bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence that mitochondrial isozymes are genetically less variable than cytoplasmic isozymes
Authors: Ward Robert D. , Skibinski David O. F.
Published: September 2009

It has been proposed that isoenzymes functioning within cell organelles (chloroplasts, mitochondria) are genetically less variable than their cytoplasmic counterparts, as a result either of constraints imposed by the need to cross organelle membranes or from the different and specialized nature of organelle metabolism. However, some recent findings concerning chloroplast and cytoplasmic isozyme variability are not consistent with this thesis. We have analyzed a number of surveys of electrophoretically detectable enzyme variation in vertebrates, and show that for each of the four tested enzymes (malate dehydrogenase, isocitrate dehydrogenase, malic enzyme, and aspartate aminotransferase), the mitochondrial isozymes are less variable than their corresponding cytosplasmic forms. The mean heterozygosities across the four enzymes are 0·083 and 0·038 for the cytoplasmic and mitochondrial forms respectively. We conclude that mitochondrial isozymes are indeed subject to greater constraints than cytoplasmic forms and have fewer sites able to accept neutral or slightly deleterious mutations. It is also noted that of the enzymes analyzed, that with the smallest subunit molecular weight (MDH) has the least variable cytoplasmic and mitochondrial isozymes, whereas the enzyme with the largest subunits (ME) has the most variable isozymes.
The effect of replicated selection for body weight in mice on vertebral shape
Authors: Johnson D. R. , O'Higgins P. , McAndrew T. J.
Published: September 2009

The shapes of T1 and T2 vertebrae from unselected Q strain mice and from strains selected for large and small body size were studied by Fourier analysis in order to ascertain whether shape change was produced by size selection. The vertebrae of large, small and control strains were easily distinguishable, but between replicate groups shape differences were less marked. The main component of shape change was size related, but mice unselected for size also showed a non-size-related shape change.
Differential inhibition of the initiation of DNA replication in stringent and relaxed strains ofEscherichia coli
Authors: Guzman Elena C. , Carrillo Francisco J. , Jimenez-Sanchez Alfonso
Published: September 2009

Starvation for isoleucine inhibits chromosome, minichromosome and pBR322 DNA replication in a stringent strain ofE. coli, but does not do so in a relaxed mutant. Starvation for other amino acids inhibits either chromosome and minichromosome replication in both strains. From these results we conclude thatoriCand pBR322 replication are stringently regulated and that isoleucine seems not to be essential for the protein synthesis required at the initiation oforiCreplication. Deprivation of isoleucine in a Rel−strain gives rise to amplification of minichromosome and pBR322 with a better yield of the latter plasmid than that following treatment with chloramphenicol.
Genome evolution in mosquitoes: intraspecific and interspecific variation in repetitive DNA amounts and organization
Authors: Black William C. , Rai Karamjit S.
Published: September 2009

DNA reassociation kinetics were used to determine the amounts and organization of repetitive and unique DNA in four mosquito species:Anopheles quadrimaculatus(Say),Culex pipiens(L.),Aedes albopictus(Skuse) andAe. triseriatus(Say). Intraspecific variation in repetitive DNA amounts was examined in two geographic strains ofAe. albopictusfom Calcutta, India and the island of Mauritius. Repetitive and unique sequences inAn. quadrimaculatuswere distributed in a pattern of long period interspersion. Repetitive DNA in all other mosquito species exhibited a pattern of short period interspersion. The amounts of fold-back, middle repetitive, and highly repetitive sequences increased with genome size. The amount of foldback DNA increased at a much slower rate than the middle and highly repetitive sequences. Intraspecific variation in genome size inAe. albopictuswas due primarily to the amounts of highly repetitive DNA. S1 nuclease digestion of repetitive DNA in all species revealed a positive correlation between genome size and the proportion of the repetitive DNA consisting of short repeats. The amounts of long and short repeats increased with genome size but short repeats increased at a higher rate. The repetitive DNA of the Mauritius strain contained approximately 15% more short repeats than the Calcutta strain. These findings suggest that genome evolution in mosquitoes has resulted from changes in both the amounts and organization of repetitive elements.
The detection of mosaics and polyploids in a hereditary mosaic strain of the silk moth, Bombyx mori, using egg colour mutants
Authors: Ebinuma Hiroyasu , Kobayashi Masahiko , Kobayashi Jun , Shimada Toru , Yoshitake Narumi
Published: September 2009

To analyze abnormal fertilization in a hereditary mosaic strain (mo/mo) of Bombyx mori, the percentages of diploidy mosaic, polyploidy mosaic and polyploid eggs in a batch were estimated by using egg colour mutants (pe re). Among 48 890 eggs from crosses of pe + / + re, mo/mo females with pe re/pe re males, 9409 abnormal eggs were obtained; 4472 of them were diploidy mosaics (red-white eggs), 4038 were polyploids (black eggs) and 899 were polyploidy mosaics (566 black-white, 256 black-red and 77 black-white-red eggs). The total number of diploidy mosaic eggs was approximately equal to that of polyploid eggs. A significant correlation was detected between the diploidy mosaic and polyploid egg ratios within a batch. This suggests that diploidy mosaics are produced by double fertilization in which two genetically non-identical egg nuclei are fertilized in turn by a sperm, and polyploids are formed by the fertilization of a diploid, non-disjunctive egg nucleus gamete by a single sperm. Our results also indicated the presence of common factors modifying both mosaic and polyploid frequency. The concordance of the observed ratio of polyploidy mosaic eggs (1·84%) with the expected value (diploidy mosaic ratio × polyploidy ratio × 2 = 1·83%) suggests that the formation of mosaics occurs independently of the formation of polyploids in this abnormal fertilization process. We point out that it is necessary to modify Goldschmidt & Katsuki's general model to explain abnormal fertilization, and we propose several possible models.
P-element-induced mutation and quantitative variation inDrosophila melanogaster: lack of enhanced response to selection in lines derived from dysgenic crosses.
Authors: Torkamanzehi A. , Moran C. , Nicholas F. W.
Published: September 2009

