, which is the product of economic weight, heritability and phenotypic standard deviation), and the correlations between them.

The conclusions are:

(i) In all circumstances the index is never less efficient than independent culling levels, though in some cases it is no more efficient. Independent culling is, in turn, never less, but in some cases no more efficient than tandem selection.

(ii) The superiority of the index over other methods increases with an increasing number of traits under selection, but decreases with increasing differences in relative importance, its superiority being at a maximum when the traits are of equal importance. The superiority of the index over independent culling levels decreases with increasing selection intensity, but its superiority over tandem selection is independent of intensity.

(iii) The superiority of independent culling over tandem selection increases with increasing selection intensity or an increasing number of traits under selection, but decreases with increasing differences in relative importance.

(iv) The relative efficiency of the index over other methods is much affected by the phenotypic correlation between traits when the traits are of equal importance, the relative efficiency of the index being higher when the phenotypic correlation is low or negative. The effect of genetic correlation is only apparent when the traits are of unequal importance and its influence on relative efficiency changes with changes in other parameters.

(v) The relative efficiency of selection methods may be changed by their use for special purposes.
Tipsy, a new mutant in linkage group VII of the mouse
Authors: Searle A. G.
Published: September 2009

Tipsy (symbol ti) is a fully penetrant recessive mutant in linkage group VII of the mouse. Homozygotes have a peculiar rabbit-like gait from the age of a week, followed soon after by a tendency for the fore-part of the body to sway from side to side, leading to a reeling locomotion with falling over in severely affected mice. There is marked variation in manifestation and some amelioration in older animals; both sexes are fertile.

Linkage relationships in group VII are discussed and tipsy is compared with other mutants showing locomotor instability.
XXY Mice
Authors: Cattanach Bruce M.
Published: September 2009

Welshons & Russell (1959) have presented data to show that the XO chromosomal constitution in the mouse is female. This conclusion was based on results of genetical tests with sex-linked markers and on chromosome counts. All XO females were matroclinous, that is, they had inherited their X-chromosome from their mother. Females of this type will arise when non-disjunction occurs in the meiotic divisions of the father and results in spermatozoa without a sex-chromosome. Alternatively, the paternal sex-chromosome may be lost from the fertilized ovum if non-disjunction of sister-chromatids occurs during the first cleavage division. This latter explanation has been urged by Ohno, Kaplan & Kinosita (1959), who found no evidence for non-disjunction of the X-and Y-chromosome in an extensive cytolosical examination of the mouse testis.
Inbreeding in artificial selection programmes
Authors: Robertson Alan
Published: September 2009

In a population under artificial selection, the effective population size may be less than the actual number of parents selected because there will be variation between families in the character under selection and consequently in the probability of selection. Expressions are developed for the magnitude of the effect, which will be greater the more intense the selection and the higher the heritability of the selected character. The inbreeding due to outstanding individuals may rise for several generations after their use.
A note on non-random mating in progeny tests
Authors: Reeve E. C. R.
Published: September 2009

The regression of progeny on mid-parent value is often used in progeny tests to estimate the heritability of a quantitative character. The statistical precision of such an estimate can be considerably increased without increasing the size of the test, by using assortative mating or selection of parents (or both together) so as to increase the mid-parent variance; but the danger arises that this may introduce bias into the estimate through correlation between non-additive gene effects.

It is shown by a mathematical argument that such bias will be negligible provided that all individual gene substitution effects are small compared with the phenotypic standard deviation of the character. Under this condition, deviations from additive effects either within or between loci will not appreciably affect the expected value of the regression on mid-parent, compared with its expected value in a test using random mating.

Correlation between the non-additive gene effects is likely to cause more serious bias to the correlation between sibs, when non-random mating is used.
The genetics ofUstilago maydis
Authors: Holliday Robin
Published: September 2009

1. Many of the Ustilaginales, or smut fungi, appear to have the qualities necessary for the application of modern techniques of microbial genetics.Ustilago maydisis considered the most suitable species.

2. Investigations of the mating system confirm reports that the production of diploid brandspores in the host is controlled by alleles at two loci.

3. Genetic markers were obtained by inducing mutations in a wild-type strain with ultra-violet light. Of 100 biochemical mutants which were isolated, the growth requirements of 94 were identified. Thirty of these were used in genetic tests.

4. The compact growth of colonies on artificial media allowed new techniques to be developed by means of which large samples of progeny could be isolated and identified easily. The analysis of brandspore colonies consisting of the products of single meiotic divisions is the quickest method for detecting linkage, but its accurate measurement appears to be achieved by examining the individual members of tetrads.

