bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental genetics of leaf formation inLolium3. Inheritance of a developmental complex
Authors: Edwards K. J. R.
Published: September 2009

Using four lines derived from a single base population ofLolium perenneby selection for large leaf size (LL), small leaf size (SL), fast rate of leaf appearance (FR), and slow rate of leaf appearance (SR), the inheritance of a number of related characters specifying various aspects of leaf development was studied.F1andF2generations were produced for all possible crosses between these four lines.

The genetic differences between the selection lines were largely additive for all characters studied and entirely so for rate of leaf appearance, duration of elongation of a single leaf and for the time interval between the maturation of leaf 3 and the unfolding of the next youngest leaf on the same side of the apex, leaf 5. The non-additive variances noted in rate of total leaf area formation, individual leaf size and its components length and width, and in the rate of leaf elongation, were associated with a tendency towards heterosis in these characters. This was quite marked in some crosses and tended to be larger for the more complex characters, rate of total leaf area formation and leaf size, suggesting that the heterosis was, to a considerable extent, due to interactions between genes controlling component characters.

The data confirmed the earlier finding that the negative correlated selection response between leaf size and rate of leaf appearance was due to a basic association between the maturation of a leaf and the unfolding (onset of rapid elongation) of the next youngest leaf on the same side of the apex. Thus an increase in rate of leaf appearance reduces the duration of elongation of a leaf and this in turn will reduce leaf length. However, the basic association, which seems to be controlled by vascular development of the young leaf, is not entirely invariate.
The influence of theylocus on DDT resistance in the mosquitoAedes aegyptiL
Authors: Wood R. J.
Published: September 2009

The influence of the linkage group II locusyon DDT resistance inAedes aegyptihas been studied in crosses between the Trinidadresistant strain and QS susceptible strain. Theylocus influences DDT resistance in bothR/RandR/+ larvae. The effect ofymay be interpreted as reducing the penetrance ofR(RDDT1), which is also located on linkage group II.y+is partially dominant and incompletely penetrant in its resistance-enhancing role (although in its pleiotropic effect on larval colour it is dominant and fully penetrant). Penetrance ofy+is influenced by an environmental factor, probably associated with the larval diet.

The effect ofyon resistance is evaluated in relation to other genetic influences on the expression ofRDDT1.

The significance of polymorphism at theylocus is discussed.
Characteristics ofE. coliK12 strains carrying both an F prime and an R factor
Authors: Willetts N. S. , Finnegan D. J.
Published: September 2009

The interrelationship between an F prime and an F-like or I-like R factor was studied inEscherichia coliK 12 strains carrying both. The donorability of such strains suggested that these plasmids were transferred independently by their own transfer systems. Plaque formation by several male- and female-specific phage was tested; the inhibition by Flacof several female-specific phage was not affected by an F-like R factor. Neither did an R factor affect the incompatibility between Flacand Fhis. However, the surface exclusion characteristic of Flacwas lost in the presence of an F-like R factor. This is probably closely related to the simultaneous loss of donorability, the F-pilus, and the f+antigen: all may be the result of the inhibition by an R product of the formation or activity of a single F product.
Genetics of nitrate reductase inUstilago maydis
Authors: Lewis C. M. , Fincham J. R. S.
Published: September 2009

Mutants ofUstilago maydishave been isolated both, deficient and derepressed for nitrate reduction. Those deficient in enzyme fall into six groups, one of which is the structural gene. Enzyme which has proved to be more labile than that of wild-type has been isolated from a temperature-sensitive mutant at this locus. All the mutants in the structural gene have xanthine dehydrogenase activity and the situation closely parallels that ofAspergillus nidulans.

The derepressed mutants fall into four complementation groups and all are partially derepressed in that they are further inducible by nitrate. Full derepression can be conferred by induction of a second mutation. In one analysed case the second reinforcing mutation proved to be pheno-typically similar to the first one when separated from it.
Development of associative overdominance through linkage disequilibrium in finite populations
Authors: Ohta Tomoko , Kimura Motoo
Published: September 2009

Associative overdominance arises at an intrinsically neutral locus through its non-random association with overdominant loci. In finite populations, even if fitness is additive between loci, non-random association will be created by random genetic drift.

The magnitude of such associative overdominance is roughly proportional to the sum ofbetween the neutral and the surrounding over-dominant loci, whereis the squared standard linkage deviation, defined between any two loci by the relation

in whichpand 1 –pare frequencies of allelesA1andA2in the first locus,qand 1 –qare frequencies of allelesB1andB2in the second locus, andDis the coefficient of linkage disequilibrium. A theory was developed based on diffusion models which enables us to obtain formulae forunder various conditions, and Monte Carlo experiments were performed to check the validity of those formulae.

It was shown that ifA1andA2are strongly overdominant whileB1andB2are selectively neutral, we have approximately

provided that 4Nec≫ 1, whereNeis the effective population size andcis the recombination fraction between the two loci. This approximation formula is also valid between two strongly overdominant as well as weakly overdominant loci, if 4Nec≫ 1.

