bluuebunny/crossref_metadata_2025 huggingface dataset:
ON THE REGULATION OF GENE EXPRESSION: INCOMPATIBILITY IN SCHIZOPHYLLUM
Authors: Ullrich Robert C
Published: April 2021

A new functional class of nucleic acids is postulated on the basis of the multiallelic incompatibility system regulating sexual morphogenesis in the higher fungi. A physical-chemical basis for distinguishing molecules active, as opposed to inactive, in promoting morphogenesis is established by the secondary structure of the resultant nucleic acid duplexes. This regulatory mechanism may be of broad import.
SELECTION FOR NURSING ABILITY AND ADULT WEIGHT IN MICE
Authors: Nagai J , Eisen E J , Emsley J A B , McAllister A J
Published: April 2021

Three selection treatments were conducted for 12 generations in each of two base populations (P and Q): (1) increased nursing ability of the mother (n12), as measured by mean 12-day weight of eight young within a crossfostering set (MP and MQ lines), (2) increased adult (42-day) body weight of the offspring (w42) (WP and WQ lines), and (3) performance combining the two traits (n12 and w42) into a selection index (BP and BQ lines). Lines CP and CQ were maintained as unselected controls in each population. In each line-generation subclass, 92 single-pair matings were made and the offspring assigned to balanced crossfostering sets of four dams each. Regression coefficients of mean performance (in grams) on generations were 0.080 ±0.029 and 0.054 ± 0.031 for n12 in MP and MQ, and 0.680 ± 0.039 and 0.868 ± 0.051 for w42 in WP and WQ, respectively. The BP and BQ lines showed genetic gains in n12 (0.090 and 0.053, respectively) and w42 (0.576 and 0.696) intermediate between the performance of MP and WP, and MQ and WQ, respectively, except for n12 of BQ. Realized heritabilities for n12 were 0.16 ± 0.05 and 0.11 ± 0.06 and those for w42 were 0.40 ± 0.02 and 0.43 ± 0.03 for P and Q, respectively. The realized genetic correlations between n12 and w42 were 0.70 ± 0.07 and 0.73 ± 0.08 in P and Q, respectively. The ratios of the predicted to observed responses in MP, BP and BQ were 0.99, 1.03 and 0.89, respectively. However, the predicted and observed responses differed in MQ, WP and WQ; the ratios were 1.29, 0.65 and 0.65, respectively. The observed combined responses for n12 and w42 in the index lines (BP and BQ) were smaller than the optimum expected from index selection. A possible cause was that the estimated genetic correlations (0.22 ± 0.16 and -0.17 ± 0.16 for BP and BQ, respectively) and heritabilities (0.39 ± 0.03 and 0.28 ± 0.02, respectively) for w42 that were used to construct the selection index were smaller than the respective realized parameters.
SINGLE-TRAIT AND ANTAGONISTIC INDEX SELECTION FOR LITTER SIZE AND BODY WEIGHT IN MICE
Authors: Eisen E J
Published: April 2021

Individual selection based on female performance only was conducted in four lines of mice: L+ for increased litter size, W+ for increased 6-week body weight, L-W+ for a selection index aimed at decreasing litter size and increasing 6-week body weight and L+W- for a selection index aimed at increasing litter size and decreasing 6-week body weight. A fifth line (K) served as an unselected control. All litters were standardized to eight mice at one day of age. Expected heritability was based on twice the regression of offspring on dam (h  2  d), which contains additive genetic variance due to direct (α2Ao) and maternal (α2  Am) effects and their covariance (αAoAm). Responses and correlated responses were measured either deviated (method 1) or not deviated (method 2) from the control line. Realized heritabilities (h2  R) for litter size were 0.19 ± 0.04 (1) and 0.16 ± 0.03 (2), which were similar to h2  d of 0.17 ± 0.04. The h2  R for 6-week body weight of 0.55 ± 0.07 (1) and 0.44 ± 0.07 (2) agreed with h2  d of 0.42 ± 0.02. Realized genetic correlations (r*GR) between litter size and 6-week body weight calculated from the double-selection experiment were 0.52 ± 0.10 (1) and 0.52 ± 0.13 (2), which were not significantly different from the base population estimate of r*Gd = 0.63 ± 0.14. Divergence (L-W+ minus L+W-) in the antagonistic index selection lines was 0.21 ± 0.01 index units (I = 0.305 PW - 0.436 PL, where PW and PL are the phenotypic values for 6-week body weight and litter size, respectively.). The h2  R of index units of 0.14 ± 0.02 calculated from divergence agreed with h2  d of 0.14 ± 0.04. Divergences in litter size (-0.19 ± 0.07) and 6-week body weight (0.46 ± 0.10) were in the expected direction. Antagonistic index selection yielded about one-half the expected divergence in litter size, while divergence in 6-week body weight was only slightly less than expected. Realized genetic correlations indicated that litter size, 6-week body weight and index units each showed positive pleiotropy with 3-week body weight, postweaning gain and weight at vaginal introitus and negative pleiotropy with age at vaginal introitus. Sex ratio and several components of fitness (days from joining to parturition, percent fertile matings and percent perinatal survival) did not change significantly in the selected lines.
SEX-LIMITED EXPRESSION OF GENE LOCI CONTROLLING FLAGELLAR MEMBRANE AGGLUTINATION IN THE CHLAMYDOMONAS MATING REACTION
Authors: Goodenough Ursula W , Hwang Carol , Warren A Jane
Published: April 2021