5. Linkage was detected relatively rarely, but eight markers, including theamating-type locus, were assigned to one or other of two linkage groups. Although recombination values were not always determined accurately owing to irregular basidiospore germination, the auxotrophic markers in each group could be mapped in a linear order. Since no indication of other linkage groups was obtained, the genetic evidence is so far consistent with cytological reports that the basic haploid chromosome number is two in the smut fungi.

6. Three linked markers were used to investigate chromatid interference by tetrad analysis. None was detected in a total of eighteen double exchanges.
‘Midget’, a new dwarfing gene in the house mouse dependant on a genetic background of small body size for its expression
Authors: Fowler Ruth E. , Edwards R. G.
Published: September 2009

Midget, a new dwarfing gene in the house mouse, was found in a line (NS) selected for small body size. Backcrosses to, and heterozygous matings of NS mice gave midget offspring in the expected 1:1 and 1:3 ratios. Backcrosses to two other lines of mice selected for small body size resulted in fewer midget offspring than expected and in a reduced phenotypic expression of the gene, though matings between these midget offspring gave all midget progeny.

A characteristic check in growth occurred between 15 and 21–24 days of age, and midgets rarely exceeded 10 g. at 6 weeks of age. They were 1·2 g. lighter than NS litter-mates at 3 weeks, and 3·6–4·4 g. lighter at 6 weeks. Fostering or transferring 3½-day-old midget embryos to the uteri of large mothers slightly increased the growth-rate, though the characteristic growth check still persisted. Transfer as embryos did not influence the midget phenotype.

Midget males were of near-normal fertility. The females were semi-sterile due to irregularity or absence of oestrous cycles, failure to ovulate, or the death of embryos before implantation. Each of these factors, which were also found in NS mice, could be remedied by the administration of exogenous hormones.

The genetic factors underlying the expression of midget are discussed, and the physiological traits associated with this and with other dwarfing genes are compared.
‘Bare’, a new hairless mutant in the mouse—genetics and histology
Authors: Randelia Homai P. , Sanghvi L. D.
Published: September 2009

1. A new hereditary defect affecting the hair coat of Swiss albino mice is described. The defect was found to be inherited as a recessive character and is designated as bare (ba).

2. The gene affected the vibrissae as well as pelage hairs. The lack of vibrissae and other sensory hairs at birth, helped to differentiate them easily from the normal animals. The first hairs on the body appeared at 13–14 days of age. The hairs were thin and tiny and remained there till about the thirtieth day. The hairs in the second hair cycle appeared at about 45 days, and again disappeared within 10 days. The animals were entirely naked when they were 6 months old.

3. Gross as well as microscopic examination of hairs in the first hair cycle did not show the four different normal types of hairs. The hairs were comparatively very small, thin, and the internal structure did not show any regularity in the arrangement of the air cells.

4. No difference was found in the number of hair follicles in the bare and the normal Swiss mice.

5. Histology revealed the presence of keratinized globular masses instead of straight hair. This abnormality persisted in all the hair cycles.

6. The bare mice were compared with the other mutants and placed in the Alopecia-Naked group where the abnormality was in the keratinization of the hair.
‘Dappled’ a new allele at the Mottled locus in the house mouse
Authors: Phillips Rita J. S.
Published: September 2009

Dappled, a new completely sex-linked semi-dominant lethal mutation, is described. It is probably a new allele at the Mottled locus and has been given the symbol Modp.

Heterozygous adult females have a variegated coat very similar to that of Brindled and Mottled females; they have curly vibrissae at birth and some also have clubbed feet. All the characteristics are variable.

Hemizygous males die at about 17 days' gestation; they show a characteristic bending and thickening of the ribs and other skeletal defects. The cause of death is unknown.
An attempt to estimate the induction by X-rays of recessive lethal and visible mutations in mice
Authors: Carter T. C. , Lyon Mary F.
Published: September 2009

The experiment was designed to form a bridge between the results of specific-locus experiments, using only a few gene loci, and those using the whole genome of the mouse. Male mice were given 600 r acute X-rays and bred from in such a way that at successive stages mutation in spermatogonia to dominant visibles and lethals, dominant semisteriles, recessive visibles and recessive lethals could be measured. The data concerning dominant mutations were relatively few but confirmed previous results. No recessive visible mutations were found, and the upper fiducial limit to the induced mutation rate to recessive visibles was set at a value 4500 times the rate to viable specific-locus mutations. From the attempt to measure recessive lethal mutations two interesting points emerged. The first was that granddaughters of the irradiated males had fewer corpora lutea per pregnancy than granddaughters of the control males, and the second was that this difference in number of ova shed was not reflected in any difference in litter-size at birth. Since this suggests intra-uterine compensation, no attempt was made to calculate mutation rates to recessive lethal genes from these data. The implications of the results are discussed.
A Revised Nomenclature for the Mouse Transferrin Locus
Authors: Cohen B. L. , Shreffler D. C.
Published: September 2009

