bluuebunny/crossref_metadata_2025_split huggingface dataset:
ERRORS IN THE ELIMINATION OF X CHROMOSOMES IN SCIARA OCELLARIS
Authors: Mori Lyria , Perondini A L P 
Published: April 2021

ABSTRACT
It was previously assumed that the X-linked recessive mutation, sepia, induced errors in X-chromosome elimination during early embryogenesis of Sciam ocellaris. The results obtained in the present analysis corroborate this assumption and permit a further classification of the type of error this mutation induces. Among 85,244individuals analyzed, three kinds of aberrant flies were identified: mosaics (0.01 %), gynandromorphs (0.42%)and phenotypically exceptional individuals (0.25%).The origin ofthese abnormal flies could be ascribed to errors in selective elimination of X chromosomes that occur in male meiosis or during the early cleavages of the zygote nuclei. This last kind of error could be classified into three types: (a) error in number, (b) error in type, and (c) error in number and type of X chromosome eliminated. Evidence is provided indicating that sepia has no direct effect on the X chromosome; it has a maternal influence and exerts its effect only in the heterozygous condition.
MUTANTS SHOWING HETEROTHALLISM FROM A HOMOTHALLIC STRAIN OF SACCHAROMYCES CEREVISIAE
Authors: Oshima Takehiro , Takano Isamu 
Published: April 2021

ABSTRACT
Mutants defective in mating-type conversion were isolated from ascospores of a perfect homothallism strain having the HO HMRa HMLα genotype. Eighty mutants, including 11 temperature-dependent mutants showing a or α mating potency, were isolated from 10,050 colonies derived from spores mutagenized with ethyl methanesulfonate. Of the 80 mutants, 48 were tested by crossing with an Ho HMRa HMLα heterothallic and an HO HMRa HMLα homothallic strain as standards. The results allowed their division into seven classes. Mutants in the first class were due to mutation of HO to an ho allele. The second class of mutants, csm, lacked the HO function as the result of a mutation unlinked with the HO locus. Mutants in the third and fourth classes were defective in HMRa and HMLα gene functions, respectively. Mutants in the fifth and sixth classes were due to a mutation at the mating-type locus showing iwensitivity to the function of the homothallic genes. Mutants in the seventh class lacked the expression of mating type as the result of a mutation unlinked to the mating-type locus. All the temperature-dependent mutants lost the mating potency at permissive temperature (25°). One belonging to the last class of mutants was inferred to be a mutation at a locus necessary for the expression of a mating type at restricted temperature (35°).
ALTERNATIVE PHENOTYPIC STATES IN GENOMICALLY IDENTICAL CELLS: INTERSTOCK GENETICS OF A TRICHOCYST PHENOTYPE IN PARAMECIUM TETRAURELIA
Authors: Nyberg Dennis 
Published: April 2021

ABSTRACT
The trichocysts of most wild stocks of Paramecium tetraurelia discharge en masse in response to picric acid. In most nonresponding wild stocks, the defective phenotype is simply determined by a single recessive gene difference from the standard wild type, stock 51. However, two wild stocks, 146 and 148, which are completely homozygous at all loci, eqress either a nondischarge, ND, or discharge, DI, phenotype. In stock 146, both ND and DI sublines generally reproduce true to type, but observed changes are highly biased. Changes from ND to DI occur more than ten times as often as changes from DI to ND. After conjugation between ND and DI cells, genomically identical exconjugant lines from the ND parent may be either ND or DI, while thme from the DI parent invariably remain D1.—Interstock crosses between stocks 146 and 51 indicate that stock 146 possesses a recessive gene, nd146, which, when hommygous in stock 51 background, produces a distinct nondischarge phenotype, KO. Crosses between stock 146 and KO phenotype nd146 homozygotes in stock 51 background demonstrate that stock 146 possesses a dominant gene, M-ndl46, which modifies the defect of nd146 homozygotes, resulting in either the ND or DI phenotype. The two loci, M-ndl46 and nd146, are linked and estimated to be 5.3 centiMorgans apart. Stock 148 has the same alleles as stock 146 at these loci.—Presumably M-nd146 is involved in the dual phenotypic states in stock 146, but M-ndl46 nd146 homozygotes backcrossed into stock 51 are invariably discharging. The possibility that the original ND state is independent of these genes is discussed and is regarded as unlikely. The phenotypic and genetic relationship discovered in these stocks should remind population biologists that phenotypic and genotypic variability do not always have a simple relationship. The nature and frequency of epistasis in the highly inbreeding P . teiraurelia are reviewed.
INHERITANCE OF A PAROTID SECRETORY PROTEIN IN MICE AND ITS USE IN DETERMINING SALIVARY AMYLASE QUANTITATIVE VARIANTS
Authors: Owerbach David , Hjorth J Peter 
Published: April 2021