Mutant strains of Chlamydomonas reinhardi that have lost their ability to undergo sexual agglutination via their flagellar tips have been induced to undergo zygotic cell fusion and meiosis, using a flagellar-directed antiserum. Genetic analysis of antiserum-mediated crosses involving five nonagglutinating mt  + mutant strains reveals the following: (1) None of the mutations is linked to the mt locus. (2) All of the mutations are "sex-limited," meaning that they can be carried and transmitted by, but not expressed in, mt  - cells. (3) Four of the mutations (imp-2, imp-5, imp-6, imp-7) are either allelic or closely linked to one another, with imp-8 defining a second locus.
GENETIC AND BIOCHEMICAL BASIS OF ENZYME ACTIVITY VARIATION IN NATURAL POPULATIONS. I. ALCOHOL DEHYDROGENASE IN DROSOPHILA MELANOGASTER
Authors: McDonald John F , Ayala Francisco J
Published: April 2021

Recent studies by various authors suggest that variation in gene regulation may be common in nature, and might be of great evolutionary consequence; but the ascertainment of variation in gene regulation has proven to be a difficult problem. In this study, we explore this problem by measuring alcohol dehydrogenase (ADH) activity in Drosophila melanogaster strains homozygous for various combinations of given second and third chromosomes sampled from a natural population. The structural locus (Adh) coding for ADH is on the second chromosome. The results show that: (1) there are genes, other than Adh, that affect the levels of ADH activity; (2) at least some of these "regulatory" genes are located on the third chromosome, and thus are not adjacent to the Adh locus; (3) variation exists in natural populations for such regulatory genes; (4) the effect of these regulatory genes varies as they interact with different second chromosomes; (5) third chromosomes with high-activity genes are either partially or completely dominant over chromosomes with low-activity genes; (6) the effects of the regulatory genes are pervasive throughout development; and (7) the third chromosome genes regulate the levels of ADH activity by affecting the number of ADH molecules in the flies. The results are consistent with the view that the evolution of regulatory genes may play an important role in adaptation.
EXPLORING THE POTENTIAL OF COMPOUND;FREE-ARM COMBINATIONS OF CHROMOSOME 2 IN DROSOPHILA MELANOGASTER FOR INSECT CONTROL AND THE SURVIVAL TO PUPAE OF WHOLE-ARM TRISOMIES
Authors: Fitz-Earle M , Holm D G
Published: April 2021

Genetic tests of second-chromosome compound;free-arm combinations ("free arms") in Drosophila melanogaster indicate that the egg hatch is approximately 50% that of standard lines and adult recovery is approximately 40%. Free-arm strains are genetically isolated from both compound-chromosome lines and standards.

A large proportion of the hybrid progeny arising from crosses between free arms and standards or free arms and compounds, survive to the pupal stage. Cytological examinations reveal that these hybrids are trisomic for one arm of chromosome 2. Such hybrid progeny may place an added constraint upon the competition between free-arm and standard strains by competing for food, but not contributing to the adult population. The fitness data, the genetic isolation characteristic and the possible impact of hybrid progeny all suggest that free arms may prove to be a valuable genetic tool for insect population control. Preliminary cage-competition experiments to test this prediction have demonstrated that free arms are able to displace standards at ratios as low as 3:1, which is close to the theoretical equilibrium predicted by the fitness data (2.5:1).
GENETICS OF HEMOGLOBIN IN THE DEER MOUSE, PEROMYSCUS MANICULATUS. I. MULTIPLE α- AND β-GLOBIN STRUCTURAL LOCI
Authors: Snyder Lee R G
Published: April 2021

Genetic data, together with molecular structure studies, have demonstrated that the complex hemoglobin phenotypes in four subspecies of P. maniculatus are generated by at least four, and probably five, globin structural loci. The Hba and Hbc loci apparently arose by duplication of an ancestral α-type locus, while Hbb, Hbd, and Hbe apparently were derived from a β-type locus. The Hba and Hbb structural loci are electrophoretically monomorphic, while Hbc, Hbd, and Hbe are each polymorphic for at least two electrophoretic alleles. Alleles at Hbc and Hbd segregate independently. The globin products of Hbc and Hbd are electrophoretically indistinguishable; therefore, it is impossible to enumerate true gene frequencies in population surveys. Combined evidence from Peromyscus, Mus and Rattus indicates a remarkable similarity in the numbers of duplicated globin structural loci and in their linkage relationships to coat color loci.
GENETIC VARIATION IN ACTIVITY OF THE ENZYMES OF GLYCOLYSIS AND GLUCONEOGENESIS BETWEEN INBRED STRAINS OF MICE
Authors: Bulfield Grahame , Moore Elizabeth A , Kacser Henrik
Published: April 2021

Variation in the activity of 21 liver and 15 erythrocyte enzymes between seven inbred strains of mice has been studied in a single area of metabolism, glycolysis and gluconeogenesis. Most of the variation between the strains is genetic. From the variation within and between inbred strains heritabilities (H  2) were determined. Out of 35, 26 showed significant values above 0.4. A comparison with previously published work suggests that enzyme activities have mainly dominance and interaction components of variance, and this is discussed in relation to the variation in quantitative characters such as growth. In nine of the pairwise comparisons of the strains, the activity of the enzyme varied more than two-fold. In these cases the genetics and biochemistry of the enzyme was studied; F2 progeny were produced and assessed for segregation, and the heat stability of the enzyme was determined. No unequivocal segregation was observed, although in one case we found a considerable difference in heat stability. The variations found were not considered to be great enough to be useful as models of human inborn errors of metabolism or to study metabolic control. If such variants are to be found, sources of variation other than inbred strains must be used.
RENEWAL PROCESS APPROACH TO THE THEORY OF GENETIC LINKAGE: CASE OF NO CHROMATID INTERFERENCE
Authors: Cobbs Gary
Published: April 2021

