bluuebunny/crossref_metadata_2025 huggingface dataset:
HETEROGENEITY OF MAIZE CYTOPLASMIC GENOMES AMONG MALE-STERILE CYTOPLASMS
Authors: Pring D R , Levings C S
Published: April 2021

Maize mitochondrial and chloroplast DNA's were prepared from normal (fertile) lines or single crosses and from members of the T, C, and S groups of male-sterile cytoplasms. Restriction endonucleases HindIII, BamI, EcoRI, and SalI were used to restrict the DNA, and the resultant fragments were electrophoresed in agarose gels. The results show that the N (fertile), T, C, and S cytoplasms each contained distinct mitochondrial DNA (mtDNA). These distinctive patterns were unaffected by nuclear genotype. No evidence of paternal inheritance of mtDNA was observed. Chloroplast DNA (ctDNA) from the N, C, and T cytoplasms was indistinguishable by HindIII, SalI, or EcoRI endonuclease digestion. The S cytoplasm ctDNA, however, was slightly different from that of other cytoplasms, as indicated by a slight displacement of one band in HindIII digests. The molecular weight of maize ctDNA was estimated to be as high as 88 x 106. Estimates of the minimum molecular weight of maize mtDNA ranged from 116-131 x 106, but the patterns were to complex for an unambiguous determination. Based on HindIII data, a comparison of the molecular weight of mtDNA bands common to the N, T. C, and S cytoplasms suggests that C cytoplasm most closely resembles N cytoplasm. The T and S sources are more divergent from the C and N cytoplasms. These results indicate a possible gradation of relatedness among male-sterile cytoplasms. The marked variation in mtDNA, with apparently less variation in ctDNA, represents circumstantial, but compelling, evidence that mtDNA may be involved in the male sterility and disease susceptibility traits in maize.
DIFFERENTIAL ALLELIC EXPRESSION AT A LOCUS ENCODING AN ENDOSPERM PROTEIN IN TETRAPLOID WHEAT (TRITICUM TURGIDUM)
Authors: Salcedo G , Aragoncillo C , Rodriguez-Loperena M A , Carbonero P , Garcia-Olmedo F
Published: April 2021

Two hydrophobic endosperm proteins, designated CM3 and CM3′, have been purified from appropriate cultivars of tetraploid wheat (T. turgidum) and characterized. They are inherited as though encoded by alleles at a single locus, designated Cm3a and Cm3b, respectively. The net amount of protein molecules has been measured for each of the alleles at one, two and three doses. The amount of CM3′ is 50%-65% of that found for CM3. For both, there is a linear gene dosage response. These effects were observed not only in the parental material and the reciprocal F1 generations, but also in the segregating F2 generation, indicating that the quantitative difference depends on differences in the structural gene or is controlled by regulatory or modifier gene(s) linked to it.
STUDIES ON THE RIBOSOMAL RNA CISTRONS IN INTERSPECIFIC DROSOPHILA HYBRIDS. II. HETEROCHROMATIC REGIONS MEDIATING NUCLEOLAR DOMINANCE
Authors: Durica D S , Krider H M
Published: April 2021

Interspecific hybrids of D. melanogaster and D. simulans normally exhibit a secondary constriction only at the D. melanogaster nucleolus organizer (NO). This phenomenon, termed nucleolar dominance, occurs only when the NO-bearing sex chromosomes of both species are present in conjunction. Experiments were initiated to localize regions on the sex chromosomes of D. melanogaster involved in mediating this suppression. Sex chromosome heterochromatic rearrangements and deficiencies were introduced into F1 hybrids and their corresponding effect on simulans NO constriction formation was examined in hybrid mitotic neuroblast tissue. Sex chromosomes deficient for both the D. melanogaster NO and adjacent heterochromatin were unable to restrict the formation of a constriction at the D. simulans NO. The presence of a D. melanogaster NO, however, was not sufficient for the establishment of nucleolar dominance. Results from an array of NO-bearing X and Y chromosome rearrangements and deficiencies indicate that at least one heterochromatic region, proximal to the NO on the D. melanogaster X and distal to the NO on the D. melanogaster Y, affects the induction of this interchromosomal phenomenon.
A COMPARISON OF HEAT AND INTERCHROMOSOMAL EFFECTS ON RECOMBINATION AND INTERFERENCE IN DROSOPHILA MELANOGASTER
Authors: Grell R F
Published: April 2021

Heat and interchromosomal effects on recombination have been compared for 23 regions comprising the predominantly euchromatic portions of the five arms of the Drosophila genome. Patterns of response are strikingly similar, with both modifiers causing proximal and distal increases and minimal effects in the middle of the arms. Changes in interference for the same regions in the presence of the two modifiers reveal little similarity, except for the X chromosome. The question of independent control of interference and recombination, as well as alternatives for their temporal sequence, is discussed. Recombination response to the two modifiers in the centric heterochromatin of chromosoaime 2 is markedly different from that found in euchromatin. The interchromosomal effect is absent here, whereas heat induces an increase roughly an order of magnitude greater than that found in euchromatin and totally unlike the lack of response in the proximal heterochromatin of the X chromosome. It is proposed that the sequestering of DNA satellite I (thermal dissociation 9-20° lower than that of the other major satellites) in the centromeric heterochromatin of chromosome 2 (but not in X or 3) may account for the increase.
OSMOTIC AVOIDANCE DEFECTIVE MUTANTS OF THE NEMATODE CAENORHABDITIS ELEGANS
Authors: Culotti Joseph G , Russell Richard L
Published: April 2021