ABSTRACT
Among inbred strains of mice, a major protein, PSP, produced and secreted by the parotid glands, shows variation in electrophoretic mobility and in the peptides produced by cyanogen bromide treatment. This variation is inherited as a single Mendelian factor with two alleles showing co-dominant expression. In genetic crosses, it segregates independently from the amylase complex and is closely linked to the agouti locus on chromosome 2. The protein ratios between amylase and PSP in saliva, obtained by scanning of electrophoretic gel separations, were found to reflect genetic differences in salivary amylase production in strains YBR/Cv and C3H/As.
VARIATION IN ACTIVITIES OF AMYLASE ALLOZYMES ASSOCIATED WITH CHROMOSOME INVERSIONS IN DROSOPHILA PSEUDOOBSCURA, D. PERSIMILIS AND D. MIRANDA
Authors: Norman R A , Prakash Satya 
Published: April 2021

ABSTRACT
Different electrophoretic alleles of amylase show associations with particular chromosome 3 inversions in D. pseudoobscura and D. persimilis. Relative adult amylase activities were compared in 37, 37and 10 strains of D. pseudoobscura, D. persimilis and D. miranda, respectively. Strains carrying the same electrophoretic allele were compared by crossing these lines individually to a reference strain carrying a different electrophoretic mobility allele. This procedure allows comparisons among species, inversions, electromorphs and strains for genetic variation in amylase activity. F2analysis established that the activity variation co-segregates with the structural amylase locus. This type of variation could be due to either structural gene differences or differences in closely linked, cis-acting regulatory regions. Variation has been detected among and within electrophoretic mobility classes. Moreover, this variation is clearly nonrandom and reveals more of the genetic structure associated with the chromosomal inversion phylogeny of D. pseudoobscura and D. persimilis. —Some of the findings are: (1) Similar electromorphs in D. pseudoobscura and D. persimilis usually show different activities. These species show nearly complete differentiation of amylase alleles, based on activities. (2) D. persimilis has the broadest range of variation in amylase activity, about four-fold between the highest and lowest alleles. D. pseudoobscura and D. miranda are also polymorphic for activity, but have more constrained ranges of variation. D. miranda alleles show on the average about four times the activity of D. pseudoobscura alleles. (3) Some association of electrophoretic mobility and activity has been found. Alleles 1.09 of D. persimilis, as well as 1.43 and 1.55 of D. miranda, have relatively high activity. It may be that these high activity alleles are part of an adaptation to cooler habitats. (4)Within electrophoretic classes, associations of activities with inversions have been found. These are especially strong in D. persimilis. The 1.00 alleles in the ST, KL,MD and WT inversions, the 0.92 allele in the ST and MD inversions and the 1.09 allele in the WT and KLinversions have levels of activities that depend upon the arrangement in which they are located. These results demonstrate that suppression of recombination in inversion heterokaryotypes can result inextensive genic divergence between inversions.
CHROMOSOME STUDIES IN WILD POPULATIONS OF DROSOPHILA MELANOGASTER. II. RELATIONSHIP OF INVERSION FREQUENCIES TO LATITUDE, SEASON, WING-LOADING AND FLIGHT ACTIVITY
Authors: Stalker Harrison D 
Published: April 2021