The significance of associative overdominance for the maintenance of genetic variability in natural populations was discussed, and it was shown thatNes′, that is, the product between effective population size and the coefficient of associative overdominance, remanis constant with varyingNe, if the total segregational (overdominant) load is kept constant.

The amount of linkage disequilibrium expected due to random drift in experimental populations was also discussed, and it was shown thatin the first generation, if it is produced by extractingnchromosomes from a large parental population in whichD= 0.
Change of host range in a resistance factor
Authors: Anderson E. S. , Threlfall E. J.
Published: September 2009

An R factor for ampicillin and streptomycin resistance (AS) was identified inSalmonella enteritidis. The AS factor transferred freely toEscherichia coliK12, but only two of 260 K12(AS) clones from this cross would transfer AS toS. typhimurium, although all lines tested transferred it toS. enteritidisand K12. A study of one of the two exceptional lines“ revealed that it also transferred AS toS. paratyphiB,S. thompsonandS. anatum. The R factor maintained its transferability when cycled between these serotypes and K12. Transfer toS. enteritidis, however, resulted in loss of the ability of AS to transfer to the heterologous serotypes, that is, it apparently became host specific forS. enteritidis. S. paratyphiB andS. anatumalso imposed host specificity on AS, butS. typhimuriumandS. thompsondid not. The R factor would always enterS. enteritidis, whatever its previous salmonella host but, once it had done so, it became specific forS. enteritidis. AS could always transfer to K12, which did not seem to modify its host range. These phenomena are most easily explained by analogy with host-controlled modification of phage. Their possible significance in relation to apparent host specificity of R factors is discussed.
A test of the functional significance of the quantity of mitochondria in the spermatozoa of mice
Authors: Woolley D. M.
Published: September 2009

Following an experiment in which mice had been selected for the length of the mitochondrial section (midpiece) of their sperm tails, an attempt has been made to determine experimentally the adaptive significance of this character; this was by the artificial insemination of mixtures of selected and unselected (control) spermatozoa, and the subsequent disclosure of their competitive fertilizing ability in the paternity of the offspring. After the birth of nearly 500 offspring, there was no indication that the control cells were—by this criterion—functionally superior. From the discrepancy between the pairs of males sampled, however, it is possible that other biological or technical factors have been important.
Selection for the length of the spermatozoan midpiece in the mouse
Authors: Woolley D. M.
Published: September 2009

A subcellular dimension, the length of the spermatozoan midpiece, has been the subject of a two-way selection programme in mice. After thirteen generations of within-family selection the divergence between the selected lines amounted to 5·4 phenotypic standard deviations. The realized heritability was found to be 0·76 ± 0·02, dominance and commonenvironmental effects being apparently very small. The reality of the selection response was verified in measurements on live spermatozoa. Other measurements have shown that the change in the length of the midpiece has been independent of its width, and has occurred without a proportionate change in the length of the main-piece of the flagellum. An electron microscope study has shown that the selection has, in fact, brought about changes in the quantity of mitochondrial material in the sperm cells.
Genetic variation in the eel II. Transferrins, haemoglobins and esterases in the eastern North Atlantic. Possible interpretations of phenotypic frequency differences
Authors: Pantelouris E. M. , Arnason A. , Tesch F. W.
Published: September 2009

Comparison, by electrophoretic methods, of eel samples from Iceland, Scotland and Germany confirmed previous reports of uniformity in haemoglobin types. When liver esterases were examined, significant differences in the frequencies of phenotypes in the ‘fast’ zone of the electropherogram were found between samples from Germany and samples from Iceland and Scotland. The frequencies of transferrin phenotypes in Icelandic and Scottish eels differed significantly from those of French and American eels.

It follows that regional differences in gene frequencies probably exist within the speciesAnguilla anguilla. The implications for the ‘atlantic eel problem’ are briefly discussed.
A new class of slow-growing non-perithecial mutants ofAspergillus nidulans
Authors: Houghton J. A.
Published: September 2009

Twenty-four mutants ofAspergillus nidulanswere isolated which grew more slowly than normal on glucose as sole source of carbon and were unable to utilize intermediates of the tricarboxylic acid cycle. By complementation tests they were divided into five groups, each group representing a different cistron and the cistrons were assigned to linkage groups by mitotic analysis. The mutant loci have been designatedsgp-1 tosgp-5 respectively. Three mutants have been mapped by meiotic analysis.
A variegated position effect inAspergillus nidulans
Authors: Clutterbuck A. J.
Published: September 2009

In mutants at the ‘bristle’ locus ofAspergillus nidulansthe conidiophore remains as a stiff hypha rather than developing a vesicle, sterigmata and conidia. ThebrlA12 allele of this locus has a variegated phenotype, and genetic analysis has shown that this is associated with a translocation which has a breakpoint in the map interval adjacent to thebristlelocus.

The mutant phenotype is partially repaired on high-salt medium at low pH, and can also be repaired by suppressors, one of which has been mapped at a locus unlinked tobrlA12.

