bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation-inducedalcohol dehydrogenasemutants in maize following allyl alcohol selection of pollen
Authors: Freeling Michael , Cheng David S. K.
Published: September 2009

Thealcohol dehydrogenase-1gene in maize presents advantages for mutational analysis. Foremost among these is the ability to chemically select ADH-negative and ADH-low gametophytes owing to their resistance to allyl alcohol vapour. Immature tassels were irradiated with either 220 kV X-rays or 400 MeV/amu accelerated neon-ions; spontaneous mutants were also selected and recovered. RBE for neon-20 was about 5. A total of 70 presumptive mutants were placed into one of four classes on the basis of allozyme profiles following electrophoresis and ADH staining: (A) dysfunction, (B) underproducer, (C) overproducer, and (D) up-Adh2gene. Mutants have been recovered and confirmed in the first three classes. These include two male-transmissible deletion-type lesions induced by X-rays, five underproducer transpositions and one overproducer transposition induced by neon-20. Certain of the neoninduced alleles are unstable in their expression. All 70 mutants are chromosomal aberrations; no intragenic lesions were recovered although our experimental design would have preferentially recovered them if they had occurred.

The Discussion considers the mutagenic action of ionizing radiation, and especially the well-documented differences between maize and Drosophila data. In particular, the effect of these chromosome derangements on the ‘programmable’ component(s) of theAdhlcistron is discussed.
Heterozygous diploid analyses via the parasexual cycle and a cytoplasmic pattern of inheritance inVerticillium spp.
Authors: Typas Milton A. , Heale James B.
Published: September 2009

Combining data from mitotic crossing over in, and haploidization of, heterozygous diploid strains, 33 markers have been mapped successfully inVerticilliumspp. One marker (Hyl), which determines the absence of darkly pigmented resting structures in many stable hyaline strains, showed an irregular segregation. In view of previous evidence from acriflavine treatment and heterokaryon analyses in the fungus, this further substantiated indications of a cytoplasmic pattern of inheritance for this marker. The phenotypic expression of dark pigment genes showing nuclear inheritance, such asSot., depends upon the cytoplasmically determined (Hyl+) presence of resting structures.
Natural selection and colour blindness: fresh data on Indian castes
Authors: Malhotra K. C.
Published: September 2009

Incidence of colourblindness among 3325 males belonging to 21 endogamous Dhangar castes (shepherds) of Maharashtra, India, has been reported. Of the 21 castes studied 5 lacked the gene for colourblindness, while in other groups it varied from 1% to 55%, with a series average of 2·65%. The low incidence of observed colourblindness has been discussed in the light of the nomadic way of the life of some of the Dhangar castes. The results have been compared with other nomadic populations of Maharashtra. The results, in general, are compatible with the Post and Pickford's hypothesis of differential selection for colourblindness.
Immunogenetics of a sheep (Ovis aries) serum antigen
Authors: Iannelli Domenico
Published: September 2009

An allotypic specificity (A1) of sheep serum is described. The antigenic determinant is located on a low molecular weight glycoprotein which has its isoelectric point at pH 5 and is capable of interacting with the lectin concanavalin A.

Family studies showed that the allotype is inherited in a simple Mendelian manner.
Meiosis inSchizophyllum commune: premeiotic DNA replication and meiotic synchrony induced with hydroxyurea
Authors: Carmi Pheya , Koltin Y. , Stamberg Judith
Published: September 2009

Hydroxyurea (HU) effectively inhibits meiosis inSchizophyllum. The predominant cytological stage in inhibited fruit bodies is fusion. The inhibition is reversible and makes possible synchronization of a naturally nonsynchronous system. Microphotometric determinations of the DNA content in prefusion nuclei treated with HU suggest that premeiotic DNA replication occurs in prefusion nuclei. Synaptinemal complexes are not completed in HU-treated nuclei, suggesting that this event is dependent on premeiotic DNA replication.
On the dispersion of imaginal progenitor cells in theDrosophilablastoderm
Authors: Wyman Robert J. , King David G.
Published: September 2009

The number of blastoderm cells inDrosophilawhose descendants form adult structures has frequently been estimated from genetic mosaics. Data from somatic recombination (method I) and gynandromorph (method II) mosaics both yield very low estimates, e.g. about 10–20 progenitor cells for the eye and antenna, wing or leg.

In gynandromorphs the mosaic dividing line has a random orientation on the blastoderm. In the 6000 cell blastoderm it should be very unlikely that the mosaic dividing line passes through any small patch of only 10–20 cells. Yet it has been reported that 10–25% of eye/antenna, wing or leg disks in gynandromorphs are mosaic. Thus the frequency of mosaicism data seems to be in contradiction to the progenitor population estimates. Similar discrepancies are found in the data for other adult structures.

In this paper we derive a formula for estimating the number of cells in a blastoderm patch from the frequency with which the gynandromorph dividing line passes through it (method III). In a second method (method IV) we use the maximum distances inside the progenitor areas on a fate map to estimate the progenitor patch size. These two estimates agree closely with each other. We find, e.g. that 50–100 cells are in the patches from which the eye/antenna, wing or leg disks derive.

