bluuebunny/crossref_metadata_2025 huggingface dataset:
The control of plastid inheritance in Pelargonium
Authors: Tilney-Bassett R. A. E.
Published: September 2009

Twenty-four reciprocal crosses between two green and six chimera cultivars, containing respectively normal green and mutant white plastids in their germ layers, were analysed for their segregation patterns of green, variegated and white embryos, and for their fertility data.

Analysis of variance of fertility data showed that W × G crosses were generally less fertile than the reciprocal G × W crosses, but this was not correlated with selection against any particular class of embryo.

Analysis of segregation patterns showed that they were essentially the same with a constant female and varying male parent, but change the female and the pattern could be radically altered. The six different mutant females with both constant green males could be arranged in a sequence in which white plastids were increasingly successful, and white and variegated embryos increasingly frequent. A similar sequence was demonstrated with three green females and two constant white males. It was concluded that the major control of plastid inheritance was determined by the female nuclear and plastid genotypes, with the male having only a minor, modifying influence even when male plastids were more successfully transmitted than female ones.

The very low frequencies of variegated embryos in some crosses led to a rejection of the classical hypothesis of sorting-out from mixed cells, and its replacement by the hypothesis that pure green or pure white embryos arise by the replication of only one plastid at a time, whereas variegated embryos arise by replication of both plastids.
Genetics of a chain-forming mutant ofEscherichia coli: Transduction and dominance of theenvAgene mediating increased penetration to some antibacterial agents
Authors: Normark Staffan
Published: September 2009

We have recently described a chain-forming mutant ofEscherichia coliwhich showed a decreased resistance to ampicillin and several other antibiotics (Normark, Boman & Mattson, 1969). The gene mediating drug sensitivity was denotedenvAand by conjugation mapped at 2–4 min. Transduction experiments have now shown thatenvAis located betweenleuandaziat 1·5 min. The mapping was facilitated by the finding thatenvAmediated sensitivity to actinomycin D, rifampicin and gentian violet. TheenvAlocus could be genetically differentiated from thepealocus mediating resistance to phenethyl alcohol (Yura & Wada, 1968). Studies using partial diploids revealed thatenvAwas recessive to its wild-type allele both when located on an episome and on the chromosome.

Assuming that revertants fromenvAto the wild-type allele could be selected as ampicillin-resistant derivatives, such mutants were isolated and their phenotype characterized. Reversion to ampicillin resistance was accompanied by reversion to insensitivity to actinomycin D. However, not all revertants exhibited wild-type tolerance to rifampicin. Three different ampicillin-resistant revertants were studied genetically. The results indicate that these strains contain suppressor mutations in theenvAregion of the chromosome. It is suggested that theenvAgene, directly or indirectly, affects the EDTA sensitive ‘permeability barrier’ of the surface layer ofEscherichia coli.
Penicillinase synthesis inStaphylococcus aureus: the effect of inducer and of the cellular location of the genetic determinants on the amount of enzyme formed
Authors: Asheshov Elizabeth H. , Woods Jennifer M. , Dyke K. G. H.
Published: September 2009

A comparison was made of the amount of penicillinase produced by strains ofStaphylococcus aureuscarrying chromosomal penicillinase genes, plasmid penicillinase genes and strains carrying both chromosomal and plasmid genes. Plasmid genes were found to produce at least twice as much enzyme as homologous chromosomal genes. The results suggest that there are, on average, two plasmids per chromosome in exponentially growing cells.

Two inducers were used in these experiments—methicillin and 2-(2′-carboxyphenyl)-benzoyl-6-aminopenicillanicacid (CBAP). The latter proved a more efficient inducer than methicillin and this difference was most apparent when more than onei+gene was present, which suggests that the efficiency of induction reflects the ability of the inducer to react with represser.
Mutant Hfr strains defective in transfer: restoration by F-like and I-like de-repressed R factors
Authors: Cooke Marylyn , Meynell Elinor , Lawn A. M.
Published: September 2009

Mutants of Hfr strains ofEscherichia coliK12 defective in conjugation owing to failure to produce sex pili were isolated by resistance to F-specific phage. Tests of the ability of six de-repressed F-like R factors and four de-repressed I-like R factors to restore Hfr donor behaviour to these mutants indicated that there were several ways in which such restoration could occur. Of a total of 26 defective mutants, 12 were restored by F-like R factors. In these twelve, the function of the integrated F factor was evidently restored, because the sex pili contained F pilin subunits, distinguishable from the R pilin by serological tests. In contrast, among the four I-like R factors, only two were effective, butin all 26 defective mutants; the restored Hfr bacteria produced only I-like pili. The I-like sex factors, in restoring Hfr donor behaviour, did not therefore act by complementing the defective F.
Mitotic mapping ofSchizosaccharomyces pombe
Authors: da Cunha Miguel Flores
Published: September 2009

Genetic mapping by means of mitotic haploidization (induced by parafluoropkenylalanine) and mitotic crossing-over was carried out with the fission yeastSchizosaccharomyces pombe. Thirty-two different genetic markers were involved in this investigation; some meiotic linkage relationships had been previously reported (Leupold, Megnet) for 16 of these loci. Mitotic haploidization experiments resulted in the genetic identification of six chromosomes in the haploid complement.