The mutant provides proof that variegation is due to instability of gene expression and not to mutability sincebrlA12 is genetically stable and can be propagated from either conidia or sterile conidiophores, the structures formed at the two extremes of variegation, and the resulting colonies in both cases are identical to the original strain.

It has been shown by mitotic recombination that the translocation associated with the variegated mutant is a ‘simple translocation’ in which the distal half of linkage group VIII is attached to the end of linkage group III. This terminal attachment site does not appear to be damaged in any genetically detectable way.
The tolerance of aneuploidy in yeast
Authors: Parry Elizabeth M. , Cox B. S.
Published: September 2009

Single ascospore cultures from triploids were screened as a potential source of disomic tester stocks for the purpose of genetical mapping of chromosomes in yeast. A high tolerance of aneuploidy was found, and strains disomic for only one chromosome were rare. There was a high occurrence of strains disomic at specific chromosomes and in certain multiple combinations of disomic chromosomes.
Genetic effects of acridines onPseudomonas aeruginosa
Authors: Stanisich Vilma , Holloway B. W.
Published: September 2009

Mutants ofPseudomonas aeruginosamale strains with altered mating properties have been obtained through treatment with nitrogen half mustards. The response varied with the type of male strain. A mutant of the infectious male PTO 13 was obtained which acts as a female strain and has apparently lost the FP sex factor. A mutant of the non-infectious strain 2 male mates not only with strain 1 females, but shows a thousand-fold increase in its ability to mate with strain 2 males, when it can act as either donor or recipient in conjugation. Derivatives of strain 1 males were obtained which had reduced recombinant forming ability.

While acriflavine is ineffective in producing such mutants, and has not been shown to cure male strains of their sex factor inP. aeruginosa, it is very effective in inhibiting infectious transfer of FP from FP+to FP−strains. Furthermore, it markedly inhibits recombinant formation in 1 FP−× 1 FP+crosses, and this latter effect is thought to be due to the inhibition of chromosome transfer by the male parent. In view of the almost complete lack of effect of AF on the normal growth ofP. aeruginosait is likely that the control of chromosome replication during vegetative cell division is different from the occurring during conjugation and that the FP factor is involved in this control during conjugation.
The inheritance of the killer character in yeast
Authors: Somers J. M. , Bevan E. A.
Published: September 2009

1. First- and second-generation crosses between killer, neutral and sensitive strains of yeast have been carried out in all combinations.

2. The results of this analysis indicated that the killer character is under the control of two types of cytoplasmic genetic determinant. One type, (k), determines killing, and the other, (n), neutrality. The absence, (o), of both types of determinants confers the sensitive phenotype.

3. That both types of cytoplasmic determinant require the same dominant nuclear allele, M, for their maintenance has been indicated in two ways. First, both types are lost when the nuclear genotype is changed from M to m. Secondly, cells of genotype m(k) or m(n), which have been shown to occur among the first formed cells arising from spores of Mm(k) and Mm(n) diploids respectively, are unable to maintain their cytoplasmic determinants. On the other hand, spore cultures of M(k) and M(n) genotype derived from these same diploide continue to maintain the determinants.

4. Thus genotype of killer cells is M(k), of neutrals M(n), and of sensitivities either M(o) or m(o).

5. Cells maintaining both types of cytoplasmic determinant (i.e. of genotype M(k)(n) or M−(k)(n)) have been obtained by appropriate crosses, and shown to be of killer phenotype.

6. Alternative hypotheses to account for the results of this genetic analysis have been discussed.
The first case of linkage in Paramecium aurelia
Authors: Beisson Janine , Rossignol Michele
Published: September 2009

In Paramecium aurelia, syngen 4, gene ts21m, which is shown to segregate normally and independently of two other genes: ts111 and m1; is closely linked to gene ts401. The frequency of then recombination is of the order of a few per cent. Genetic analysis was carried out to confirm the genotypes of both double mutants and wild-type recombinants among F2 clones from crosses ts21m × ts401. This is the first case of linkage so far reported in P. aurelia.
Cytogenetical study in Spalax leucodon Nordm. in Moldavia (Rumania)
Authors: Raicu Petre , Duma Doina
Published: September 2009

The karyotype of Spalax leucodon (2n = 56) from Moldavia (Rumania) shows 27 pairs of autosomes: two metacentrics, three submetacentrics, eight suhtelocentrics and 14 acrocentrics. The X chromosomes are the longest subtelocentrics and the Y chromosome is a submetacentric of medium size. In metaphase I we have found a partial homology between the short arm of the X and the Y chromosome.

The population of S. leucodon from Moldavia shows considerable differences of karyotype as compared with other populations of the same species from the south of Europe. This species presents a high degree of chromosomal polymorphism in different populations.
A comparison of two methods for predicting changes in the distribution of gene frequency when selection is applied repeatedly to a finite population
Authors: Pike Derek J.
Published: September 2009

Robertson (1960) used probability transition matrices to estimate changes in gene frequency when sampling and selection are applied to a finite population. Curnow & Baker (1968) used Kojima's (1961) approximate formulae for the mean and variance of the change in gene frequency from a single cycle of selection applied to a finite population to develop an iterative procedure for studying the effects of repeated cycles of selection and regeneration. To do this they assumed a beta distribution for the unfixed gene frequencies at each generation.

