bluuebunny/crossref_metadata_2025_split huggingface dataset:
Survey of line crosses in a Brown Leghorn flock 1. Egg Production
Authors: Blyth J. S. S. , Sang J. H. 
Published: September 2009

Six isolate lines of long standing, from the Centre's Brown Leghorn flock, were intermated in all possible directions, providing thirty cross and six pure line samples. Half the birds from each line and reciprocal cross were kept in floor pens and the rest caged in an adjacent battery house.Sexual maturity, survivors' production to 500 days of age, and November through June egg numbers, all showed two main factors contributing to variations in cross performance: (1) a significant association with parental production levels as measured by mid-parent averages, and (2) an additional hybrid gain. For November to June production in pens, this hybrid gain appeared to approach a constant for the cross groups. Additional sources of variation were present in age at sexual maturity.The 500-day records for the penned hybrids exceeded the line average by 50 eggs. Caged samples did less well and showed an advantage of only 34 eggs. In this location the hybrid gain for individual groups decreased with increases in mid-parent level.Egg weight varied negatively with egg numbers only in the upper half of the wide egg-size range. The best layers fell at the lower end of the covariant range for egg size.The importance of improving closed strains may not have been lessened by the expansion of the hybrid side of the poultry industry, for the pattern of relationships of line and cross production in this flock is consistent enough to justify the inference that the best hybrids come from the best-producing parents.
Comparative mutability of wild-type isoalleles at the white loci inDrosophila melanogaster
Authors: Green M. M. 
Published: September 2009

1. The X-ray mutability of wild-type isoalleles of thewhite-eyeloci inDrosophila melanogasterhas been determined.2. No difference in the mutability of the isoalleles was found. However, an appreciable difference in mutation rate of the two halves of thewloci was found.3. The bearing of these data on the problems of isoallelism and pseudoallelism are discussed.
Developmental sequence of chromosome number in a cytologically unstable Rubus hybrid
Authors: Haskell G. , Tun N. N. 
Published: September 2009

1. Serial cytological observations were made on one abnormal seedling from the thornless segregants of the F2 progeny from crossing two tetraploid (2n = 28) Rubus species. The number of root-tip chromosomes was found to vary between 9 and 46 per cell, with the mode always at 35. The wide variation in chromosome number decreased with time, until there was almost stability at 2n = 35. A vegetative (stipule) cell was 2n = 39. The numbers lower than 35 were not due to terminal fusion.2. Evidence from the number of satellites per cell suggests that not always were the same chromosomes being eliminated, although there is a general increase in satellite number with increased numbers of chromosomes per cell.3. There was a correlation between the chromosome numbers and corresponding cell sizes within the aneuploid series. This may be associated with the incremental change of DNA following the addition or subtraction of individual chromosomes, which are highly similar in Rubus.4. The cause of the instability was not definitely established. Its initiation is probably attributable to the egg mother cell, as Rubus pollen reacts sensitively to chromosome unbalance. No abnormalities were observed in the mitoses, and virus infection was not responsible for the instability.5. Chromosome number instability of this plant is discussed in relation to other examples from the same and different genera: it is suggested that the changes in chromosome number known in various Rubi may have arisen somatically.
A further examination of the relative efficiency of three methods of selection for genetic gains under less-restricted conditions
Authors: Young S. S. Y. 
Published: September 2009

The relative efficiency of three methods of selection (index, independent culling levels and tandem) is compared in terms of genetic gains in economic units. The comparison covers cases where variances, heritabilities and economic weights are unequal, while the case of two correlated characters is also examined. Various factors may influence the relative efficiency, including selection intensity, the number of traits under selection, the relative importance of those traits (in terms of a factor λ, which is the product of economic weight, heritability and phenotypic standard deviation), and the correlations between them.The conclusions are:(i) In all circumstances the index is never less efficient than independent culling levels, though in some cases it is no more efficient. Independent culling is, in turn, never less, but in some cases no more efficient than tandem selection.(ii) The superiority of the index over other methods increases with an increasing number of traits under selection, but decreases with increasing differences in relative importance, its superiority being at a maximum when the traits are of equal importance. The superiority of the index over independent culling levels decreases with increasing selection intensity, but its superiority over tandem selection is independent of intensity.(iii) The superiority of independent culling over tandem selection increases with increasing selection intensity or an increasing number of traits under selection, but decreases with increasing differences in relative importance.(iv) The relative efficiency of the index over other methods is much affected by the phenotypic correlation between traits when the traits are of equal importance, the relative efficiency of the index being higher when the phenotypic correlation is low or negative. The effect of genetic correlation is only apparent when the traits are of unequal importance and its influence on relative efficiency changes with changes in other parameters.(v) The relative efficiency of selection methods may be changed by their use for special purposes.
Tipsy, a new mutant in linkage group VII of the mouse
Authors: Searle A. G. 
Published: September 2009