We examine a number of possible explanations for why the first two estimates are so much smaller than the last two. The former estimates refer to the number of progenitor cells which actually have descendants in the adult structure; the latter estimates refer to the total patch area in which the progenitor cells sit. With the present information the most reasonable conclusion is that the progenitor cells for the adult structures are dispersed among other cells which have different developmental fates. If confirmed by experiment, this result has many implications for the process of determination.
Cell numbers and cell sizes in organs of mice selected for large and small body size
Authors: Falconer D. S. , Gauld I. K. , Roberts R. C.
Published: September 2009

Cell numbers in four organs of large, control and small mice were estimated by nuclear counts. Average cell mass was estimated from the cell number and the organ weight. The mice were from the selected Q-strain with six replicate lines in each size-group. The organs were lung, liver, spleen and kidney. At 6 weeks of age the large mice had more cells and larger cells than the controls in all organs; the small mice had fewer and smaller cells than the controls. The regression of log cell-number on log-organ weight provides a measure of how much, proportionately, cell number contributes to the differences in organ weight. In the lung and spleen, cell number contributed about 70% of the strain differences in organ weight, cell mass contributing about 30%; in the liver and kidney the relative contributions were about equal, at 50%.

Cell counts at different ages from 3 to 15 weeks showed that cell number and cell mass contributed to the increases of organ weights during growth in roughly the same proportions as stated above. From this it is concluded that the main effect of selection for body weight has been to speed up or slow down the normal processes of cellular growth.
The alcohol dehydrogenase polymorphism in populations ofDrosophila melanogaster: 3. Differences in developmental times
Authors: Van Delden W. , Kamping A.
Published: September 2009

From the F2ratios of crosses betweenDrosophila melanogasterstrains homozygous for theAdhF(F) and theAdhs(S) allele it has been concluded that the developmental time ofFFhomozygotes is shorter than that ofSShomozygotes. This difference is found to be reinforced by increasing levels of crowding. A further analysis of developmental times has been performed by the transfer of larvae to agar medium after they have stayed for periods of variable length on regular food. From the percentage of emerging adults it can be concluded thatFFlarvae and, to a lesser extentFSlarvae, either reach their critical weights for pupation earlier thanSSlarvae or possess a lower critical weight. These differences in developmental time influence the course of allele frequencies. Between populations kept on a 2-week transfer schedule and on a 3-week schedule a divergence of allele frequencies is observed, in the former a decrease inSfrequency occurs. The relevance of the observed differences in developmental time for the maintenance of theAdhpolymorphism is discussed for laboratory populations kept on regular food and at varying densities.
A lethal mutation (cab) affecting heart function in the mouse
Authors: Essien Francine B.
Published: September 2009

A new autosomal recessive gene (cab, ‘cardiac abnormality’), which affects heart differentiation appeared spontaneously in our mouse colony. The affected homozygotes die approximately half a day prior to birth or at term, with the myocardium exhibiting vacuolation and large areas of mesenchyme-like cells. A significant finding in mutant foetuses is the lack of histochemically detectable glycogen.
A note on the symmetry constraints imposed by dominance in multiple locus genetic models
Authors: Slatkin Montgomery
Published: September 2009

A method is introduced that allows the simplification of the calculation of equilibrium solutions in multiple locus genetic models of a single infinite population. The method can be applied when the number of different fitnesses is equal to or less than one more than the number of independent allelic frequencies. The results are in terms of relationships – the symmetry constraints – between the gametic frequencies that must be satisfied at any boundary or internal equilibrium. The symmetry constraints are independent of the fitness values and of the recombination fractions. This can lead to some understanding of the equilibrium structure of a model when the full equilibrium solution is not obtained and reduces the number of independent variables in the calculations of the full equilibrium solutions. Examples of two locus models with two alleles at each locus and with two alleles at one locus and three at the other are discussed.
The effects of normalizing and disruptive selection on genes for recombination
Authors: Smith J. Maynard
Published: September 2009

Deterministic simulations have been carried out of populations under normalizing and disruptive selection for a trait determined by genes with additive effects at six loci. In some simulations a pair of alleles at a seventh locus determined the rate of recombination between the seven loci. Normalizing selection with a single optimum, fixed or fluctuating, invariably led to genetic homozygosity. If the optimum fluctuates widely, the approach to homozygosity may be accompanied by a large decline in the mean fitness of the population. Disruptive selection was simulated by having two ‘niches’ with separate optima and separate density-dependent regulation, but with the adult population mating randomly. If the optima are widely separated, this leads to stable polymorphism. Selection produced linkage disequilibrium, normalizing selection causing repulsion and disruptive selection coupling between + and − alleles. This linkage disequilibrium accelerates the phenotypic response to selection, but delays changes in gene frequency. Selection always favoured alleles for low recombination at the expense of alleles for high recombination.
Germ line aberrations associated with a case of hybrid dysgenesis inDrosophila melanogastermales
Authors: Engels William R.
Published: September 2009

