bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical analysis of chromosome distribution to the poles in interspecific hybrids with variable chromosome pairing
Authors: Sficas A. G.
Published: September 2009

A probability distribution of chromosome separation to the poles was developed to test the randomness of movement of univalents in asynaptic material where a variable amount of meiotic pairing occurs. Two tables were calculated, one for 24 chromosomes which can be used for any even number equal or less than 24, and the other for 19 chromosomes which can be used for any odd number equal or less than 19.

ThreeNicotianahybrids, namelyN. glutinosa×N. otophora, N. glutinosa, N. sylvestris, andN. tabacum×N. glutinosa, and one polyhaploid were investigated. All hybrids had a tendency towards an equal distribution of unpaired chromosomes to the poles. The polyhaploidN. tabacum(with a substitutedN. plumbaginifoliachromosome) had an opposite tendency, i.e. towards a flatter distribution than expected from random distribution of univalents. A short discussion of the problem is given.
A comparison of the interaction, with two types of environment, of pure strains or strain crosses of poultry
Authors: Hull P. , Gowe R. S. , Slen S. B. , Crawford R. D.
Published: September 2009

In these experiments comparisons were made between the magnitude of the interaction of ‘pure’ strains and strain crosses of poultry with two types of environments—location effects and a restricted-feed versus a full-feed rearing programme. The ‘pure’ strains were closed flocks of White Leghorns that had been selected for increased egg production, while the strain crosses were the reciprocal crosses of all combinations of these pure strains. Data from four separate experiments in four consecutive years used for this study involved 8320 laying birds. Six traits of the adult laying birds were used for these analyses.

It was expected that the ‘pure’ strains would differ in performance amongst themselves to a greater extent than the strain crosses, and for the two traits, body-weight at housing and sexual maturity, this was found to be the case in three out of four years. These two traits were affected to the greatest extent by the rearing treatment. Also, the genotype-environment interaction variance was found to be significant and of important magnitude relative to the genetic variance for these two traits. Where the environmental effect was found to be smaller, the interaction variance made up a smaller proportion of the genetic variance.
Genetic radiosensitivity of specific post-dictyate stages in mouse oöcytes
Authors: Edwards R. G. , Searle A. G.
Published: September 2009

The induction of dominant lethals after X-irradiation of dictyate, later meiotic stages, and the pronuclear stage after fertilization have been compared using the technique of induced ovulation in mice. The injection of gonadotrophins ensures that the time at which the synchronously dividing oöcytes reach any particular meiotic stage is accurately known. Embryonic lethality up to 13½ days was studied after 0 r., 100 r. and 200 r. acute X-irradiation. Metaphase I, anaphase I and metaphase II were the most sensitive stages, with LD50's of about 120 r., 130 r. and 170 r. respectively. The dictyate and pronuclear stages were much less sensitive, with LD50's in the region of 500 r., and sensitivity rose steeply during prophase I. Numbers of corpora lutea decreased with irradiation, the decrease being greatest with irradiation at metaphase I and anaphase I. The ovulation of large numbers of eggs, which increased the preimplantation loss of embryos above normal, and the low luteal counts probably masked lethality to some extent. Results generally agree well with those reported in a number of plant and animal species.
Transduction analysis using leucine requiring mutants ofSalmonella typhimurium
Authors: Smith-Keary P. F. , Dawson G. W. P.
Published: September 2009

1. Data is presented in support of the hypothesis that inSalmonella typhimuriumthe fragments participating in the transduction of a particular linkage group arise by breakages at constant positions in the genome of the donor bacteria.

2. Data from three factor transduction experiments are used to construct a linkage map of theleu-araBregion which defines not only the relative order of the markers but also the relative distances between them.
The inheritance of lymph proteins in Drosophila
Authors: Pantelouris E. M. , Duke E. J.
Published: September 2009

The inheritance of three lymph protein fractions separable by starch-plate electrophoresis has been studied. Each fraction is under the control of a separate gene, the dominant allele determining its presence and the recessive its absence.

The gene for the fastest fraction is sex-linked, whilst those for the other two are autosomal and linked.
Heterogeneity among spermatogonia ofDrosophila melanogasterin sensitivity to X-rays
Authors: Slizynska H.
Published: September 2009

1. Sensitivity ofDrosophila melanogastermale germ-cells to chromosome breakage by X-rays has been measured by the structural changes found in the salivary gland chromosomes of larvae from irradiated fathers and untreated mothers. The genetical effectiveness of irradiation on the same males was measured by the frequency of sex-linked lethals.

2. Assessed by the overall percentage of germ-cells carrying structural changes, sensitivity follows the well-known pattern: it is highest in spermatids and decreases over spermatozoa and spennatocytes to spermatogonia.

3. This overall sensitivity has been analysed on three levels:

(a) The proportion in successive broods of ‘positive’ males,i.e.males which respond to irradiation. The results indicate that spermatozoa and spermatids in most or all males are equally sensitive to X-rays, while in regard to spermatogonia the males represent a heterogeneous population consisting of positive and negative males. This is fully confirmed by statistical analysis which was carried out by Dr B. Woolf.