ABSTRACT
In the midwestern and eastern U.S. populations of Drosophila melanogaster, the Standard gene arrangements show higher frequencies in the north than in the south. In a Missouri population, and to a lesser extent in a south Texas population, the frequencies of Standard chromosomes regularly rise during the cold season and drop during the warm season, thus paralleling the north-south frequency differences. In the Missouri population in 1976 and 1978, wild males were tested far their ability to fly to bait at different ambient temperatures. In both years, males flying in nature in the temperature range of 13° to 15° showed significantly higher frequencies of Standard chromosomes than did those flying in the 16° to 28° range. Wild males flying at 13° to 15° also have different tharax/wing proportions and significantly lower wingloading indices than do those flying at 16° to 28°. Moreover, wild flies homozygous Standard in 2R and/or 3R have significantly lower wing-loading indices than flies carrying inversions in these arms. Thus, wild flies with high frequencies of Standard chromosommes are karyotypically northern, are selectively favored during the cold season, have a relatively low wing-load and are most capable of flying at critically low ambient temperatures.—In summary, in Missouri, presence or absence of the common cosmopolitan inversions is an important factor in low temperature adaptation, and at least part of the adaptive mechanism involves control of thorax/wing proportions and thus control of wing-loading.
THE SELECTION OF AMBER MUTATIONS IN GENES REQUIRED FOR COMPLETION OF START, THE CONTROLLING EVENT OF THE CELL DIVISION CYCLE OF S. CEREVISIAE
Authors: Reed Steven I 
Published: April 2021

ABSTRACT
Using a modification of a procedure developed for the isolation of temperature-sensitive mutants defective in the start event of cell division, amber mutations were obtained for two Class-I start genes, cdc28 and cdc37. Genetic analysis demonstrated that co-segregation of an amber suppressor with such alleles was required for viability of spores subsequent to meiosis. These mutations are expected to be useful in the identification of the molecular products of the genes cdc28 and cdc37.
UNEQUAL CROSSING OVER AT THE rRNA TANDON AS A SOURCE OF QUANTITATIVE GENETIC VARIATION IN DROSOPHILA
Authors: Frankham R , Briscoe D A , Nurthen R K 
Published: April 2021

ABSTRACT
Abdominal bristle selection lines (three high and three low) and controls were founded from a marked homozygous line to measure the contribution of sex-linked "mutations" to selection response. Two of the low lines exhibited a period of rapid response to selection in females, but not in males. There were corresponding changes in female variance, in heritabilities in females, in the sex ratio (a deficiency of females) and in fitness, as well as the appearance of a mutant phenotype in females of one line. All of these changes were due to bb alleles (partial deficiencies for the rRNA tandon) in the X chromosomes of these lines, while the Y chromosomes remained wild-type bb+. We argue that the bb alleles arose by unequal crossing over in the rRNA tandon.—A prediction of this hypothesis is that further changes can occur in the rRNA tandon as selection is continued. This has now been shown to occur.—Our minimum estimate of the rate of occurrence of changes at the rRNA tandon is 3 × 10-4. As this is substantially higher than conventional mutation rates, the questions of the mechanisms and rates of origin of new quantitative genetic variation require careful re-examination.
TRANSLATIONAL COUPLING DURING EXPRESSION OF THE TRYPTOPHAN OPERON OF ESCHERICHIA COLI
Authors: Oppenheim Daniel S , Yanofsky Charles 
Published: April 2021

ABSTRACT
E. coli trpE polar mutations are 10 times more polar on trpD gene expression than on downstream (trpC, B, or A) gene expression. This effect was shown to be the result of "translational coupling," in which efficient translation of trpD mRNA reqiures efficient translation of the end of trpE mRNA. The trpE-trpD intercistronic punctuation region consists of overlapping stop and start codons, and the trpE and trpD gene products form a functional complex in the cell. In light of these observations and characteristics, several models for the mechanism of translational coupling are considered.
INTRACELLULAR POPULATION GENETICS: EVIDENCE FOR RANDOM DRIFT OF MITOCHONDRIAL ALLELE FREQUENCIES IN SACCHAROMYCES CEREVISIAE AND SCHIZOSACCHAROMYCES POMBE
Authors: Thrailkill Kathryn M , Birky C William , Lückemann Gudrun , Wolf Klaus 
Published: April 2021