A wild-type strain of the nematode Caenorhabditis elegans has been shown to avoid high concentrations of a number of sugars and salts. Individual and population assays for this response were developed and mutants were selected for their inability to avoid high concentrations of fructose or NaCl. Seven nonavoiding mutants representing six complementation groups were isolated and characterized. Genetic studies indicate that the mutants each carry a single recessive mutation responsible for the defective osmotic avoidance behavior. The map locations of the six complementation groups identified by these mutations have been determined. Mutants isolated for their inability to avoid fructose are also unable to avoid NaCl and vice versa. The mutants move normally, exhibit normal touch sensitivity, and, like wild type, follow isotherms in a radial thermal gradient. All of the mutants are at least partially defective in the attraction to sodium chloride exhibited by wild type. None of the mutants is temperature sensitive, and all exhibit defective osmotic avoidance behavior as young L1 larvae. Preliminary anatomical studies indicate selective sensory neuron changes in at least one mutant.
PARAMETERS OF MALE AND FEMALE RECOMBINATION INFLUENCED BY THE T-007 SECOND CHROMOSOME IN DROSOPHILA MELANOGASTER
Authors: Slatko Barton E
Published: April 2021

The T-007 second chromosome line of Drosophila melanogaster, previously shown to contain genetic elements responsible for male recombination induction, appears to affect several parameters of recombination in females. In T-007 heterozygous females, the distribution of recombination (but not the total frequency) is changed from that observed in control females; relative increases are observed in the more proximal regions of the second, third and X chromosomes, while relative decreases are observed more distally. These changes are paralleled by altered coefficient of coincidence values and in an increased nondisjunction frequency of second chromosomes. The distribution of recombination in females is strikingly similar to that observed in males as measured along the second and third chromosomes, and the frequency of nondisjunction of the X and Y chromosomes is increased in T-007 heterozygous males. Based upon these results and responses to the effect of structurally rearranged heterologues (the "interchromosomal effect"), it is suggested that T-007 affects the preconditions for meiotic exchange in females. It is not yet known if elements responsible for these effects are the same elements responsible for the numerous other traits associated with the T-007 second chromosome.
THE EFFECTS OF B, K10, AND AR CHROMOSOMES ON THE RESISTANCE OF MAIZE TO VIRAL INFECTION
Authors: McGirr Scott C , Endrizzi J E
Published: April 2021

Studies were conducted to determine if accessory (B) chromosomes, the abnormal tenth (K10) chromosome or the aberrant ratio (AR) phenomenon of maize (Zea mays L.) affect the resistance of the plants to viral infection. Genetically similar stocks of maize with and without these elements were compared to determine what effect they would have on the plants response to Brome Mosaic Virus (BMV), Maize Dwarf Mosaic Virus (MDMV), Wheat Streak Mosaic Virus (WSMV) and Barley Stripe Mosaic Virus (BSMV).—The test results with BSMV were not found to be conclusive. With BMV and MDMV, neither the B orK10 chromosomes were found to alter infections; however, these chromosomes were found to affect the resistance of the plants to WSMV infection. The B chromosomes were found to delay the onset of leaf necrosis by 15%, while the K10 chromosome was found to increase the susceptibility to necrosis by 100%. The AR phenomenon was not found to alter the resistance of maize to BMV infection. However, it was found to increase the susceptibility of maize to MDMV infection by 36% and to decrease the susceptibility of maize to WSMV infection by 92%.
THE EVOLUTION OF CONTINUOUS VARIATION. III. JOINT TRANSMISSION OF GENOTYPE, PHENOTYPE AND ENVIRONMENT
Authors: Cavalli-Sforza L L , Feldman M W
Published: April 2021

Evolutionary models of continuous traits are developed. The models are based on the ideas that: (1) the phenotype is the result of the interaction between genotype and environment; (2) the phenotype is the object of natural selection; (3) not only the genotype but also environmental variables and even phenotypes can be directly transmitted. The phenotype of an offspring at birth is a linear combination of its genotypic value, the phenotypic values of its parents, and their environmental values, all measured on the phenotypic scale. The genetic effects are additive polygenic, and a mutation contribution to the within family variance is admitted.—The values of the offspring phenotype and environment before selection are each linear combinations of these values at birth, the coefficients defining what we call "development." Selection is mostly stabilizing of the Gaussian type, but directional selection is introduced using a Gaussian fitness function with a large variance and a mean far from the current population.—Assortative mating for both phenotype and environment are considered. The analysis in all cases is made by iteration of the means, variances and covariances of the trivariate random variable (genotype, phenotype, environment) whose changes over time completely specify the evolution. In most cases numerical methods are used. The problems of estimating the relative roles of each of the variates in the parents in determining the variates in the offspring are discussed. The major results concern the relative magnitudes of the variances and correlations of the three variates, genotype, phenotype and environment, in a variety of selective, developmental and assorting situations with complex transmission in which G-(genetic), F-(phenotypic), E-(environment) inheritance mechanisms operate jointly. The transmission rules and development patterns (i.e., interactions between phenotype and environment during development) are of major importance in determining qualitative features of the equilibrium distribution.
GENETIC DISSECTION OF CLONALLY INHERITED GENOMES OF POECILIOPSIS. I. LINKAGE ANALYSIS AND PRELIMINARY ASSESSMENT OF DELETERIOUS GENE LOADS
Authors: Leslie James F , Vrijenhoek Robert C
Published: April 2021