In independent investigations, reported almost simultaneously (Cohen, 1960; Shreffler, 1960), the authors have described a protein variant system in the serum of mice, involving an electrophoretic difference in the iron-binding beta-globulin component, transferrin, and have shown the difference to be genetically determined by a pair of co-dominant alleles at a single locus. Both reports introduced the same gene symbol, Trf, for this locus, but in one, letter designations were used (Cohen, 1960), making the allele symbols TrfA and TrfB, and the three phenotypes TrfA, TrfAB and TrfB, while in the other, number designations were used (Shreffler, 1960), with the corresponding symbols Trf1, Trf2, Trf-1, Trf-1·2 and Trf-2. To avoid confusion in future reference to this locus, due to the two differing systems of nomenclature, the authors have agreed upon the revised nomenclature proposed in this communication.
Timing imbalance in the meiosis of the F1hybridOryza sativa×O. australiensis
Authors: Shastry S. V. S. , Rao D. R. Ranga
Published: September 2009

The meiosis in theF1hybridOryza saliva×O. australiensiswas studied. Contrary to the observations of Gopalakrishnan (1959), true allosyndetic bivalents were not found at metaphase I. The most frequent associations were non-chiasmatic, end-to-end pseudobivalents. Autosyndetic bivalents were recorded mostly in the complement belonging toO. sativa, which are distinguishable by their smallness and lighter staining. The meiotic cycle exhibits timing imbalance with earlier condensation, and possibly migration, of the univalents belonging toO. australiensis. The data on meiotic pairing in the F1hybrid and the comparative morphology ofO. sativa, O. officinalisandO. australiensisinicate that the last species is the most primitive member, having originated from the pre-Sativa and pre-Officinalis complex.
Genetical studies on the skeleton of the mouse XXX. A search for correlations between some minor variants
Authors: Truslove Gillian M.
Published: September 2009

A systematic search for correlations between numerous minor skeletal variants in the mouse showed that these are few in number and feeble in extent. This apparent lack of integration is probably due to the fact that these characters are at the extreme limits of genetical determination and so are overwhelmingly influenced by chance in their manifestation.
Chromosomal polymorphism inDrosophila subobscurapopulations from Barcelona (Spain)
Authors: Prevosti Antonio
Published: September 2009

1. Chromosomal polymorphism in two populations ofD. subobscurafrom Barcelona has been analysed and compared with the polymorphism which has been reported from other populations.

2. In spite of microclimatic differences between the Barcelona sites, there is no evidence of differences in the frequency of inversion types nor of seasonal differences within one of these sites.

3. Regularities in the array of frequencies of chromosomal types in Barcelona and other populations suggest that the polymorphism is mainly adaptive although there is also evidence of differences due to distance which are not obviously associated with differences in habitat.

4. In general the index of free recombination gives higher values in the marginal populations ofD. subobscura, but further data are needed to arrive at a definite conclusion on this point since the present evidence is rather ambiguous.
Egg albumen polymorphisms in the Fowl: lociIIandIII
Authors: Lush I. E.
Published: September 2009

The genetics of two polymorphic loci in the fowl was studied. Each affects the electrophoretic mobility of a different egg albumen protein, and at each locus two alleles were shown to segregate in a Mendelian manner.

The polymorphic proteins are not any of the well-characterized egg albumen proteins, viz. ovalbumin, ovomucoid, ovomucin, flavoprotein, avidin and lysozyme.

In contrast to all others, two hens were found to have an anomalous, variable, phenotype. A tentative explanation of this was offered.
Infection into paramecia of metagons derived from other mate-killer paramecia
Authors: Gibson I. , Beale G. H.
Published: September 2009

1. It has been shown that metagons, gene-controlled units necessary for maintenance of mu particles inParamecium aurelia, can be extracted from cells containing one or both of the dominant genesM1andM2, and reinfected into other paramecia. Provided the latter contain mu particles before infection, the introduced metagons resume their normal function of maintaining the mu particles.

2. Homogenates containing metagons have been fractionated in various ways. The metagon activity is found in the sediment after centrifuging at 105,000 g. for 90 min., and is retained after deoxycholate treatment removing the microsomal membranes, and after phenol extraction removing the ribosomal protein. By lowering the magnesium concentration, some metagon activity passes from the microsomes into the supernatant.

3. Metagon activity in RNA fractions is destroyed by ribonuclease at a concentration of 5 μg. per ml.

4. The metagons both in extracts and inside the cells appear often to be aggregated in clumps, the individual units of which are each functionally active in maintaining mu particles in living cells.