ABSTRACT
We report evidence for random drift of mitochondrial allele frequencies in zygote clones of Saccharomyces cerevisiae and Schizosaccharomyces pombe. Monofactorial and bifactorial crosses were done, using strains resistant or sensitive to erythromycin (alleles ER, ES), oligomycin (OR, OS), or diuron (DR, DS). The frequencies of resistant and sensitive cells (and thus the frequencies of the resistant and sensitive alleles) were determined for each of a number of clones of diploid cells arising from individual zygotes. Allele frequencies were extremely variable among these zygote clones; some clones were "uniparental," with mitochondrial alleles from only one parent present. These observations suggest random drift of the allele frequencies in the population of mitochondrial genes within an individual zygote and its diploid progeny. Drift would cease when all the cells in a clone become homoplasmic, due to segregation of the mitochondrial genomes during vegetative cell divisions. To test this, we delayed cell division (and hence segregation) for varying times by starving zygotes in order to give drift more time to operate. As predicted, delaying cell division resulted in an increase in the variance of allele frequencies among the zygote clones and an increase in the proportion of uniparental zygote clones. The changes in form of the allele frequency distributions resembled those seen during random drift in finite Mendelian populations. In bifactorial crosses, genotypes as well as individual alleles were fixed or lost in some zygote clones. However, the mean recombination frequency for a large number of clones did not increase when cell division was delayed. Several possible molecular mechanisms for intracellular random drift are discussed.
INDUCTION AND SEGREGATION OF CHLOROPLAST MUTATIONS IN VEGETATIVE CELL CULTURES OF CHLAMYDOMONAS REINHARDTII
Authors: Lee Robert W , Haughn George W 
Published: April 2021

ABSTRACT
The single chloroplast of the alga Chlamydomonas reinhardtii contains at least 100 copies of the chloroplast chromosome. It is not known how the chloroplast (or cell) becomes homoplasmic for a mutation that arises in one of these copies. Under suitable selection conditions, clones with chloroplast mutations for streptomycin resistance induced by methyl methanesulfonate can be recovered with direct plating after mutagenesis. Using an adaptation of the Luria-Delbrück fluctuation test, mutagenized cultures grown on nonselective liquid medium for seven to nine doublings show negligible proliferation of cells capable of forming such mutant colonies. In contrast, cells among the same cultures with reduced nuclear mutations conferring streptomycin resistance reveal considerable clonal propagation prior to plating on selection medium. Reconstruction growth-rate experiments show no reduced growth of cells with chloroplast mutations relative to either wild-type cells or to those with nuclear mutations. We propose that newly arising chloroplast mutations and their copies are usually transmitted to only one daughter cell for several cell generations by reductional divisions of the chloroplast genome. In the absence of recombination and mixing, such a reductional partition of chloroplast alleles would readily permit the formation of homoplasmic lines without the need for selection.
PROTOPLASMIC INCOMPATIBILITY IN PODOSPORA ANSERINA: A POSSIBLE FUNCTION FOR INCOMPATIBILITY GENES
Authors: Boucherie Hélian , Bernet Jean 
Published: April 2021

ABSTRACT
The suppression of protoplasmic incompatibility resulting from nonallelic gene interactions has been obtained by the coupled effect of mutations in the modA and modB genes (Bernet 1971). Due to their female sterility, modA modB strains provide an experimental tool to determine whether or not the mod and incompatibility loci are involved in a function other than protoplasmic incompatibility. Present results show that modA modB female sterility is a nonautonomous trait since heterokaryotic mycelia that include a modA modB nucleus and a female fertile nucleus (wild-type, modA or modB) produce modA modB protoperithecia, which are also formed by culture on medium supplemented with specific amino acids. Using modA modB strains, which are sterile at 32° and fertile at 26°, we have shown that the mod genes have no specific sequential timing. Indeed, the mod mutations may prevent the achievement of the female sexual cycle at any developmental stage from before early differentiation of protoperithecia until ascospore maturation. Employing different modA and modB mutations, we have shown that protoperithecia in modA modB cultures are generally distributed in female fertile rings; this result indicates that protoperithecia occur only in mycelial areas that have a restricted range of age at the time that modA modB thalli complete growth. Furthermore, nonsense mutations of incompatibility genes suppress the modA modB female fertile rings or restrict their width, suggesting that incompatibility loci, like the mod loci, are involved in protoperithecium formation. Taken together, these results lead to the postulate that mod and incompatibility genes do not determine, sensu stricto, protoperithecial function, as previously supposed (Boucherie and Bernet 1974), but may be involved in the homeostatic control of stationary cell functions essential for the complete development of the female sexual cycle.
HIGH MUTABILITY IN MALE HYBRIDS OF DROSOPHILA MELANOGASTER
Authors: Simmons Michael J , Johnson Nancy A , Fahey Thomas M , Nellett Sue M , Raymond John D 
Published: April 2021