Theoretical considerations suggest that a high load of deleterious mutations should accumulate in asexual genomes. An ideal system for testing this hypothesis occurs in the hybrid all-female fish Poeciliopsis monacha-lucida. The hybrid genotype is retained between generations by an oogenetic process that transmits only a nonrecombinant haploid monacha genome to their ova. The hybrid genotype is re-established in nature by fertilization of these monacha eggs with sperm from a sexual species, P. lucida. The unique reproductive mechanism of these hybrids allows the genetic dissection of the clonal monacha genome by forced matings with males of P. monacha. The resultant F1 hybrids and their backcross progeny were examined to determine the amount and kinds of genetic changes that might have occurred in two clonal monacha genomes.—Using six allozyme markers, four similar linkage groups were identified in each clonal genome. Segregation and assortment at these loci revealed no apparent differences between monacha genomes from sexually and clonally reproducing species. Mortality of F1 and backcross progeny revealed differences between the two clonal genomes, suggesting that deleterious genes may accumulate in genomes sheltered from recombination.
EFFECTS OF MARKER CHROMOSOMES ON RELATIVE VIABILITY
Authors: Cockerham C Clark , Mukai Terumi
Published: April 2021

Viability relative to Cy/Pm as a standard was studied in Drosophila melanogaster. One experiment, E1, consisted of progeny from eleven distinct 7 x 7 factorial mating designs with reciprocals for second chromosomes extracted from a natural population. The other experiment, E2, consisted of two distinct sets of heterozygotes with reciprocals and corresponding homozygotes. It was established from E1 that there are little to no synergistic effects among different genotypes in a vial and that Cy and Pm heterozygotes vary almost as much as would be expected if one chromosome were held constant for wild-type heterozygotes. In wild-type heterozygotes, variances were estimated to be 0.0099 for average chromosomal effects, 0.0054 for interactions of chromosomes, 0.0021 for maternal effects, 0.0079 for paternal effects, and -0.0010 for the remaining interaction effects, all being significantly different from zero except the last. The variances of Cy and Pm heterozygotes, covariance of Cy and Pm heterozygotes, and covariances of Cy and Pm heterozygotes with wild-type heterozygotes, as well as the comparable statistics available in E2, all showed a large paternal component of variance and a smaller maternal component of variance, both unexpected results.—From E2 the variance of homozygotes, excluding error variance, was estimated to be 0.0149, and the covariances of homozygotes with wild-type heterozygotes to be 0.0056 for maternally derived chromosomes common and 0.0126 for paternally derived chromosomes common, again showing the larger paternal than maternal influence. The average genetic regression of heterozygotes on homozygotes of 0.61 was reduced only slightly to 0.56 by correcting for maternal and paternal variances. These genetic regressions, generally utilized as estimators of the average degree of dominance, are larger than any previously reported.—Differential meiotic drive in Cy and Pm parents was shown to be compatible with the large paternal and maternal variances, but other causes cannot be ruled out.—Approximations were developed for translating various variances, covariances, and regressions between single- and double-marker experiments, assuming that marker chromosomes behave as typical wild-type chromosomes in one case and assuming a (partially) recessive model with the population in mutation selection balance in another case. Various features, particularly the estimation of dominance, were compared and discussed between the two cases.
LACK OF SPONTANEOUS SISTER CHROMATID EXCHANGES IN SOMATIC CELLS OF DROSOPHILA MELANOGASTER
Authors: Gatti M , Santini G , Pimpinelli S , Olivieri G
Published: April 2021

Neural ganglia of wild type third-instar larvae of Drosophila melanogasier were incubated for 13 hours at various concentrations of BUdR (1, 3, 9, 27 μg/ml) . Metaphases were collected with colchicine, stained with Hoechst 33258, and scored under a fluorescence microscope. Metaphases in which the sister chromatids were clearly differentiated were scored for the presence of sister-chromatid exchanges (SCEs) . At the lowest concentration of BUdR (1 μg/ml), no SCEs were observed in either male or female neuroblasts. The SCEs were found at the higher concentrations of BUdR (3, 9 and 27 μg/ml) and with a greater frequency in females than in males. Therefore SCEs are not a spontaneous phenomenon in D. melanogasier, but are induced by BUdR incorporated in the DNA. A striking nonrandomness was found in the distribution of SCEs along the chromosomes. More than a third of the SCEs were clustered in the junctions between euchromatin and heterochromatin. The remaining SCEs were preferentially localized within the heterochromatic regions of the X chromosome and the autosomes and primarily on the entirely heterochromatic Y chromosome.—In order to find an alternative way of measuring the frequency of SCEs in Drosophila neuroblasts, the occurrence of double dicentric rings was studied in two stocks carrying monocentric ring-X chromosomes. One ring chromosome, C(I)TR94-2, shows a rate of dicentric ring formation corresponding to the frequency of SCEs observed in the BUdR-labelled rod chromosomes. The other ring studied, R(1)2, exhibits a frequency of SCEs higher than that observed with both C(I)TR94-2 and rod chromosomes.
FREQUENCY-DEPENDENT SELECTION AT THE LAP LOCUS IN DROSOPHILA MELANOGASTER
Authors: Nassar R
Published: April 2021

Results of fitness estimates for the Lap locus in Drosophila melanogaster revealed that under crowded media conditions gene frequency equilibrium was maintained by frequency-dependent selection. Evidence was obtained that indicated that mating and egg-to-adult viability were frequency dependent.
EXPERIMENTAL POPULATION GENETICS OF MEIOTIC DRIVE SYSTEMS II. ACCUMULATION OF GENETIC MODIFIERS OF SEGREGATION DISTORTER (SD) IN LABORATORY POPULATIONS
Authors: Lyttle Terrence W
Published: April 2021