5. It is concluded that the metagon may be considered as a very stable and repeatedly functioning form of ‘messenger’ RNA.
Killing activity from lysed kappa particles ofParamecium
Authors: Preer Louise B. , Preer John R.
Published: September 2009

Lysis of stock 7 killers with ½% sodium deoxycholate, yields preparations with one half as much killing activity as homogenates, while lysing virtually all of the bright particles known to have killing activity in homogenates. The killing activity which persists is associated with particles which sediment at the same rate as the refractile bodies, the only visible remnant of the bright particles. It is concluded that killing activity is probably associated primarily, if not exclusively, with the refractile bodies of the bright kappa particles. Partially purified killer particles when stored at 27° C. for more than one day, progressively lose their ability to produce spinning of sensitives but retain their ability to produce paralysis. Loss of activity in crude preparations of refractile bodies kept 2 hours at 31° C. can be retarded by homogenates of either killers or sensitives.
A mechanism for gene conversion in fungi
Authors: Holliday Robin
Published: September 2009

A mechanism for gene conversion is proposed which overcomes many of the difficulties that any copy choice model encounters. It is suggested that along with general genetic pairing of homologous genomes at meiosis, effective pairing over short regions of the genetic material occurs at the molecular level by the separation of the strands of the DNA double helices, followed by the annealing of strands from two homologous chromatids. If the annealed region happens to span a heterozygous site, mispairing of bases will occur. Such a situation may be analogous to that in DNA which is damaged by mutagens; the same or similar repair mechanisms may operate, and these, by adjusting the base sequences in order to restore normal base pairing, would bring about gene conversion in the absence of any genetic replication. The model indicates how precise breakage and rejoining of chromatids could occur in the vicinity of the conversion, so that conversion would frequently be accompanied by the recombination of outside markers. The model also proposes that the distance between two mutant sites on a fine structure map depends not so much on the frequency of a recombinational event occurring between them, but rather on the degree of inhibition of the processes of genetic pairing by the mutants themselves.

The model will explain almost all the data in a formal way, and it has the advantage over copy choice mechanisms for gene conversion in (1) being compatible with semi-conservative replication of DNA, (2) not invoking DNA synthesis during or after genetic pairing, (3) providing a molecular mechanism for close specific pairing, (4) making it unnecessary to postulate sister strand exchange or a process akin to this, (5) suggesting why rates of gene conversion in opposite directions are sometimes unequal and (6) providing an explanation of the clustering of mutant sites, a basis formap expansionand for the apparently capricious departure of fine structure maps from additivity. Although the model proposed is a general rather than a specific one, it suggests that the process of conversion and intragenic recombination is more complex than is usually believed, since it depends on several interacting factors. Nevertheless, it is hoped that the introduction of a model with this complexity will help to stimulate specific experiments, and that these will provide definitive information which would never be obtained if simpler models of conversion and intragenic recombination were believed to explain the genetic data sufficiently well.
Mitotic recombination in thepaba 1cistron ofAspergillus nidulans
Authors: Putrament A.
Published: September 2009

The results of the analysis of 393 mitotic recombinants within thepaba1region ofAspergillus nidulanscan be summarized as follows:

1. Reciprocal, non-reciprocal and probably inexactly reciprocal exchanges occur in intra-cistron mitotic recombination.

2. Negative interference observed in intra-cistron mitotic recombination in thepaba1region ofAspergillus nidulansis more intense than that observed in meiotic recombination in the same cistron.

3. In intragenic mitotic recombination multiple exchanges can involve three or even four chromatids within one effective pairing segment.
Cytology of the XXY mouse
Authors: Slizynski B. M.
Published: September 2009

The XXY male mouse, of otherwise normal chromosome complement, is characterized by small testes, few spermatogonia, and spermatocytes in which the first stage of meiosis up to the pachytene stage can occur, although with a very low frequency. Pachytene autosomes are morphologically similar to those of the oöcytes. The sex vesicle is smaller and more condensed than in the normal male.
Distribution of chromosomes in metaphase plates of Mesocricetus newtoni
Authors: Raicu Petre , Vladescu Barbu , Kirilova Maria
Published: September 2009

Fifty-one metaphase figures from male Mesocricetus newtoni bone-marrow cells were analysed with respect to the distribution of chromosomes. The peripheral location of the sex chromosomes (XY) and that of the chromosome pairs 3 and 9, as well as the non-peripheral location of the chromosome pairs, 16, 17, 18 was revealed. The significance of the peripheral location of the X chromosome and a possible explanation of the characteristic distribution of the chromosomes are discussed.
Purine-excreting mutants ofSaccharomyces cerevisiae: I. Isolation and genetic analysis
Authors: Armitt Susan , Woods Robin A.
Published: September 2009