Dysgenic and non-dysgenic base populations were made by reciprocal crossing of Harwich (P) and Canton-S (M) strains. From each cross, two up and two down selection lines were established, with selection on abdominal bristle number for ten generations. The intensity of selection was 10 out of 50 individuals from each sex. Mean bristle number, phenotypic variation and heritabilities were compared between dysgenic and non-dysgenic populations under selection. Except for an anomalous non-dysgenic downline in which a mutation of large effect occurred, all lines showed similar responses to selection. These results contrast with the results reported by Mackay (1984, 1985) in which substantial increases were obtained for response to selection, phenotypic variation and heritability in the dysgenic compared to non-dysgenic lines. There are some indications that the higher response in our aberrant non-dysgenic downline is the result of transposition. Possible explanations for the occurrence of transposition and dysgenesis in the lines derived from nondysgenic crosses are discussed.
Heterogeneity in the Sxr (sex-reversal) locus of the mouse as revealed by synthetic probes
Authors: Epplen Jörg T. , Studer Roland , McLaren Anne
Published: September 2009

The sex-reversal mutation, Sxr and a variant form, Sxr′ have been established on the inbred C57BL/6Mcl background by repeated backcrossing to form the CB and CB′ strains, respectively. DNAs of normal XY, XX Sxr and XX Sxr′ as well as XY Sxr and XY Sxr′ carrier male mice have been digested with the restriction enzymes Hae III and Hinf I and electrophoresed. The DNAs show many common but also differing hybridization bands with synthetic oligonucleotide probes. In XY Sxr (and XY Sxr′) carrier males, the hybridization patterns of normal XY and those of XX Sxr (and XX Sxr′) males are simply superimposed. Individual differing bands can be categorized by their differential hybridization behaviour to the (GATA)4, (GACA)4, (GATA)2 GACA (GATA)2 and (GATA)3 (GACA)2 probes. In general, the hybridization patterns are regularly inherited. In addition to the predominant pattern in each strain, one additional XX Sxr and one additional XX Sxr′ hybridization pattern was observed: the additional pattern in the CB strain was transmitted (via variant XY Sxr carriers) while the secondary XX Sxr′ pattern in the CB′ strain could only be observed once. Thus ‘DNA finger printing’ with oligonucleotide probes can successfully be used to discriminate the DNAs of normal Y chromosomes, XX Sxr and XX Sxr′ variants as well as XY Sxr and XY Sxr′ carrier mice. Implications of the comparatively high unequal recombination rate involving the murine Y chromosome are discussed, as well as possible mechanisms.
Xcegenotype has no impact on the effect of imprinting onX-chromosome expression in the mouse yolk sac endoderm
Authors: Bücher Theodor , Linke Ingrid M. , Dünnwald Manfred , West John D. , Cattanach Bruce M.
Published: September 2009

The effect of theXce(x-chromosome controlling element) genotype on the randomness ofX-chromosome inactivation in the mouse was studied by monitoring the expression of theX-linked locuspgk-1. The main aim was to test whether theXcegenotype modified the preferential expression of the maternally derivedX-chromosome in the yolk sac endoderm. Quantitative electrophoresis of phosphoglycerate kinase (PGK-1) was used to studyPgk-1expression in the foetus, yolk sac mesoderm and yolk sac endoderm at 13½ dayspost coitum. TheXcea/Xcecgenotype caused non-randomX-chromosome expression in the foetus and yolk sac mesoderm. However, there was no evidence that theXcegenotype moderates the preferential expression of the maternally derivedX-chromosome in the yolk sac endoderm, as reported by Rastan & Cattanach (1983).
Screening of guinea pig strains for electrophoretic isoenzyme polymorphisms
Authors: Csaikl F.
Published: September 2009

Seven strains of guinea pig (Cavia porcellus) with different degrees of inbreeding were investigated for genetic variability by starch gel electrophoresis. Variants for six out of 31 loci (Gpd-1, Aat-1, Ak-2, Pgm-1, Ada and Gpi) are reported. The data suggest that the strains all come from a small founding population and therefore are genetically more homogenous than the visible characteristics imply. Differences between isoenzyme data and other genetic characters are described and possible underlying genetic mechanisms are discussed.
Is offspring—midparent regression affected by assortative mating of parents?
Authors: Gimelfarb A.
Published: September 2009