Furthermore, in an attempt to study the mechanism of action of parafluorophenylalanine (pFPA) on mitotic haploidization, pedigree analyses were performed by micromanipulation of diploid cells growing in the presence of pFPA. Haploid cells were detected after 40 hours of contact with the analogue and many lethal pedigree branches were observed. These observations seem to agree with Käfer's (1961) and Lhoa's (1968) suggestion that mitotic haploidization in Fungi is achieved by progressive loss of chromosomes throughout cell divisions.
The inhibitory action of transfer factors on lysis ofEscherichia coliK 12 by phages μ 2 and Φ 2
Authors: Pitton J. S. , Anderson E. S.
Published: September 2009

A selection offi+resistance factors and transfer factors, when introduced into K 12F+, showed a range of inhibitory activity of lysis by the male-specific phage μ 2. This range can be used to subdivide thefi+factors intofi+1,fi+2,fi+3andfi+4classes, according to the degree of inhibition of μ 2 lysis. To this subdivision can be added restriction of the ‘female-specific’ phage φ 2.

Introduction of all thefi+factors tested into K 12 HfrH totally inhibited lysis by μ 2 in spot tests, but with twofi+1and onefi+2factors visible lysis was obtained in agar-layer tests. These three factors caused least inhibition of transfer ofproby HfrH. It can be assumed that both tests reflect lower inhibition of sex fimbrial formation by thesefi+factors than by the remainder.

Thefi−factors, when introduced into K 12, can be subdivided on the basis of restrictive effects on phage φ 2.

These effects can be added to phage restriction in the salmonellae for the purposes of further classification of the transfer factors and R-factors.
Genetic studies of thebincompatability locus ofUstilago maydis
Authors: Puhalla John E.
Published: September 2009

Theblocus ofUstilago maydisis both an incompatibility locus and a pathogenicity locus. There are several differentbfactors, and they are randomly distributed and equally frequent in the natural population. A sample of 62 lines contained 18bgroups and permitted an estimate of no more than 25bgroups in the natural population. All lines within the samebgroup are indistinguishable in their mating behaviour. No linkage was detected betweenband any of the four biochemical markers tested. No intrafactor recombinants atbwere found among more than 6700 progeny. Differences in degree of pathogenicity between solopathogenic diploids and comparable haploid by haploid crosses were detected.
OnXinactivation inXOembryos of mammals
Authors: Chandra H. Sharat
Published: September 2009

By analogy with the situation in coccids it is suggested that in mammalianXOembryos the singleXturns heterochromatic in some cells, but that such a change does not result in cell death because theXthen reverts back to an euchromatic and active state. This testable alternative to the Gartler–Sparkes hypothesis would imply that the anomalies of theXOTurner syndrome are largely due to imbalance of sex-linked genes rather than developmental damage resulting from cell death and that mammalianXinactivation might become reversed in response to special developmental needs.
The founder effect and response to artificial selection
Authors: James J. W.
Published: September 2009

The response to selection in any line depends on the size of the initial sample by which the line is founded. For a single locus with additive gene action the effects of number of founders on early rate of response and on final limits are studied in relation to selection intensity and number of parents in the selected line. The reduction in total response caused by a small number of founders is greatest for large populations under intense selection, especially when the desirable alleles are rare in the base population. If these alleles are at high frequencies it is possible that a line which has gone through a bottleneck may be more sensitive to a reduced population size during subsequent selection than a line which has not. Under some conditions replicate selection lines founded with small samples are likely to be less variable in response than lines founded with moderately large samples.
Genetic aspects of fertility and endocrine organ size in rats
Authors: Mullen R. J. , Hoornbeek F. K.
Published: September 2009

An investigation of the genetic aspects of fertility was conducted among inbred and hybrid generations of rats. The high-fertility LEW strain and the low fertility CAS strain were crossed and their hybrids inbred for four generations. Litter size, ovulation rate, sterility, and the weights of the thyroid, pituitary, adrenals, testes, seminal vesicles, ventral prostate, uterus, and ovaries were analysed in inbred and hybrid rats for evidence of strain differences and heterosis and in successive generations of sib matings for inbreeding depression.

CAS females produced smaller litters and had smaller thyroids, pituitaries, adrenals, ovaries, and uteri than LEW females. CAS males had larger testes but smaller adrenals than LEW males. Results of crosses included heterosis for female pituitary and ovary weights, but inbreeding depression for the weights of male adrenals, seminal vesicles, and ventral prostates, and female thyroids and uteri. Ovulation rate did not differ between strains and was not an important determinant of litter size in this study.