Purine-excreting mutants of yeast have been obtained by selecting for (a) adenine-insensitive pigment accumulation in a strain carryingad-2and (b) by isolating prototrophic mutants which crossfeed to an adenine-requiring indicator strain. The first method yielded both auxotrophic and prototrophic mutants. The auxotrophs were assigned toad-12which specifies adenylosuccinate synthetase. The prototrophs were affected by a gene,su-pur, which prevented purine excretion, and the majority of them showed anomalous behaviour of mating-typeaassociated with the mutations causing excretion. Mutants obtained by the second method were allocated to six unlinked genes. Those assigned topur-1topur-5are recessive and affected bysu-pur. pur-6is a complex locus with both dominant and recessive alleles; it is closely linked or allelic tosu-purandad-4. Functional tests involving mutants ofpur-3andpur-6in combination withpur-1andpur-4did not show normal intergenic complementation. The suppressor shows gene-specific dominance/recessiveness. Some metabolic lesions which could give rise to purine excretion are discussed.
Parental influence onX-autosome translocation-induced variegation in the mouse
Authors: Cattanach B. M. , Perez J. N.
Published: September 2009

Females heterozygous for theT(1; X)CtX-autosome translocation tend to have lower levels ofc-variegation when their rearrangedXis inherited from the father rather than from the mother. The difference is not due to a maternal effect. It is postulated that a paternal or parental-source effect, such as that found to modify position effect variegation inDrosophila, is operating but the possibility that a bias in the inactivation of the maternal and paternalXchromosomes is responsible cannot be ruled out.
Mutagenesis inEscherichia coli
Authors: Bridges B. A. , Dennis Rachel E. , Munson R. J.
Published: September 2009

A system has been developed for the study of reversion of an amber mutation responsible for a deficiency in DNA synthesis in T4 phage E51. When complexed with bacteria able to suppress the amber mutation the induced mutation rate per phage genome per rad is

When complexed with bacteria unable to suppress the amber mutation (and being thus unable to synthesize phage DNA) the induced mutation rate is at least 14 times lower indicating that DNA synthesis is necessary for the production of the majority of functional reversions at the amber site. The induced mutation rate in suppressor-containing bacteria is independent of multiplicity of infection between 0·2 and 5, suggesting that recombination immediately after irradiation between phage genomes is unlikely to be a requirement for the mutation process.
Functional analysis of host-specificity mutants inEscherichia coli
Authors: Glover S. W.
Published: September 2009

Evidence from a functional analysis of host-specificity mutants in merodiploids is presented which supports the suggestion that three genes,hss, hsrandhsm, are necessary for the expression of host-controlled restriction and modification. The host-specificity phenotype expressed by the merodiploids provides evidence that at least two genes,hssandhsr, are concerned in the expression of host-specific restriction of DNA and one of these genes,hss, is responsible for the strain specificity of the restriction enzyme. A class of modification-deficient mutants isolated from restriction-deficient, modification-proficient mutants, was also tested for complementation in merodiploids and the phenotype of these merodiploids provides evidence that at least two genes,hssandhsm, are concerned in the expression of host-specific modification of DNA and one of these genes,hss, is responsible for the strain specificity of the modification enzyme. How these three genes function at the molecular level is discussed in terms of models based on the interaction of subunits to form oligomeric enzymes.
Chromosomal basis of dosage compensation in Drosophila: II. The DNA replication patterns of the male X-chromosome in an autosome—X insertion in D. melanogaster
Authors: Lakhotia S. C.
Published: September 2009

The functional morphology and the replication pattern of the male X-chromosome in an autosome-X insertion stock (T(1;3) 05) of Drosophila melanogaster have been examined. In larval salivary glands carrying this insertion neither the enlargement and pale staining of the single male X, nor the characteristic early completion of replication cycle, as revealed by 3H-TdR autoradiography is in any way changed. The normal properties of the inserted autosomal segment are also unaltered. The results appear to support a ‘piecemeal’ type of dosage compensation mechanism in Drosophila operating through the male.
A chromosomal factor exerting a predetermining effect on morphogenesis in the multicellular green alga Ulva mutabilis
Authors: Fjeld Asbjørn
Published: September 2009

A new spontaneous mutant bubble (bu) with a marked effect on early morphogenesis in the multicellular green alga, Ulva mutabilis is described. It behaves as a recessive chromosomal mutant. The bu+ gene product formed in heterozygous sporophytes exerts a predetermining effect on morphogenesis of haploid gametophytes with the bu genotype. It is suggested that the product of the bu+ gene affects the orientation of the mitotic spindles during early development.
Genetic analysis of an unequal chromosomal translocation inAspergillus nidulans
Authors: Bainbridge B. W.
Published: September 2009