Models are presented in which the distribution of crossovers at a four-four-strand stage of meiosis results from a renewal process. Probability distributions are obtained for the number of crossover events on a meiotic bivalent and for the number of exchange points in random meiotic products. These distributions are found to fit the observed distribution of these variables reasonably well. Using these distributions and assuming no chromatid interference, relations between map distance and the recombination fraction are obtained. These relations give either better or equivalent fit to data when compared to relations that are designed to account for both chromatid and chiasma interference.
THE SPATIAL DISTRIBUTION OF TRANSIENT ALLELES IN A SUBDIVIDED POPULATION: A SIMULATION STUDY
Authors: Slatkin Montgomery , Charlesworth Deborah
Published: April 2021

The spatial distributions of newly introducted alleles in a subdivided population are generated using a computer program to model the processes of selection, gene flow and genetic drift. Advantageous, neutral and deleterious alleles are considered, and certain aspects of the patterns generated by new alleles that are ultimately fixed and ultimately lost are examined. To characterize the spatial pattern of rare alleles, the distribution, Pi, the probability that the new allele is found in exactly i local populations before it is lost, is defined and estimated from the simulations. The shape of the Pi distribution is surprisingly similar for selected and neutral alleles. For advantageous alleles going to fixation, the "wave of advance" is set up quickly, but stochastic effects reduce the wave speed from Fisher's (1937) value. Gene flow is much more effective in dispersing alleles in a two-dimensional array than in one dimension. Long distance gene flow has a much smaller effect in two dimensions than in one dimension.
MUTANTS OF SEXUAL MATURITY IN PARAMECIUM CAUDATUM SELECTED BY ERYTHROMYCIN RESISTANCE
Authors: Myohara Koji , Hiwatashi Koichi
Published: April 2021

Cells of Paramecium caudatum, syngen 3 usually become sexually mature about 50 fissions after conjugation. In order to study the genetic mechanisms that control fission-dependent expression of maturity, an attempt was made to obtain early mature mutants by treatment with N-methyl-N′-nitro-N-nitro-soguanidine. A new cytoplasmic marker, erythromycin resistance, was used to eliminate nonconjugant and macronuclear regeneration clones. Twenty early mature clones were obtained from five different mutagenized cultures. Three of them were genetically analyzed by crosses to wild-type stocks. The results show all three mutants to be controlled by incompletely dominant genes, i.e., the homozygotes became mature 20-25 fissions and the heterozygotes 15 fissions earlier than the wild-type clones. At least two different loci are suggested for the early maturity.
CYTOGENETIC ANALYSIS OF CHROMOSOME 3 IN DROSOPHILA MELANOGASTER: ISOLATION AND CHARACTERIZATION OF FOUR NEW ALLELES OF THE PROBOSCIPEDIA (pb) LOCUS
Authors: Kaufman Thomas C
Published: April 2021

Previous studies on proximal 3R have cytologically localized the dominant homeotic loci Antennapedia (Antp), Multiple Sex Comb (Msc), Nasobemia (Ns), and Extra Sex Comb (Scx). In this study we set out to find the site of the proboscipedia (pb) locus. In order to accomplish this, four new alleles of this homeotic gene were induced with gamma rays. Genetic and cytogenetic analyses have shown that the pb locus resides in polytene chromosome bands 84A1-6, immediately adjacent to the Antp gene complex in 84B1-2. An analysis of the morphology of the proboscis and the dose relationships of the four new alleles have shown that this homeosis is unusual in at least two respects. First, the two different developmental fates realized in the proboscis at 18° (labial palps → arista) and 29° (labial palps → leg) under the influence of pb1 grown at 18°, while the remaining three are like pb  1 at 29°. Dosage studies reveal that this difference reflects a hypomorphic vs. amorphic condition. Second, like the original, these new alleles produce a prothoracic rather than a mesothoracic leg in the proboscis. Both of these results indicate that pb is unique among the homeotics, and as such it may offer some new insights into developmental processes.
DYNAMICS OF CORRELATED GENETIC SYSTEMS. IV. MULTILOCUS EFFECTS OF ETHANOL STRESS ENVIRONMENTS
Authors: Cavener D R , Clegg M T
Published: April 2021

Four replicate populations of Drosophila melanogaster, two reared on medium supplemented with ethanol and two reared on standard medium, were electrophoretically monitored for 28 generations. During the first 12 generations, allelic, genotypic and gametic frequencies were determined for eight polymorphic enzymes: GOT, α-GPDH, MDH, ADH, TO, E6, Ec and ODH. Samples from generation 18 and 28 were electrophoretically typed for ADH and α-GPDH. In addition, samples from generation 27 were analyzed for the presence of inversion heterozygous.—The experimental results showed rapid gene-frequency divergence between control and treatment populations at the Adh locus in a direction consistent with the activity hierarchy of Adh genotypes. Gene-frequency divergence between control and treatment populations also occurred at the α-Gpdh locus, although the agreement among replicates appeared to have broken down by generation 28. No differential gene-frequency change occurred at any of the six remaining marker loci. Furthermore, values of linkage disequilibria among all linked pairs of genes were initially small and remained small throughout the course of the experiment. Taking these facts into account, it is argued that the gene-frequency response observed at ADH is most probably caused by selection at the Adh locus. The gene frequency response at α-Gpdh can also be be accounted for in terms of the effect of ethanol on energy metabolism, although other explanations cannot be excluded.
REGULATION OF NEWLY EVOLVED ENZYMES. IV. DIRECTED EVOLUTION OF THE EBG REPRESSOR
Authors: Hall Barry G
Published: April 2021