Tipsy (symbol ti) is a fully penetrant recessive mutant in linkage group VII of the mouse. Homozygotes have a peculiar rabbit-like gait from the age of a week, followed soon after by a tendency for the fore-part of the body to sway from side to side, leading to a reeling locomotion with falling over in severely affected mice. There is marked variation in manifestation and some amelioration in older animals; both sexes are fertile.Linkage relationships in group VII are discussed and tipsy is compared with other mutants showing locomotor instability.
A note on non-random mating in progeny tests
Authors: Reeve E. C. R. 
Published: September 2009

The regression of progeny on mid-parent value is often used in progeny tests to estimate the heritability of a quantitative character. The statistical precision of such an estimate can be considerably increased without increasing the size of the test, by using assortative mating or selection of parents (or both together) so as to increase the mid-parent variance; but the danger arises that this may introduce bias into the estimate through correlation between non-additive gene effects.It is shown by a mathematical argument that such bias will be negligible provided that all individual gene substitution effects are small compared with the phenotypic standard deviation of the character. Under this condition, deviations from additive effects either within or between loci will not appreciably affect the expected value of the regression on mid-parent, compared with its expected value in a test using random mating.Correlation between the non-additive gene effects is likely to cause more serious bias to the correlation between sibs, when non-random mating is used.
The genetics ofUstilago maydis
Authors: Holliday Robin 
Published: September 2009

1. Many of the Ustilaginales, or smut fungi, appear to have the qualities necessary for the application of modern techniques of microbial genetics.Ustilago maydisis considered the most suitable species.2. Investigations of the mating system confirm reports that the production of diploid brandspores in the host is controlled by alleles at two loci.3. Genetic markers were obtained by inducing mutations in a wild-type strain with ultra-violet light. Of 100 biochemical mutants which were isolated, the growth requirements of 94 were identified. Thirty of these were used in genetic tests.4. The compact growth of colonies on artificial media allowed new techniques to be developed by means of which large samples of progeny could be isolated and identified easily. The analysis of brandspore colonies consisting of the products of single meiotic divisions is the quickest method for detecting linkage, but its accurate measurement appears to be achieved by examining the individual members of tetrads.5. Linkage was detected relatively rarely, but eight markers, including theamating-type locus, were assigned to one or other of two linkage groups. Although recombination values were not always determined accurately owing to irregular basidiospore germination, the auxotrophic markers in each group could be mapped in a linear order. Since no indication of other linkage groups was obtained, the genetic evidence is so far consistent with cytological reports that the basic haploid chromosome number is two in the smut fungi.6. Three linked markers were used to investigate chromatid interference by tetrad analysis. None was detected in a total of eighteen double exchanges.
‘Midget’, a new dwarfing gene in the house mouse dependant on a genetic background of small body size for its expression
Authors: Fowler Ruth E. , Edwards R. G. 
Published: September 2009

Midget, a new dwarfing gene in the house mouse, was found in a line (NS) selected for small body size. Backcrosses to, and heterozygous matings of NS mice gave midget offspring in the expected 1:1 and 1:3 ratios. Backcrosses to two other lines of mice selected for small body size resulted in fewer midget offspring than expected and in a reduced phenotypic expression of the gene, though matings between these midget offspring gave all midget progeny.A characteristic check in growth occurred between 15 and 21–24 days of age, and midgets rarely exceeded 10 g. at 6 weeks of age. They were 1·2 g. lighter than NS litter-mates at 3 weeks, and 3·6–4·4 g. lighter at 6 weeks. Fostering or transferring 3½-day-old midget embryos to the uteri of large mothers slightly increased the growth-rate, though the characteristic growth check still persisted. Transfer as embryos did not influence the midget phenotype.Midget males were of near-normal fertility. The females were semi-sterile due to irregularity or absence of oestrous cycles, failure to ovulate, or the death of embryos before implantation. Each of these factors, which were also found in NS mice, could be remedied by the administration of exogenous hormones.The genetic factors underlying the expression of midget are discussed, and the physiological traits associated with this and with other dwarfing genes are compared.
‘Bare’, a new hairless mutant in the mouse—genetics and histology
Authors: Randelia Homai P. , Sanghvi L. D. 
Published: September 2009