An analysis based on a model that is different from the traditional Fisher's model for quantitative characters under assortative mating reveals that the genotypic offspring–midparent regression can be affected by assortative mating of parents. It is demonstrated that the prediction that mating parents assortatively introduces only a negligible bias in the estimated coefficient of linear offspring-midparent regression is limited to Fisher's model and cannot be generalized.
Biased conversion as the primary function of recombination
Authors: Bengtsson B. O.
Published: September 2009

Recombination is hard to understand in darwinian terms when the process is identified with the production of crossover chromosomes. As an alternative explanation I propose instead that biased conversion is the primary function of meiotic recombination. In particular I show that a conversion process directed against the most common type of genetic damage can substantially reduce the mutational load, even if the conversion force is weak and if the conversion process occasionally creates new mutations.
Biochemical variation in purebred and crossbred strains of domestic rabbits (Oryctolagus cuniculusL.)
Authors: Hartl G. B. , Höger H.
Published: September 2009

Genetic variation in 40 domestic rabbits (Oryctolagus cuniculus) from eight different strains was investigated by horizontal starch gel electrophoresis. Twenty nine enzyme systems were examined in different tissues, 10 isoenzymes were found to be polymorphic. Indices of genetic variation show values comparable to those found in most other mammalian species. Thus the unusually high values reported previously by other authors may be due to a limited and not randomly chosen set of enzymes studied.
DK/Lm: A Strain of Laboratory Mouse with an Unusual Expression of the Lethal Yellow (Ay) Phenotype
Authors: Lamoreux M. Lynn , Galbraith Donald B.
Published: September 2009

DK/Lm is a new inbred mouse strain with over 20 generations of brother–sister mating. The genotype of the DK/Lm mouse at the black-brown locus isb/band heterozygosity at the agouti locus (Ay/a) is maintained. DK/Lm-Ay/amice become sable in phenotype at the first moult, whereas C57BL/6J-Ay/amice do not. The sable phenotype is defined as that of a mouse whose basic colour is yellow (phaeomelanic) but whose dorsal aspect is more or less darkened by the presence of nonyellow (eumelanic) pigment. At about 6 months of age the DK/Lm mouse gradually reverts to yellow in phenotype.

Mice of the two strains are compared. Observations are discussed and related to hypotheses regarding gene action at theaandeloci. The new strain is a useful experimental model for study of the relationship between gene action at the agouti locus and the important pleiotropic effects influenced by this locus.
A different level ofX-chromosomal transcription in an In(1)BM2(reinverted) strain and in its hyperploid derivatives resolves anX-coded regulatory activity for dosage compensation inDrosophila
Authors: Mukherjee A. S. , Ghosh Mita
Published: September 2009

The transcriptional competence of theX-chromosome of a mutant strain ofDrosophila melanogaster, [in(1)BM2(reinverted)], and of hyperploid derivatives with different additional segments of theX-chromosome has been examined. The singleXin the mutant male shows twice as much puffiness and RNA synthesis as does that in the normal male, revealing a level ofX-coded activity in addition to the normal male and female levels. Feulgen cytophotometry reveals no duplication of DNA content in the mutantX. When duplication for the segments 1A-3E, 9A-20F, 11A-20F and 16A-20F of theX-chromosome are combined in the male with the mutant chromosome, the super-hyperactivity of the mutantXis completely abolished. In combination with theBs.Yduplication, which contains 16A7-B2, the two-fold activity is also completely suppressed.

The mutant chromosome can appear in three discrete manifestations, namely, highly flabby, intermittently flabby and normal, suggesting a leaky nature of the mutant. The effect is also temperature-sensitive. Our results suggest that there may be a modulator gene complex (M+) in the 16A7-B2 region as well as regulators elsewhere on theX, which in combination influence the hyperactivity of the maleXinDrosophila. We suggest that the In(1)BM2(reinverted) chromosome carries a hypomorphic mutation of M+(Mm). The results presented here and earlier data on variousX-chromosomal and autosomal hyperploids are discussed in the light of a model for dosage compensation inDrosophila.
Transposable element-induced fitness mutations inDrosophila melanogaster
Authors: Mackay Trudy F. C.
Published: September 2009

P element mutagenesis was used to contaminate M strain second chromosomes with P elements. The contaminated lines were compared to uncontaminated control lines for homozygous and heterozygous fitness and its components. Mean homozygous fitness, viability and fertility of chromosome lines contaminated with P elements is decreased relative to the uncontaminated control lines by, respectively, 55, 28 and 40%. Variance among contaminated homozygous lines of total fitness increases by a factor of 1·5, variance of viability by a factor of 5·9, and variance of fertility by a factor of 1·9, compared to variance of these traits among the population of uncontaminated homozygous chromosomes. Estimates of P-element-induced mutational variance among second chromosome lines for homozygous fitness, viability and fertility are, respectively, 2 × 10−2, 5 × 10−2and 2 × 10−2. This magnitude of mutational effect is equivalent, in terms of incidence of induced recessive lethal chromosomes and D:L ratio, to a dose of approximately 1·0–2·5 × 10−3m EMS. The distributions of fitness traits among M-derived second chromosome homozygous lines contaminated with P elements are remarkably similar in many regards to distributions of fitness and viability of chromosomal homozygotes derived from naturalDrosophilapopulations. It is possible that a proportion of the fitness variation previously observed (reviewed by Simmons & Crow, 1977) following homozygosis of wild chromosomes was not present in the natural populations, but was generated by P-element transposition during the chromosome extraction procedure. P-element-induced fitness mutations appear to be completely recessive. Implications for models of evolution of transposable elements are discussed.
High levels of fitness modifiers induced by hybrid dysgenesis inDrosophila melanogaster
Authors: Fitzpatrick Benjamin J. , Sved John A.
Published: September 2009