The decrease in litter size as a result of inbreeding was due partly to the inbreeding of the parents and partly to the inbreeding of the litter.
Controlling elements in the mouseX-chromosome III. Influence upon both parts of anXdivided by rearrangement
Authors: Cattanach B. M.
Published: September 2009

Data are presented which support the conclusion that in thefleckedtranslocation,T (1; X) Ct, there is a spread of inactivation into both sides of the autosomal region inserted into theX. This would indicate that both parts of the dividedXare subject to theX-inactivation process. The data also demonstrate that the inactivation of autosomal genes lying near each end of the insertion are modified by theX-chromosome controlling element system,Xce. Since the element modifies the heterozygous expression ofX-linked genes on one side of the insertion, it would therefore be expected that it similarly modifies the heterozygous phenotypes of those on the other side. The data thus support the concept that the controlling element is the master gene, receptor site or inactivation centre which regulates theXinactivation process.
Substitution of rye chromosome 5R for its three wheat homoeologues
Authors: Bielig L. M. , Driscoll C. J.
Published: September 2009

Chromosome 5R ofSecale cerealevar. Imperial has been substituted for chromosomes 5A, 5B and 5D of hexaploid wheat. There is evidence of compensation, in terms of vigour, in all substitution lines. Chromosome 5R rectifies the male sterility of nullisomics 5A and 5D; however, it is unable to circumvent the meiotic irregularity and male sterility of 5B-deficient stocks. Another instance of wheat-rye chromosome pairing, in the absence of chromosome 5B, is reported. The data reported here demonstrate that the long arm of 5R is the more essential arm and indicate that chromosome 5R is homoeologously related to the group 5 chromosomes of wheat.
Induced variation in chiasma frequency in Rye in response to phosphate treatments
Authors: Bennett M. D. , Rees H.
Published: September 2009

Plants of two rye genotypes, one highly inbred, the other not, were grown with varying amounts of available mineral phosphate. In two experiments, one using culture solutions, the other a field experiment, the results show an effect of phosphate treatments on mean chiasma frequency at first metaphase in meiocytes. Plants given increased amounts of phosphate showed an increase in chiasma frequency. A similar effect of phosphate on chromosome size and mass at mitotic metaphase in meristems is known and there may be a direct link between chromosome size and chiasma frequency.
Genetic evidence of an unorthodox chromosomal system in the lac insectKerria lacca(Kerr)
Authors: Chauhan N. S.
Published: September 2009

The colour difference (crimson and yellow) inKerria lacca(Kerr) was used to test the ‘Lecanoid’ system of chromosome behaviour proposed on cytological evidence. The colour strains bred true for colour. Reciprocal matings between the colour strains produced only crimson sons and daughters, confirming that the colour difference is not sex-linked and that the male is somatically a diploid. The phenotypes of the F2and the backcross generations differed according to the heterozygosity and the direction of cross of the F1parents, since heterozygous females produced two kinds of gamete but heterozygous males produced only the maternal kind. Thus, while elimination of the paternal gene and hence chromosome was confirmed during the formation of male sex-cells, demonstration of somatic diploidy of the male is not compatible with a ‘Lecanoid’ system inK. lacca. Instead, the available cytogenetic evidence is suggestive of a chromosome system with heterochromatization and elimination of the paternal chromosome-set confined to the male germ line.
Chromosomal analysis of cultured skin fibroblasts from patients with infectious mononucleosis
Authors: Monteleone Patricia L. , Cherry James D. , Monteleone James A.
Published: September 2009

In the present study, skin fibroblasts and leukocyte cultures from patients with acute infectious mononucleosis were examined to determine if any in vitro marker chromosomes could be detected. No alterations in chromosomes could be found in fibroblasts either from the region of the typical rash or from other areas of skin. This would tend to suggest but does not necessarily prove that this tissue was not extensively involved in the disease process.
Two mutations giving low-level streptomycin resistance inEscherichia coliK12
Authors: Roberts Lilian M. , Reeve E. C. R.
Published: September 2009

A mutation inEscherichia coliK12 giving resistance to about 5 μg/ml of streptomycin was found to be cotransducible by P1 withproAandproB, and is located at about 8·5 min on the chromosome map. The locus is namedstrB. A second mutation to the same resistance level was not cotransducible with eitherproAorproBand must be located elsewhere. Both mutations cause a marked increase in R-factor mediated streptomycin resistance, and significant decreases in resistance to several other antibiotics, both in the presence and absence of an R-factor determinant for the same antibiotic. The two mutations differ in their effects on bacterial sensitivity to crystal violet and EDTA.
Factor responsible for spermatozoan abnormality located on theYchromosome in mice
Authors: Krzanowska H.
Published: September 2009

Two inbred strains of mice differing in the mean percentage of spermatozoa with abnormal heads were used: KE (16·1%) and CBA (5·9%). TheF1resulting from the crosses exhibited a heterosis effect, while in the backcrosses an obvious segregation of genotypes was observed; both generations showed a reciprocal difference, depending on the source of theYchromosome. The character of sperm head abnormality seems to be polygenically determined, one of the genes being located on chromosomeY.

Seven generations of backcrosses were performed in which theYchromosome from CBA was introduced to the genetical background of the KE strain. In the seventh generation 10·2% of abnormal spermatozoa were found, which is significantly lower than in the KE strain. The difference shows the net effect of theY-linked locus. A correlated difference was found in the fertilization rate, indicating that a factor influencing male fertility is located on chromosomeY. It does not seem to influence the shape of normal spermatozoan heads.