1. A new hereditary defect affecting the hair coat of Swiss albino mice is described. The defect was found to be inherited as a recessive character and is designated as bare (ba).2. The gene affected the vibrissae as well as pelage hairs. The lack of vibrissae and other sensory hairs at birth, helped to differentiate them easily from the normal animals. The first hairs on the body appeared at 13–14 days of age. The hairs were thin and tiny and remained there till about the thirtieth day. The hairs in the second hair cycle appeared at about 45 days, and again disappeared within 10 days. The animals were entirely naked when they were 6 months old.3. Gross as well as microscopic examination of hairs in the first hair cycle did not show the four different normal types of hairs. The hairs were comparatively very small, thin, and the internal structure did not show any regularity in the arrangement of the air cells.4. No difference was found in the number of hair follicles in the bare and the normal Swiss mice.5. Histology revealed the presence of keratinized globular masses instead of straight hair. This abnormality persisted in all the hair cycles.6. The bare mice were compared with the other mutants and placed in the Alopecia-Naked group where the abnormality was in the keratinization of the hair.
‘Dappled’ a new allele at the Mottled locus in the house mouse
Authors: Phillips Rita J. S. 
Published: September 2009

Dappled, a new completely sex-linked semi-dominant lethal mutation, is described. It is probably a new allele at the Mottled locus and has been given the symbol Modp.Heterozygous adult females have a variegated coat very similar to that of Brindled and Mottled females; they have curly vibrissae at birth and some also have clubbed feet. All the characteristics are variable.Hemizygous males die at about 17 days' gestation; they show a characteristic bending and thickening of the ribs and other skeletal defects. The cause of death is unknown.
Chromosomal polymorphism inDrosophila subobscurapopulations from Barcelona (Spain)
Authors: Prevosti Antonio 
Published: September 2009

1. Chromosomal polymorphism in two populations ofD. subobscurafrom Barcelona has been analysed and compared with the polymorphism which has been reported from other populations.2. In spite of microclimatic differences between the Barcelona sites, there is no evidence of differences in the frequency of inversion types nor of seasonal differences within one of these sites.3. Regularities in the array of frequencies of chromosomal types in Barcelona and other populations suggest that the polymorphism is mainly adaptive although there is also evidence of differences due to distance which are not obviously associated with differences in habitat.4. In general the index of free recombination gives higher values in the marginal populations ofD. subobscura, but further data are needed to arrive at a definite conclusion on this point since the present evidence is rather ambiguous.
Egg albumen polymorphisms in the Fowl: lociIIandIII
Authors: Lush I. E. 
Published: September 2009

The genetics of two polymorphic loci in the fowl was studied. Each affects the electrophoretic mobility of a different egg albumen protein, and at each locus two alleles were shown to segregate in a Mendelian manner.The polymorphic proteins are not any of the well-characterized egg albumen proteins, viz. ovalbumin, ovomucoid, ovomucin, flavoprotein, avidin and lysozyme.In contrast to all others, two hens were found to have an anomalous, variable, phenotype. A tentative explanation of this was offered.
Infection into paramecia of metagons derived from other mate-killer paramecia
Authors: Gibson I. , Beale G. H. 
Published: September 2009

1. It has been shown that metagons, gene-controlled units necessary for maintenance of mu particles inParamecium aurelia, can be extracted from cells containing one or both of the dominant genesM1andM2, and reinfected into other paramecia. Provided the latter contain mu particles before infection, the introduced metagons resume their normal function of maintaining the mu particles.2. Homogenates containing metagons have been fractionated in various ways. The metagon activity is found in the sediment after centrifuging at 105,000 g. for 90 min., and is retained after deoxycholate treatment removing the microsomal membranes, and after phenol extraction removing the ribosomal protein. By lowering the magnesium concentration, some metagon activity passes from the microsomes into the supernatant.3. Metagon activity in RNA fractions is destroyed by ribonuclease at a concentration of 5 μg. per ml.4. The metagons both in extracts and inside the cells appear often to be aggregated in clumps, the individual units of which are each functionally active in maintaining mu particles in living cells.5. It is concluded that the metagon may be considered as a very stable and repeatedly functioning form of ‘messenger’ RNA.
A mechanism for gene conversion in fungi
Authors: Holliday Robin 
Published: September 2009