Male sterility, male recombination, and transmission ratio distortion – all examples of a syndrome known as hybrid dysgenesis inDrosophila melanogaster– were found to involve chromosome–cytoplasm interactions. The latter two have temperature optima near 25° and involve pre-meiotic events. In addition, sex ratio distortion, and induction of certain translocations of theXandYchromosomes (but not the autosomes) were found to be part of hybrid dysgenesis. Both are caused by chromosome–cytoplasm interactions with pre-meiotic events playing a crucial role. The results agree with previous data on female sterility in hybrid dysgenesis, which also has cytoplasmic components and premeiotic origins.
Gene for a serum protein on chromosome 9 in the mouse
Authors: Håkansson E. M. , Juneja R. K. , Lundin L.-G.
Published: September 2009

An electrophoretic variation in a mouse serum protein moving closely to the vitamin D binding protein is described. The variation is determined by two codominant alleles at one locus with the allele in DBA causing fast mobility and that in C57BL causing slow mobility. This locus is located in the proximal part of chromosome 9, 14·3 cM from thedlocus and 31·9 cM from theBgslocus. The protein has not yet been identified but possible candidates among the serum proteins are discussed.
Complementation reactions of a lethal mouset-haplotype believed to include a deletion
Authors: Lyon Mary F. , Jarvis Susan E. , Sayers Irene , Johnson D. R.
Published: September 2009

The lethalt-haplotypes of the mouse fall into several distinct complementation groups, and varying degrees of partial complementation occur when haplotypes from different groups are crossed. The haplotypeth20arose as a mutant from the haplotypet6, and is thought to include a small deletion covering loci near thet-lethals. In this paper the complementarity ofth20was compared with that of its parent haplotypet6.th20showed weaker complementation thant6of the haplotypestw5,tw32andtw1. Hence the loci of these lethals were probably exposed by the deletion inth20. However,th20showed full complementation oftw18and showed full viability in compound with the dominant brachyury allele hairpin-tail,Thp. Therefore, theth20deletion probably does not overlap the presumed deletion inThp, nor extend to the locus of thetw18lethal. The significance of the weak complementation oftw5,tw32andtw1is discussed.
A sex-linked coat-colour mutation in the mouse non-transmissible through the female
Authors: Guenet Jean-Louis
Published: September 2009

A sex-linked mutation with a phenotype similar to that of an allele of the Mottled series has been discovered in a mosaic male. This mutation can be normally transmitted through the sperm of the original male but not through the oocytes. Several interpretations of this abnormal transmission are discussed.
Path analysis under generalized assortative mating
Authors: Rao D. C. , Morton N. E. , Cloninger C. R.
Published: September 2009

Assortative mating is generalized to include social homogamy and phenotypic homogamy as two special cases. This generalization, called mixed homogamy, enables tests of hypotheses on the nature of assortment. Cultural inheritance is also extended to include two components: transmitted from parental environments, and non-transmitted sibship environment. Familial correlations are derived for a variety of relationships under mixed homogamy.
A mathematical model of meiotic segregation in trisomics of yeast
Authors: MacMartin Stuart J. , James A. P.
Published: September 2009

Segregations at five loci on the left arm of chromosome VII and other data from published sources were used to test a new mathematical model of meiotic segregation in trisomics of the yeastSaccharomyces cerevisiae. Results support this model which predicts that non-centromere-linked genes in trivalent complexes segregate at random. The data indicate that bivalent–univalent complexes are infrequent in trisomics and that recombination between all three homologues is frequent in regions close to the centromere. A test of homologue interference produced no evidence that a crossover between two homologues has any influence on the probability that the same two homologues will be involved in an adjacent crossover.
Hybrid dysgenesis inDrosophila melanogaster: the relationship between theP–MandI–Rinteraction systems
Authors: Kidwell Margaret G.
Published: September 2009

Two systems of hybrid dysgenesis, theP–Msystem and theI–Rsystem, are characterized by two different specific types of non-reciprocal hybrid sterility referred to, respectively, asGDandSFsterility. In order to determine the relationship between these two systems, strains representative of the four single-system interactive types were crossed in almost all possible combinations and tested for both types of sterility. The results suggest that the two systems are at least partially independent of one another. There are several examples of single strains that contribute the maternal component for interaction in theP–Msystem and contribute the paternal component in theI–Rsystem. Using parents with the potential for the two types of interaction and. appropriate temperature manipulation, bothGDandSFsterility can be manifested in the same hybrid females. In other crosses, a single type of sterility is observed, or none at all, according to the dual designation of the parental strains. The evidence from a number of additional crosses suggests that most strains of this species have the potential for both types of interaction to varying degrees when mated in appropriate combinations. Some theoretical and practical implications of these results are discussed.
Hybrid dysgenesis inDrosophila melanogaster: rules of inheritance of female sterility
Authors: Engels William R.
Published: September 2009