Wild-type chromosomes ofD. melanogastermutagenized by passage through a single generation of hybrid dysgenesis have been compared against identical chromosomes passed through a reciprocal, non-dysgenic cross. Fitness of the chromosome in homozygous condition has been examined in population cages using the technique of balancer chromosome equilibration. The results indicate that amongst chromosomes with no lethal or visible mutation, more than 50% have suffered a measurable decline in fitness. The magnitude of this decline is estimated to be in the range 10–20%.
Heterosis among lines of mice selected for body weight: 3. Thermoregulation
Authors: Lynch Carol Becker , Roberts R. C. , Hill W. G.
Published: September 2009

Crosses were made among 18 lines of mice, six previously selected for large 6-week weight, six for small 6-week weight, and six unselected controls, comprising a complete diallel cross among sizes and a partial diallel cross among replicate lines within sizes, and all purebred matings. Across all groups large size was associated with lower weight-specific food consumption and brown adipose tissue, and increased nest-building. Overall the crosses had lower weight-specific food consumption, and increased nest-building, body temperature, and brown adipose tissue than the purebreds. In general, heterosis in crosses between lines of different size, especially those involving large lines, tended to exceed that in crosses between lines of the same size.
Growth, efficiency and body composition of mice selected for post-weaning weight gain onad libitumor restricted feeding
Authors: Hetzel D. J. S. , Nicholas F. W.
Published: September 2009

After seven generations of selection, a line of mice selected for post-weaning (21–42 days) weight gain on full feeding (SF) showed significant increases of 49% in weight gain, 31% in efficiency and 14% in food intake, when compared with its control on full feeding between 21 and 42 days. After day 42, SF mice continued to eat more food and were 28% heavier than control mice at 91 days. Because SF mice were heavier than control mice at almost all ages, they were fatter on an age basis. There was, however, no change in the rate of deposition of fat, protein and ash relative to body weight. On restricted feeding between 21 and 42 days, SF mice showed a non-significant increase in weight gain, and hence in efficiency, of 12%. They deposited more fat than control mice during the feeding period but there was no significant difference when comparisons were made on a weight basis.

A contemporary line of mice selected for post-weaning (21–42 days) weight gain on restricted feeding (SR) had significant increases of 12% in weight gain, 17% in efficiency but no significant change in food intake, when compared with its control on full feeding between 21 and 42 days. SR mice were the same weight as control mice at all ages except day 21, when they were significantly lighter due to direct genetic effects rather than maternal effects. SR mice had a lower (P<0·10) rate of fat deposition per unit body weight and became less fat relative to their control as body weight increased. The rate of deposition of other components was not altered by selection. On restricted feeding, SR had a significant increase in weight gain, and hence in efficiency, of 37%. Changes in body composition were similar to those on full feeding.

It was concluded that the use of a restricted feeding regime had enabled the exploitation of heritable variation in the partitioning of energy for growth. This variation was independent of genetic variation for appetite and body weight.

Overall performance at each level of feeding was best improved by selection on that feeding level. The realized genetic correlation between post-weaning weight gain on full and restricted feeding was estimated to be 0·28 ± 0·08, indicating a very different genetic basis for the same character in the two feeding environments.
Actual number of alleles contained in a multigene family
Authors: Ohta Tomoko
Published: September 2009

By using a simple model of gene conversion, the actual number of alleles contained in a multigene family was theoretically studied. It was shown that the Ewens' sampling theory is applicable to predict the actual number in a gene family of a genome. However, the actual number of the gene family forming the total population becomes larger or smaller than the predicted value by the sampling theory, depending upon the relative magnitude of the rates of two homogenization processes, i.e. intra-genome and in the population.
Models of long-term artificial selection in finite population with recurrent mutation
Authors: Hill William G. , Rasbash Jonathan
Published: September 2009

The effects of mutation on mean and variance of response to selection for quantitative traits are investigated. The mutants are assumed to be unlinked, to be additive, and to have their effects symmetrically distributed about zero, with absolute values of effects having a gamma distribution. It is shown that the ratio of expected cumulative response to generation t from mutants, , and expected response over one generation from one generation of mutants, , is a function of t/N, where t is generations and N is effective population size. Similarly, , is a function of t/N, where is the increment in genetic variance from one generation of mutants. The mean and standard deviation of response from mutations relative to that from initial variation in the population, in the first generation, are functions of . Evaluation of these formulae for a range of parameters quantifies the important role that population size can play in response to long-term selection.
Selection for oviposition preference inDrosophila melanogaster
Authors: Bird Stephen R. , Semeonoff Robert
Published: September 2009