These two methods are discussed and a result used in Kojima's paper is proved. A number of sets of calculations are carried out using both methods and the results are compared to assess the accuracy of Curnow & Baker's method in relation to Robertson's approach.

It is found that the one real fault in the Curnow-Baker method is its tendency to fix too high a proportion of the genes, particularly when the initial gene frequency is near to a fixation point. This fault is largely overcome when more individuals are selected. For selection of eight or more individuals the Curnow-Baker method is very accurate and appreciably faster than the transition matrix method.
The rate of selection advance for non-additive loci
Authors: Hill W. G.
Published: September 2009

Expected changes in the gene frequency and the population mean for a quantitative trait are described for selection in a population of sizeNat a single locus where the favoured allele has initial frequencyq0and selective values. Models of additive and completely dominant gene action are compared. Results are generally expressed as the half-life of the total change relative toN.

If the favoured allele is additive or recessive the half-life of the gene frequency and mean of the trait are usually reduced whenq0orNsis increased. However, if the dominant allele is favoured the half-life of gene frequency is still generally reduced asNsis increased, but has a minimum at low or intermediate values ofq0. Since inbreeding depression and selection oppose each other when the dominant allele is favoured the response in the mean of the quantitative trait may change in direction during selection.
Kappa, mu and the metagon hypothesis inParamecium aurelia
Authors: Byrne Barbara J.
Published: September 2009

1. The loss of mu 540, mu 138, and kappa 51 following the loss of the dominant genes required for their maintenance was studied. With mu 540 and mu 138 the loss usually occurred within 4–7 cell generations, but occasional cells with mu were found as late as generation 12 with mu 540 and generation 17 with mu 138. Kappa 51 was lost between 5 and 60 fissions in different clones. The variability in time of loss remains unexplained.

2. No trail of inheritance of resistance to specific kappa killing comparable to the trail of inheritance reported for mu 540 by Gibson & Beale (1962) was found.

3. No loss of kappa 51, mu 540, mu 138, or mu 130 was found following treatment of paramecia with RNase.

4.Didinium nasutumwas shown to be able to acquire and maintain kappa 51 when it could not possibly have acquired any RNase-sensitive metagons from paramecia.

5. These results show that the metagon hypothesis cannot be accepted without a number ofad hocand at present untestable assumptions.
Nucleic acid content and Chromosome morphology in Chrysanthemum
Authors: Dowrick G. J. , El Bayoumi A. S.
Published: September 2009

1. The DNA contents of twenty-eight different species and forms of Chrysanthemum have been measured by photometry. It is shown that there are large differences in DNA content between some species with identical chromosome numbers.

2. The DNA contents of natural polyploids are frequently not those expected when comparison is made with diploid forms of the same species. The DNA contents of induced polyploids are those expected.

3. Chromosome length and volume are positively correlated with DNA content.

4. The relationship between chromosome number, chromosome size, DNA content and gene number is considered, and it is suggested that the differences in DNA content may result from the presence of differing amounts of genetically inactive DNA in the chromosomes.
Gene-environment interactions of theeyelessmutant inDrosophila melanogaster
Authors: Hunt David M. , Burnet Barrie
Published: September 2009

A method is described for quantifying the phenotypic expression ofeyelessusing gauged estimates of the mean and standard deviation of the distribution of facet numbers.

Gene-environment interactions of foureyelessallelesey,ey2ey4andeyKare compared in different genetic backgrounds and on a standardized Pacific background. The original strains differ in mean phenotypic value and in direction of response to variations in the ribonucleic acid content of the larval culture medium, whereas the four Pacific strains are more concordant. Consequently these differences are in part attributable to modifier genes present in the different genetic backgrounds of the original strains. Modifier genes also influence the periods in development at whicheyelessis sensitive to nutritional treatments.

On the standardized Pacific background deficiencies of cholesterol cause an increase, whereas deficiencies of RNA or thiamine cause a decrease in the expressvity of all foureyelessalleles, but non-identity of their interaction profiles over an array of different suboptimal environments suggest that they may form a group of heteroalleles.
The production of partially sterile mutants inGlossina austeni
Authors: Curtis C. F.
Published: September 2009