In Escherichia coli, the wild-type repressor of ebg (evolved β-galactosidase) enzyme synthesis, specified by the ebgR  + gene, responds very weakly to lactulose (fructose-β-D-galactopyranoside). Selection for a functional repressor that responds strongly to lactulose as an inducer reveals the existence of ebgR+L mutants, which occur spontaneously at a frequency of about 2 x 10-10. ebgR+L mutants are pleiotropic in that they specify ebg repressor with a greatly increased response to lactulose, lactose, galactose-arabinoside and methyl-galactoside as inducers. Selection of ebgR+L mutants is discussed within the framework of directed evolution of a regulatory function.
APPARENT TRANS CONTROL OF MURINE βGLUCURONIDASE SYNTHESIS BY A TEMPORAL GENETIC ELEMENT
Authors: Meredith Susan A , Ganschow Roger E
Published: April 2021

A difference in the heat-inactivation kinetics between the β-glucuronidases of C3HeB/FeJ and C57Bl/6J mice was utilized to assess the mode of action of a temporal genetic element in controlling the expression of the β-glucuronidase structural gene Gus. The heat-inactivation kinetics of liver and kidney β-glucuronidase from F1 C3HeB/FeJ x C57Bl/6J animals were intermediate with respect to the parental enzyme patterns, suggesting that equal concentrations of the two allelic products were present in β-glucuronidase tetramers of F1 progeny. β-glucuronidase heteropolymers assembled in vivo under conditions where equal concentrations of the two structural alleles of the enzyme were known to be present also exhibited intermediate heat-inactivation kinetics. These observations are consistent with a trans mode of action of a genetic element that controls the rate of murine β-glucuronidase synthesis.
THE RELATIONSHIP BETWEEN SYNAPTINEMAL COMPLEXES, RECOMBINATION NODULES AND CROSSING OVER IN NEUROSPORA CRASSA BIVALENTS AND TRANSLOCATION QUADRIVALENTS
Authors: Gillies C B
Published: April 2021

Reconstruction of serially sectioned zygotene and pachytene nuclei has allowed the estimation of both the number and position of central component recombination nodules in the synaptinemal complexes of two chromosomally different strains of Neurospora crussa. In both strains the number of nodules is that expected if each nodule represents one crossover event (50 map units). The distribution of nodules within the arms of bivalents shows evidence of centromeric repulsion and telomeric localizatioa. Nodules appear quite early in the zygotene before pairing of chromosomes is complete. Evidence was found of size differences in nodules, and multiple nodules were occasionally seen. Chromosome lengths and nuclear sizes increased from early zygotene to late pachytene. The three quadrivalents present in the alcoy translocation heterozygotes were readily distinguishable in reconstructions, and their cytological dimensions were in agreement with predictions from linkage map distances.
X-RAY STAGE SENSITIVITY OF MOUSE OOCYTES AND ITS BEARING ON DOSE-RESPONSE CURVES
Authors: Brewen J G , Payne H S
Published: April 2021

A detailed cytogenetic study of maturing mouse oocyte radiosensitivity was performed. Oocytes were collected at various intervals ranging from 1.5 days to 28.5 days after irradiation with 50, 100, 200, and 300R of acute X-rays. The observed sensitivity to chromatid aberration induction varied greatly over this time span. Sensitivity was lowest at the shortest time interval before ovulation and gradually increased up to 9.5 days; it then remained constant until insufficient numbers of oocytes could be collected. The data were analyzed in three ways. First, the data from all time intervals at each dose were pooled; second the data from the least sensitive time intervals, at each dose, were pooled, and third, the data from the period of uniform sensitivity, at each dose, were pooled. Dose-response regression analyses were done on these pooled data and the best fits obtained were to the models Y= a + bD  + cD2 and Y= a + cD2 for both deletions and interchanges. This result is interpreted as indicating that the aberrations result from a predominantly two-track process. The cytogenetic data were compared to specific-locus mutation induction data in comparable oocyte stages, and qualitative similarity in dosei esponse characteristics were observed. This similarity is interpreted to mean that both events result from the same mechanism, and that the large dose-rate effect, observed for both events, is a reflection of the two-track component in the dose-response curves.
GENETIC ORGANIZATION IN CAENORHABDITIS ELEGANS: FINE-STRUCTURE ANALYSIS OF THE unc-22 GENE
Authors: Moerman D G , Baillie D L
Published: April 2021

Fine-structure analysis of the unc-22 gene of Caenorhabditis elegarns has revealed a number of sites that are separable by recombination. Eight new ethyl methanesulfonate-induced recessive mutations of the unc-22 gene have been isolated. Using these new alleles, as well as e66, a number of separable sites have been identified and positioned relative to one another. The map distances obtained are found to be comparable to those associated with intragenic recombination in Drosophila melanogaster, indicating that genetic finestructure analysis is feasible in Caenorhabditis elegans. Evidence of possible gene conversion is presented. A preliminary estimate of the unc-22 gene size is 2.4 × 10-2 map units.
FUNCTIONAL INTERACTIONS BETWEEN THE DNA LIGASE OF ESCHERICHIA COLI AND COMPONENTS OF THE DNA METABOLIC APPARATUS OF T4 BACTERIOPHAGE
Authors: Karam J D , Leach M , Heere L J
Published: April 2021

T4 phage completely defective in both gene 30 (DNA ligase) and the rll gene (function unknown) require at least normal levels of host-derived DNA ligase (E. coli lig gene) for growth. Viable E. coli mutant strains that harbor less than 5% of the wild-type level of bacterial ligase do not support growth of T4 doubly defective in genes 30 and rll (T4 30- rll- mutants). We describe here two classes of secondary phage mutations that permit the growth of T4 30- rll- phage on ligase-defective hosts. One class mapped in T4 gene su30 (KRYLO1V9 72) and improved T4 30- rll- phage growth on all E. coli strains, but to varying degrees that depended on levels of residual host ligase. Another class mapped in T4 gene 32 (heliz-destabilizing protein) and improved growth specifically on a host carrying the lig2 mutation, but not on a host carrying another lig- lesion (lig4). Two conclusions are drawn from the work: (1) the rde of DNA ligase in essential DNA metabolic processes in T4-infected E. coli is catalytic rather than stoichiometric, and (2) the E. coli DNA ligase is capable of specific functional interactions with components of the T4 DNA replication and/or repair apparatus.
EXPANDED LINKAGE MAP OF VIBRIO CHOLERAE
Authors: Parker Charlotte , Gauthier Dorothy , Tate Ann , Richardson Katie , Romig W R
Published: April 2021