Populations ofDrosophila melanogasterwere subjected to selection for differing oviposition preference under allopatric and sympatric conditions. Flies were presented with the choice of a potato-based medium and a medium containing sugar and killed yeast on which to lay their eggs. Some gene flow was possible under sympatric conditions. In the allopatric lines selection was successful in rapidly generating an increased preference for sugar, and in the sympatric lines divergent oviposition preferences were generated in two cases out of four. A significant degree of reproductive isolation between one pair of allopatric lines was generated after eighteen months of selection.
A theoretical analysis of linkage disequilibrium produced by genetic drift inDrosophilapopulations
Authors: Montchamp-Moreau Catherine , Katz Mariano
Published: September 2009

We analyse the progression of linkage disequilibrium produced by random genetic drift in populations subject to cyclical fluctuations in size. Our model is applied to natural populations ofDrosophilawhich show an annual demographic cycle of bottleneck (finite size) and demographic burst (size supposed to be infinite). In these populations, linkage disequilibrium stabilizes in such a way that, at equilibrium, the expected square of the correlation of gene frequenciesE(r2) shows a stable cycle from year to year. If two loci are tightly linked,E(r2) barely varies during the annual cycle. Its values remain close to the value expected in a population of the same but constant effective size. If two loci are loosely linked, fluctuations inE(r2) are large. The maximum value, reached at the end of the bottleneck, is 10 to 100 times greater than the value obtained at the end of the burst. Our results show that the interpretation of observed linkage disequilibrium, by means of statistical tests, requires an accurate knowledge of population demography.
A chromosomal segment conserved since divergence of lineages leading to man and mouse: The gene order of aminoacylase-1, transferrin, and beta-galactosidase on mouse Chromosome 9
Authors: Nadeau Joseph H.
Published: September 2009

Linkage crosses were used to determine the gene order of aminoacylase-1, beta-galactosidase, and transferrin on mouse Chromosome 9. The most likely gene order, which was more than 107times more likely than the next most likely order, was transferrin, aminoacylase-1, beta-galactosidase. These results demonstrate that aminoacylase-1 and beta-galactosidase mark a chromosomal segment that has been conserved since divergence of lineages leading to man and mouse. The length of this segment is about 11 cM and the estimate of the true length of the conserved segment marked by these two genes is 33 cM. A second aminoacylase allozyme, which requires MgCl2, is described.
Acyadeletion mutant ofEscherichia colidevelops thermotolerance but does not exhibit a heat-shock response
Authors: Delaney John M.
Published: September 2009

An adenyl cyclase deletion mutant (cya) ofE. colifailed to exhibit a heat-shock response even after 30 min at 42 °C. Under these conditions, heat-shock protein synthesis was induced by 10 min in the wild-type strain. These results suggest that synthesis of heat-shock proteins inE. colirequires thecyagene. This hypothesis is supported by the finding that a presumptive cyclic AMP receptor protein (CRP) binding site exists within the promotor region of theE. coli htp Rgene. In spite of the absence of heat-shock protein synthesis, when treated at 50 °C, thecyamutant is relatively more heat resistant than wild type. Furthermore, when heat shocked at 42 °C prior to exposure at 50 °C, thecyamutant developed thermotolerance. These results suggest that heat-shock protein synthesis is not essential for development of thermotolerance inE. coli.
The extended survival of tw5/tw5 mouse embryo cells in vitro
Authors: Garside William , Hillman Nina
Published: September 2009

The tw5 haplotype is a recessive mutation which is lethal when homozygous in mouse embryos following implantation. This series of studies was undertaken to determine the effect of the tw5/tw5 genotype on embryos developing in vitro. Blastocyst embryos from + / tw5inter se matings were compared with control blastocysts obtained from matings between T/ + and + / + females and + / tw5 males for their abilities to continue development in vitro in two culture media. The data show that there are no significant differences between the percentages of experimental and control blastocyst embryos which attach and outgrow or which contain inner cell masses on any day of culture up to equivalent gestation day 21 in either media. These findings show that the life span of cells from tw5 / tw5 embryos can be extended significantly by in vitro culture.
Meiotic drive in female mice heterozygous for the HSR inserts on chromosome 1
Authors: Agulnik Sergei I. , Agulnik Alexander I. , Ruvinsky Anatoly O.
Published: September 2009

Chromosome 1 with one or two long insertions has been previously found in natural mouse populations. The inheritance of chromosome 1 with two insertions from the Yakutsk population is analysed in this paper. It was demonstrated that heterozygous females transmit this chromosome to 80–85% of offspring. The observations made at M II, in conjunction with the recombination data, allowed us to conclude that preferential passage of the chromosome 1 with insertions to the oocyte and egg, rather than to the first and second polar bodies at meiosis, is the causative factor of the distorted segregation. A meiotic drive of such potency has not been previously reported for female mammals. The possible mechanism of the drive is discussed.
The distribution of allelic effects under mutation and selection
Authors: Frank Steven A. , Slatkin Montgomery
Published: September 2009

The Price (1970, 1972) equation is applied to the problem of describing the changes in the moments of allelic effects caused by selection, mutation and recombination at loci governing a quantitative genetic character. For comparable assumptions the resulting equations are the same as those obtained by different means by Barton & Turelli (1987; Turelli & Barton, 1989). The Price equation provides a natural framework within which to examine certain kinds of non-additive allelic effects, recombination and assortative mating. The use of the Price equation is illustrated by finding the equilibrium genetic variance under multiplicative dominance and epistasis and under assortative mating at an additive locus. The limitations of the use of recursion equations for the moments of allelic effects are also discussed.
Interactions among modifiers of retrotransposon-induced alleles of thewhitelocus ofDrosophila melanogaster
Authors: Rabinow Leonard , Birchler James
Published: September 2009