An attempt is described to produce chromosome translocations inGlossina austeniwhich, it is hoped, might ultimately be used for tsetse fly control. The method consisted of selecting among the progeny of irradiated males for cases of inherited partial sterility. Thirty-four per cent of the testable sons of males which received doses of 5–7 krads showed these properties. In two cases the inheritance was patrilineal which suggests that theYchromosome was involved. In most of the other cases a segregation among both male and female progeny of the partially sterile and normal types occurred and in these cases it appears that autosomes only were involved. Among males in these stocks the segregation ratio was close to 1:1, but in females there was a deficit of the partially sterile type. This may be partly associated with the fact that a large proportion of totally sterile and in-viable females were produced by these stocks. The proportion of zygotes which died at the embryonic, larval and pupal stages as a result of the action of the partial sterility factors varied between factors of different mutational origin. In view of the pattern of inheritance of these factors and their high frequency of induction it is argued that in all probability they are translocations in the heterozygous state.
The isolation of mutants affecting ascus development inNeurospora crassaand their analysis by a zygote complementation test
Authors: Srb Adrian M. , Basl Mary
Published: September 2009

A large number of mutants that affect the morphology of the ascus ofNeurospora crassahas been isolated by means of a screening technique that utilizes the filtration principle to separate colonial type mutants from wild type. In relationships with each other and with wild-type alleles, the mutant genes exhibit zygote dominance and recessiveness. A zygote complementation test for placing the recessive mutants into functional groupings is described. Results obtained by use of the test place the mutants into seven functional groups. Dominance relations in the developing ascus ofNeurosporaare discussed.
I sex factors and chromosomal recombination inSalmonella typhimurium
Authors: Edwards Susan , Meynell G. G.
Published: September 2009

Colicin factors Ib-P9 and Ela-16 both convert their hosts to chromosomal donors. However, negative fluctuation tests suggest that chromosomal transfer does not result from the formation of stable Hfr variants.
Lethal effect of attached-X deletion in Drosophila melanogaster
Authors: Thompson James N. , Braver Gerald
Published: September 2009

Attached-X stocks appear to be deficient in a small region, probably heterochromatic, which is normally covered by an homologous region on the short arm of the Y chromosome. There is an homologous deficiency in the ec dx stock Y chromosome. When this Ys deficiency occurs in crosses involving attached-X stocks, the matroclinous females are not recovered.
Acriflavin resistant rII deletions of bacteriophage T4
Authors: Parma David H.
Published: September 2009

The extent and phenotype of acriflavin-resistant rII deletions have been examined. The properties of these deletions confirm that acriflavin resistance may result from a loss of function at the ac locus and that the ac locus coincides with the rII distal portion of the dispensable region which is adjacent to the rIIB cistron.
The mechanism whereby the genesM1andM2inParamecium aurelia, stock 540, control growth of the mate-killer (mu) particles
Authors: Gibson I. , Beale G. H. , Reeve E. C. R
Published: September 2009

1. Replacement of the dominant genesM1andM2inParamecium aurelia, stock 540 (syngen/variety 1), results in loss of ability to maintain mu particles and manifestation of mate-killing after a delay of eight to fifteen fissions in most cells. The change, when it does occur, is relatively abrupt, extending over less than the space of one inter-fission period.

2. The delay between change of genotype and loss of mu particles is interpreted as being due to presence in the initial cytoplasm of some thousand ‘metagons’, which are non-replicating gene derivatives having the physiological activity of the corresponding genes. During successive fissions of paramecia deprived ofM1andM2the metagons are passively distributed amongst the progeny, until virtually all animals lack them.

3. On reaching a stage at which some individuals of genotypem1m1m2m2contain only a single metagon, the paramecia still contain large numbers of mu particles and are mate-killers. Fission of such animals gives rise to one daughter again with mu particles, and another in which the latter are destroyed during the next inter-fission period.

4. By induced cytoplasmic exchange between conjugants, metagons can be transferred from one animal to another via the cytoplasm. Where such transference is into an animal not originally containing mu particles, that animal is converted into a condition in which it favours the maintenance of mu particles and transmits the latter to one or more of its offspring.

5. Distribution of metagons amongst progeny of dividing paramecia is not random, due possibly to clumping of the metagons. Induced cytoplasmic exchange seems to break up the clumps.

6. Reintroduction of a dominant gene (M2) into a cell recently deprived of the same gene, succeeds—even after fifteen fissions—in re-establishing the ability to support growth of mu particles, provided that the recipient cell contains at least one metagon and one or more mu particles. There is a regular lag of only one fission between introduction of such a dominant gene and its phenotypic manifestation.

7. Mathematical formulae are developed for calculating the expected initial number of metagons, the proportions of animals lacking mu particles at each fission following loss of the dominant genes, and the proportions of cells containing 0, 1, 2 …, etc. metagons per cell at any stage. The consequences of one of the possible types of irregular distribution of metagons in dividing paramecia are also considered mathematically.
Selection for rate of larval development usingDrosophila melanogastercultured axenically on deficient diets
Authors: Sang James H.
Published: September 2009

1. The problem of improving rate of larval development ofDrosophilaby selecting for this ‘character’ on deficient diets is examined by culturing larvae axenically on low-casein and low-pyridoxine media. Under these conditions it is possible to develop strains which grow faster than the parent population.