Karyotype analysis did not reveal gross abnormalities in the KE strain.
Genetic studies of ovulation rate in the mouse
Authors: Land R. B. , Falconer D. S.
Published: September 2009

Genetic and physiological studies of ovulation rate, both natural and induced, in a random bred population of laboratory mice led to the following results.

(1) The heritability of natural ovulation rate in nulliparous females was 22±19%, estimated from the correlation between paternal half-sibs.

(2) Selection applied to natural ovulation in primiparous females led to a response in both directions, with a realized heritability of 31% (h2within litters = 0·18 ± 0·013). The number of eggs shed by the High, Control and Low lines after 12 generations were respectively 21, 16 and 14.

(3) Selection applied to ovulation induced by 4 i.u. of PMS led also to a response in both directions, with a realized heritability of 22% (h2within litters = 0·11 ± 0·038). The induced ovulation rates of the High, Control and Low lines after 12 generations were respectively 29, 19 and 14 eggs.

(4) PMS-equivalents were calculated from dose-response curves, and were found to be nearly the same in all lines except the line selected for high natural ovulation rate, which had a PMS-equivalent nearly double that of the Control. From this it was inferred that the increase of ovulation rate resulting from selection for high natural ovulation was due to an increased FSH activity, whereas the changes of ovulation rate resulting from selection for low natural ovulation and for both high and low induced ovulation were due to changes of ovarian sensitivity.

(5) Genetic correlations, estimated from correlated responses to selection, were: (i) between natural and induced ovulation in primiparous females, 0·33; (ii) between primiparous and nulliparous females in natural ovulation, 0·46; (iii) between primiparous and nulliparous females in induced ovulation, 0·82.

(6) The selection for induced ovulation produced changes in litter size following natural ovulation that were nearly equal to the changes in natural ovulation rate. The selection for natural ovulation, however, produced no clear changes of litter size.
Linkage disequilibrium due to random genetic drift
Authors: Ohta Tomoko , Kimura Motoo
Published: September 2009

The behaviour of linkage disequilibrium between two segregating loci in finite populations has been studied as a continuous stochastic process for different intensity of linkage, assuming no selection. By the method of the Kolmogorov backward equation, the expected values of the square of linkage disequilibriumz2, and other two quantities,xy(1 −x) (1 −y) andz(1 − 2x) (1 − 2y), were obtained in terms ofT, the time measured inNeas unit, andR, the product of recombination fraction (c) and effective population number (Ne). The rate of decrease of the simultaneous heterozygosity at two loci and also the asymptotic rate of decrease of the probability for the coexistence of four gamete types within a population were determined. The eigenvalues λ1, λ2and λ3related to the stochastic process are tabulated for various values ofR=Nec.
Investigation of the mating system of Pseudomonas aeruginosa strain 1: IV. Mapping of distal markers
Authors: Loutit J. S.
Published: September 2009

Thirteen selected distal markers have been mapped by time of entry studies and linkage analysis. They appear to fall on two distinct linkage groups and with the ten previously described there are nineteen markers on one group and four on the other. There is as yet no clear evidence that the two groups are linked, but this possibility has not been excluded.

Of the thirteen markers described, six can be mapped by measuring their time of entry into suitable recipients. It should now be possible to establish the order of any further marker and to provide more accurate information for any marker transferred within 35 min from the time of mixing the cells.
A correction to our earlier paper on ‘The effect of repeated cycles of selection and regeneration in populations of finite size’
Authors: Curnow R. N. , Baker L. H.
Published: September 2009

The basic recurrence equations given in our previous paper have to be modified when males and females are differentiated. The modifications we gave are incorrect because we ignored the deviations from Hardy–Weinberg equilibrium when sampling and selection are applied separately to the two sexes. Appropriate corrections are presented in this paper.
Induction of cytoplasmic respiratory deficiency in yeast by phenethyl alcohol
Authors: Wilkie D. , Maroudas N. G.
Published: September 2009

Phenethyl alcohol is shown to induce cytoplasmic respiratory deficiency (petite mutation) in various strains ofSaccharomyces cerevisiae. Apart from petite induction, phenethyl alcohol also affects cell growth both in respiratile and non-respirable media. This sensitivity to growth inhibition appears to be complex, and does not correlate with the degree of induction of respiratory deficiency.
On the theory of artificial selection in finite populations
Authors: Hill W. G.
Published: September 2009

The effect of selection on individual performance for a quantitative trait is studied theoretically for populations of finite size. The trait is assumed to be affected by environmental error and by segregation at a single locus. Exact formulae are derived to predict the change in gene frequency at this locus, initially by finding the probability distribution of the numbers of each genotype selected from a finite population of specified genotypic composition. Assuming that there is random mating and no natural selection the results are extended to describe repeated cycles of artificial selection for a monecious population. The formulae are evaluated numerically for the case of normally distributed environmental errors.