An expanded linkage map of the Vibrio cholerae classical strain 162 chromosome has been prepared using a variety of new auxotrophic mutants. The chromosome consists of a single, linear linkage group. The map consists of 17 markers, which have been ordered; 20 mutational sites, which are tentatively ordered; five markers (ura-1, ser-2, mal-1, man-1, suc-1), which are linked but unordered; and three mutations (aro-2, cys-2 and cys-6) which showed little or no linkage. A proposal is made to standardize genetic nomenclature in V. cholerae genetic studies.
A PRELIMINARY GENETIC INVESTIGATION OF VOLVOX CARTERI
Authors: Huskey Robert J , Griffin Barbara E , Cecil Patricia O , Callahan Ann M
Published: April 2021

A preliminary genetic analysis of a number of genetic variants of Volvox carteri f. nagariensis is presented. Techniques are outlined for mutagenesis of Volvox, isolation of mutants and routine genetic analysis. All of the mutants show simple Mendelian segregation patterns and have been tentatively placed in 14 linkage groups.
USE OF TWO-DIMENSIONAL ELECTROPHORESIS TO IDENTIFY AND MAP NEW MOUSE GENES
Authors: Elliott Rosemary W
Published: April 2021

Cytosol polypeptides from mouse liver have been examined using twodimensional electrophoresis. About 250 spots were readily discernible. When cytosols from strains BALB/cBy and C57BL/6By were compared, eight genetically determined differences were observed. Other strain pairs show comparable numbers of differences. These eight phenotypes were scored in seven recombinant inbred lines derived from the two parental strains, and their strain distribution patterns were compared with previously determined patterns for other genetic markers that differ between the two progenitor strains. Using this information, tentative chromosome assignments for the genes controlling five of the variant phenotypes have been made, and two of the assignments have been confirmed using congenic resistant strains. These eight genes will be useful reference markers in fiiture crosses designed to map new genes.
BEHAVIORAL MUTANTS IN PARAMECIUM CAUDATUM
Authors: Takahashi Mihoko
Published: April 2021

Mutants of Paramecium caudatum with abnormal swimming behavior or responses to cations were obtained by mutagenesis with N-methyl-N-nitro N-nitrosoguanidine. Some of the mutants, like pawn in P. tetraurelia, cannot swim backward and are called CNR. Seven independently obtained CNR mutants belonged to three complementation groups, designated as cnrA, cnrB and cnrC. Some characteristics of double homo- and heterozygotes were compared with single homo- and heterozygotes. Other behavioral mutants shown to have a genic basis included K+-sensitive, temperature-shack behavioral and slow swimmer. All those mutants except for slow swimmer had lesions in the membrane because Triton-extracted models of them show almost the same swimming behavior as wild type.
NON-MENDELIAN FEMALE STERILITY IN DROSOPHILA MELANOGASTER: PRINCIPAL CHARACTERISTICS OF CHROMOSOMES FROM INDUCER AND REACTIVE ORIGIN AFTER CHROMOSOMAL CONTAMINATION
Authors: Picard Georges
Published: April 2021

Strains of Drosophila melanogaster can be divided into two main classes, inducer and reactive, in relation to non-Mendelian female sterility. The genetic element responsible for the inducer condition (I factor) is chromosomal and may be linked to any inducer-strain chromosome. Each chromosome carrying the I factor (i  + chromosome) can produce females showing more-or-less reduced fertility when it is introduced by paternal gametes into a reactive oocyte. As long as i+ chromosomes are transmitted through heterozygous males with reactive originating chromosomes (r chromosomes), I factor strictly follows Mendelian segregation. In contrast, in heterozygous i+/r females, a varying proportion of r chromosomes may acquire I factor independently of classical genetic recombination, by a process called chromosomal contamination. This paper reports investigation of the characteristics of the three kinds of chromosomes produced by females in which contamination occurs. It appears that the contaminated reactive chromosomes have irreversibly acquired I factor and behave like i  + chromosomes, while the i  + chromosomes used as contaminating elements and the reactive originating chromosomes that have not been contaminated have not undergone any change.
FREQUENCY-DEPENDENT SELECTION FOR PLASMID-CONTAINING CELLS OF ESCHERICHIA COLI
Authors: Adams Julian , Kinney Thomas , Thompson Susan , Rubin Lori , Helling Robert B
Published: April 2021

Colicin-producing plasmid-containing cells of E. coli exhibit frequency dependent selection when grown in glucose-limited continuous culture with the corresponding plasmid-free strain. The bases of this frequency-dependent effect are shown to be (1) the lower growth rate of the plasmid-containing strain under these conditions, and (2) the production of colicin, which attenuates the growth rate of the plasmid-free strain. These results are discussed in relationship to the maintenance of genetic variation in prokaryotes.
CYTOGAMY: AN INDUCIBLE, ALTERNATE PATHWAY OF CONJUGATION IN TETRAHYMENA THERMOPHILA
Authors: Orias Eduardo , Hamilton Eileen P
Published: April 2021