Mutations in five loci that modify the phenotype ofwhiteapricot(wa), caused by the retrotransposon,copia, were examined in two-way combinations to determine whether their effects were additive or epistatic. All two-way combinations of mutations in these five loci,mottler of white(mw),suppressor of forked(su(f)),suppressor of white apricot(su(wa)),Enhancer of whiteapricot, (E(wa)) andDarkener of apricot(Doa), are additive in their effects onwa, implying that each second-site modifier locus affects a different process. Three othercopia-induced mutations,HwUa, whd81b25andctnswere also examined for responsiveness to mutations in these modifier loci. None clearly responded. Mutations associated withB104insertions, includingGl, vgni, ctnandwricwere also examined for responsiveness tomwmutations, which have specificity for this element as well. Bothvgniandwricrespond to mutations inmw. The former interaction demonstrates thatmwis capable of interacting withB104 elements in loci other thanwhite. The significance of the results with respect to the nature of second-site modifier loci is discussed.
Induced recombination in the mitotic cell cycle of the yeastSaccharomyces cerevisiae
Authors: Johnston Leland H. , Johnson Anthony L.
Published: September 2009

The occurrence of induced recombination in the mitotic cell cycle in yeast has been analysed using conditional cell-cycle mutants held at the restrictive temperature. The strains used were heteroallelic atgalland assaying for functional galactokinase shortly after irradiation (Johnston, 1982) allowed an unambiguous determination of the cell cycle stages in which recombination could occur. Recombination was observed in most strains, including those with thecdc36mutation, defective in ‘start’; thecdc4, 7anddbf4mutations which arrest cells in G1; thedbf1, 2andcdc6mutations affecting S phase;cdc16andcdc17which block cells in G2 and alsocdc14and15which arrest cells in ‘late nuclear division’. Recombination can therefore occur within each of the major phases of the yeast cell cycle. This analysis has also revealed that thecdc8mutation results in a defect in induced mitotic recombination.
Genetic analysis of axonemal mutants inParamecium tetraureliadefective in their response to calcium
Authors: Hinrichsen Robert D. , Kung Ching
Published: September 2009

Six axonemal mutants ofParamecium tetraureliahave been isolated that are unable to respond properly to calcium. The mutants, designated atalantas, cannot swim backward when stimulated by ions or heat. Genetic analyses reveal that all six mutants are recessive and fall into four complementation groups. Three of the mutants in one complementation group are phenotypically non-leaky, one is leaky and two are extremely leaky, only displaying their phenotypes at elevated temperatures. The complete mutants,ataA, are also abnormal in their forward swimming. This abnormality co-segregates with the inability to swim backward.ataA1is not allelic to several membrane mutants ofP. tetraurelia.
Knobbly, a new dominant mutation in the mouse that affects embryonic ectoderm organization
Authors: Jacobs-Cohen R. J. , Spiegelman M. , Cookingham J. C. , Bennett D.
Published: September 2009

Knobbly,FuKb, a dominant mutation on chromosome 17 of the mouse, causes a kinked tail in heterozygotes and embryonic lethality at about nine days in homozygotes. Abnormal organization of the embryonic ectoderm is first apparent at about embryonic day 7, and the retarded and malformed embryos die by mid 9 days.

Kink,FuKi, a dominant gene that maps in the same region, is also an embryonic lethal in homozygotes; heterozygotes have kinked tails and often a circling gait. We have shownFuKbandFuKiare allelic; theFuKb/FuKicompound dies at the same time asFuKb/FuKbembryos with the same morphological syndrome.

TheFuKbphenotype is not seen in offspring in expected ratios. TheFuKbmales may have a low transmission ratio or penetrance may be incomplete.

An incidental finding of our histological studies is a high incidence of complete twinning whenFuKbheterozygotes mateinter seor whenFuKb×FuKimatings are made.
Effects of selection on growth, body composition and food intake in mice I. Responses in selected traits
Authors: Sharp Gillian L. , Hill William G. , Robertson Alan
Published: September 2009

Mice were selected for one of three criteria: appetite (A), measured as 4- to 6-week food intake, adjusted by phenotypic regression to minimize change in 4-week body weight, fat percentage (F), using the ratio of gonadal fat pad weight to body weight in 10-week-old males, and total lean mass (protein, P), using the index, body weight in 10-week-old males − (8 × gonadal fat pad weight). For each selection criterion, there were 3 high, 3 low and 3 unselected control lines. At generation 11, the high and low A lines diverged by 17% of the control mean and the realized heritability from within family selection of adjusted food intake was 15%. Selection for this character produced changes in body weight, gross efficiency from 4 to 6 weeks, and percentage of fat, the high lines being heavier, more efficient and less fat than the lows. The high and low F lines diverged by 80% of the control mean and the realized heritability of the ratio of gonadal fat pad weight to body weight was 44%. Selection for this character produced changes in total fat per cent, but little change in percentage protein, body weight, food intake or gross efficiency. The high and low P lines diverged by 40% of the control mean and realized heritability of the lean mass index (10-week weight − [8 × gonadal fat pad weight]) was 51%. Selection for an increase in the index increased body weight at all ages, food intake and 4- to 6-week gross efficiency. There was no change in percentage fat. Responses in the selected traits were not highly correlated, and the different lines provide an opportunity for investigating responses in physiology, metabolism and gene products.
Sex determination in birds: progeny of nondisjunction canaries of Durham (1926)
Authors: Sittmann K.
Published: September 2009