The accumulation of modifiers of the meiotic-drive locus Segregation Distorter (SD) in Drosophila melanogaster was monitored by measuring the changes in the mean and variance of drive strength (in terms of "make" value) that occur in laboratory populations when SD and SD+ chromosomes are in direct competition. The particular SD lines used are T(Y;2),SD translocations showing pseudo-Y drive. Four sets of population cages were analyzed. Two sets were monitored for changes in SD fitness and drive strength (presumed to be positively correlated) and analyzed for the presence of autosomal dominant or X-linked modifiers after long periods of time. The remaining two sets were made up of cages either made isogenic or variable for background genetic material, and these were used to test whether the rate of accumulation of modifiers was dependent on initial genetic variability.—Contrary to previous studies in which most suppression of SD action could apparently be attributed to a few dominantly acting modifiers of large effect, the conclusion here is that laboratory populations that are initially free of such major dominant loci evolve to suppress SD action by accumulating polygenic, recessive modifiers, each of small effect, and that much of the required genetic variability can be generated de novo by mutation. Possible explanations for these seemingly incompatible results and the evolutionary implications for SD are considered.
A PROBABILITY MODEL FOR EVALUATING THE RANDOMNESS OF THE ASSORTMENT OF CHROMOSOMES DURING SOMATIC REDUCTION
Authors: Geng Shu , Dvorak Jan , Schneeman Paul
Published: April 2021

Pollen mother cells with reduced numbers of chromosomes have been observed in wheat, its hybrid derivatives and amphiploids. Models are presented here for calculating the exact probability of the occurrence of any particular combination of single chromosomes and chromosome pairs in any reduced cell. Hence, it is possible to evaluate randomness of chromosome assortment in somatic reduction. Several sets of data reported by other investigators on somatic reduction in Triticum are analyzed, and we conclude that in those instances chromosomes assort at random.
RESPONSES TO SELECTION FOR BODY WEIGHT IN DESCENDANTS OF X-IRRADIATED RATS
Authors: Gianola Daniel , Chapman A B , Rutledge J J
Published: April 2021

The effectiveness of selection for high and low body weight at six weeks of age was studied in descendants of X-irradiated (R) and nonirradiated (C) inbred rats. There were two replicates of each of the direction of selection irradiation treatments. In C lines, there were no consistent responses to selection, probably due to a low level of genetic variability. In R rats, selection was effective only for decreased body weight. The results of this experiment do not suggest the use of irradiation combined with selection as a means of enhancing responses to selection in animals.
VARIANCE IN QUANTITATIVE TRAITS DUE TO LINKED DOMINANT GENES AND VARIANCE IN HETEROZYGOSITY IN SMALL POPULATIONS
Authors: Avery P J , Hill W G
Published: April 2021

The influence of small population size (N) on the genetic variance within and between randomly bred unselected lines, with selfing permitted, is investigated for a model of a quantitative trait determined by linked genes that show dominance within loci but are additive over loci. Formulae for within-line variance include terms in linkage disequilibrum, which occurs by chance in the lines and these are evaluated in terms of N, map length and gene number. —The expected variance within lines is increased by this disequilibrium, quite substantially if there are many loci, with most of the increase being between or within full-sib families and almost no change expected between half-sib families or in the covariance of offspring and parent. If all loci are unlinked, there is no increase in variance within full-sib families. The variance between lines is little affected by disequilibrum generated by chance.— Expressions for the variance between individuals in heterozygosity over the whole genome are special cases of those for the variance due to linked dominated genes, and formulae are given and evaluated. The coefficient of variation of heterozygosity is at least 1/√3N and can be much higher for species with few chromosomes.
THE DYNAMICS OF FINITE HAPLOID POPULATIONS WITH OVERLAPPING GENERATIONS. I. MOMENTS, FIXATION PROBABILITIES AND STATIONARY DISTRIBUTIONS
Authors: Emigh Ted H
Published: April 2021

Much of the work on finite populations with overlapping generations has been limited to deriving effective population numbers with the tacit assumption that the dynamics of the population will be similar to a population with nonoverlapping generations and the appropriate population number. In this paper, some exact and approximate results will be presented on the behavior of the first two moments of the gene frequencies. The probability of fixation of a neutral gene is found equal to the initial average reproductive value of the gene, and the means and covariances of the stable distribution with mutation in both directions are found by a simple extension of the values found by assuming nonoverlapping generations.
POPULATION GENETICS OF DROSOPHILA AMYLASE. II. GEOGRAPHIC PATTERNS IN D. PSEUDOOBSCURA
Authors: Powell Jeffrey R
Published: April 2021

Morph frequencies of three related polymorphisms were determined in ten natural populations of Drosophila pseudoobscura. They are the well-known inversion polymorphism of the third chromosome and the polymorphism for a-amylase produced by the structural gene Amy (which resides on the third chromosome). The third polymorphism was for tissue-specific expression of Amy in adult midguts; a total of 13 different patterns of activity have been observed. The preceding paper (POWELL and LICHTENFELS 1979) reports evidence that the variation in Amy expression is under polygenic control. Here we show that the polymorphism for midgut activity patterns occurs in natural populations and is not an artifact of laboratory rearing.—From population to population, Amy allele freuencies and frequencies of inversions belonging to different phylads vary coordinately. The geographic variation in α-amylase midgut activity patterns is uncorrelated with that for the other two types of polymorphisms. Furthermore, no correlation was detected between activity pattern(s) and Amy genotype(s) when both were assayed in the same individual.——These results imply that whatever the evolutionary-ecological forces are that control frequencies of the structural gene variants, they are not the same factors that control the frequencies of polymorphic genetic factors responsible for the tissue-specific expression of the enzyme.
A MODEL ALLOWING CONTINUOUS VARIATION IN ELECTROPHORETIC MOBILITY OF NEUTRAL ALLELES
Authors: Cobbs Gary
Published: April 2021