Translocation T(III–VIII) inAspergillus nidulanshas been analysed by the detection of meiotic linkage between markers previously located separately on linkage groups III and VIII. The breakage points have been mapped by the detection of linkage between the crinkled type and genetic markers in the region of the break. A segment from linkage group III, approximately 43 units long and including the markersmoC96, sC12, sA1andcnxH3, has been translocated into linkage group VIII. The breakage point is betweensu6proAandmoC96and the attachment point is close tochain linkage group VIII. It seems probable that the segment has been inserted into linkage group VIII.
Acridine treatment of F+and Hfr strains ofEscherichia coli K12carrying a neomycin-kanamycin resistance determinant
Authors: Grindley June N. , Grindley N. D. F. , Anderson E. S.
Published: September 2009

The F factor and the K resistance determinant form an R factor (KF) inE. coliK12. In this R factor the two plasmids are independent of each other and occupy different attachment sites in the host cell.

Treatment of an F+(K) strain with acriflavine and acridine orange yielded the following classes: F+K−; F−K+; and F−K−. The K determinant was thus curable independently of F, which supports the hypothesis of independence of the two plasmids. In Hfr(K) strains, K remains curable with acridines while F is immune. Thus, K remains independent of F in both the F+and Hfr states.

The use of higher concentrations of acridine orange than those needed for cure of K in the F+(K) strain resulted in no elimination of K, although the F factor was absent from all surviving lines tested. It is suggested that this is caused by equal inhibition of replication of both the chromosome and K, and greater inhibition of that of F.
Transformation ofSarcina flavaandMicrococcus flavocyaneus
Authors: Kane Caroline M. , Kloos W. E.
Published: September 2009

Sarcina flavaATCC 540 (ade) andMicrococcus flavocyaneusATCC 8673 (ade), two related micrococci, were transformed to prototrophy at frequencies as high as 0·02% and 0·005% of colony-forming units, respectively. Both of these organisms were transformed by selected prototrophic strains ofMicrococcus lysodeikticus, M. flavocyaneus, S. flavaandSarcina lutea.
Studies on genetic organization in higher organisms: III. Confirmation of the single cistron-allele complementation model of organization of themaroon-likeregion ofDrosophila melanogaster
Authors: Finnerty Victoria , Chovnick Arthur
Published: September 2009

A genetic fine-structure experiment onDrosophila melanogasteris described, which makes use of a lethal selective system which permits survival only of recombinants in thema-lregion, including exchanges between site mutants ofma-l. On the basis of prior mapping information, the experiment was designed to select forma-ldouble mutant recombinants. Utilizing a pair of complementingma-lmutants, double mutant meiotic products were recovered whose complementation properties provide independent support for the single-cistron, allele complementation model of organization of the maroon-like region inferred from other experiments described earlier.
Different frequencies of cotransduction ofmotCandH1inSalmonella
Authors: Enomoto Masatoshi , Yamaguchi Shigeru
Published: September 2009

The frequency of cotransduction ofmotCandH1in Salmonella has been investigated, using four Salmonella serotypes and many serotypic recombinants as donors andS. typhimurium motCmutant as recipient. The frequency varied with the four serotypes from 7% to 52%. It is suggested that the difference in frequency arises from not only differences in genetic homology between the chromosome of the recipient and the fragment from the donor, but also from differences in genetic composition of the chromosome fragments carried by the phage. The frequency of serotypic recombinants selected formotC+andH1gene of the donor is generally higher than with recombinants selected forflaK+andH1. The difference in genetic homology betweenS. typhimuriumand other species is more marked in the region betweenH1audflaKthan betweenmotCandH1.
The action of the geneprune (pn)inDrosophila melanogaster
Authors: Lifschytz Eliezer , Falk Raphael
Published: September 2009

The genepnwas found to be active already in larvae 30 h old, long before eye-pteridines accumulated. At this developmental stagepninteracts with the geneK-pn. From studies with induced somatic recombination, gynandromorphs, and inducedpnmutations, in aK-pnbackground it was concluded that the interactionpn-K-pnis non-autonomous in the epidermis, but in some internal organs it is apparently autonomous and causes the death ofpn–K-pnflies. It is proposed thatpnmutants interfere with an early step of the conversion of guanosine to pteridine, so that a deficiency of drosopterines, but not of the competing sepiapterine and biopterine, is caused. The accumulated precursor is presumably the substrate for a poisonous reaction triggered byK-pn.
Somatic segregation of the killer (k) and neutral (n) cytoplasmic genetic determinants in yeast
Authors: Bevan E. A. , Somers J. M.
Published: September 2009

When killer and neutral strains of Saccharomyces cerevisiae are crossed the resulting diploid clones possess a killer phenotype and when spored yield a complete range of tetrad ratios.