We report the occurrence of cytogainy in Tetrahymena thermophila. By analogy to Paramecium, cytogamy generates exconjugant clones that derive their entire genetic information from a single meiotic product of their cytoplasmic parent. Thus, "instant" whole-genome homozygotes are created. Cytogamy has been induced in every strain of T.thermophila tested, and most of the excytogamous progeny have exhibited high fertility. The high frequency with which cytogamy can be induced by hyperosmotic shock, coupled with the foregoing genetic properties, make this process a practical (and already proven) method for the isolation of recessive mutants in T.thermophila. We also report that the cytogamy-inducing treatment induces other rare abnormalities of genetic transmission, which have not yet been characterized.
A NEW MATING COMPATIBILITY LOCUS IN PHYSARUM POLYCEPHALUM
Authors: Youngman Philip J , Pallotta Dominick J , Hosler Betsy , Struhl Gary , Holt Charles E
Published: April 2021

The rate and extent of plasmodium formation were studied in mating tests involving pairs of largely isogenic amoeba1 strains compatible for matingtype (mt) alleles. A systematic variability was observed: plasmodia formed either rapidly and extensively or slowly and inefficiently. Plasmodium formation was found to be 103- to 104-fold more extensive in "rapid" crosses than in "slow" crosses. A genetic analysis revealed that the variability reflects the influence of a multiallelic compatibility locus that determines mating efficiency. This compatibility locus (designated matB), together with the original mating type locus mt (in this work designated matA), constitute a tetrapolar mating specificity system in Physarum polycephalum.
THE GENETICS OF A SMALL AUTOSOMAL REGION OF DROSOPHILA MELANOGASTER CONTAINING THE STRUCTURAL GENE FOR ALCOHOL DEHYDROGENASE. I. CHARACTERIZATION OF DEFICIENCIES AND MAPPING OF ADH AND VISIBLE MUTATIONS
Authors: Woodruff R C , Ashburner M
Published: April 2021

The position of the structural gene coding for alcohol dehydrogenase (ADH) in Drosophila melanoguster has been shown to be within polytene chromosome bands 35B1 and 35B3, most probably within 35B2. The genetic and cytological properties of twelve deficiencies in polytene chromosome region 34-35 have been characterized, eleven of which include Adh. Also mapped cytogenetically are seven other recessive visible mutant loci. Flies heterozygous for overlapping deficiencies that include both the Adh locus and that for the outspread mutant (osp: a recessive wing phenotype) are homozygous viable and show a complete ADH negative phenotype and strong osp phenotype. These deficiencies probably include two polytene chromosome bands, 35B2 and 35B3.
HYBRID DYSGENESIS IN DROSOPHILA MELANOGASTER: THE BIOLOGY OF FEMALE AND MALE STERILITY
Authors: Engels William R , Preston Christine R
Published: April 2021

High levels of female and male sterility were observed among the hybrids from one of the two reciprocal crosses between a wild strain of D. melanogaster known as π2 and laboratory strains. The sterility, which is part of a common syndrome called hybrid dysgenesis, was found to be associated with the rudimentary condition of one or both of the ovaries or testes. All other tissues, including those of the reproductive system were normal, as were longevity and mating behavior. The morphological details of the sterility closely mimic the agametic condition occurring when germ cells are destroyed by irradiation or by the maternal-effect mutation, grandchildless. We suggest that sterility in hybrid dysgenesis is also caused by failure in the early development of germ cells. There is a thermo-sensitive period beginning at approximately the time of initiation of mitosis among primordial germ cells a few hours before the egg hatches and ending during the early larval stages. Our results suggest that hybrid dysgenesis, which also includes male recombination, mutation and other traits, may be limited to the germ line, and that each of the primordial germ cells develops, or fails to develop, independently of the others. This hypothesis is consistent with the observed frequencies of unilateral and bilateral sterility, with the shape of the thermo-sensitivity curves and with the fact that males are less often sterile than females. The features of this intraspecific hybrid sterility are found to resemble those seen in some interspecific Drosophila hybrids, especially those from the cross D. melanogasfer × D. simulans.
A REFINED MAP OF THE hisG GENE OF SALMONELLA TYPHIMURIUM
Authors: Hoppe I , Johnston H M , Biek D , Roth J R
Published: April 2021

The hisG gene is the most operator-proximal structural gene of the histidine operon; it encodes the feedback-inhibitable first enzyme of the biosynthetic pathway. Previously, hisG mutants were mapped into seven intervals defined by the available deletion mutations having endpoints in the hisG gene. The map has been refined using over 60 new deletion mutants. The new map divides the gene into 41) deletion intervals, which average approximately 30 base pairs in length. The map has been used to analyze the distribution of insertion sites for the transposable element Tn10 and has permitted conclusions on the distribution of duplication endpoints. The map promises to be useful in analysis of his regulation and, more particularly, in the determination of the possible role of the hisG enzyme in this mechanism.
LYSOSOMAL DYSFUNCTIONS ASSOCIATED WITH MUTATIONS AT MOUSE PIGMENT GENES
Authors: Novak Edward K , Swank Richard T
Published: April 2021

Melanosomes and lysosomes share several structural and biosynthetic properties. Therefore, a large number of mouse pigment mutants were tested to determine whether genes affecting melanosome structure or function might also affect the lysosome. Among 31 mouse pigment mutants, six had 1.5- to 2.5- fold increased concentrations of kidney β-glucuronidase. Three mutants, pale ear, pearl and pallid, had a generalized effect on lysosomal enzymes since there were coordinate increases in kidney β-galactosidase and a-mannosidase. The effects of these three mutations are lysosome specific since rates of kidney protein synthesis and activities of three nonlysosomal kidney enzymes were normal. Also, the mutants are relatively tissue specific in that all had normal liver lysomal enzyme concentrations.—A common dysfunction in all three mutants was a lowered rate of lysosomal enzyme secretion from kidney into urine. While normal C57BL/6J mice daily secreted 27 to 30% of total kidney β-glucuronidase and β-galactosidase, secretion of these two enzymes was coordinately depressed to l to e%, 8 to 9% and 4 to 5% of total kidney enzyme in the pale-ear, pearl and pallid mutants, respectively. Although depressed lysosomal enzyme secretion is the major pigment mutant alteration, the higher lysomal enzyme concentrations in pearl and pallid may be partly due to an increase in lysosomal enzyme synthesis. In these mutants kidney glucuronidase synthetic rate was increased 1.4 to 1.5-fold.—These results suggest that there are several critical genes in mammals that control the biogenesis, processing and/or function of related classes of subcellular organelles. The mechanism of action of these genes is amenable to further analysis since they have been incorporated into congenic inbred strains of mice.
A NOTE ON EFFECTIVE POPULATION SIZE WITH OVERLAPPING GENERATIONS
Authors: Hill William G
Published: April 2021