The infinite-sites model with no recombination is extended to include mutations that affect electrophoretic mobility. The model allows the effect of a single-site mutation to have a continuous effect on mobility. Formulae are obtained for the variance of electrophoretic mobility of alleles after an arbitrary length of time. A special case of the general model is the case of stepwise production of neutral alleles with an arbitrary number of steps.
GENETIC MAPPING OF THE CODING REGIONS FOR THREE HEAT-SHOCK PROTEINS IN DROSOPHILA MELANOGASTER
Authors: Peterson Nancy S , Moller Galina , Mitchell Herschel K
Published: April 2021

We describe variants of three heat-shock proteins of Drosophilg melanogaster and their use to map the chromosome regions that contain the coding sequences for these proteins. All three map to a region on chromosome 3L that includes only one heat-shock puff, designated as 67B. The results imply that the genes coding for at least three heat-shock proteins are included within the 67B region.
MATHEMATICAL COMPARISON OF HOMOLOGOUS AND HOMOEOLOGOUS CHROMOSOME CONFIGURATIONS AND THE MODE OF ACTION OF THE GENES REGULATING PAIRING IN WHEAT
Authors: Driscoll C J
Published: April 2021

Analyses of frequencies of chromosome configurations in wheat and wheat hybrids are extended to include data from hybrids of three chromosome-pairing mutants of wheat with Aegilops variabilis and from autotetraploid Triticum monococcum. These data confirm and extend the theory proposed by DRISCOLL, BIELIG and DARVEY (1979). Homoeologous and homologous chromososme pairing are fundamentally identical. The mode of action of the genes regulating pairing in wheat involves either physical alteration in thr chromosomes themselves or changes in an enzyme system that monitors pairing.
TWO MUTATORS AND THEIR SUPPRESSORS IN DROSOPHILA ANANASSAE
Authors: Hinton Claude W
Published: April 2021

Assays of seven mutant stocks exposed a ten-fold range in spontaneous Minute mutation frequencies. Genetic analysis of the difference between the px (0.0006 Minutes) and bri (0.0042 Minutes) stocks revealed that each of these stocks lacks one of two complementary, autosomally transmitted, maternally expressed, dominant suppressors of a dominant 3-linked mutator present in the bri stock. Analysis of the ca; stw stock (0.0013 Minutes) with respect to the former two indicated the presence of the autosomal suppressor functions in addition to a maternally expressed, extrachromosomally transmitted, suppressor of a paternal chromosome-breaking mutator, which is also extra-chromosomally transmitted. The lesions induced by tlie two mutators in male carriers are probably different, but bsth kinds are subject to modification by the maternal suppressors soon after fertilization. The existence of these diverse controls of mutability is viewed as confirmation of STURTEVANT'S (1937) argument that natural selection invokes a variety of devices to minimize mutation rates while retaining mutational potential.
ORGANIZATION OF THE CHORION GENES OF BOMBYX MORI, A MULTIGENE FAMILY. II. PARTIAL LOCALIZATION OF THREE GENE CLUSTERS
Authors: Goldsmith Marian R , Clermont-Rattner Eileen
Published: April 2021

Chorion genes of the inbred stock Ascoli have been localized to three linked clusters by analysis of testcross progeny. Electrophoretic variants screened by isoelectric focusing served as markers. The clusters are designated Ch 1, Ch 2, and Ch 3. The gene order is Ch 1-Ch 2-Ch 3-Y, with relative map distances of approximately 0.4 m.u. for Ch 1-2, 3.3 ± 0.9 m.u. for Ch 2-3, and 21 m.u. for Ch 3-Y. In a separate testcross using different markers, two chorion regions were localized 2.3 mu. and 3.1 mu. from p. These markers could not be assigned to Ch 1, 2, or 3 because there is at present no test for allelism in this system.
A STUDY OF ENZYME ACTIVITIES IN A DOSAGE SERIES OF THE LONG ARM OF CHROMOSOME ONE IN MAIZE
Authors: Birchler James A
Published: April 2021

The enzyme activity levels of alcohol, malate, isocitrate, glucose-6-phosphate and 6-phosphogluconate dehydrogenases were determined in mature maize scutella in a series of one to four doses of the long arm of chromosome 1, produced by the B-A translocation 1La. Although the Adh structural locus was varied, ADH levels did not exhibit a gene-dosage effect. The levels of GGPDH, GPGDH and IDH were negatively correlated with the dosage of 1L. MDH was unresponsive. The esterase-8 enzyme, whose structural locus was demonstrated to be elsewhere in the genome, was also negatively correlated with 1L dosage. The portion of the B chromosome involved in the translocation was shown to have no effect on the enzyme levels. Measurements of cell size and hydrolysable DNA per mg dry weight revealed no change in the number of cells through the one, two and three dose series. The topic of enzyme alterations in aneuploids is reviewed.
THE UNIT OF SELECTION IN DROSOPHILA MERCATORUM. II. GENETIC REVOLUTION AND THE ORIGIN OF COADAPTED GENOMES IN PARTHENOGENETIC STRAINS
Authors: Templeton Alan R
Published: April 2021