Hybrid dysgenesis has been described as a syndrome of aberrant traits including sterility, male recombination, and mutation, which occurs in some inter-strain hybrids of Drosophila, but only from one of the two reciprocal crosses. In a series of experiments in which hybrids of various pedigrees were tested for sterility, it was found that a case of hybrid dysgenesis could be most easily interpreted as the interaction of two components. One component was found to be a polygenic Mendelian factor linked to each of the major chromosomes of π2, the paternally contributing strain (‘Pstrain’). These chromosomes were capable of causing sterility when inherited from either parent, provided the appropriate maternal component was also inherited. The ability to transmit this maternal component was designated ‘cytotype’ to indicate that it is a property of the entire cell. It was possible to classify nearly all hybrid females as eitherPorMcytotype on the basis of their ability to produce sterile daughters. All daughters of theM-cytotype mothers were susceptible to the sterilizing effects of the π2chromosome, whereas all, or nearly all daughters ofP-cytotype mothers were immune. When more than one of the π2chromosomes were received by daughters ofM-cytotype females, chromosomal interactions could be detected statistically, but the model of independent action remained a useful approximation. Cytotype was shown to be determined by chromosomal factors, but with limited cytoplasmic transmission. This unusual mode of inheritance can be compared with other cases of hybrid dysgenesis where the behaviour resembles that of self-replicating cytoplasmic particles which are dependent on certain chromosomes. The lack of sterility from intra-strain crosses can be explained by the fact that chromosomes capable of causing sterility also induce thePcytotype, and thus prevent sterility in the next generation.
Genetic aspects of fertility differentials in ponderosa pine
Authors: Linhart Yan B. , Mitton J. B. , Bowman D. M. , Sturgeon K. B. , Hamrick J. L.
Published: September 2009

There is a strong genetic component to fertility differentials among individuals of ponderosa pine. Prolific cone-producers as a group were markedly different from low cone-producers at the three protein loci which were monitored. The two groups did not differ significantly in age, but trees with high cone production had slower growth rates and smaller diameters than trees with low cone production. To our knowledge, these results provide the first demonstration of fertility differentials associated with specific genes in a woody plant.
A comparison of genetic variability atX-linked and autosomal loci in kangaroos, man andDrosophila
Authors: Cooper D. W. , Johnston P. G. , Vandeberg J. L. , Maynes G. M. , Chew G. K.
Published: September 2009

This paper tests the hypothesis that haplodiploidy orXlinkage leads to less genetic variability. Although haplodiploid organisms exhibit a low level of genetic variability the wide variation existing between different diploid organisms implies that factors other than the genetical system could also be responsible. In order to test the hypothesis critically it is necessary to compare the level of genetic variability betweenX-linked and autosomal genes within a closely related group of organisms. For kangaroos, the ascertainment bias forX-linked loci has been removed by assuming the correctness of Ohno's law of conservation of the mammalianX, i.e. that genes found to beX-linked in man can be assumed to beX-linked in kangaroos. For Man andDrosophila, it has been assumed that the percentage of the karyotype which isXchromosome can be used as the expectation for the percentage ofX-linked polymorphisms. No difference between the two classes of loci is evident in kangaroos and man for percentage polymorphism. The data however have confidence limits which would allow autosomal loci to have three times greater percentage polymorphism. InDrosophilathe published data of Prakash show that autosomal loci are polymorphic about twice as frequently as are theirX-linked counterparts. Thus theremaybe a modest reduction in percentage polymorphism as a result ofX-linkage (i.e. haplodiploidy). No reduction in the number of alleles per locus or average heterozygosity at those loci which are polymorphic is evident in kangaroos, man, orDrosophila. More data on moreX-linked enzymes are necessary to establish firmly that there is a real reduction in percentage polymorphism and to estimate its extent. The kangaroo data are incompatible with the hypothesis that a large fraction of the variability is maintained by simple overdominance since overdominance is very unlikely in the quasi-haploid genetical system which results from the paternalXinactivation mode of dosage compensation used by kangaroos. This is the first report on level of enzymic variability in marsupials. 17% of autosomal loci and 18% ofX-linked loci are polymorphic, average heterozygosity is 4% for autosomal and 4% forX-linked loci and number of alleles per locus is 1·25 for autosomal and 1·21 forX-linked loci. These figures are somewhat lower than for eutherian mammals.
Absence of mitochondrial malic enzyme in mice carrying two complementing lethal albino alleles
Authors: Eicher Eva M. , Lewis Susan E. , Turchin Howard A. , Gluecksohn-Waelsch Salome
Published: September 2009

Mitochondrial malic enzyme (MOD-2) was found to be missing in partially complementing genotypes between lethal deletion alleles at the albino locus in Chromosome 7 of the mouse. Since such partial complementers survive to adulthood, the absence of normal mitochondrial malic enzyme is compatible with life; however, the sterility of both females and males may be correlated with this enzyme deficiency. Of the six radiation-induced lethal albino mutations, five includedeletions for theMod-2locus mapping 1 centimorgan distally fromc.Our data indicate that the maximum genetic distance occupied by any of these deletions is 6 centimorgans.
Digynic triploidy in rabbit blastocysts after delayed insemination
Authors: Beatty R. A. , Coulter V. J.
Published: September 2009