The combined results of analysing tetrads and vegetative cells of diploid clones derived from two different neutral × killer crosses (K1 × N1 and K2 × N1) demonstrate that the range of tetrad ratios can be accounted for by the occurrence of somatic segregation of killer (k) cytoplasmic determinants prior to sporulation. Such results support the genetic model for the inheritance of the killer character in yeast already proposed (Somers & Bevan, 1969).

During the course of these studies a correlation was found between the strengths of the killer phenotypes of diploid colonies and the proportions of killer spore cultures obtained after sporulation of their cells.
A method for isolating paralysed (mot−) mutants from non-flagellated cells of Salmonella
Authors: Enomoto Masatoshi
Published: September 2009

A method for concentrating flagella-paralysed (mot−) cells existing in a large number of non-flagellated cells of Salmonella was invented. Themot−cells expressing the phase-1 flagellar antigeniwere agglutinated by anti-iserum with carriers, the dead cells of TM2 expressing the phase-1 antigeni; only the agglutinated cells were harvested by a low speed of centrifugation and incubated in broth. About tenfold concentration was brought about by one treatment, which was repeated for further concentration. By this method, themotA257 motC244double mutant which was produced by transduction at a frequency of about 3 × 10−6per non-flagellated recipient cell was isolated from the broth culture concentrated five times, in which about 30% of the cells were the double mutant.
Investigation of the mating system ofPseudomonas aeruginosastrain 1: V. The effect ofN-methyl-N′-nitro-N-nitrosoguanidine on a donor strain
Authors: Loutit J. S.
Published: September 2009

N-methyl-N′-nitro-N-nitrosoguanidine treatment of a donor strain ofPseudomonas aeruginosaresulted in the isolation of strains which were presumably cured of their sex factors, strains which possibly contained mutant defective sex factors and one strain which showed enhanced donor activity. The latter was apparently due to a change in the bacterium and the sex factors of OT 302 and OT 15 were both shown to be similar to the original in OT 1 when the three were transferred into the same strain.
Mitotic non-conformity inAspergillus nidulans: the production of hypodiploid and hypohaploid nuclei
Authors: Roper J. A. , Nga B. H.
Published: September 2009

Strains ofAspergillus nidulanswith a chromosome segment additional to the normal complement are vegetatively unstable. Previous work suggested that the deletions occurring at mitosis were confined to the unbalanced segments. It has been shown now that deletions, while probably always involving a duplicate segment, may extend beyond it to produce hypohaploids and hypodiploids, respectively, from unbalanced haploid and unbalanced diploid parents.

Hypoploids have been proposed tentatively as an explanation for some cases of phenotypic variegation; on this basis it is possible to account for some of the diverse phenomena shown by, for example, position-effect variegation.
Genetic evidence for restriction targets in the DNA of phages λ and φ 80
Authors: Franklin Naomi C. , Dove William F.
Published: September 2009

Temperate phages φ 80 and λ grown inE. colistrain C differ markedly in the degree to which they are restricted byE. colistrain K. The basis of this difference is subject to genetic recombination and deletion. The loss of restriction sensitivity by deletion shows that sensitivity is determined by loci in the phage genome. These loci are interpreted to be targets of the restriction mechanism, in agreement with previous biochemical evidence.
The study of multiallelic genetic systems by matrix methods
Authors: Cannings C.
Published: September 2009

A matrix notation is developed to facilitate study of natural selection in large populations. The processes of mating (taking into account differences between genotypes in fertility in both sexes), segregation, and differential viabilities are each expressed in matrix notation. Assortative mating and non-random segregation can also be described by the method. The separate processes can then be combined to give simple equations relating the genic and genotypic frequencies in one generation to those in the previous generation. This will facilitate computer treatment of natural selection processes.

The method can also be used to study equilibria and the conditions of their stability by examining the latents roots of the matrix. Several special cases of selection at an autosomal locus are examined. The method can be extended to sex-linked loci and two special cases are discussed.
The genetics ofDacus oleae: III. Amount of variation at two esterase loci in a Greek population
Authors: Zouros E. , Krimbas C. B.
Published: September 2009