(b) The proportion of ‘sensitive’ germ-cells per positive male,i.e.germ-cells carrying at least one structural change. While the proportion of sensitive cells per positive male is about 1:3 for spermatozoa, spermatocytes and spermatogonia, it is higher for spermatids. This is the main reason for the observed increase in overall sensitivity from spermatozoa to spermatids and for its subsequent drop in spermatocytes. On the contrary, the drastic drop in overall sensitivity from spermatocytes to spermatogonia results entirely from a drop in the proportion of positive males.

(c) The distribution of breaks in sensitive cells. The clustering of breaks in sensitive cells is highest in spermatogonia, somewhat lower in spermatids, and lowest in spermatocytes and spermatozoa. It indicates that spermatogonial cells are a heterogeneous population, consisting of cells that are either highly sensitive to X-rays or not sensitive at all.

4. The fact that the sensitivity of spermatogonia varies both between and within individual males is tentatively attributed to the presence or absence of spermatogonial mitoses.
The effect of unbalanced growth on recombinant formation inE. coli
Authors: Gross J. D.
Published: September 2009

When zygotes formed by conjugation between Hfr and F- cells ofE. coliare transferred from an amino-acid rich medium to one lacking amino-acids the probability of genetic recombination is reduced. This result is interpreted as indicating that recombination can only occur during a limited period after zygote formation and that the metabolic imbalance caused by the change of medium leads to temporary inhibition of recombination. By an hour after zygote formation the yield of recombinants is no longer affected by transfer to amino-acid free medium.
Genetic analysis of the phosphatases in Aspergillus nidulans
Authors: Dorn G.
Published: September 2009

1. A histochemical method has been applied to the detection of alkaline and acid phosphatase mutants in single colonies of Aspergillus nidulans.

2. With the above method it has been possible to isolate mutants in which the alkaline and acid phosphatase activities are affected either separately or simultaneously.

3. Crude extracts of wild-type A. nidulans contain four electrophoretically distinct phosphatase components, two with activity at alkaline pH and two with activity at acid pH. Genes affecting three of the four components have been identified.

4. Two suppressor mutants of an alkaline phosphataseless mutant (palB7) have been isolated. In a strain carrying palB7 and one of these suppressors, the restoration of an alkaline phosphatase component is accompanied by loss of the faster acid phosphatase component. In a similar strain carrying the other suppressor, the partial restoration of the alkaline phosphatase component goes with an electrophoretic alteration of the slower acid phosphatase component.

5. Genetic analysis of twenty-seven mutants has resulted in the identification of fifteen loci affecting the phosphatases. All these loci have been assigned to linkage groups, and twelve of them were also mapped meiotically in relation to other loci.

6. One possible model (based on heteropolymeric proteins) has been proposed to account for the electrophoretic and genetic data on the various phosphatase and suppressor mutations.
Genetic analysis of actidione resistance inSaccharomyces cerevisiae
Authors: Wilkie D. , Lee B. K.
Published: September 2009

1. Individual genes of a multigenic system of resistance to actidione in yeast were analysed in a series of crosses involving resistant strains and sensitive strains.

2. Resistance conferred varied in the range 0·5 p.p.m. to 20 p.p.m.

3. Positive interaction was seen between resistance genes in recombinant strains.

4. Recessive modifier genes were found which do not themselves confer resistance but which modify the activity of specific resistance genes in a positive way, that is towards a greater degree of resistance. Both a two-fold and a five-fold increase in resistance is seen depending on the gene combination.

5. In selection experiments, strains resistant to relatively high concentrations of actidione (1000 p.p.m.) were obtained but only by selection on media containing successively higher concentrations of the drug, that is, by the step wise build up of multiply mutant forms. Mutations of interacting resistance genes and specific modifier genes were obtained by selection methods including pretreatment of cells with ultra-violet light.
Genetic divergence in M. Vetukhiv's experimental populations of Drosophila pseudoobscura 2. Longevity
Authors: Mourad Abd El-Khalek
Published: September 2009

Six experimental populations of Drosophila pseudoobscura were maintained in three different environments for almost four and a half years. All the populations have originally descended from the same founders. The populations were examined for evidences of genetic divergence. The longevity of the flies from four of these populations, and their F1 and F2 hybrids, was studied at 16°C. and at 27°C. The results indicate that the gene pools of some of the populations have diverged from each other.
Induction of lethal mutations in Drosophila melanogaster by DNA
Authors: Gershenson S.
Published: September 2009

Addition to the food of Drosophila larvae of DNA from calf thymus induces a considerable number of recessive lethal mutations in the 2nd chromosome. An analysis of sixty-six such lethals showed that most of them affect the same segment containing probably some thirty to thirty-five sub-units capable of mutating together or separately.
The production and behaviour of diploids ofCoprinus lagopus
Authors: Casselton Lorna A.
Published: September 2009

Diploid strains ofCoprinus lagopushave been synthesized from commonAheterokaryons either as oidial colonies or sectors. The criteria of growth rate and colony morphology on selective medium were used to distinguish between diploid and heterokaryon colonies. The average oidial size and hyphal width of diploid strains was significantly greater than that of the haploid parental strains.