2. Selection for fast- and slow-growing larvae on a low-pyridoxine diet proceeds with a realized heritability of about 20%, but progress ceases after eight to nine generations. The selected larvae show no alteration of pyridoxine requirements up to the tenth generation, but the lines develop at different rates under optimal conditions. This difference is exaggerated when the diets are low in pyridoxine. By the fourteenth generation, requirements of the two lines for optimal growth have become distinct, the fast line requiring less pyridoxine than the control. Casein requirements show about the same optimum for the two lines but this is lower than that of the control, foundation population.

3. Selection for fast- and slow-development lines on a low-casein diet continues to be effective throughout the fifteen generations of the test. The realized heritability in this case is about 10%. The optimal requirements of the two lines are the same, and there is little difference in their development rates when reared on this optimal diet. The response is found only under sub-optimal conditions, both of deficiency and of excess casein. Pyridoxine requirements do not seem to be altered in the two lines.

4. Crosses between the selected lines show that each genotype has its own optimal environment, as judged by pyridoxine and casein requirements. Crosses among the lines after fourteen generations show that all the hybrids are superior to the mid-parent and three grew faster than the better parent. Other environments would have given different results.
The effects of inbreeding and artificial selection on reproductive fitness
Authors: Latter B. D. H. , Robertson Alan
Published: September 2009

The competitive-index method of measurement of over all fitness inDrosophilahas been used to measure the effect of inbreeding and of artificial selection for metric characters in a large population ofDrosophila melanogaster. The technique itself was examined in detail with particular reference to its repeatability and to the effect on it of the modification of various environmental variables.

With continued full-sib mating the decline in the competitive index was very rapid (it was reduced to a half by a single generation of full-sib mating) and there were no indications that interactions between deleterious genes at different loci were important in determining the rate of decline of fitness as inbreeding increased. Other unselected lines with ten pairs of parents in each generation were carried to serve as a control for the lines under artificial selection. At the same theoretical degree of inbreeding the control lines had a much higher average fitness than the lines produced by continued full-sib mating.

From the base population lines were selected in both directions for abdominal bristles, sternopleural bristles and for wing length, there being two replicates in all cases. Four control lines were kept with the same number of parents as the selected lines. In all cases the selected lines declined in fitness below the value for the base population. However, in three of the lines the fitness was not significantly below the value for the control lines. The effect of artificial selection on fitness was asymmetrical, the decline being greater with down selection for all characters.

The relevance of these results to various theoretical models is discussed. If the variation in these characters is actively maintained in the base population by the selection of heterozygotes then the results are consistent with an average selection disadvantage of homozygotes relative to heterozygotes of about 0·5%.
Genetical studies on the skeleton of the mouse XXXI. The Muscular Anatomy of Syndactylism and Oligosyndactylism
Authors: Kadam K. M.
Published: September 2009

1. Changes in muscles and tendons in sm/sm are confined to hands and feet. They are closely correlated with the changes in the osseous skeleton.

2. In Os/+, muscular changes are much more complex and not confined to hands and feet, but include the muscles of the forearms and of the lower legs. Some of the muscular changes, especially on the postaxial side, are not correlated with the changes in the osseous skeleton.
Immunological analysis of incompatibility (S) proteins and of cross-reacting material in a self-compatible mutant ofOenothera organensis
Authors: Mäkinen Y. L. A. , Lewis D.
Published: September 2009

Proteins of pollen ofOenothera organensisfrom heterozygousS2S3,S2S6,S3S6andS4S6and homozygousS6S6genotypes produce characteristic precipitation lines in agar-gel plates against antisera prepared from the pollen. The maximum number of precipitation lines was three, and with some genotypes only one line was formed. The lines were characteristic of the differentSalleles, but there was a strong cross-reaction betweenS4pollen andS6antiserum. TheSprotein diffused out from intact pollen grains as readily as from macerated pollen indicating that the normal site of action of theSprotein, when the pollen tubes are growing down the style, is near the surface of the pollen tube. The self-compatible mutantS6′S6in which theS6′allele has lost the ability to produce an active pollenSprotein, has a protein which cross-reacts strongly withS6antiserum.
The effects of stabilizing selection on the time of development in Drosophila melanogaster
Authors: Prout Timothy
Published: September 2009

The length of time of development, from oviposition to emergence in Drosophila melanogaster was subjected to stabilizing selection. In each generation only the individuals emerging close to the mean development time were used as parents of the next generation. This line was designated the ‘S’ line. In a parallel line disruptive selection was practised; where in each generation the earliest flies to emerge were mated to the flies last to emerge; those emerging at intermediate times were discarded. This line was designated the ‘D’ line. Two control lines were also carried, where the flies were mated at random with respect to time of emergence. The experiment extended for 40 generations and produced the following results:

(1) The variance of development time decreased in the S line and increased in the D line, relative to the control lines.

(2) The mean development time decreased in the S line and increased in the D line.

(3) The coefficients of variation decreased in the S line and increased in the D line.

(4) The viability, measured as per cent flies emerging, decreased in the D line.