The origin of triploid (3N) 5½-day blastocysts in rabbits is inferred from the segregation of sex chromosomes and of an autosomal M-marker whose properties are described. 39 triploids and no tetraploids were scored among 1454 chromosomally scored blastocysts. A delay of 8 h between an ovulatory injection and subsequent insemination raised the estimated normal incidence of 0·59% triploid blastocysts to 3·13%. The increase is ascribed primarily to digyny (17 blastocysts), and to diandry probably mediated by dispermy (1 blastocyst). The triploid components of the two 2N/3N mosaics and the one 3N/6N were digynic. Neither superovulation nor insemination of excessive numbers of spermatozoa could be shown to give rise to triploid embryos. The diandric triploid was X Y Y, the first of this constitution apparently reported in the rabbit. There was some evidence that X X Y triploid blastocysts up to 5½-day gestation are more viable than X X X. In the 2N/3N mosaics each component had been entered by one spermatozoon, and the dliploid component could not have been merely a contamination by dliploid maternal somatic cells. In 2N/4N, 2N/4N/8N and 3N/6N mosaics, each polyploid component showed an exact doubling of the marker chromosome constitution of a component of lower ploidy; their origin is ascribed to doubling or redoubling of chromosome number in isolated embryonic cells. With earlier data included, 49·08 (± s.e. 1·96)% of 652 diploid blastocysts were X Y. 460 non-experimental weaned rabbits were all cliploid.
Interaction between the plasmid R6K andEscherichia coliwith defective DNA polymerase I
Authors: Tweats D. J. , Smith J. T.
Published: September 2009

Initial experiments demonstrated that the plasmid R6K cannot be transferred to or maintained readily in theE. coliDNA polymerase I deficient strain JG138polA1. Results withE. coliMM386polA12(R6K), which has a temperature sensitive polymerase I enzyme, showed cell division becomes abnormal when the polymerase I enzyme of the host bacteria is inactivated at the restrictive temperature. Under conditions of polymerase I deficiency, R6K replication, as measured by monitoring R-factor-mediated β-lactamase activity, also becomes abnormal with the loss of multiple R6K copies per cell and the apparent maintenance of a single R-factor copy per cell.
A new type of genetic control of gene conversion, fromAscobolus immersus
Authors: Lamb B. C. , Helmi S.
Published: September 2009

A new type of genetic control of gene conversion is described from the Pasadena strains of the fungusAscobolus immersus. It is characterized bycis/transposition effects and incomplete dominance. TheP, Kand91factors segregated from each other like Mendelian alleles and controlled the conversion frequencies and patterns of four nearby, closely-linkedwhiteascospore colour mutations, although they did not usually coconvert with thesewsites. Mutations of different origin responded similarly to the same control factors.

These control factors greatly affected the total conversion frequencies, the relative frequencies of the different detected conversion classes and various other conversion parameters. The detailed results are consistent either withP, Kand91affecting both the frequency of hybrid DNA formation and the correction processes for removing mispaired bases, or if they do not affect the correction processes directly, then they must have large effects on the frequency of asymmetrical hybrid DNA formation, which must usually be much more common than symmetric hybrid DNA, and there must be both an inequality in the frequency with which the two homologous chromosomes (in these crosses, + bearing andwbearing) invade each other, and in the frequency with which the two strands of each chromatid invade the homologue in asymmetric hybrid DNA formation.
Non-mendelian female sterility inDrosophila melanogaster: variations of chromosomal contamination when caused by chromosomes of various inducer efficiencies
Authors: Pélisson Alain
Published: September 2009

A quite specific kind of sterileF1female, calledSFfemales, arises only when females of strains denoted reactive are crossed with males of the other class (inducer). It was previously shown that this sterility results from a nucleocytoplasmic interaction between the maternal reactive cytoplasm and a factor, calledI, which may be born by any one of the paternal chromosomes. InSFfemales, but not in their brothers, a varying proportion of reactive chromosomes are able to acquire irreversibly theIfactor, independently of any classical genetic recombination with the inducer chromosome(s). During this process, called chromosomal contamination, the contaminating chromosome(s) do not undergo any apparent change. The present paper deals with the efficiency of both original inducer and contaminated chromosomes to yield a more or less intenseSFsterility. TheOtanuinducer laboratory strain contains at least two types ofXchromosomes (calledstrongandweak) which differ genetically with respect to their inducer efficiency. Reactive third chromosomes were contaminated by thesestrongorweak Xchromosomes and their inducer efficiencies compared. Results show that they are on averagestrongerwhen they have been contaminated bystrong Xchromosomes than when contaminated byweakones. Such a correlation favours the hypothesis that chromosomal contamination is due to the insertion of some genetic element(s) into reactive chromosomes.
Analysis of central equilibrium configurations for certain multi-locus systems in subdivided populations
Authors: Karlin Samuel , Campbell R. B.
Published: September 2009

The multi-locus systems expressing non-epistatic and generalized symmetric selection lend themselves to the study of the stability of certain central polymorphic equilibria. These equilibria persist when any form of migration connects demes which share a common equilibrium. The analysis of the stability of the equilibrium in the global system is tractable, thus supplementing known protection results for two alleles at one locus with stability conditions on an internal equilibrium involving an arbitrary number of loci, each with an arbitrary number of alleles. Two of the principal findings are that stability of central Hardy–Weinberg type equilibria increase with ‘more’ migration and ‘more’ recombination. As a corollary, local stability in each deme implies stability in a system with migration superimposed; but instability in each deme when isolated does not imply instability when migration is superimposed.
Growth hormone function in strains of mice selected for large and small size
Authors: Pidduck Heather G. , Falconer D. S.
Published: September 2009