Diploid monokaryons were very stable and only rarely produced haploid segregants. However, aneuploid intermediates in haploidization have been identified and these segregated further to give haploid monokaryons with recombinant genomes.

Dikaryons formed from diploid and haploid strains produced fruiting bodies. Meiosis and basidiospore production were irregular owing to the formation of triploid or partially triploid fusion nuclei in the basidia. In contrast to their stability in monokaryons, diploid nuclei tended to be unstable when combined in a dikaryon with a haploid nucleus, and often underwent partial haploidization before fruiting. Segregation of genes in the basidiospore progeny reflected whether haploidization had occurred before or after the formation of the fruiting body. If the haploid nucleus had aBmating-type allele common to the diploid nucleus, haploidization effected loss of the common allele.
New data on the linkage map ofStreptomyces coelicolor
Authors: Hopwood David A.
Published: September 2009

Linkage data, obtained by a combination of selective analysis of haploid recombinants and analysis of segregating heterozygotes, are given for twenty-eight loci inStreptomyces coelicolorA3(2). This brings the total known loci for the organism to thirty-nine. The two linkage groups previously recognized remain separate, and their lengths have been increased to about 60 and 70 recombination units respectively. Whether the two linkage groups correspond to two chromosomes remains an open question.

Three further examples of close linkage of pairs of functionally related loci have been found (a trio of such loci was already known), and three other pairs provide possible examples of the same phenomenon. Some loci which are clustered inSalmonellaare unlinked inStreptomyces.
Congenital defects as indicators of lifelong abnormal processes
Authors: Grüneberg H. , Gray Jean M. , Truslove Gillian M.
Published: September 2009

Congenital defects due to genes are the static end results of abnormal processes in embryonic development. Are these ‘burnt out’ and no longer in operation later in life, or do they continue as active physiological processes? To answer this question, thirteen genes with comparatively trivial morphological effects have been subjected to a screen test. For eight of them (bp, f, Ts, Sd, un, se, OsandPh) aprima faciecase has been established for the existence of continuing processes of one kind or another. For the remaining five genes (dn, Pt, T, vtandMiwh) there is no such evidence though the possibility remains that such processes might be detectable by different means.
Absence of clustering of functionally related genes inPseudomonas aeruginosa
Authors: Fargie Barbara , Holloway B. W.
Published: September 2009

Phage F116 transduces sufficiently large fragments of thePseudomonas aeruginosachromosome for co-transduction of linked markers to occur. The linkage relationships of 176 auxotrophic mutants have been examined by means of this technique, following characterization of the mutants for their nutritional requirements and by other biochemical means. Thirty-two different loci from fourteen biosynthetic pathways have been differentiated by such combined means. Unlike other bacteria, the clustering of related loci of a biosynthetic pathway appears to be rare. This situation was confirmed for the leucine, methionine, adenine, isoleucine plus valine and arginine pathways. No evidence for linkage of markers within the histidine, proline, cysteine and uracil pathways has been found but further data is needed to completely confirm this conclusion for these groups of markers. The importance of these findings in relation to the genetic control of enzyme biosynthesis in P.aeruginosais discussed. For markers of the tryptophan pathway, two are possibly linked but the other three are definitely not linked. The only confirmed linkage of related markers was between a homoserine locus and a threonine locus.
Multi-step resistance to Chloramphenicol in RC-stringentEscherichia coliK12—its effect on the induction of RNA synthesis by antibiotics under amino acid starvation
Authors: Reeve E. C. R. , Bishop J. O.
Published: September 2009

A multi-step Chloramphenicol (CM)-resistant derivative of an RC-stringent strain ofEscherichia coliauxotrophic for threonine and leucine was resistant also to Aureomycin (AM) and Puromycin (PM). All three antibiotics released the repression of RNA synthesis due to amino acid starvation in the CM-sensitive parent strain, their relative activities being about 1:10:100 for AM: CM: PM. High doses of AM and CM failed to induce RNA synthesis. The CM-resistant strain required greater concentrations of each antibiotic than the sensitive strain to induce the same level of RNA synthesis, and appeared to be about one hundred times, ten times and five times more resistant to CM, AM and PM, respectively, than the sensitive strain.
Variations in resistance to three antibiotics among some single-step mutants to Chloramphenicol resistance in a strain ofEscherichia coliK 12
Authors: Reeve E. C. R. , Bishop J. O.
Published: September 2009

Chloramphenicol (CM), Aureomycin (AM) and Puromycin (PM) induce RNA synthesis inRC-stringent Escherichia colistarved of a required amino acid. This fact has been used to develop a method for comparing the levels of resistance of single-stepCM-rmutants to the three antibiotics. Three levels of resistance to each antibiotic were found among four mutants selected in a singleCM-sstrain. The mutant with the highest CM resistance has the lowest AM resistance, and vice versa, while the level of PM resistance was not correlated with that of either CM or AM. The four mutants all differed from each other in their patterns of resistance to the three antibiotics.
Inherited histocompatibility changes in progeny of irradiated and unirradiated inbred mice
Authors: Bailey D. W. , Kohn H. I.
Published: September 2009

(1) F1-hybrid mice derived from a cross of the highly inbred strains: C57BL/6 and BALB/c, were tested for inherited changes of histocompatibility by an orthotopic inter-exchange of tail-skin grafts. The fathers of tested mice received either 522 rads of gonadal X-irradiation, or received no irradiation 2 months prior to mating.