Toward the end of the experiment the amount of additive genetic variance in the selected lines and in the control lines was estimated from the response to directional selection. The estimates showed that (i) the loss of total variance in the S line can be accounted for completely by a loss in additive genetic variance, and (ii) the increase in the total variance of the D line cannot be ascribed to an increase in the additive genetic variance. It was probably due to an increase in the environmental component of variance, i.e. to a loss of ‘buffering capacity’.
Genetic gains under three methods of selection
Authors: Finney D. J.
Published: September 2009

Results obtained by Young for the expectation of genetic gain in an arbitrary linear function of several traits under selection by independent culling levels, under tandem selection, and under index selection have been obtained in slightly more general form and their dependence on basic genetic and phenotypic parameters exhibited. A warning is given about the effects of selection in modifying the distribution of traits; when the distribution has become appreciably non-normal, any calculation of genetic gains from formulae based on normality will tend to overestimation.
Valine-resistant mutants ofEscherichia coliK-12
Authors: Glover S. W.
Published: September 2009

Sixty-two mutants ofE. coliK-12 resistant to 40 μg./ml. valine were isolated from a sensitive strain. Transduction experiments using phage P1 showed that one group of these mutants,val-r-C, is closely linked toleu, another group,val-r-Bis closely linked tothr, and a third mutant,val-r-D57, lies betweenleuandthr. Conjugation experiments showed that the remainder of the mutants could be divided into three groups,val-r-A, val-r-Eandval-r-Fon the basis of their different times of transfer from Vhf donors toval-sF−recipients. All the mutants are sensitive to 10,000 μg./ml. valine;val-r-Bandval-r-Dmutants are resistant up to 80 μg./ml. valine;val-r-Cmutants are resistant up to 1000 μg./ml. valine, andval-r-A,val-r-Eandval-r-Fmutants up to 5000 μg./ml. The functional significance of the genetic locations of these groups is discussed.
The production of visible mutations inDrosophilaby chloroethyl methanesulphonate (CB 1506)
Authors: Auerbach C.
Published: September 2009

The claim that CB 1506 produces an unusually high proportion of visible to lethal mutations could not be confirmed. The ratio of visible to lethal sex-linked mutations was less than 1:10 in bothMuller-5and attached-X tests. In one brood it rose to 1:5 when unconfirmed visible mutants were included. The much higher ratio obtained by Fahmy and Fahmy is interpreted as a methodological artifact, due to the inclusion in their calculations of mosaic visibles but not of mosaic lethals.

Two visible mutations—twisted abdomen andwsatsuma—occurred more than once. This suggests the possibility of a locus or allele specific effect of CB 1506.
Polarized negative interference in thepaba 1region ofAspergillus nidulans
Authors: Siddiqi Obaid H. , Putrament A.
Published: September 2009

The intensity of negative interference in 28 crosses involving 14 allelicpabamutants in different combinations has been measured. Among selected cross-overs between two such mutants, when the distance between the mutants is large, additional exchanges on the distal side (relative to the centromere) greatly exceed those on the proximal side. With decreasing length of the interval of selection, the inequality disappears. It is suggested that this polarity may be the outcome of a undirectional process which imposes a time sequence on the recombination events within an effectively paired segment. Some alternative explanations of this result are discussed.
The action of ribonuclease and 8-azaguanine on mate-killer paramecia
Authors: Gibson I. , Beale G. H.
Published: September 2009

1. Mate-killer paramecia (derived from stock 540, P. aurelia) were treated with ribonuclease and 8-azaguanine to determine the effect of these two substances on the mu particles and metagons.

2. Ribonuclease destroyed the metagons in living paramecia but had no direct effect on the viability of the mu particles. The latter were however destroyed precisely after one fission of cells whose metagons had been eliminated by ribonuclease treatment.

3. Re-synthesis of metagons was found to take place between the second and third fissions after treatment with ribonuclease, if the dominant gene M2 was present.

4. Increasing the concentration of ribonuclease in the external medium, or in the duration of exposure of paramecia to ribonuclease, resulted in destruction of increasing proportions of metagons.

5. 8-azaguanine did not destroy metagons already present, but destroyed the mu particles immediately.

6. It is concluded that the results obtained with these two substances are consistent with the view that RNA is an essential constituent of metagons.
Attempts to test the inactive-X theory of dosage compensation in mammals
Authors: Lyon Mary F.
Published: September 2009

The inactive-X theory of dosage compensation postulates that in all somatic cells of adult female mammals one or other of the two X chromosomes is genetically inactive. This means that in a female heterozygous for two non-allelic genes acting through the same cells, and carried one on each X chromosome, one or other gene should act in all cells. Conversely, if the two genes are carried on the same X, then both genes should act in some cells and neither gene in the remainder. This point has been tested by breeding experiments with mice, using pairs of genes affecting coat colour and coat texture. In female mice carrying the colour mutant dappled,Modp, on one X and a translocation including the wild-type alleles of pink-eye,p, and albino,c, on the other, eitherModpor the translocation acted in all cells. With the genes tabby,Taand striated,Str, affecting coat texture, inStr + / + Tafemales tabby acted only in the non-Strpatches, while inStrTa/ + + it acted only in theStrones. Thus these experiments confirm that only one of the two X chromosomes is active in the somatic cells of female mammals.
The mating-type substances of Paramecium bursaria
Authors: Cohen L. W. , Siegel R. W.
Published: September 2009

The detached cilia from sexually reactive cells of Paramecium bursaria will agglutinate with the cilia of intact sexually reactive animals of a complementary mating type. No such reaction will occur if incompetent cells are used or if the cells are of the same mating type. Particulates other than cilia do not adhere to tester cells; the cilia which carry the specific mating-type substances are restricted to the ventro-lateral surface of the animal.