The gene (dw) causing hypopituitary dwarfism was transferred by repeated backcrosses into strains of mice differing genetically in growth-rate through previous selection. The dwarf mice lack growth hormone, and the purpose was to find out if the differences in growth-rate between the strains were in any part due to differences in their growth hormone status – amount of hormone or tissue sensitivity. In the absence of growth hormone, i.e. in the dwarfs, the strains still grew at different rates, proving that growth hormone status was not the only cause of their differences. The effect of substituting the dw gene was, however, greater in the large strain than in the unselected control, and less in the small strain than in the control. The growth differences between the strains were therefore in part due to growth hormone. Tissue sensitivity in the three strains was compared by their responses to graded doses of exogenous growth hormone. The large and control strains did not differ, but the small strain had a lower sensitivity. The results suggest that the increased growth-rate of the large strain is partly due to an increased amount, or activity, of its circulating growth hormone, while the reduced growth-rate of the small strain is in part due to a reduced sensitivity of its target organs to growth hormone.
Some approaches to the question of Drosophila laterality
Authors: Ehrman Lee , Thompson James N. , Perelle Ira , Hisey Brent N.
Published: September 2009

The question of Drosophila laterality has been investigated in two species and in several strains by attempting to modify degrees of laterality (wing folding and directional choices in mazes) via selection and by ascertaining individual courtship behaviour preferences (circling, foreleg tapping, and wing extending). The results of courtship studies in D. paulistorum strains and in D. melanogaster indicate that, although individual members of a strain may be entirely right or left dominant, the majority of individuals are ambidextrous. As a group, there was no preference for right or left behaviours, and laterality was not a factor in success of courtship. The absence of lateral preference in courtship is consistent with the failure to demonstrate any genetic component for D. melanogaster left and right wing folding and maze behaviours.
Evidence for a transmissible catabolic plasmid inPseudomonas putidaencoding the degradation ofp-cresol via the protocatechuateorthocleavage pathway
Authors: Hewetson L. , Dunn H. M. , Dunn N. W.
Published: September 2009

Evidence is presented that a strain ofPseudomonas putidaharbours a catabolic plasmid which encodes for the degradation ofp-cresol through the protocatechuateorthocleavage pathway. This plasmid can transfer giving approximately 10−3transconjugants per donor cell, can be cured with mitomycin C, belongs to the P-9 plasmid incompatibility group and can be transduced with the bacteriophage pf16.
Estimation of heritability by regression using collateral relatives: linear heritability estimation
Authors: Hill William G.
Published: September 2009

The method of heritability estimation proposed by Abplanalp (‘linear heritability’ estimation) is reviewed and the formulation simplified. It is equivalent to the regression of performance of sibs of an individual, itself excluded, on that of the individual. The method is found to be slightly biased in small samples but, in terms of sampling variance, can make efficient use of the data.
Non-mendelian female sterility and hybrid dysgenesis inDrosophila melanogaster
Authors: Picard G. , Bregliano J. C. , Bucheton A. , Lavige J. M. , Pelisson A. , Kidwell M. G.
Published: September 2009

Systematic crosses between various strains ofDrosophila melanogasterlead in some cases to partly sterile F1females (SFfemales). Two main classes of strain, inducer and reactive, have been denned on the basis of this sterility, which shows very specific physiological features.SFfemales arise only when reactive females are crossed with inducer males. In contrast, F1females (RSF) produced by the reciprocal cross between inducer females and reactive males have normal fertility. All wild populations tested are of the inducer category, laboratory strains are either inducer or reactive. Sterility is the result of interaction between two genetic factors denotedIandR, respectively responsible for the inducer and reactive conditions and whose unusual genetic behaviour has been described in other papers. The present paper reports experiments showing that theI–Rinteraction is also responsible for high levels ofXnondisjunction and of mutation in theSFfemale germ-line. The analogy with the P-M system of Kidwell, Kidwell & Sved (1977b), is discussed as are also the implications of the existence of theI-Rsystem for spontaneous mutation research inD. melanogaster.
Parameters in gene conversion: An algebraic analysis of the hybrid DNA model at thegraylocus ofSordaria fimicola.
Authors: Kalogeropoulos Angelos , Thuriaux Pierre
Published: September 2009

We have extended previous algebraic analyses of aberrant segregation at thegraylocus ofSordaria fimicola(Whitehouse, 1965; Emerson, 1966; Fincham, Hill & Reeve, 1980) to the more complex situation where aberrant segregations are detected in three factor crosses involving two flanking markers. This algebra has been applied to sevengrayalleles which have been extensively characterized for their pattern of gene conversion and postmeiotic segregation by Kitani & Olive (1967). It is based on seven major types of aberrant segregation which can be distinguished in the presence of flanking markers spanning the converting site, and allows us to use up to six parameters to describe hDNA formation and mismatch repair. We present solutions which predict a spectrum of aberrant segregation fitting the experimental data at theP> 0·05 level for six of the seven alleles tested. They are consistent with the following properties of hDNA at thegraylocus: (1) the single stranded DNA transferred during hDNA formation has always the same chemical polarity. (2) hDNA is mostly, if not entirely, symmetric, and its probability of formation is constant over the whole gene. (3) Disparity in aberrant segregation is mostly, if not entirely due to disparity in mismatch repair.
Mechanism of suppression inDrosophila melanogasterVIII. Comparison ofsu(s) alleles for ability to suppress the mutants purple, vermilion, and speck
Authors: Jacobson K. Bruce , Grell E. H. , Yim John J. , Gardner April L.
Published: September 2009