Using numerical examples comparisons are made between the exact values for the predicted change in gene frequency with values obtained using approximate, but simpler, methods. Unless the gene has a large effect (α) on the quantitative trait, relative to the standard deviation of the environmental errors, the agreement between exact and approximate methods is satisfactory for most predictive purposes. The chance of fixation after repeated generations of selection is also evaluated using the exact method, and by means of a diffusion approximation and simple transition probability matrix methods. Except for very small values of population size (N) and large α the results from the diffusion equation agree closely with those from the exact method. Similar results are found from tests made of the prediction from the diffusion equation that the limit is only a function ofNα for a given intensity of selection and initial frequency, and that the rate of advance in gene frequency is proportional to 1/Nfor the same set of parameters.
Selection for larval growth inTriboliumunder two levels of nutrition
Authors: Yamada Yukio , Bell A. E.
Published: September 2009

Selection for large and small 13-day larval weight inTribolium castaneumwas studied for sixteen generations in a replicated experiment to evaluate the effectiveness of various selection methods and the importance of genotype by environment interactions under two levels of nutrition.

Direct selection responses generally were larger than correlated ones under both Good and Poor nutritional environments. However, contrary to theoretical expectations, those populations selected on average performance in both environments were not superior for this attribute.

Asymmetrical responses were observed to be dependent on the environment of selection. When selection was based on performance in the optimal environment, the asymmetry was observed toward small size. This situation in the sub – optimal environment was completely reversed. This phenomenon was discussed in terms of physiological limits rather than gene frequency and directional dominance.

It was proposed that selection of compound traits such as body weight at a fixed age may affect the component characters quite differently. As the latter are differentiated by direction and environment of selection, the compound trait may reflect parametric changes and enhanced genotype by environment interactions. Such changes hamper the precision of current selection theory for predicting response even in the short run.
A comparison of some biological characteristics of the mouse-passaged scrapie agents, 22A and ME7
Authors: Dickinson A. G. , Meikle Veronica M. H.
Published: September 2009

Two mouse-adapted scrapie agents of different sheep origin were compared. The titre, reached in the brains of mice in the terminal stage of scrapie, is of the same order for both agents. There is a threefold difference between the incubation periods of the two agents in some mouse strains, of which C57 is one, and in this strain incubation of the 22A agent, given as a large dose by a peripheral route, occupies almost the whole life-span.

The most fundamental difference between the agents concerns the reversal of the ranking of incubation periods, typically in the VM and C57 mouse strams: incubation of ME7 in VM takes almost twice as long as in C57, whereas most sub-lines of 22A take half as long in VM as in C57. The implications of this type of host-genotype, agent-strain interaction are discussed in terms of the possible nature of agent differences, the possibility of latent infection and the consequences for scrapie eradication programmes.
Genetics of host-controlled restriction and modification inEscherichia coli
Authors: Glover S. W. , Colson C.
Published: September 2009

The sites of mutations affecting host-controlled modification (HCM) have been mapped inE. coliK andE. coliB by conjugation and transduction experiments between mutants. These mutations all map close to theserBlocus on the opposite side to the markerthr. Non-parental HCM has been observed among colonies obtained from Pl transduction experiments between HCM mutants. Control experiments have shown that these non-parental recombinants can not be accounted for by reversion of either parent and must result from recombination between mutants. Several genetic models are suggested which could account for these recombinants and an attempt is made to distinguish between various models by testing for complementation between mutants in a zygotic induction complementation test.
The spread of genes in random mating control populations
Authors: James J. W.
Published: September 2009

1. The effect of genetic sampling, when this sampling is without replacement, on variation in gene frequency is studied, and equations describing the genetic drift are derived. The effective size turns out to be about one greater than under sampling with replacement.

2. The relation between ‘spread of genes’ and genetic drift is worked out.

3. The University of Queensland control poultry flock is analysed by these methods.

4. The design of control populations is discussed with particular reference to the relative importance of genetic drift and phenotypic sampling.
Recombination in a Myxomycete, Physarum polycephalum Schw.
Authors: Dee Jennifer
Published: September 2009

1. Techniques were developed to facilitate genetic analysis of a Myxomycete, Physarum polycephalum. The uninucleate cells that form part of the life-cycle (the ‘amoebae’), in two-membered culture with Pseudomonas fluorescens, were found to be suitable for handling by some of the standard techniques of microbial genetics, including plating.

2. As reported previously, a single-factor (+/−) mating-type system was discovered in P. polycephalum controlling the formation of plasmodia by the amoebae. Plasmodia are formed only when amoebae of different mating-type are mixed together. A single spore gives a culture of amoebae of one mating-type only, which may be assumed to be a clone.

3. A strain of amoebae resistant to emetine hydrochloride was isolated and was found to maintain its resistance through many subcultures in the absence of the drug.

4. A cross was made between the emetine-resistant strain (mating-type −) and an emetine-sensitive strain (mating-type +). Spores obtained from the hybrid plasmodium were plated and four sets of isolates of amoebae were made from these spores, and separately tested for mating-type and for emetine resistance.