(2) Thirty-two mice with altered histocompatibilities were found in a total of 2572 complete tests. All of those mutant mice (twenty-one) that produced an adequate number of offspring were shown to pass the incompatibility on to their progeny.

(3) Mutants were classified as to whether they effected a gain, a loss or both a gain and a loss in antigen specificity as determined by whether they rejected skin of donor mice or their skin was rejected by host mice. Twenty-six were clearly of the gain type, five were most likely gain type and only one showed both a loss and a gain effect. There was no clearcut evidence that loss types had occurred. The preponderance of gain types was tentatively explained as an artifact of the system used for the assay.

(4) Several of the detected mutants were probably from parents carrying mutations that originated in past generations, for some mutant mice occurred in clusters.

(5) There was no apparent effect of paternal irradiation (522 rads) on mutation frequency. The induced mutation rate was estimated to be less than 2·6 × 10−5/ gamete/rad.

(6) Independent data on isografts from F1hybrids of proven non-carrier pedigreed parents provided an estimate of spontaneous mutation rate of 6·75 × 10−3/ gamete.

(7) The estimate of doubling dose (greater than 260 rads) was consistent with the estimates for recessive lethals and visibles in mice.
The use ofp-fluorophenylalanine with ‘master strains’ ofAspergillus nidulansfor assigning genes to linkage groups
Authors: McCully Kilmer S. , Forbes E.
Published: September 2009

Four ‘master’ strains ofAspergillus nidulans, three of which are marked on each of the eight chromosomes, are used for assigning genes of unknown location to linkage groups. In this technique a heterozygous diploid is synthesized between one ‘master’ strain and a strain carrying an unlocated marker. This diploid is haploidized by growth onp-fluorophenylalanine, and the haploids thus obtained are classified for recombination between the unlocated marker and each of the markers of the ‘master’ strains. The marker or markers of the ‘master’ strain which show no recombination with the unlocated marker identify the chromosome pair on which the latter is located. One example is presented for each of the four ‘master’ strains.
Quantitative genetic analysis in Phalaris tuberosa II. Assortative mating and maternal effects in the inheritance of date of ear emergence, seed weight and seedling growth rate
Authors: Latter B. D. H.
Published: September 2009

The variation shown by the Australian Commercial population of P. tuberosa in respect of date of ear emergence, seed weight and seedling weight has been analysed, and the interrelationships among the variables characterized. All three characters show appreciable additive genetic variation, in the sense that approximately seven generations of artificial selection would be sufficient to push the population mean for each trait beyond the range shown by introduced ecotypes.

Apart from the positive association between seed weight and seedling weight due to maternal influence, the three variables are to a large extent genetically independent in this locally adapted interbreeding population. It is therefore probable that the negative ecotypic correlations between seedling growth rate and date of ear emergence, and between seed weight and date of ear emergence, would rapidly be dispelled under random mating in a synthetic population.

Under open-pollination, date of ear emergence has been shown to be subject to phenotypic assortative mating of degree ρ = 0·78, approximately 53% of the variation being additive genetic. Variation in seed weight within the strain is extensive, with a heritability of 0·79. Neither character shows evidence of important genotype × years interaction.

Variation in seedling weight involves an appreciable genotype × environment interaction component, and has a heritability of only 0·17 which includes variation due to genetically determined maternal effects. The correlation between the seed weight of an ovule parent and the ‘ true’ mean seedling weight of the derived maternal half-sib group is of the order of 0·57. It has been estimated that the correlated response per generation in seedling weight, due to selection for seed weight, is 0·54 times that expected from direct selection.
Complementation and enzyme studies of revertants induced in anammutant ofN. crassa
Authors: Pateman J. A. , Fincham J. R. S.
Published: September 2009

A total of eighty-seven revertants were induced by ultra-violet light in anam3strain. All of these revertants appear to be the result of mutation at sites in or close to theamlocus. Fourteen of the eighty-seven revertants were partial revertants in that under some conditions of assay they possessed low glutamate dehydrogenase activity compared with the wild-type although their growth rate was similar to that of the wild-type. Enzyme extracts of thirteen of the partial revertants were assayed for glutamate dehydrogenase in various ways in order to establish qualitative distinctions between different kinds of mutant enzyme. On the basis of these tests six different groups were established, of which one contained six revertants, one three and the others one. All except one of the mutant enzyme types showed a marked activation when incubated with α-oxoglutarate plus NADPH2, and all of these had Michaelis constants for ammonium ion much higher than is found for the wild-type enzyme. The remaining group of three revertants gave, at first, no enzyme activity in any of the assay systems. Two of these (the third was not tested) were shown to produce an enzyme variety which becomes quite inactive in phosphate buffer at pH 8·0 but can be fully activated by the addition of ethylenediamine tetra-acetic acid. Forced heterocaryons between each of six partial revertants and elevenammutants were made and the resultant sixty-six heterocaryons assayed for glutamate dehydrogenase activity. The partial revertants differed among themselves in their complementation characteristics. Some complemented with none of theammutants, some witham1only, and some witham1or witham7. The complementation tests confirmed the differences established by the enzyme studies. The data presented here, together with previous work, demonstrate that ultra-violet light induced mutation in anamstrain can result in at least eight types of revertant differing from each other in respect of the glutamate dehydrogenase variety which each can produce.
Effects on genetic recombination ofEscherichia coliK 12 produced by P32decay in the Hfr male
Authors: Krisch Robert
Published: September 2009