Drosophila mercatorum is a sexual species that can reproduce partheno-genetically. Previous studies revealed that parthenogenetic strains had "co-adapted genomes" with high fitness under parthenogenesis and total homozygosity due to nonadditive and nonmultiplicative fitness interactions between chromosomal segments scattered throughout the genome. To study the evolutionary origins of such coadapted genomes, females from sexual matings in nature were isolated as virgins and challenged to reproduce parthenogenetically. Fitness studies were performed on genomes derived from these sexual females and upon their successful parthenogenetic progeny. By straddling the reproductive transition from sex to parthenogenesis, these fitness studies demonstrated that coadapted genomes arise immediately, apparently due to an intense selective bottleneck accompanying the reproductive transition, and are not due to the slow accumulation of epistatic complexes via mutation after parthenogenesis has already been established. The reproductive transition may also serve as an experimental model of the "genetic revolution" theory of speciation because the transition involves (1) the ultimate founder effect (one genome), (2) maximal genetic drift and fixation, (3) a drastic change in genetic environment characterized by total homozygosity, and (4) an intense selective bottleneck that interacts with the change in genetic environment and the need to adapt to a laboratory environment and a novel system of reproduction. Thus, all the elements theorized to underlie genetic revolution are present, albeit in extreme form. This study indicates that genetic revolutions are real phenomena that can quickly alter morphology, development, life history parameters and behavior. Indeed, the alterations can be so drastic that a new "species" evolves, complete with pre- and post-mating isolating mechanisms. However, isozyme loci do not appear to be the target of this genetic revolution, but rather loci regulating fundamental developmental processes. However, isozyme loci may be useful in predicting the a priori chance of a successful revolution since they can indicate how the population structure of the parent population influences levels of individual heterozygosity, the prime source of the genetic variability in the founder population that must pass through the selective bottleneck.
PHYSIOLOGICAL CHARACTERIZATION OF POLAR Tn5-INDUCED ISOLEUCINE-VALINE AUXOTROPHS IN ESCHERICHIA COLI K-12: EVIDENCE FOR AN INTERNAL PROMOTER IN THE ilvOGEDA OPERON
Authors: Berg Claire M , Shaw Karen J , Vender Joyce , Borucka-Mankiewicz Maryla
Published: April 2021

The properties of 22 isoleucine-valine auxotrophs induced in Escherichia coli K-12 by the transposable element, Tn5, were characterized on the basis of growth requirements, cross-feeding behavior, and enzyme activity. Mutants defective in ilvA, ilvC, ilvD and ilvE were found. Mutations in ilvE were not completely polar on ilvD and ilvA enzyme activities (that is, ilvE mutants possessed a low constitutive level of expression of the enzymes coded by ilvD and ilvA), while mutations in ilvD were completely polar on ilvA enzyme activity. The data suggest that there is an internal promoter between the sites of Tn5 insertion in ilvE and ilvD.
GENETIC CHARACTERIZATION OF THE 87C REGION OF THE THIRD CHROMOSOME OF DROSOPHILA MELANOGASTER
Authors: Gausz Janos , Bencze Gabor , Gyurkovics Henrik , Ashburner Michael , Ish-Horowicz David , Holden Jeanette J
Published: April 2021

Ethyl methanesulphonate (EMS) was used to induce 39 lethal and 13 karmoisin mutations within Df(3R)kar3J, a nine-band deficiency extending from 87C1 to 87C9 (inclusive). Five complementation groups (four lethal and one visible) were identified and cytologically mapped between 8764-5 and 87C9, one complementation group per band, with the exception of complementation group A, which is localized to 87C4-5. These positions were determined using a set of overlapping deficiencies, each having at least one break-point in the 87C1-9 region. Mutations within a single complementation group have similar lethal phases or subvital phenotypes, consistent with the notion that each complementation group represents a single functional locus. No mutations localized to 87CI-C3. The inability to induce mutations in the 87C1 heat-shock puff locus is consistent with the current interpretation of a duplication of coding sequences at the 87A7 and 87C1 heat-shock puffs.
THE ROLE OF RADIATION (rad) GENES IN MEIOTIC RECOMBINATION IN YEAST
Authors: Game J C , Zamb T J , Braun R J , Resnick M , Roth R M
Published: April 2021

In yeast, the functions controlled by radiation-repair genes RAD6, RAD50, RAD52 and RAD57 are essential for normal meiosis; diploids with lesions in these genes either fail to sporulate (rad6) or sporulate but produce inviable spores (rad50, 52, 57). Since RAD genes may control aspects of DNA metabolism, we attempted to define more precisely the role of each gene in meiosis, especially with regard to possible roles in premeiotic DNA replication and recombination. We constructed diploids singly homozygous for each of the four rad mutations, heteroallelic at his1 and heterozygous for a recessive canavanine-resistance marker. Each strain was exposed to sporulation-inducing conditions and monitored for (1) completion of mitotic cell cycles, (2) cell viability, (3)utilization of acetate for mass increases, (4)premeiotic DNA synthesis, (5) intragenic recombination at his1, and (6) formation of viable haploid spores. Control strains heterozygous for the rad mutations completed mitosis, metabolized acetate, replicated their DNA, and showed typically high levels of gene conversion and viable-spore formation. The mutant diploids also completed mitosis, utilized acetate, and carried out premeiotic DNA replication. The mutants, however, showed little or no meiotic gene conversion. The rad50, 52 and 57 strains sporulated, but the spores were inviable. The rad6 strain did not sporulate. The rad50, 52 and 57 strains exhibited viability losses that co-incided with the period of DNA synthesis, but not with later meiotic events; the rad6 strain did not lose viability. We propose that the normal functions specified by RAD50,52 and 57 are not essential for either the initial or terminal steps in meiosis, but are required for successful recombination. The rad6 strain may be recombination-defective, o r it may fail to progress past DNA replication in the overall sequence leading to formation and recovery of meiotic recombinants.
GENETIC CONTROL OF GLYCOLYSIS IN HUMAN ERYTHROCYTES
Authors: Gilroy Thomas E , Brewer George J , Sing Charles F
Published: April 2021