The suppressor of sable [su(s)2] restores the function of vermilion (v), purple (pr) and speck (sp) as well as sable (s) inDrosophila melanogaster. In this report various alleles ofsu(s) are compared for their relative effectiveness on three target mutations,v,prandsp. Three criteria for suppression ofprandvwere employed: visible phenotype, eye pigment levels (drosopterins and xanthommatin) and enzyme levels (sepiapterin synthase and tryptophan oxygenase). Forsponly the visible phenotype was examined. By all three criteriaprwas found to be more easily suppressed thanv;vandspwere comparable. By use ofprwith various alleles ofsu(s) either homozygously or in heterozygous combination withsu(s)+, the extent of suppression ofprcan be best demonstrated by observing the levels of sepiapterin synthase; normal levels of drosopterins were found in females when sepiapterin synthase was only 20% of normal. On the other hand, the extent of suppression ofvis best demonstrated by the amount of xanthommatin eye pigment, because even the suppressed vermilion fly has < 10% of wild-type activity of tryptophan oxygenase when 1-day-old flies are examined; in older flies this enzyme can be as high as 50% of wild type. From these results we also demonstrated thatsu(s)2, and other alleles, are not recessive but, in heterozygous combination withsu(s)+, cause marked suppression ofprand slight, but reproducible, suppression ofv. The purple mutation, therefore, is particularly useful for studying the mechanism of suppression as well as for obtaining new mutant alleles ofsu(s).
Novel pleiotropic effect of rifampicin resistance mutation in aMicromonosporasp
Authors: Gadó István , Kari Csaba , Széll Valéria , Szvoboda György
Published: September 2009

Rifampicin-resistant mutants have been isolated from aMicromonosporasp. In one of these, rifampicin failed to inhibit [3H]UTP incorporation in osmotically shocked cells; consequently, resistance was probably not due to the alteration of rifampicin permeability. Parallel to the rifampicin resistance there was a substantial increase in the novobiocin sensitivity of the mutants. Rifampicin-sensitive revertants exhibited their original novobiocin sensitivity. At the same time there was no increase in their sensitivity towards coumermycin A1, an agent of related structure and activity. The possible mechanism for this pleiotropy is discussed.
Models of mitochondrial DNA transmission genetics and evolution in higher eucaryotes
Authors: Chapman Robert W. , Stephens J. Claiborne , Lansman Robert A. , Avise John C.
Published: September 2009

The future value of mitochondrial DNA (mtDNA) sequence information to studies in population biology will depend in part on understanding of mtDNA transmission genetics both within cell lineages and between animal generations. A series of stochastic models has been constructed here based on various possibilities concerning this transmission. Several of the models generate predictions inconsistent with available data and, hence, their assumptions are provisionally rejected. Other models cannot yet be falsified. These latter models include assumptions that (1) mtDNA's are sorted through cellular lineages by random allocation to daughter cells in germ cell lineages; (2) the effective intracellular population sizes (nM's) of mtDNA's are small; and (3) sperm may (or may not) provide a low level ‘gene-flow’ bridge between otherwise isolated female lineages. It is hoped that the models have helped to identify and will stimulate further empirical study of various parameters likely to strongly influence mtDNA evolution. In particular, critical experiments or measurements are needed to determine the effective sizes of mtDNA populations in germ (and somatic) cells and to examine possible paternal contributions to zygote mtDNA composition.
Association of the cyanogenic loci in white clover
Authors: Ennos Richard A.
Published: September 2009

The inheritance of cyanogenesis inTrifolium repensis governed by two unlinked genes, Ac/ac and Li/li which determine the presence/absence of cyanogenic glucosides and their hydrolysing enzyme linamarase respectively. Plants possessing dominant alleles at both loci release hydrogen cyanide when their leaves are damaged. Analysis of phenotype frequencies in ten natural populations showed a significant positive association in phenotypic state between these two loci within populations. Taking into account the results of a subsidiary study which showed no significant deviation from random mating in a natural population ofT. repens, the most likely explanation for the observed association in phenotypic state is selection favouring the cyanogenic phenotype.
Estimation and interpretation of genetic distance in empirical studies
Authors: Mueller Laurence D. , Ayala Francisco J.
Published: September 2009

Linear functions of Nei's genetic-distance statistic are calculated frequently in the literature of population genetics. Variance estimates for these linear functions are either not presented or incorrectly calculated. Part of the problem stems from the common assumption that distance statistics are independent random variables. This assumption is not generally correct. We describe methods for estimating the variance of linear combinations of genetic-distance statistics. We also suggest a method for constructing confidence intervals on genetic-distance statistics when these values are small (< 0·10) and their distribution deviates substantially from normal.
Primary non-random X-inactivation caused by controlling elements in the mouse demonstrated at the cellular level
Authors: Rastan Sohaila
Published: September 2009