Two polymorphic esterase loci, EstA and EstB, of the olive-fruit flyDacus oleaewere studied in a natural population. The analysis of about 500 individuals revealed the presence of 15 alleles for EstA and 12 alleles for EstB. A ‘silent’ allele was found segregating at both loci. Segregation data for most of the alleles are presented. The allele frequency distribution follows the same pattern at both loci: one allele of each gene has a frequency of nearly 0·50, a few have frequencies between 0·05 and 0·15 and many are below 0·05. Two main hypotheses, those of overdominance and selective neutrality, were examined in order to explain these polymorphisms. We deduced that under both hypotheses a relatively high mutation rate is necessary to balance the result of random drift. This rate was estimated to be higher than 4 × 10−5for the EstA locus. Since homozygotes for the ‘silent’ allele at the first or at the second locus were found in the population in expected frequencies, it was concluded that these alleles are not inferior to active ones under natural conditions.
A method for selecting streptomycin-sensitive mutants of R factors which adenylate streptomycin
Authors: Harwood J. H. , Janjigian J. , Smith D. H.
Published: September 2009

An Arg−conditionally streptomycin (Sm)-dependent strain ofE. coliB that carries an R factor mediating Sm adenylation cannot grow on minimal agar containing 20 μg Sm/ml unless the strain either becomes Arg+or loses the ability to adenylate Sm (Harwood & Smith, 1969b). We have therefore studied the efficacy of this selection with respect to enriching for SmSmutants of such R factors. Following u.v. mutagenesis, cells were plated on the selective medium; of the clones which were examined, Arg−R-SmScolonies were found up to 3000 times more frequently than Arg+R-SmRcolonies.
The genetics of three polymorphic larval colour forms of Chlosyne lacinia (Lepidoptera, Nymphalidæ)
Authors: Gorodenski Stanley A.
Published: September 2009

Chlosyne lacinia (Geyer) is a nymphalid butterfly ranging from the Southwestern United States and thence southward to Argentina (Ehrlich & Ehrlich, 1961). The insect is multibrooded and preferably feeds on sunflower (Helianthus annuus L.), although high populations have also been observed to be maintained on cocklebur (Xanthium saccharatum Wallr.).
Production of auxotrophic mutants in ferns
Authors: Carlson Peter S.
Published: September 2009

A method has been devised for the selection of auxotrophic mutants in higher plants. The method depends upon the incorporation of BUdR into the DNA of non-auxotrophic cells and upon its lack of incorporation into the DNA of auxotrophic cells. A wide range of auxotrophic types were recovered.
A note on the inheritance of erythromycin-resistance in Paramecium aurelia
Authors: Beale G. H.
Published: September 2009

In yeast it has been reported that some types of erythromycin-resistance are due to cytoplasmic genetic factors, localized in mitochondria (Thomas & Wilkie, 1968; Slonimski, 1969). In view of the current interest in genetical aspects of mitochondria, and the ease with which cytoplasmic heredity can be demonstrated in Paramecium aurelia, some tests have been made to determine whether erythromycin-resistant variants could be obtained in this ciliate and, if so, to determine their genetic basis.
Complementation tests on closely linked flagellar genes inChlamydomonos reinhardii
Authors: Starling David
Published: September 2009

Complementation tests have been performed on a group of closely linked genes affecting the formation of the central pair of microtubules in the flagella ofChlamydomonas reinhardii. The procedure adopted involved the selective isolation of diploid strains in which the mutant genes were recessive to then wild-type alleles. The mutations tested were found to be in the same cistron.
The effect of suppressing crossing-over on the response to selection inDrosophila melanogaster
Authors: McPhee C. P. , Robertson Alan
Published: September 2009

A selection experiment for sternopleural bristles inDrosophila melanogasterwas undertaken to measure the effect of suppressing crossing-over on chromosomes II and III using the inversions Curly and Moiré marked with a dominant gene, which severely reduce crossing-over. In one set of lines selected wild-type males were mated to selected females, heterozygous forCyandMé, and in a parallel set selected males carrying the inversions were mated to selected wild-type females. Because there is no crossing-over in the males in this species, crossing-over is much reduced in the first set and is at its usual level in the second. The effect of the selection was measured on flies which did not carry the inversions. The suppression of crossing-over reduced the advance at the limit by 28 ± 8% for selection upwards and by 22 ± 7% for selection downwards. The segregation ratios of the inversions were observed throughout the experiment. At the end, the proportion of wild-type flies emerging was not different in the two sets of lines. The results are consistent with an assumption of initial linkage equilibrium between loci affecting sternopleural bristles in the base population.
A genetic analysis of non-disjunction and mitotic recombination inNeurospora crassa
Authors: Threlkeld S. F. H. , Stoltz J. M.
Published: September 2009

The frequency of the more common patterns of non-disjunction in Neurospora was studied. Detection of these asci was accomplished by the use of pantothenate requiring strains grown on reduced amounts of pantothenate, so that combinations of dark, pale, and aborted spores provided evidence of non-disjunction. The isolates from five non-disjunction asci were examined in detail and an apparently high frequency of mitotic recombination was detected for presumed disomic isolates. An hypothesis concerning a mechanism of non-disjunction is presented.