A mechanism for gene conversion is proposed which overcomes many of the difficulties that any copy choice model encounters. It is suggested that along with general genetic pairing of homologous genomes at meiosis, effective pairing over short regions of the genetic material occurs at the molecular level by the separation of the strands of the DNA double helices, followed by the annealing of strands from two homologous chromatids. If the annealed region happens to span a heterozygous site, mispairing of bases will occur. Such a situation may be analogous to that in DNA which is damaged by mutagens; the same or similar repair mechanisms may operate, and these, by adjusting the base sequences in order to restore normal base pairing, would bring about gene conversion in the absence of any genetic replication. The model indicates how precise breakage and rejoining of chromatids could occur in the vicinity of the conversion, so that conversion would frequently be accompanied by the recombination of outside markers. The model also proposes that the distance between two mutant sites on a fine structure map depends not so much on the frequency of a recombinational event occurring between them, but rather on the degree of inhibition of the processes of genetic pairing by the mutants themselves.The model will explain almost all the data in a formal way, and it has the advantage over copy choice mechanisms for gene conversion in (1) being compatible with semi-conservative replication of DNA, (2) not invoking DNA synthesis during or after genetic pairing, (3) providing a molecular mechanism for close specific pairing, (4) making it unnecessary to postulate sister strand exchange or a process akin to this, (5) suggesting why rates of gene conversion in opposite directions are sometimes unequal and (6) providing an explanation of the clustering of mutant sites, a basis formap expansionand for the apparently capricious departure of fine structure maps from additivity. Although the model proposed is a general rather than a specific one, it suggests that the process of conversion and intragenic recombination is more complex than is usually believed, since it depends on several interacting factors. Nevertheless, it is hoped that the introduction of a model with this complexity will help to stimulate specific experiments, and that these will provide definitive information which would never be obtained if simpler models of conversion and intragenic recombination were believed to explain the genetic data sufficiently well.
Mitotic recombination in thepaba 1cistron ofAspergillus nidulans
Authors: Putrament A. 
Published: September 2009

The results of the analysis of 393 mitotic recombinants within thepaba1region ofAspergillus nidulanscan be summarized as follows:1. Reciprocal, non-reciprocal and probably inexactly reciprocal exchanges occur in intra-cistron mitotic recombination.2. Negative interference observed in intra-cistron mitotic recombination in thepaba1region ofAspergillus nidulansis more intense than that observed in meiotic recombination in the same cistron.3. In intragenic mitotic recombination multiple exchanges can involve three or even four chromatids within one effective pairing segment.
Distribution of chromosomes in metaphase plates of Mesocricetus newtoni
Authors: Raicu Petre , Vladescu Barbu , Kirilova Maria 
Published: September 2009

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

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

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

SUMMARYA system has been developed for the study of reversion of an amber mutation responsible for a deficiency in DNA synthesis in T4 phage E51. When complexed with bacteria able to suppress the amber mutation the induced mutation rate per phage genome per rad isWhen complexed with bacteria unable to suppress the amber mutation (and being thus unable to synthesize phage DNA) the induced mutation rate is at least 14 times lower indicating that DNA synthesis is necessary for the production of the majority of functional reversions at the amber site. The induced mutation rate in suppressor-containing bacteria is independent of multiplicity of infection between 0·2 and 5, suggesting that recombination immediately after irradiation between phage genomes is unlikely to be a requirement for the mutation process.
Functional analysis of host-specificity mutants inEscherichia coli
Authors: Glover S. W. 
Published: September 2009

SUMMARYEvidence from a functional analysis of host-specificity mutants in merodiploids is presented which supports the suggestion that three genes,hss, hsrandhsm, are necessary for the expression of host-controlled restriction and modification. The host-specificity phenotype expressed by the merodiploids provides evidence that at least two genes,hssandhsr, are concerned in the expression of host-specific restriction of DNA and one of these genes,hss, is responsible for the strain specificity of the restriction enzyme. A class of modification-deficient mutants isolated from restriction-deficient, modification-proficient mutants, was also tested for complementation in merodiploids and the phenotype of these merodiploids provides evidence that at least two genes,hssandhsm, are concerned in the expression of host-specific modification of DNA and one of these genes,hss, is responsible for the strain specificity of the modification enzyme. How these three genes function at the molecular level is discussed in terms of models based on the interaction of subunits to form oligomeric enzymes.