We have studied heritability of the concentration of each glycolytic intermediate and adenine nucleotide in the cytosol of human erythrocytes obtained from a random sample of apparently healthy young individuals. Preliminary to analysis of heritability, each trait was statistically described and the effects attributable to variation in measured concomitants were removed by regression. Heritability was estimated using the family-set method. This method removes covariances between the index case, sibling and first cousin, due to those environmental determinants of the phenotypic values that are shared with a matched, unrelated control member of the family set. It also removes covariances due to environments that are shared by siblings and first cousins. Heritability was estimated by employing the fact that the variance of differences between first cousins minus the variance of differences between full siblings estimates three-fourths of the additive genetic variance. The heritability estimates for G6P†, F6P, ATP and some other metabolite concentrations are high and significantly greater than zero. The heritabilities of G6P and F6P are likely attributable to genetic variation in the in vivo activity of HK and/or PFK, because the concentrations of these metabolites are tightly controlled by the two regulatory enzymes. Statistically significant heritability estimates for HK and PFK mass action ratios strongly suggest genes are responsible for a portion of the quantitative variation in these enzyme activities. Since HK and PFK regulate glycolysis and the production of ATP, genetic variation in their activities might be causally related to the heritability of ATP concentration.
SPONTANEOUS ALLOZYME MUTATIONS IN DROSOPHILA MELANOGASTER: RATE OF OCCURRENCE AND NATURE OF THE MUTANTS
Authors: Voelker Robert A , Schaffer Henry E , Mukai Terumi
Published: April 2021

After additional generations of accumulation of allozyme mutants, the 1,000 lines of MUKAI and COCKEFUXAM (1977) were again screened for the same five loci (a-Gpdh, cMdh, Adh, Hex-C and α-Amy), as well as for two new loci (Got-2 and Dip-A). Based on 3,111,598 allele generations: (1) the average mutation rate to new mobility variants with normal function was estimated to be 1.28 x 10-6, and (2) the average mutation rate to null alleles was estimated to be 3.86 x 10-6. A qualitative analysis of the nulls provided evidence that most of the mutants recovered are due to base substitutions. No apparent correlation was observed between structural gene size and mutation rate.
COMPLEXITY OF RNA IN EGGS OF DROSOPHILA MELANOGASTER AND MUSCA DOMESTICA
Authors: Hough-Evans Barbara R , Jacobs-Lorena Marcelo , Cummings Michael R , Britten Roy J , Davidson Eric H
Published: April 2021

Comparative measurements are presented of the sequence complexity of the RNA stored in the eggs of two dipteran flies, Musca domestica and Drosophila melanogaster. The genome of Musca is about five times the size of the Drosophila genome and contains about 3.6 times as much single-copy sequence. As shown earlier, the interspersion of repetitive and single-copy sequence is of the short-period form in Musca, and is of the long-period form in Drosophila. The egg RNA complexities were determined by hybridization of excess RNA with radioactively labeled single-copy DNA. Complexity is expressed as the length (in nucleotides) of diverse single-copy sequence represented in the RNA. The complexity of the RNA of the Musca egg is about 2.4 x 107 nucleotides, and that of the Drosophila egg is about 1.2 x 107 nucleotides. The RNA of the Musca egg is similar to or very slightly lower in complexity than that of other egg RNAs, e.g., those of Xenopus and sea urchin. Compared to all previously measured egg RNAs, Drosophila egg RNA is low in sequence complexity.
THE ISOLATION AND CHARACTERIZATION OF MUTANTS DEFECTIVE IN NITRATE ASSIMILATION IN NEUROSPORA CRASSA
Authors: Tomsett A Brian , Garrett Reginald H
Published: April 2021

The isolation and characterization of mutants altered for nitrate assimilation in Neurospora crassa is described, The mutants isolated can be subdivided into five classes on the basis of growth tests that correspond to the growth patterns of existing mutants at six distinct loci. Mutants with growth characteristics like those of nit-2, nit-3 and nit-6 are assigned to those loci on the basis of noncomplementation and lack of recombination. Mutants that, from their growth patterns, appear to lack the molybdenum-containing cofactor for both nitrate reductase and xanthine dehydrogenase subdivide into three loci (nit-7, nit4 and nit-9), all of which are genetically distinct from nit-1. nit-9 is a complex locus consisting of three complementation groups and thus appears similar to the cnxABC locus of Asperillus nidulans. Extensive complementational and recombinational analyses reveal that nit-4 and nit-5 are alleles of the same locus, and two new alleles of that locus have been isolated. The results indicate that, as in A. nidulans, nitrate assimilation in N. crassa requires at least four loci (nit-1,7,8 and 9) to produce the molybdenum co-factor for nitrate reductase (and xanthine dehydrogenase), one locus (nit-3) to code for the nitrate reductase apoprotein, one locus (nit-6) to code for the nitrite reductase approtein and only one locus (nit-4/5) for the regulation of induction of the pathway by nitrate and nitrite.
DEVELOPMENTAL VARIATION IN AMYLASE ALLOZYME ACTIVITY ASSOCIATED WITH CHROMOSOME INVERSIONS IN DROSOPHILA PERSIMILIS
Authors: Norman R A , Prakash Satya
Published: April 2021