A simple derivation is given far a formula obtained previously for the effective size of random-mating populations with overlapping generations. The effective papulation size is the same as that for a population with discrete generations having the same variance of lifetime family size and the same number of individuals entering the population per generation.
THE DYNAMICS OF FINITE HAPLOID POPULATIONS WITH OVERLAPPING GENERATIONS. II. THE DIFFUSION APPROXIMATION
Authors: Emigh Ted H
Published: April 2021

The dynamics of a gene in a haploid population can be explained approximately by considering the average reproductive value of the gene. The dynamics of the average reproductive value are similar to those of a gene in a population with nonoverlapping generations with the following modifications: The effective population size, Ne, replaces N; the average mutation rates,μ* and v* replace μ and v; the average overall selection r*+(T-l)s** replaces s; and time is measured in terms of generations, T. The implications of the average selection coefficient to adaptive life histones are discussed.
MUTAGENESIS BY CYTOSTATIC ALKYLATING AGENTS IN YEAST STRAINS OF DIFFERING REPAIR CAPACITIES
Authors: Ruhland Axel , Brendel Martin
Published: April 2021

Reversion of two nuclear ochre nonsense alleles and cell inactivation induced by mono-, bi-, and tri-functional alkylating agents and by UV has been investigated in stationary-phase haploid cells of yeast strains with differing capacities for DNA repair. The ability to survive alkylation damage is correlated with UV repair capacity, a UV-resistant and UV-mutable strain (RAD REV) being least and a UV-sensitive and UV-nonmutable strain (rad1 rev3) most sensitive. Mutagenicity of alkylating agents is highest in the former and is abolished in the latter strain. Deficiency in excision repair (radl rad2) or in the RAD18 function does not lead to enhanced mutability. Mutagenesis by the various agents is characterized by a common pattern of induction of locus-specific revertants and suppressor mutants. Induction kinetics are mostly linear, but UV-induced reversion in the RAD REV strain follows higher-than-linear (probably "quadratic") kinetics. The alkylating agent cyclophosphamide, usually considered inactive without metabolic conversion, reduces colony-forming ability and induces revertants in a manner similar but not identical to the other chemicals tested. These findings are taken to support the concept of mutagenesis by misrepair after alkylation, which albeit sharing common features with the mechanism of UV-induced reversion, can be distinguished therefrom.
ULTRAVIOLET-INDUCED REVERSION OF cyc1 ALLELES IN RADIATION-SENSITIVE STRAINS OF YEAST. III. rev3 MUTANT STRAINS
Authors: Lawrence Christopher W , Christensen Roshan B
Published: April 2021

The role of the REV3 gene function in UV-induced mutagensis in the yeast Saccharomyces cerevisiae has been examined by determining the reversion of 12 well-defined cycl mutations in diploid strains homozygous for the rev3—1 or rev3—3 allele. The 12 cycl alleles include one ochre, one amber, four initiation, two proline missense, and four frameshift mutations. We find that the rev3 mutations reduce the frequency of UV-induced reversion of all of the cycl alleles, though different classes of alleles respond to a different extent. These results imply that the REV3 gene function is required for the production of a wide variety of mutational events, though probably not all, and show that each of the three REV loci have different mutational phenotypes. Such diverse phenotypes are not predicted by the unitary model for bacterial mutagenesis (CAILLET-FAUQUET, DEFAIS and RADMAN 1977; WITKIN 1976), suggesting that this is at best an incomplete description of eukaryotic mutagenesis.
CORRELATIONS BETWEEN CHROMOSOME SEGMENTS AND FITNESS IN DROSOPHILA MELANOGASTER. II. THE X CHROMOSOME AND EGG VIABILITY
Authors: Chapco William
Published: April 2021

Unmarked segments within the X chromosomes of four different Drosophila melanogaster isogenic lines were assessed with respect to egg-to-adult viability. The results were compared with those of an earlier study involving egg production. All segments influence both traits, but to extents that are dependent upon the strains being compared. Segmental effects are also a function of the genetical background, which, in this case, constitutes material within the same chromowme. With respect to both traits, the segments are not necessarily parallel in their effects. A segment that increases fecundity, for example, may or may not augment viability. The possibility of manipulating chromosomal segments to improve "yield" in organisms is explored.
THE PROPHAGE OF SPβc2dcitK1, A DEFECTIVE SPECIALIZED TRANSDUCING PHAGE OF BACILLUS SUBTILIS
Authors: Rosenthal Richard , Toye Patryce A , Korman Ruth Z , Zahler Stanley A
Published: April 2021