5. The results of testing these isolates agree with the hypothesis that mating-type and emetine resistance are determined by pairs of alleles at two unlinked loci provided that factors disturbing the segregation for emetine resistance are assumed to be present.

6. Consideration of factors that could have disturbed the segregation for emetine resistance shows that selfing did not occur in the cross but that some misclassification for emetine resistance probably did occur.
The efficiency of food utilization, digestibility of foodstuffs and energy expenditure of mice selected for large or small body size
Authors: Fowler Ruth E.
Published: September 2009

The efficiency of food utilization, the digestibility of foodstuffs, energy metabolism, and body activity have been studied in three lines of mice, one selected for large, another for small body size, and a third, control, line.

The gross efficiency of food utilization was highest in the large line, intermediate in the control line and lowest in the small line between 21 and approximately 35 days of age. During this period, gross efficiency declined in the large and control lines with increasing size and decreasing growth-rate, presumably due to an increase in maintenance costs in comparison with the weight gained. In the small line, the efficiency of food utilization increased up to 35 days of age but declined thereafter. The energetic efficiency (measured in Calories) was higher in the large than in the small line up to 4 weeks of age, i.e. when the growth-rate was high, and after 6 weeks of age, when fat was being deposited at an increased rate.

The increased efficiency of large mice was not entirely associated with a greater proportion of the ingested food being absorbed from the gut. Large mice absorbed a greater proportion of protein, though the difference was not sufficient to account for the large weight difference between the large and small lines.

The energy expenditure of mice of the large line was greater than that of the small line at all ages and similar for the same body weights. The reduced growth-rate of small mice was not due to abnormally high or low energy costs. There was no evidence that body activity determined or restricted the rate of growth in either line.

Mice selected for small size were phenotypically unlike pituitary dwarf mice, although the low nitrogen retention during the growing-period indicated a deficiency of some growth stimulus.
The fine genetic structure of thepabalregion ofAspergillus nidulans
Authors: Siddiqi Obaid H.
Published: September 2009

The linear relationship between fourteen allelicp-aminobenzoic-acid-requiring mutants ofAspergillus nidulanswas investigated. The mutants were assigned to twelve different mutational sites within one functional region. No case of intra-cistron complementation was found. The order of sites as determined by the distribution of the outside markers in different crosses betweenpabaalleles is consistent and the recombination fractions between the sites are approximately additive. Crossing-over between alleles is associated with strong localized negative interference. The topography of thepabalregion is characterized by a marked concentration of the mutational sites in a small part of the cistron.
Genetical studies on the skeleton of the mouse XXXII. The Development of Shaker with Syndactylism
Authors: Grüneberg Hans
Published: September 2009

1. The first known effect of the gene for shaker with syndactylism (sy) in the mouse is a reduction, both preaxial and postaxial, of the foot plates at the 12½-day stage. This reduction forces the blastemata of digits 2, 3 and 4 to be laid down more nearly parallel to each other, with a subsequent tendency for adjacent blastemata to coalesce with each other. The possibility is considered that this essentially quantitative reduction of the foot plate material may itself be the consequence of some more specific and qualitative (but hitherto undiscovered) change in the limb buds.

2. The physiological connexion between syndactylism and the systemic changes in the cartilaginous and osseous skeleton which arise later in sy/sy mice remains obscure.
The application of tissue-culture techniques to the chromosomal analysis of Bos taurus
Authors: Crossley R. , Clarke G.
Published: September 2009

Until 1960 all the chromosome counts performed on cells of this species were done on histologically prepared specimens of testicular tissue. In January 1960, Chiarelli et al. published the results of their experiments to grow renal tissue in culture. Their specimens were obtained from male and female calves. They confirmed that 2n = 60 and described the chromosomes as being all acrocentric except the X chromosome, which was submetacentric.

The purpose of the work described below was to try to apply the peripheral-blood culture technique of Moorhead to bovine blood, and to attempt to grow bovine muscle cells in a tissue culture.
‘Shrivelled’: a hereditary degeneration of the lens in the house mouse
Authors: Fraser F. Clarke , Schabtach Gretchen
Published: September 2009

Shrivelled, a new mutant in the house mouse, is characterized by degeneration of the fibres of the ocular lens, followed by the development of cataracts. The condition is caused by a mutant autosomal gene showing intermediate dominance.
Haploid intersexes inMormoniella
Authors: Saul George B.
Published: September 2009

Intersexual individuals occurring among the progeny of a single virgin femaleMormoniellaare described and compared with similar cases of intersexuality described forHabrobracon. Evidence is presented in support of the hypothesis that the intersexuality resulted from a mutation at a single locus.
The size and endocrine activity of the pituitary in mice selected for large or small body-size
Authors: Edwards R. G.
Published: September 2009

Mice of two strains, N and C, were used in studies on body-size, pituitary size, and endocrine potency of the pituitary. Strain N had been selected for large (NL) and small (NS) body-size; strain C had also been selected for large body-size (CL) but had been crossed to an outbred strain segregating pituitary dwarfism.