The heterogametic sex in birds (ZW) is female for presence of theWor for lack of a secondZchromosome. These alternatives can be distinguished givenZOorZZWaneuploids and segregation of aZ-linked marker in their progeny. Having discovered theZ-linkedcinnamonlocus with two alleles (B, black eyes;b, red eyes), Durham observed 21 black-eyed daughters (BOorBbW) ofbbcocks andBhens. Using Durham's data on sex–colour phenotypes of 14 young of two of the 21 matroclinous females show that the sex chromosome constitution of the two exceptional hens were more likelyZOthanZZW. This case plus that of Crew's (1983) trisomic rooster (ZZW) shows that sex determination in birds follows the ‘genic balance’ scheme as inDrosophila, not the ‘dominant Y’ scheme as in mammals.
Studies of esterase 6 inDrosophila melanogaster: XIV. Variation of esterase 6 levels controlled by unlinked genes in natural populations
Authors: Tepper Craig S. , Terry Anne L. , Holmes James E. , Richmond Rollin C.
Published: September 2009

The esterase 6 (Est-6) locus inDrosophila melanogasteris located on the third chromosome and is the structural gene for a carboxylesterase (E.C.3.1.1.1) and is polymorphic for two major electromorphs (slow and fast). Isogenic lines containingXchromosomes extracted from natural populations and substituted into a common genetic background were used to detect unlinked factors that affect the activity of theEst-6locus. Twofold activity differences of esterase 6 (EST 6) were found among males from these derived lines, which differ only in theirXchromosome. These unlinked activity modifiers identify possible regulatory elements. Immunoelectrophoresis was used to estimate quantitatively the levels of specific cross-reacting material in the derived lines. The results show that the variation in activity is due to differences in the amount of EST 6 present. The data are consistent with the hypothesis that there is at least one locus on the X chromosome that regulates the synthesis of EST 6 and that this regulatory locus may be polymorphic in natural populations.
Aspects of temperature regulation in mice selected for large and small size
Authors: Lynch Carol Becker , Roberts R. C.
Published: September 2009

We measured traits involved in physiological and behavioural thermoregulation in the 6 replicates of a selection experiment for large and small size (6-week weight) in mice, including control lines (18 lines in all). The observed genetic correlations between body size and thermoregulatory traits are consistent with a thermoregulatory advantage of large size, including decreased weight-specific food consumption and increased nest-building, with no change in body temperature. The differences in food consumption were closely paralleled by differences in amount of brown adipose tissue, strongly suggesting that much of the decreased efficiency of the small lines is due to heat production by brown fat. These results are consistent with available observations on natural populations, that selection for temperature adaptation probably has had some influence on body size in this species.
Genetic variation in the dietary sucrose modulation of enzyme activities inDrosophila melanogaster
Authors: Geer Billy W. , Laurie-Ahlberg Cathy C.
Published: September 2009

Genetic variation in the modulating effect of dietary sucrose was assessed inDrosophila melanogasterby examining 27 chromosome substitution lines coisogenic for theXand second chromosomes and possessing different third isogenic chromosomes derived from natural populations. An increase in the concentration of sucrose from 0·1% to 5% in modified Sang's medium C significantly altered the activities of 11 of 15 enzyme activities in third instar larvae, indicating that dietary sucrose modulates many, but not all, of the enzymes ofD. melanogaster. A high sucrose diet promoted high activities of enzymes associated with lipid and glycogen synthesis and low activities of enzymes of the glycolytic and Krebs cycle pathways, reflecting the physiological requirements of the animal. Analyses of variance revealed significant genetic variation in the degrees to which sucrose modulated several enzyme activities. Analysis of correlations revealed some relationships between enzymes in the genetic effects on the modulation process. These observations suggest that adaptive evolutionary change may depend in part on the selection of enzyme activity modifiers that are distributed throughout the genome.
Energy partitioning and growth in mice selected for high and low body weight
Authors: Stephenson S. K. , Malik R. C.
Published: September 2009

The partitioning of digestible energy intake on anad libitumdiet of standard mouse nuts was investigated in mice selected for high and low body weight at eight weeks and in an unselected control population. In selected mice aged from four to six weeks and housed at a temperature of 24·5 °C, almost all their energy intake could be attributed to basic maintenance and the deposition of extra protein and fat. Control mice, however, had an energy intake considerably in excess of their apparent maintenance and growth requirements. It was concluded that the unaccountable energy loss of the control line could be used to increase growth efficiency in the selected lines. The result is analogous to those obtained from studies on normal and obese mouse genotypes and indicates genetic changes in mechanisms controlling the conversion of food energy to heat.