The amylase locus in Drosophila persimilis is polymorphic for allozymes, two of which show associations with naturally occurring chromosome 3 inversions. Amy  1.09 occurs at high frequencies only in Whitney (WT), while the other common arrangements-Standard (ST), Klamath (KL) and Mendocino (MD) —are predominantly Amy  1.00. We have examined numerous strains, representing various electromorphs and inversions, for variation in cis-specific activity expression in both third-instar larvae and adults. Comparisons of these two life stages also allows the survey of developmental variation in amylase activities. The amount of activity variation exceeds electrophoretic variation at this locus. Moreover, this variation is largely nonrandom and reveals more genic divergence among inversions. The 1.00 allozyme of MD is more active than 1.00 KL in larvae and adults and shows a different developmental pattern. The activity of the 1.00 allozyme of KL is greater than 1.00 allozyme of ST in larvae and adults, but these two arrangements have similar developmental patterns. WT 1 with a 1.00 allele is dramatically different from the 1.00 allozymes of other arrangements in its developmental pattern. The 1.09 allozyme has high activity in WT and KL, but these arrangements differ in their developmental pattern of expression, WT being more active in adults. F2 segregational analyses are consistent with the variation being due to either structural enzyme variants or closely linked cis-acting regulatory elements. We argue that the suppression of recombination between arrangements has allowed the divergence in amylase activity among inversions.
CLAN LETHALS AND INTER-YEAR ALLELISM IN DEATH VALLEY DROSOPHILA PSEUDOOBSCURA
Authors: Bryant Stephen H
Published: April 2021

A chromosome 2 lethal allelism rate of about 3% was found in the 1974 population of D. pseudoobscura in Death Valley, California. This rate was significantly higher than allelism rates in other Southern California populations. The Death Valley population was sampled again in 1975 and 1977, with allelism rates of 1% and 0.5%, respectively. In 1974, several lethals were in high frequencies (about 1%), a pattern that reappeared in 1975 and 1977. However, none of the lethals in high frequency one year were in high frequency another year; the particular lethal alleles present in this ephemeral population appear to be due to their random presence in the flies which refound the population every winter. The results for the Death Valley population are compared with a Japanese population of D. melanogaster in which lethals in high frequency one year are also in high frequency in succeeding years and with earlier work on chromosome 3 of D. pseudoobscura, which showed a lower lethal frequency and higher allelism rate.
GENETICS AND ULTRASTRUCTURE OF A CYTOPLASMICALLY INHERITED YELLOW MUTANT IN SOYBEANS
Authors: Palmer Reid G , Mascia Peter N
Published: April 2021

A chimeric plant was observed in the F2 generation of a cross between a male-sterile line and a plant introduction homozygous for a chromosome interchange in soybeans [Glycine max (L.) Merr.]. F3 progeny of this plant included one chimera, 36 yellow plants and 16 green plants. The yellow plants, which progressively turn green, were viable and fertile in field, greenhouse and growth-chamber environments. Reciprocal cross-pollinations were made between these yellow plants and four known nuclear yellow mutant plants, between these yellow plants and sibling green plants and between these yellow plants and unrelated green plants. Segregation data from F1 and F2 generations indicated cytoplasmic inheritance of the newly discovered yellow phenotype. Pollinations in which reciprocal F1 hybrid plants were used as male or female parents were made with unrelated green plants. Observations in F1 and F2 generations substantiated the hypothesis of cytoplasmic inheritance. No interactions have been observed between this mutant and the various nuclear backgrounds. This is the first report of a cytoplasmically inherited mutant affecting plant color in soybeans. Exchange grafts were made between cytoplasmic yellow plants and sibling green plants and between cytoplasmic yellow plants and unrelated green plants. The phenotype was controlled by the scion, indicating that graft-transmissible agents were not involved. When grown in darkness, cytoplasmic yellow plants and normal green plants accumulated the same amount of protochlorophyllide. Cytoplasmic yellow plants grown in dim light accumulated slightly less chlorophyll than did their green siblings. Electron photomicrographs showed that the prolamellar body (a structure associated with synthesis of protochlorophyllide) and chloroplast ultrastructure were normal in the cytoplasmic yellow mutant. These observations led to the hypothesis that the synchrony involved in deposition of nuclear and cytoplasmic gene products during organelle development is impaired in this cytoplasmic mutant.
MAPPING OF THE PROTEINASE B STRUCTURAL GENE PRB1, IN SACCHAROMYCES CEREVISIAE AND IDENTIFICATION OF NONSENSE ALLELES WITHIN THE LOCUS
Authors: Zubenko George S , Mitchell Aaron P , Jones Elizabeth W
Published: April 2021

We report the mapping of the structural gene for proteinase B, PRB1. It is located 1.1 cM proximal to CAN1 on the left arm of chromosome V of Saccharomyces cerevisiae. We have identified 34 amber and 12 ochre mutations among the 126 prb1 mutations in our collection.