Pituitary weights and body-weights were highly correlated, the regression lines being common in NL and NS mice. Female pituitaries were considerably heavier than male pituitaries in CL mice. In relation to body-weight, CL pituitaries were consistently heavier than those of NL or NS mice.

No differences were detected in the unit potency of gonadotrophins in the pituitaries of NL and NS mice as estimated by the uterine response of immature outbred mice to subcutaneous injections of pituitary tissue. The uptake of 131I into the thyroid was comparable in NL and NS mice per unit of body-weight, and the thyroid secretion rate was also similar using animals of the same body-weight. Immature mice of both lines responded by increased growth to injections of growth hormone or fresh mouse pituitary, though the response was greater in NS than in NL mice.

The primary response to selection has probably been in the size of the pituitary rather than in its unit potency. The interrelationships between body-size, body components, organ size and endocrine levels are discussed.
XO mice
Authors: Cattanach Bruce M.
Published: September 2009

The inactive-X hypothesis (Lyon, 1961) states that in the normal female mouse only one of the two X chromosomes is genetically active in each cell of the body other than the germ-cells, and that the choice of which X is to be inactivated occurs at an early stage of embryogenesis, and is at random in each cell. The descendants of these cells then abide by the decision so that females are mosaics for two lines of cells and may show a mosaic phenotype if they are heterozygous for a sex-linked gene. One requisite for the validity of this hypothesis is that only one X is necessary for the development of a normal female mouse, and evidence substantiating this supposition is the apparent normality of XO mice (Welshons & Russell, 1959; Cattanach, 1961a, b). On the other hand it has been suggested that XO mice are not fully viable (Russell, Russell & Gower, 1959), but no data on the comparative viability and growth of XO female mice have yet been reported. In the present communication data of this nature, collected in the process of setting up an XO stock, are presented and support the hypothesis that only one X chromosome is necessary for normal female mouse development.
The phenogenetics of hair mutants in the house mouse: Opossum and Ragged
Authors: Mann Stanley J.
Published: September 2009

1. The development and morphology of the semi-dominant mutations Ragged and Opossum are compared. The results of the present study support evidence of previous linkage studies which suggest that Ragged (Ra) and Opossum (Raop) are alleles.

2. Examination of embryos from 18-day-old first parity matings of + + × Raop + reveals that there is no deficiency of Raop + embryos. However, in Ra + × Raop + and Raop + × Raop + matings some Raop + embryos die in utero in addition to the pre-natal death of the RaRaop and RaopRaop embryos.

3. In all matings of Ragged and Opossum, there is a high frequency of oedematous Raop + embryos. In + + × Raop + matings, the frequency of oedema increases with increased age of the embryos.

4. Although the pattern of hair follicle formation is the same in both the mutant and normal embryos, follicles begin initiation later in the mutant embryos. The delay in follicle initiation is increased in the following order: Ra +, Raop + (non-oedemic), RaRa and Raop + (oedemic).

5. Heterozygous Opossum and Ra + mice have a full complement of pelage follicle primordia, but some follicles fail to differentiate. The differentiating follicles pass through the same developmental stages and require the same time for development as follicles in + + mice.

6. Heterozygous Ragged and Raop + mice have a full complement of tylotrichs, whereas the concentration of awls is variable. In Ra + mice there is a reduction in zigzags, and Raop + mice usually lack zigzags. No auchenes are observed in the mutant mice.

7. Hair growth is asynchronous in Ra + and Raop + mice, with the exception of the first pelage coat. The quiescent phase of the hair growth cycle is short or even missing.

8. The degree of Ra and Raop gene activity is in the following order of increased severity: Ra +, Raop + (semi-lethal), RaRa (semi-lethal), RaRaop (lethal) and RaopRaop (lethal).
F-prime transfer and multiplication of sexduced cells
Authors: de Haan P. G. , Stouthamer A. H.
Published: September 2009

A variable delay among mating pairs in the time between contact formation and the initiation ofFtransfer was found. The conjugation process has no effect on the multiplication of the recipient cell.

In liquid medium newly infectingF-particles multiply faster than the host cell.

The experiment strongly suggests that the number of episomes per cell is small and that the distribution of theF-factor among the daughter cells is non-random.
Mutations of theAmating type factor inCoprinus lagopus
Authors: Day P. R.
Published: September 2009

TenAfactor mutants and an unlinkedAsuppressor mutant were isolated from fruit bodies formed by commonAheterokaryons ofCoprinus lagopus. AllAfactor mutants formed false clamps and lackedAmating-type specificity. FourA5and twoA6mutants had functional α sub-units which were recovered in tests for intra-factor recombination in matings between mutant and wild-type factors. No functional β sub-units were recovered in tests of two of theA5mutants and the twoA6mutants which possessed functional α sub-units. From three other mutants (twoA5and oneA6) neither α nor β sub-units were recovered.