Previous studies have shown that different alleles of the mouseXchromosomal controlling element locus,Xce, cause non-randomX-chromosome inactivation as judged by variegation in the coats of female mice heterozygous for X-linked coat colour/structure genes, or Cattanach's translocation (Is (X; 7) Ct), or the relative activity of biochemical variants of theX-linked enzyme PGK. This paper presents evidence using the Kanda differential staining method on 6½ d.p.c. and 13½ d.p.c. female mouse embryos heterozygous for the markerXchromosome Is (X; 7) Ct and carrying differentXcealleles, that theXcelocus affects the randomness ofXchromosome inactivation. Furthermore the fact that a markedXceeffect is demonstrable in female embryos as early as 6½ d.p.c. (i.e. very soon after the initial time ofX-inactivation) is strong evidence that theXcelocus exerts its effect by causing primary non-randomX-inactivation rather than by cell selection after initial randomX-inactivation.
Mutations relieving hypersensitivity to paromomycin caused by ribosomal suppressors inPodospora anserina
Authors: Coppin-Raynal Evelyne , Le Coze Denise
Published: September 2009

In the fungusPodospora anserina, mutations were selected which relieved the hypersensitivity to paromomycin caused by four suppressors assumed to be ribosomal ambiguity mutations (su1–31,su1–49,su1–60,su2–5). Our first purpose was to isolate new antisuppressor mutations and in fact a new antisuppressor gene,AS7was uncovered. TheAS7–1mutant displays a pleiotropic phenotype and particularly a sporulation defect. On the other hand, a newsu1mutant was obtained which acts as a suppressor and also as an antisuppressor: it can specifically reduce the suppressor effect of certainsu2mutations. This property of somesu1andsu2mutations was already known. Apart from these mutations probably involved in the control of translational fidelity, six mutations conferring cross-resistance to paromomycin and neomycin were isolated. While four of them are localized in thePm1andPm2loci previously identified, the two others define a new gene which controls paromomycin and neomycin resistance,Pm3. Strains carrying thePm3–1allele are sensitive to temperature at the level of growth and sporulation. The three last mutations which were obtained confer no mutant phenotype when separated from thesu1background. They are closely linked to thesu2locus.
Conventional and unconventional analysis of an inversion inNeurospora
Authors: Turner Barbara C. , Perkins David D.
Published: September 2009

In(IL; IR)O Y348is a pericentric inversion of linkage group I inN. crassa, with a breakpoint betweenfrandun-5in the left arm and a breakpoint betweenad-9andnit-1in the right arm. Approximate breakpoint location was found by tabulating crossovers between the rearrangement and markers in normal chromosome sequence. Inversion structure was verified by markedIn O Y348×In O Y348crosses. Precise mapping of breakpoints was by duplication coverage. Inversions likeO Y348do not produce progeny with segmental chromosome duplications when crossed to normal sequence, but duplications were produced by crossing it toIn(IL; IR)O Y323(Barry & Leslie, 1982), another standard pericentric inversion, and toT(I → VI)NM103(Turner, 1977), a translocation to a tip. Each of these rearrangements has a breakpoint within the inverted region ofIn O Y348. Two duplications fromIn O Y348×In O Y323were converted to normal chromosome sequence by double mitotic recombination. Besides expediting mapping, the technique of intercrossing rearrangements increasingly enables us to make segmental duplications exactly tailored for studying specific included genes.
Temperature-sensitive paralytic mutations on the second and third chromosomes ofDrosophila melanogaster
Authors: Kulkarni Shankar J. , Padhye Asha
Published: September 2009

Seven temperature-sensitive paralytic mutants were recovered from 4544 lines of ethylmethanesulphonate (EMS) treated autosomes inDrosophila melanogaster. These mutants have been designated temperature-induced paralytic (tip). Thetipmutations belong to six different genes; four of these,tip-A, Tip-B, tip-Candtip-Dare on the second chromosome whiletip-Eandtip-Fare on the third chromosome. This paper describes the paralysing behaviour and genetic localization of thetipmutants.
Competitive mating inDrosophila melanogaster
Authors: Sharp Paul M.
Published: September 2009

Selective differences among maleDrosophila melanogasterdue to differences in ability to compete for mates may often have been under-estimated in the past because, under the test procedure used, females did not represent a limited resource. In the experiment reported here, no difference was detected between inbred and outbred males ‘competing’ to mate with an equal number of females. When the receptive female: male ratio was halved a large reduction in male mating ability due to inbreeding became apparent.
Location on chromosome 6 of the locus for a major liver protein (Lvp-1) of the house mouse
Authors: Wilcox Frank H. , Roderick Thomas H.
Published: September 2009

The linkage of the locus of the major liver protein,Lvp-1, has been established on chromosome 6. Testcross data show the following gene order and recombination percentages:

centromere −Hd−7·4 ±2·4%−Lvp-1−13·2±3·1% −mi

Data from 39 recombinant inbred strains show complete concordance of theLvp-1locus and theLyt-2locus on chromosome 6.