The defective specialized transducing phage SPβc2dcitK1 carries two known bacterial genes, kauA and citK, as well as SPβ phage markers including the heat-sensitive repressor allele, c2. Some phage genes (including essential ones) are missing. When SPβc2dcitK1 transduces SPβ-sensitive cells of Bacillus subtilis, the defective prophage is inserted into sites in the homologous bacterial DNA of the attSPβ-kauA-citK region of the recipient chromosome. During the growth of these transductants, occasional excisions occur that result in the loss of the phage genes and OI the heterogenotic state. These excisions increase greatly in frequency during growth at repressor-inactivating temperatures. The kinds of insertions and excisions seen suggest that a Campbell-type (CAMPBELL 1962) circular phage genome may occur transiently. If the transductants are superinfected by SPβc2 or by the clear-plaque mutant SPβc1, the resulting double lysogen can be heat induced to release high-frequency of-transduction (HFT) lysates for kauA and citK.
A MUTATOR AFFECTING THE REGION OF THE ISO-1-CYTOCHROME c GENE IN YEAST
Authors: Liebman Susan W , Singh Arjun , Sherman Fred
Published: April 2021

The mutator gene DEL1 in the yeast Saccharomyces cerevisiae cauces a high rate of formation of multisite mutations that encompass the following three adjacent genes: CYC1, which determines the structure of iso-l-cyto-chrome c; RAD7, which controls UV sensitivity; and OSM1, which controls osomotic sensitivity. The simplest hypothesis is that these multisite mutations are deletions, although it has not been excluded that they may involve other types of gross chromosomal aberrations. In contrast, normal strains do not produce such multisite mutations even after mutagenic treatments.——The multisite mutations arise at a rate of approximately 10-5 to 10-6 per cell per division in DEL1 strains, which is much higher than rates observed for mutation of genes in normal strains. For example, normal strains produce all types of cycl mutants at a low rate of approximately 10-8 to 10-9. No evidence for multisite mutations was obtained upon analysis of numerous spontaneous adel, ade2, met2 and met15 mutants isolated in a DEL1 strain. DEL1 segregates as a single Mendelian gene closely linked to the CYC1 locus. DEL1 appears to be both cis- and trans-dominant. The location of the DEL1 gene and the lack of effect on other genes suggest that the mutator acts only on a region adjacent to itself.
GENETIC INSTABILITY IN DROSOPHILA MELANOGASTER: THE INDUCTION OF SPECIFIC CHROMOSOME 2 DELETIONS BY MR ELEMENTS
Authors: Green M M , Shepherd S H Y
Published: April 2021

We describe the spontaneous induction of deletions by MR elements at the l(2)gl, net, pr and cn loci. The frequent induction of l(2)gl deletions mimics the high frequency of l(2)gl alleles found in wild populations of D. melanogaster. We suggest that these and other data that we present militate far the conclusion that, in the wild, autonomous MR elements occur and function as mutators. We contend that MR elements are not simply the by-products of hybridization between wild and laboratory strains.
SPONTANEOUS UNEQUAL EXCHANGE IN THE ROSY REGION OF DROSOPHILA MELANOGASTER
Authors: Gelbart William M , Chovnick Arthur
Published: April 2021

A selective system for recovery of exchanges between trans mutations at adjacent loci, l(3)S12 and rosy, is described. In addition to the expected cross-over and conversion classes, two exceptional types of offspring were recovered. Triploid offspring arose as 0.01% of all zygotes; the diploid chromosome set was apparently of maternal origin. Nine tandem duplications derived from unequal exchange between nonsister homologues were recovered among 2.25 × 106 zygotes screened. From considerations of the proportion of the genome that was assayed in this system, and on the assumption that the rate of unequal exchange observed is typical for the genome as a whole, it appears that one unequal exchange occurs per 500 female meioses in Drosophila.
TWO NEW B-10 TRANSLOCATIONS INVOLVED IN THE CONTROL OF NONDISJUNCTION OF THE B CHROMOSOME IN MAIZE
Authors: Lin Bor-Yaw
Published: April 2021

A B-A translocation, TB-1O(18), has been established involving breakpoints in the proximal region of the long arm of chromosome 1O and the minute short arm of the maize B chromosome. TB-l0(18) differs in its nondisjunctional behavior at the second microspore division froin TB-10(19), which has a breakpoint in the same region of IO but in the heterochromatic region of the long arm of B, in the following ways: (1) Nondisjunction of the B10 chromosome of the TB-l0(18) translocation occurs in the absence of the reciprocal element (10B), albeit at low frequency. (2) Presence of 1OB increases the frequency of B10 nondisjunction but not tc the level found for TB-l0(19) and certain other translocations. (3) The frequency of B10 nondisjunction varies among closely related sublines both when 1OB is present and when it is absent. It is inferred that the B10 of TB-lO(18) carries all the components of B necessary for nondisjunction but that expression is weak in the absence of 10B, suggesting the existence in the B chromosome short arm of a factor influencing efficient nondisjunction.
ENZYME POLYMORPHISM AND CYCLIC PARTHENOGENESIS IN DAPHNIA MAGNA. I. SELECTION AND CLONAL DIVERSITY
Authors: Young J P W
Published: April 2021

Genotype frequencies and fecundities were recorded over a period of two years for three polymorphic enzyme loci (Est, Mdh and Got) in a parthenogenetic natural population of Daphnia magna Straus (Crustacea: Cladocera) . There was a large excess of heterozygotes at each locus, and some nonrandom association between loci, although 29 different three-locus genotypes were detected. There were small but significant changes in genotype frequencies that did not follow any clear seasonal cycles or overall trends, and the genotypes often differed significantly in fecundity, although the direction of the difference was not constant. These fitness differences were probably not attributable to the specific loci studied.—Models of balancing selection are of two types: segregation-balanced (e.g., heterosis) and competition-balanced (e.g., frequency dependence). Only the latter type can stabilize diversity in a clonal population. The observed selection was not heterotic, but it is not certain that it was stabilizing either. Clonal competition did not lead to victory by a single, fittest clone; genotypic diversity remained high.