Studies of the heat inactivation of the ability of detached cilia to agglutinate confirm in detail the hypothesis of Metz which holds that cell unions leading to conjugation are brought about by the interaction of two pairs of complementary substances, A and a and B and b; the former pair of substances is more heat labile than the latter. The data suggest that animals of each of the four mating types carry a unique combination of two substances, namely, AB, aB, ab, and Ab.
Genetical studies on growth and form in the fowl 1. Phenotypic variation in the relative growth pattern of shank length and body-weight
Authors: Cock A. G.
Published: September 2009

Body-weight and shank length from 2 weeks of age to adult (and from 8 weeks onwards, shank width) have been measured on 154 fowls all hatched on the same date, belonging to two F1breed crosses: White Leghorn × Rhode Island Red (L × R) and Indian Game × Light Sussex (G × S). After logarithmic transformation the data have first been analysed cross-sectionally (analysis of the age-means for each sex and cross). A longitudinal analysis (fitting a regression line to the data of each individual) has then been made of the approximately linear portions of the curves. The following conclusions are drawn.

(1) Growth in shank length relative to body-weight between 2 and 10 weeks conforms closely to simple allometry. The coefficient of ontogenetic allometry (heter-auxesis),k, is approximately 0·4, being 0·02 higher in L × R than in G × S and 0·05 higher in males than in females. In femaleskdeclines (eventually to zero) after 10 weeks; the decline occurs about 4 weeks later in males. For shank width relative to body-weightkis about 0·25.

(2) At a given body-weight males have longer and thicker shanks than females; L × R have longer but thinner shanks than G × S.

(3) Within sexes and crosses there is highly significant individual variation ink, but the allometry lines do not pass, within the limits of error, through any single point. This implies that variation in relative shank length is complex in its ontogenetic origin.

(4) There is no appreciable correlation within sexes and crosses between shank width and shank length at a given body-weight; this implies (as does (2)) that variation is also complex anatomically.

(5) Differences in shape and rate-of-change of shape contribute only a small part of the total variation within sexes and crosses; most is due to differences ingeneralsize andgeneralgrowth rate.

(6) Shank width at a given body-weight is positively correlated with body-weight at a given age (r= + 0·36 within sexes and crosses). This agrees with the finding that the coefficient of static allometry (allomorphosis) for shank width is much higher than the ontogenetic coefficient. For shank length the ontogenetic and static coefficients are approximately the same.
Epigenetic polymorphism in wild populations ofMus musculus
Authors: Berry R. J.
Published: September 2009

It has been suggested (Berry & Searle, 1963) that the discontinuous (‘quasi-continuous’) variants studied by Grüneberget al.in the skeleton of rodents can be regarded as constitutingepigenetic polymorphismin different populations. Comparisons have been made between the incidences of skeletal variants in house mouse populations collected from: corn ricks on a single farm in Hampshire; eleven separated localities in different parts of the British Isles; and nine other places throughout the world. These showed that the method could profitably be used for genetically characterizing and hence comparing populations. There was evidence suggestive of genetical drift between local populations and stabilizing selection over a larger area.
A failure to induce heritable changes in four generations of the White Leghorn chicken by inter- and intra-specific blood transfusion
Authors: Kosin I. L. , Kato Masaru
Published: September 2009

1. A three-year study was conducted to test the efficacy of inter- and intra-specific blood transfusions in domestic poultry for inducing heritable changes in the recipients. The latter were pure-bred White Leghorns. Pure-bred Broad Breasted Bronze turkeys and New Hampshire chickens served as blood donors to two distinct lines of recipients. All injections started when the recipient chicks were 2–5 days old. Altogether, more than 3000 chicks from blood injected lines were involved in the study, conducted between 1959 and 1961 and distributed between the parental and three subsequent generations. Each injected chick received a total of some 155 ml. of whole blood in the course of a five-month injection period. An adequate number of control (non-injected) birds was used throughout. Observations were made on plumage colour, body-weight, egg-weight, egg-shell colour, fertility and hatchability. Furthermore, blood plasma and muscle tissue of appropriate birds were subjected to immunological, chromatographic and electrophoretic analyses.

2. On the basis of all these criteria, no evidence of heritable shifts in the direction of the donor organism was discerned among birds belonging to either of the two treated lines.