The effects of P32disintegration in the Hfr donor cell on the genetic recombination ofEscherichia coliK 12 have been studied. The dose-response relationship for the transfer of markers at a distancexfrom the chromosomal origin,N/N0=e−αxD, which summarizes the findings of Fuerstet al.(1956) for early markers of Hfr H, has been found to hold true to a good approximation for more distal selected markers in this strain, as well as for selected markers of Hfr CS, which transfers its chromosome in the opposite direction. The inheritance by recombinants of non-selected male markers located between the origin and the selected marker is not affected at all by prior P32dose to the Hfr. The sensitivity of each Hfr strain studied to the lethal effects of P32decay corresponds to the sensitivity to transfer effects of a male marker located about one-third of the total chromosomal length away from the origin. Genetic and lethal effects in Hfr H showed the same dependence on storage temperature during P32decay. Our data, therefore, supports the concept of a common origin for the lethal and genetic effects of P32decay.

The quantitative predictions of current models for chromosome transfer with regard to radiation mating experiments have been examined. A simple model, involving no DNA synthesis, as well as the replicon model of Jacobet al.(1963) predict exponential marker inactivation curves of the kind found experimentally. The model of Bouck & Adelberg (1963) predicts a more complex dose dependence, but one not nearly so different from that of the other two models as was anticipated by Jacobet al.It appears unjustified to attempt to exclude any of the three models on the basis of presently available data from radiation mating experiments.
Mutants ofEscherichia colisensitive to methylene blue and acridines
Authors: Sugino Yoshinobu
Published: September 2009

A mutant (Mb-s) ofEscherichia coliK12 which is more sensitive than wild-type (Mb-r) to such dyes as methylene blue or acridines was studied. TheMb-smutant can also be disinfected of F factor with lower concentrations of acridine orange thanMb-rbacteria. TheMblocus was mapped by crosses between Hfr and F−, F-duction with F13, and transduction with phage P1. It was found to be situated between thepurandT6loci on the chromosome. Moreover, it was found to be contained in the chromosomal fragment carried by the F-prime, F13. In a heterogenote obtained by F-duction, theMb-rgene is dominant over theMb-sgene. TheMbgene was transduced jointly with thepurgene by phage P1.
Glutamic dehydrogenase in revertants ofammutants inneurospora
Authors: Stadler David R.
Published: September 2009

Five allelic mutants of Neurospora which lack glutamic dehydrogenase (ammutants) were induced to revert with ultra-violet. The glutamic dehydrogenase produced by the revertants was compared to that of wild-type. Several distinct classes of revertants could be distinguished by these tests. However, genetic analysis showed that all the reversions resulted from events at or near the site of the originalammutation. The spectrum of reversion types depended on the nature of theammutant employed. One mutant, which produces anamprotein believed to be altered in its active site, yielded revertants which were all indistinguishable from wild-type. Another mutant, which produces a protein with a functional active site but altered folding properties, gave at least six classes of revertants which were different from wild-type.
Genetics of MuBl and of a complement defect in inbred strains of mice
Authors: Cinader B. , Dubiski S. , Wardlaw A. C.
Published: September 2009

A mouse antigen, MuB1, has been shown by the study of backcrosses to be inherited in a unifactorial dominant manner. Its inheritance is not linked with gamma globulin allotypes, but has been shown to be linked with the presence of the haemolytic complement system. The concentration of MuB1 in the serum of several inbred strains of mice showed sex-associated differences; however, the presence of MuBl did not depend on the sex of the parents or on the sex of the offspring. The inheritance of antibody responsiveness is discussed in terms of the inheritance of the antigen, MuB1.
The case for somatic crossing over in the mouse
Authors: Grüneberg Hans
Published: September 2009

A review is given of published accounts of mosaics in mice and other rodents, of mutations and of certain unexplained events. The cumulative weight of evidence makes a strong case for the existence of somatic crossing over in the laboratory rodents.
The multiple electrophoretic bands of mouse haemoglobins
Authors: Morton J. R.
Published: September 2009

A survey of past work shows that certainty in the electrophoretic classification of mouse haemoglobins requires further understanding of the meaning of the multiple electrophoretic bands observed.