Provision of a nest to reduce thermoregulatory heat production caused a minor reduction in energy intake and a corresponding decrease in the energy discrepancy. There was no effect on growth.
Characterization of an antibiotic resistance plasmid pAV5 and its constituent replicons inAcinetobacter calcoaceticus
Authors: Divers Mark , Hinchliffe Edward , Vivian Alan
Published: September 2009

A non-transmissible plasmid, pAV5, was isolated from a hospital strain ofAcinetobacter calcoaceticus, JC17. pAV5 confers resistance to the antibiotics tetracycline and neomycin in the genetically characterized strain of A.calcoaceticusEBF 65/65. Transfer of pAV5 can be mediated by the sex factors pAV1 and R751; transfer is occasionally associated with the segregation of the resistance determinants amongst the transconjugants. Phenotypic dissociation of pAV5 corresponds with the formation of two independent plasmids designated pAV51 and pAV52 mediating resistance to neomycin and tetracycline respectively.
Weight and age at puberty in female and male mice of strains selected for large and small body size
Authors: Falconer D. S.
Published: September 2009

Puberty was studied in mice of the ninth selected generation of the Q-strain. There were 6 replicate lines selected for large body size (6-week weight), 6 replicates selected for small size and 6 replicate unselected controls. Female puberty was assessed by the opening of the vagina and male puberty by the first copulation plug. The sexes differed in the mean age at puberty, males being older by 13 days in the large, 4 days in the control and 8 days in the small lines. The sexes differed also in the way size affected puberty. In males the large and small lines reached puberty at the same age and both were older than the controls. In females the large lines on average were heavier and younger at puberty than the controls, and the small lines were lighter and older than the controls, though not significantly older. The replicates within each size-group, however, reached puberty at about the same weight, irrespective of their differences in growth rate. Thus, the differences of growth between the large, control and small groups affected both the weight and the age of females at puberty, but the differences of growth between the replicate lines within each size affected only the age at puberty. No explanation was found for this inconsistency between size-groups and replicates. Several lines of evidence led to the conclusion that in females puberty is partly or mainly weight-dependent, whereas in males it is almost wholly age-dependent.
An extension of path analysis revisited
Authors: Gimelfarb Alexander
Published: September 2009

A method for analysing probabilistic models representing an extension of path analysis, and a model of mixed homogamy based on this method were introduced recently (Rao, Morton & Cloninger, 1979; Cloninger, 1980). However, constraints imposed by the method on linear models, or a rationale for and implications of the mixed homogamy model have not been clearly stated.

A mathematical treatment of the extension of path analysis and of the mixed homogamy model is presented in this paper. Constraints on linear models imposed by the extension are obtained. It is demonstrated that the mixed homogamy model, when applied to analysing nuclear families in a population, implies the following mating system in the population: some individuals choose their mates strictly on the basis of group membership, others choose their mates strictly on the basis of phenotype, and no individual chooses a mate on the basis of both group membership and phenotype.
A new allele of the Gpi-1t temporal gene that regulates the expression of glucose phosphate isomerase in mouse oocytes
Authors: West John D. , Fisher Graham
Published: September 2009

The dimeric enzyme glucose phosphate isomerase (GPI-1) is regulated in oocytes by a cis-acting temporal gene (Gpi-1t) that maps close to the structural gene (Gpi-1s). Quantitative cellulose acetate electrophoresis of GPI-1 allozymes from unfertilized eggs produced by various Gpi-1sa / Gpi-1sb heterozygous females revealed a new Gpi-1t allele that we have designated Gpi-1tc. This allele is present in 101/H mice and a partially congenie stock that carries the Gpi-lsa gene derived from the AKR strain. We have confirmed that Gpi-1tc is closely linked to Gpi-1s and that it is cis-acting. It produces higher levels of GPI-1 in unfertilized eggs than the other two Gpi-lt alleles that are known (Gpi-1ta and Gpi-1tb) but has no effect on GPI-1 in somatic tissues or spermatozoa. This new Gpi-1t allele represents a third developmental programme for GPI-1 expression in oocytes.
Characterization of dominant cataract mutations in mice: penetrance, fertility and homozygous viability of mutations recovered after 250 mg/kg ethylnitrosourea paternal treatment
Authors: Favor Jack
Published: September 2009

Seventeen dominant cataract mutations of the mouse recovered in ethylnitrosourea mutagenesis experiments have been genetically characterized as to penetrance, fertility, and homozygous viability. Nine mutations were shown to be fully penetrant with no fertility effects, four mutations were classified as having reduced penetrance with no fertility effects, one mutation had reduced penetrance and reduced fertility, two mutations were shown to have a reduced frequency of mutant offspring due to penetrance and viability effects, and one mutation most likely has a reduced viability of carrier individuals. Of the eleven mutations for which definitive homozygous viability data were obtained, ten were shown to be homozygous viable and only one was shown to be homozygous lethal. In similar experiments in which dominant cataract, dominant skeletal or dominant visible mutations were recovered after radiation treatment, comparable frequencies of mutations with reduced penetrance were observed but there was a strikingly higher frequency of homozygous lethal mutations. These observations support the hypothesis of a qualitative difference in the mutations recovered after ethylnitrosourea as compared to radiation treatment. Finally, it is argued that a systematic comparison of the induced mutation rates to dominant and recessive alleles with subsequent genetic characterization of the recovered mutations provides a critical set of data necessary for an improvement in the indirect and direct procedures of genetic risk estimation.