ABSTRACT
The frequencies of sex-linked lethal mutations arising in hybrid male offspring from various crosses and in nonhybrid controls were determined. The hybrids were produced by crossing representative strains of the P-M system of hybrid dysgenesis in all possible combinations. Males from the cross of P males × M females had a mutation rate about 15 times higher than that of nonhybrid males from the P strain. Genetically identical males from the reciprocal cross had a mutation rate 3 to 4 times that of the nonhybrids. For crosses involving a Q strain, a significant increase in the mutation rate was detected in males produced by matings of Q males with M females. No increase was observed in genetically identical males from the reciprocal mating. Crosses between P and Q strains gave male hybrids with mutation rates not different from those of nonhybrids. Many of the lethals that occurred in hybrids from the cross of P males × M females appeared to be unstable; fewer lethals that arose in hybrids from the cross of Q males × M females were unstable. The relationship between P and Q strains is discussed with respect to a model of mutation induction in dysgenic hybrids.
LINKAGE DISEQUILIBRIUM IN ISOLATED POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Yamaguchi Osamu , Ichinose Motoshi , Matsuda Muneo , Mukai Terumi 
Published: April 2021

ABSTRACT
In order to test the interaction effect of overdominance and random genetic drift on the formation of linkage disequilibria under the condition of multiplicative gene action, linkage disequilibria between isozyme genes, inter se, and between polymorphic inversions and isozyme genes were tested for the second chromosomes of Drosophila melanogaster sampled from two isolated Pacific islands and one locality of the northern district of the mainlands of Japan. The effective sizes of these populations were known to be approximately 3,000 to 6,000 on the basis of the allelism rate of lethal chromosomes and their frequencies. The following results were obtained: (1) No linkage disequilibrium considered to be induced by epistasis, including the interaction between overdominance and random genetic drift, was detected. (2) Nonrandom association between polymorphic inversions and isozyme genes that are included in the inversions or located in the adjacent region outside the inversions was detected. (3) On the basis of the comparison of χ2 values, indicating the magnitudes of linkage disequilibrium, between the present isolated populations and the Raleigh, N. C., population (Mukai et al. 1974, 1977), the characteristics of the isolated populations and the nature of these linkage disequilibria are discussed.
ASSOCIATION OF DISOMIC CHROMOSOME LOSS WITH EMS-INDUCED CONVERSION IN YEAST
Authors: Campbell Douglas 
Published: April 2021

ABSTRACT
Experimental tests with the yeast Saccharomyces cerevisiae of a previously proposed model suggesting a causal relationship between disomic chromosome loss (n + 1 → n) and centromere-adjacent mitotic gene conversion were performed. Disomic haploid cells heteroallelic at two loci on the left arm of chromosome III were exposed to ethyl methanesulfonate (EMS) under nonlethal conditions; EMS-induced prototrophic gene convertants were selected and tested for coincident chromosome loss. The principal results are: (1) The frequency of chromosome loss among EMS-induced gene convertants selected to arise near the centromere is markedly enhanced over basal levels and remains constant, independent of EMS exposure. There is little such enhancement among EMS-induced convertants selected to arise far from the centromere. (2) Chromosome loss is almost completely associated with induced conversion of the centromere-proximal allele at the centromere-adjacent heteroallelic locus. This result is identical to (and confirms) results found previously for spontaneous loss-associated conversion. (3) The conversion polarity at the centromere-adjacent locus among unselected (nonloss-associated) induced or spontaneous mitotic convertants is identical to that among meiotic convertants and markedly favors the contromere-distal allele. These findings are wholly consistent with, and strengthen, the hypothesis that structural involvement of centromeric regions in nearby recombinational events may interfere with proper segregational function and lead to mitotic chromosome loss.
ULTRASTRUCTURAL ANALYSIS OF SPERMIOGENESIS IN SEGREGATION DISTORTER MALES OF DROSOPHILA MELANOGASTER: THE HOMOZYGOTES
Authors: Kettaneh Nizam P , Hartl Daniel L 
Published: April 2021

ABSTRACT
We have studied spermiogenesis at the ultrastructural level in males of genotype SD(NH)-2/SD-72, which are nearly sterile owing to the dysfunction of virtually all of their sperm. Ultrastructural aspects of spermiogenesis in these homozygous SD males are qualitatively similar to those found among dysfunctional sperm produced by heterozygous SD males. In particular, chromatin condensation and/or compaction has been found to be abnormal. However, major quantitative differences have been noted. Most of the dysfunctional sperm in SD(NH)-2/SD-72 males are individualized and coiled. Then, the sperm evidently undergo degeneration, as few mature sperm can be found in the seminal vesicle. The relevance of these findings to the mechanism leading to near sterility in homozygous SD males is discussed.