Six electrophoretic bands are observed in all. Numbered in order of mobility they give the formulae 2 for Hb-s, 1235 for Hb-d, 1246 for Hb-p and 12345 for foetal haemoglobin (Hb-f). When mercaptoethanol is added to the electrophoretic medium these formulae become: 2 for Hb-s, 23 for Hb-d, 24 for Hb-p, 234 for Hb-f. Bands 5 and 6 and a fast ultra-centrifuge fraction both increase when samples are stored.

Bands 5 of Hb-d, 6 of Hb-p, and probably 5 of Hb-f, are dimers of the whole haemoglobin molecule almost certainly joined by sulphur bridges. The monomers are bands 2 and 3 of Hb-d and 2 and 4 of Hb-p. Within each type interconversion of bands 2 and 3 and bands 2 and 4 has been observed.

The hypothesis is suggested that Hb-d and Hb-p both exist as two conformational isomers. In each case one isomer is electrophoretically indistinguishable from Hb-s: the other permits the electrophoretic recognition of their differences in bands 3 and 4, and the formation of sulphur bridges to give bands 5 and 6.
Variability and restrictions against inbreeding and unequal family size in control populations ofTribolium
Authors: Bray D. F.
Published: September 2009

Data from three experiments bearing on the relative stability of the four mating systems required to test the restrictions against inbreeding and unequal family size were examined in relation to the results given by Robinson & Bray (1965).Tribolium castaneumwas the experimental animal used in these experiments.

An analysis of variance indicated that both restrictions were probably effective (Papproximately 0·10) in reducing the phenotypic variability of control population means. It seems likely that the apparent gain in stability obtained when the inbreeding restriction was used in addition to the restriction against unequal numbers is due to non-random genotypic proportions which would affect estimates of genetic variability based on assumptions of random mating.
Suppression of ‘purple’ in Coprinus lagopus—an anomalous genetic situation
Authors: Morgan D. H.
Published: September 2009

The spontaneous reversion to white of three purple mutants of Coprinus lagopus has been demonstrated to be due to suppression. Forty-one of the fifty suppressed purples isolated were crossed to wild-type and all crosses gave fewer than 25% purple progeny, i.e. all the suppressors appeared to be linked to the gene suppressed. Values for the percentage of purples segregated from these crosses varied continuously from 0% to nearly 20%. The functional relationships of the fifty suppressors were investigated by the technique of complementation in dicaryons. The pattern of results formally indicate two suppressor loci with extensive inter-allelic complementation at one of them. The functional allelism indicated by the complementation results is not compatible, in conventional terms, with the apparent positional spread of the suppressors. Several possible explanations are discussed but more data are required before a choice can be made between them. It seems most probable that the same genetic entity is involved in each independent event of suppression and that the characteristic segregations of purples from crosses of suppressed purples with wild-type will have to be explained in terms other than of normal recombination.
Stable and unstable alterations of the host-induced modification properties ofEscherichia coliB, K and C
Authors: Glover S. W. , Colson C.
Published: September 2009

Strains with altered properties of host-induced modification (HIM) have been isolated. Someof these variants were stable on first isolation but the majority of them are unstable. They segregate during many generations two different stable HIM phenotypes and a third type which continues to segregate. Usually this instability disappears during repeated serial single colonyisolation, but in one case it still persisted after nine such single colony isolation steps. Evidence suggesting that they are unstable partial diploids is discussed.
Somatic recombination in the dikaryon ofCoprinus lagopus
Authors: Cowan J. W. , Lewis D.
Published: September 2009

A technique based upon auxotrophic mutants and recessive suppressor genes has been used to select for somatic recombinants in the dikaryon ofCoprinus lagopus. Both haploid and disomic nuclei with a reassortment of chromosomes from the two component nuclei of the dikaryon were found. The presence of the disomics indicates that the recombination process is one of fusion of nuclei with a gradual haploidization by loss of chromosomes at mitotic divisions. An extensive test for crossing-over in theAchromosome failed to give an unambiguous crossover recombinant, but it produced a stock with a normalAchromosome and a fragment of the chromosome.
Mechanically caused damage to Hfr cells ofEscherichia coliK12
Authors: Fisher K. W.
Published: September 2009

When mating pairs ofEscherichia coliK12 are separated by physical means, e.g. by violent agitation, the Hfr cell is unable to mate with a second F−cell. This effect can be simulated by agitation of the Hfr cells prior to mating and, in addition, such cells can be shown to have an impaired ability to adsorb the male-specific coliphage μ2. Inhibitory concentrations of chloramphenicol block the repair of the damage.
On the localization of a factor responsible for host-controlled restriction inEscherichia coliK(P1)
Authors: Schell J. , Glover S. W.
Published: September 2009

The restriction of phage λ.C by K(P1) cells is reduced when the cells are subjected to an EDTA cold-wash treatment which has been shown to remove surface-localized enzymes. We conclude that a surface-localized enzyme plays an essential role in host-controlled restriction.
Characteristics of some single-step mutants to chloramphenicol resistance inEscherichia coliK12 and their interactions with R-factor genes
Authors: Reeve E. C. R.
Published: September 2009