The suppressor mutant also formed false clamps but was recessive since stocks carrying it retained theirAandBspecificities when mated with wild-type testers. Fruit bodies formed by monokaryons carrying the suppressor mutant had pale gills bearing varying proportions of abnormal tetrads with less than four spores.
Serum transferrins in Merino sheep
Authors: Ashton G. C. , Ferguson K. A.
Published: September 2009

Serum samples from 1963 Merino sheep were examined for serum transferrin type. Two of the five transferrin alleles previously described in British breeds of sheep, viz.T fAandT fc, were found, butT fB,T fDandT fEwere absent. Evidence for seven further transferrin alleles was obtained. These alleles were codedT fF,T fG,T fH,T fJ,T fN,T fKandT fLin decreasing order of mobility of the zones they produce in starch gel.

Gene frequency data is presented for the populations studied.
Genetically determined organ specific responses to the teratogenic action of 6-aminonicotinamide in the mouse
Authors: Goldstein Marc , Pinsky Merrille Feiner , Fraser F. C.
Published: September 2009

1. A two-hour relative deficiency of nicotinamide, produced by maternal treatment with 6-aminonicotinamide, resulted in a maximum frequency of vertebral fusions following treatment on day 9·5 of gestation, and a maximum frequency of cleft palates following treatment on day 13·5.

2. Both defects appeared with higher frequencies in the A/Jax than in the C57BL/6J inbred strain.

3. The frequency of induced vertebral fusions in F1embryos from crosses between the strains was higher when the father was from the A/Jax strain than when the mother was—a patroclinous reciprocal cross difference.

4. The frequency of induced cleft palate in F1embryos from crosses between the strains was higher when the mother was from the A/Jax strain than when the father was—a matroclinous reciprocal cross difference.

5. Since the reciprocal cross differences in frequency of vertebral fusions and for cleft palates were in opposite directions, the hereditary factors influencing susceptibility to the teratogen appear to differ for the respective organ anlage. These differences appear to be, in part, cytoplasmic.

6. The frequency of induced cleft palate in the offspring of backcrosses of (untreated) F1female hybrids to A/Jax males differed according to the cytoplasmic origin of the F1mothers. Thus the susceptibility of an embryo to the teratogen appears to be influenced by factors transmitted through the cytoplasm.
Formal and physiological genetics of ascospore colour in Aspergillus nidulans
Authors: Apirion D.
Published: September 2009

By nitrous acid or UV treatment ascospore colour mutants of two kinds, blue and colourless, were obtained in Aspergillus nidulans (wild-type has red ascospores). Four blue mutants were located in linkage group II within 0·5 unit of one another (locus symbol: b11). Of the colourless mutants, four were located in linkage group I within one unit of one another (locus symbol: c16), and one in linkage group IV (locus symbol: c14). In diploids the mutants were recessive. Colourless was epistatic to blue.

In crosses these characters behaved as ‘non-autonomous’ both in the ascospores and in the asci; all the ascospores of the asci in one perithecium as well as the perithecium wall were of the same colour. In crosses between strains with blue perithecia and strains with colourless perithecia, red, blue and colourless perithecia were found; each type included both crossed and selfed perithecia. Red selfed perithecia were of either parental genotype but blue or colourless selfed perithecia always had the corresponding genotype.

The phenotype of the perithecium (perithecial wall and ascospores) is considered to be determined by the homo- or heterokaryotic constitution of the protoperi-thecium which gave origin to it.
Genetic stability of the Cornell randombred control population of White Leghorns
Authors: King Steven C. , Van Vleck L. Dale , Doolittle Donald P.
Published: September 2009

Six years of data collected from two shifts of Cornell random bred control matings each year are analysed. Approximately 900 progeny were tested per year from 50 sires mated to 250 dams.

Means for the important economic traits are presented by years and regressions for nine such traits, together with their standard deviations, are shown. The only significant regressions are those for both egg production and specific gravity score in shift II. An abnormally low egg production the first year for this shift is considered responsible for this result and the reality of the regression is discounted.

Genetic variances are presented by trait and year. Year to year variability is evident, but no trends are indicated.

Estimates of heritability and genetic correlations between traits are presented. These estimates are considered to be quite reliable and will be useful as estimates of genetic parameters when this population is used in selection experiments. Estimates of heritability from the sire components of variance were as follows: 8-week body-weight, 0·29; 32-week body-weight, 0·48; 55-week body-weight, 0·44; age at maturity, 0·09; egg production to 500 days, 0·07; 32-week egg-weight, 0·51; 55-week egg-weight, 0·53; USDA albumen score, 0·29; blood spot score, 0·13; and specific gravity score, 0·34.

Important maternal effects were found for 8, 32 and 55-week body-weight, sexual maturity and egg production. Selection programmes should take into consideration the fact that maternal effects accounted for 13% of the total variation in egg production. Genetic correlations utilizing combined sire and dam components revealed no serious antagonisms between egg production and other economic traits. However, this conclusion must be considered in the light of what influence maternal effects may have, since correlations computed from sire and dam components separately may have opposite signs and be important.

The many negative estimates of interaction components (SH, genetic by environment) and (I, sire by dam) indicate that these elements of the model contributed little to the variation of the traits studied.