Six one-step Chloramphenicol (Cm)-resistant mutants ofEscherichia coliK12 were graded for resistance to Cm, Tetracycline (Tc) and Puromyein (Pm) by streaking on minimal agar plates containing antibiotic. They fell into at least three distinct groups on the basis of their resistance patterns. One mutant showed increased sensitivity to Pm. Most of the mutants expressed their effect on resistance to Cm and Tc in the presence of R-factors carrying resistance genes for these antibiotics, but one mutant with a relatively high level of resistance to Cm had its resistance effect completely masked in the presence of R-mediated resistance. Similar cases were found among mutants selected for Cm-resistance in another strain of K12.
The interaction between effective population size and linkage intensity under artificial selection
Authors: Latter B. D. H.
Published: September 2009

The effects of tight linkage on the total response due to pairs of identical additive loci, segregating in a population initially in linkage equilibrium, have been studied both algebraically and by means of computer simulation. Particular attention has been given to the effects of finite population size on the probabilities of (a) the elimination from the population of the gamete carrying both ‘plus’ alleles; (b) the joint preservation of the two types of repulsion gametes; (c) the recovery of the desired combination of plus alleles through crossing-over; and (d) the fixation of the gamete in the population following its recovery.

The study is restricted to situations in which linkage is known to have an appreciable effect on total selection response, i.e. to the case of genes of large effect initially at low frequency. A comparison of regimes with the same expected response under free recombination has shown the probability of (a) to be high, and the probability of (b) to be very nearly the same for all regimes tested. Provided that the recovery of the gamete carrying both plus alleles is an unlikely event at any given point in time, the probability of the fixation of the gamete, once reconstituted, is expected to be independent of population size for genes of large effect. In this context, approximate algebraic expressions have been derived for the probability of effective recovery of the required gamete, and for the mean waiting time involved.
Genetic control of flagellar structure inChlamydomonas reinhardii
Authors: Warr J. R. , McVittie A. , Randall John , Hopkins J. M.
Published: September 2009

Seventeen non-motile strains ofChlamydomonas reinhardiiisolated by Dr Lewin and thirty-six newly isolated strains have been examined in the electron microscope for structural abnormalities of the flagella. Fourteen of them have straight, paralysed flagella in which the central fibres are replaced by an irregular core of disorganized material. The fourteen mutations map at four unlinked loci. Some of them are leaky; light and electron microscope observations on leakiness are described. In the former case leakiness is measured by the proportion of motile cells, and in the latter by the proportion of intact centre fibres seen in transverse sections. The degree of leakiness is to some extent characteristic of particular loci.

A partial suppressor of some of these mutations has been isolated which acts on all the mutant alleles at two loci and to a much lesser extent on four out of five alleles at a third locus.
The probable mode of gene action in the circling mutants of the mouse
Authors: Deol M. S.
Published: September 2009

A close examination of reports on circling mutants of the mouse suggested that the commonly held view that the abnormalities of the inner ear are responsible for the waltzing syndrome was probably without foundation. It was thought that a study of kinky (Fuki/+) mice might resolve the doubt, because this mutant has the widest range of abnormalities of the inner ear and behaviour. The results showed that correlation between the two types of abnormalities, although high, was far from complete. This is interpreted as signifying that they are related collaterally rather than lineally. It is argued that they both originate in some primary abnormality of the central nervous system, and circumstantial evidence is presented in support of this argument. It is further suggested that the mode of gene action is essentially similar in all circling mutants, that is the abnormalities of the inner ear are consequent on some early abnormality of the neural tube and the ganglia in the region of the otic vesicle.
Genetic control of the hydrolysis of aromatic esters by sheep plasma A-esterase
Authors: Lee R. M.
Published: September 2009

1. The rate of hydrolysis by sheep plasma of some carboxylic and phosphate esters has been determined for a random flock, and for a flock previously selected for its ability to hydrolyse di-(2-chloroethyl) aryl phosphates.

2. A discontinuous variation in hydrolysis rate was found with all substrates tested and, using combinations of substrates, six types of plasma could be distinguished, each type having a different pattern of esterase activity.

3. The most useful substrates for distinguishing between phenotypes were 1-naphthyl acetate and 4-ethoxycarbonylcoumarin-7-yl acetate. Three rates of hydrolysis were possible for each of these esters, and the highest rate for one was invariably combined with the lowest rate for the other, although the converse did not apply.

4. To explain these results, and those of Lee (1964), it has been postulated that the quantitative production of esterase hydrolysing 1-naphthyl acetate is governed by the presence of an allele, termed Esa, at a particular gene locus. Similarly, the production of esterase hydrolysing 4-ethoxycarbonylcoumarin-7-yl acetate is determined by allele Esb, and where neither substrate is attacked the presence of a third allele, Esc, is proposed.

5. The hydrolysis rates of haloxon, 1-naphthyl butyrate and 4-nitrophenyl butyrate varied in the same way as that of 1-naphthyl acetate, whereas the hydrolysis of indophenyl acetate followed the same pattern as that of 4-ethoxycarbonylcoumarin-7-yl acetate. The variation in hydrolysis rate of Coroxon could be explained by assuming that Esa and Esb are equal in this respect.

6. A mating experiment produced results which were in accordance with the genetic hypothesis, but were too few in number to provide confirmation.

7. The genetic marking of six types of sheep is possible, utilizing the variation in plasma A-esterase activity.
Genetical and embryological studies of the jt form of syndactylism in the mouse
Authors: Center Elizabeth M.
Published: September 2009

1. A form of syndactylism (jt) involving two or three digits on one or more feet has been found in the descendants of Swiss-albino mice treated with HN2. The fusions are in a proximo-distal direction and usually involve only the skin and soft tissues; digits 1 and 5 are unaffected.

2. This type of syndactylism is apparently due to a single recessive gene, jt, whose penetrance is influenced by ‘genetic background’. Apparently the identical mutation has occurred independently in stock maintained at Bar Harbor and Stanford. Linkage tests indicate that jt is not linked with c or lu.

3. Embryological studies of the developing footplate reveal a loss in both preaxial and postaxial footplate tissue, primarily the latter, prior to and during the condensation of mesenchyme into the precartilage of the digital elements in the jt/jt limb.

4. The importance of the shape and amount of footplate tissue to the resultant morphology of the foot is apparent. It is evident that genes such as jt are responsible for changes in footplate development, but the immediate underlying factors which cause these alterations remain an unsolved problem.
A genetical study of thymineless mutants ofE. coliK12
Authors: Alikhanian S. I. , Iljina Tamilla S. , Kaliaeva Eza S. , Kameneva Svetlana V. , Sukhodolec V. V.
Published: September 2009

The 150 independently isolatedthy−mutants ofE. coliK12 Hfr 3.OSO were studied genetically and phenotypically. Variants were found among the mutants in respect to the lag period of thymineless death, and temperature sensitivity. The latter correlates with mutations located at a specific site on the genetical map.

Thethylocus is located between thecysandser/glygenes, and is a linear structure where 134thymutants are distributed over more than 17 sites. The site distribution of the mutants is not regular: about a half of them (62) are localized within one site and all these are temperature-sensitive.

Two further genes involving utilization of thymine—tlrandtd—were found. Mutations oftlrlead to a reduced thymine requirement (0·5 μg./ml.instead of 20 μg./ml.). A mutation oftdresults in thymidine sensitivity.

This latter character is expressed when thetd-sallele is transferred intoE. coliK12, prototrophic for thymine, by conjugation. Thymidine inhibition can be reversed by the addition of any riboside to the growth medium. Both genes map at the proximal end of the Hfr 3.OSO chromosome and are linked with thethrgene. The most probable gene order is:tlr-td-thr.

The following results have been obtained from14C-thymine incorporation experiments with wild-type cells, as well as withthy−tlr+andthy−tlr−cells: (1) Wild-type cells incorporate exogenous thymine extremely poorly, but incorporate thymidine better. (2) Thethy−tlr+mutants are able to incorporate thymine only when high concentration are used, but can utilize a low concentration of thymidine. (3) Thethy−mutants are able to incorporate exogenous thymine as well as thymidine at low concentration. (4) Thetlrmutation is a thymine-specific one.
Curly-whiskers and its linkage with tail-kinks in linkage group II of the mouse
Authors: Falconer D. S. , Isaacson J. H.
Published: September 2009

Curly-whiskers (cw) is a recessive gene which was found in 1958 by Mr C. J. W. Smith of the Chester Beatty Research Institute, London. It arose in a subline of the CBA/Cbi inbred strain. The first mutant animals were one male and one female in a litter of five. The two mutants were mated together and a sib-mated subline was continued from them in which 500 mice were bred, all of which were curly-whiskered. This established the mutant to be fully penetrant. Curly-whiskers resembles the hair-waving genes in causing waving of the vibrissae, but it has no obvious waving effect on the hairs of the coat. The coat texture is, however, slightly abnormal and Mr Smith noted also that on the CBA background there was an appreciable darkening of the coat colour. Homozygotes (cw/cw) are easily classifiable soon after birth by the curled vibrissae. Heterozygotes (+/cw) often have slightly curled vibrissae, and the gene is therefore not fully recessive; but the distinction between +/cw and +/+ could not be relied on, and in the linkage tests cw was treated as a recessive gene.
Evidence for polarity of chromosome replication in F−strains ofEscherichia coli
Authors: Donachie W. D. , Masters Millicent
Published: September 2009

The inducibility of three enzymes (β-galactosidase, tryptophanase and D-serine deaminase) has been measured at various times during the cell cycles of three strains ofEscherichia coli(K12 58–161 F−, B/r F–and 15T−). In each strain sharp increases in inducibility of these enzymes occurred at characteristic periods in each cell cycle. Such increases depend on DNA replication and therefore probably reflect synchronized gene replication. It is inferred that chromosome replication in these F−strains is sequential from a fixed origin.

Infection with F′Lack+results in an extra period of increase in inducibiity of β-galactosidase in each cell cycle. It is concluded that the F′ episome replicates once in each cell cycle at a time soon after cell separation.