bluuebunny/crossref_metadata_2025_split huggingface dataset:
GENETIC DETERMINATION OF THE DEVELOPMENTAL PROGRAM FOR MOUSE LIVER β-GALACTOSIDASE: INVOLVEMENT OF SITES PROXIMATE TO AND DISTANT FROM THE STRUCTURAL GENE
Authors: Berger Franklin G , Breen Gail A M , Paigen Kenneth 
Published: April 2021

ABSTRACT
The identification and mode of action of genetic loci that program gene expression during development are important for understanding differentiation in higher organisms. Previous work from this laboratory has identified two patterns for the postnatal development of liver β-galactosidase among inbred mouse strains: type I, where activity levels remain constant after about 30 days of age, is found in strains DBA/BJ, CBA/J, and BALB/cJ, among others; type 11, where activity levels increase between 25 and 50 days of age to reach a new adult level, is found in strain C57BL/6J and related strains. It has been shown that the type I vs. type II developmental difference between strains C57BL/6S and DBA/2J is due to variation at a locus, Bgl-t, that maps with the β-galactosidase complex, [Bgl], on chromosome 9. In the present study, we have confirmed the existence of Bgl-t as a temporal locus within [Bgl] by analysis of both a congenic strain carrying the β-galactosidase complex of strain CBA/J in the C57BL/6J genetic background and a cross of strains CBA/J and C57BL/6J. The existence of additional temporal loci for β-galactosidase that segregate independently of the structural gene and participate in determination of the type I vs. type II difference was revealed by analysis of: (1) a congenic strain containing the β-galactosidase complex of strain BALB/cJ in the C57BL/lOSn background; (2) recombinant inbred lines derived from progenitor strains C57BL/6ByJ and BALB/cByJ; and (3) a genetic cross between strains C57BL/6ByJ and BALB/cByJ. Thus, for these pairs of strains, the type I us. type II developmental difference is due to variation at a temporal locus (or loci) unlinked to the enzyme structural gene, and not at Bgl-t. These facts, together with information gathered from an examination of the distribution of β-galactosidase phenotypes among over 100 inbred strains (BREEN, LUSIS and PAIGEN 1977), have led us to conclude that the postnatal developmental pattern for liver β-galactosidase is determined by a set of interacting temporal genes. One of these, Bgl-t, is located within [Bgl], and one or more are separable from [Bgl] by recombination. A possible mode of interaction among the temporal and structural loci is suggested.
ON THE NATURE OF SISTER-CHROMATID EXCHANGES IN 5-BROMODEOXYURIDINE-SUBSTITUTED CHROMOSOMES
Authors: Schvartzman J B , Cortés F , González-Fernández A , Gutiérrez C , LÓpez-Sáez J F 
Published: April 2021

ABSTRACT
Sister-chromatid exchanges (SCE) were studied in Allium cepa L. meristematic cells at the second and third divisions after BrdUrd-substitution during just the first or during the second and third cycles, respectively. The observed SCE nonreciprocal/reciprocal ratios detected at the third division in both experiments, as well as comparison of the lowest SCE frequency observed per cycle and expressed per picogram of DNA with data from different species expressed accordingly, strongly suggest that most of the exchanges detected in BrdUrd-substituted chromosomes are BrdUrd-dependent events. Hypotheses suggesting some different mechanisms are discussed to explain the formation of these BrdUrd-dependent SCEs.
ALLOZYMIC VARIATION AND LINKAGE DISEQUILIBRIUM IN SOME LABORATORY POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Laurie-Ahlberg C C , Weir B S 
Published: April 2021

ABSTRACT
Nine laboratory populations of D. melanogaster were surveyed by starch gel electrophoresis for variation at 17 enzyme loci. A single-fly extract could be assayed for all 17 enzymes, so that the data consist of 17-locus genotypes.— Pairwise linkage disequilibria were estimated from the multilocus genotypic frequencies, using both BURROWS' and HILL'S methods. Large amounts of link-age disequilibrium were found, in contrast to the results reported for natural populations.—Knowledge of the approximate sizes of these populations was used to compare the observed heterozygosities and linkage disequilibria with predictions of the neutral allele hypothesis. The relatively large amount of linkage disequilibrium is consistent with the small sizes of the populations. However, the levels of heterozygosity in at least some populations suggest that some mechanism has been operating to retard the rate of decay by random drift. Several examples of significant deviation from Hardy-Weinberg frequencies and the large amount of linkage disequilibnim present in these populations indicate that a likely mechanism is selective effects associated with neutral alleles because of linkage disequilibrium with selected loci (e.g., "associative overdominance"). The results are therefore consistent with both neutralist, and selectionist hypotheses, but suggest the importance of considering linkage disequilibrium between neutral and selected loci when attempting to explain the dynamics of enzyme polymorphisms.
THE BAM H1 RESTRICTION SITE IN THE BACTERIOPHAGE T4 CHROMOSOME IS LOCATED IN OR NEAR GENE 8
Authors: Wilson Geoffrey G , Neve Rachael L , Edlin Gordon J , Konigsberg William H 
Published: April 2021

ABSTRACT
Bacteriophage T4 cytosine-containing DNA is cleaved at a single site by the restriction endonuclease, Bam H1. The site lies within the late region of the T4 genome, close to, or within, gene 8, one of the structural genes of the phage particle baseplate.
GENETIC MODULATION OF RNA METABOLISM IN DROSOPHILA. III. REQUIREMENT FOR AN rDNA-DEFICIENT X CHROMOSOME IN YbbSuVar–5-MEDIATED INCREASES IN RNA SYNTHESIS
Authors: Strausbaugh Linda D , Kiefer Barry I 
Published: April 2021

ABSTRACT
Males of the genotype car bb/YbbSuVar-5 have an approximately two-fold increase in the rate of accumulation of 4S, 5S, 18s + 28s and poly-A+ RNA molecules when compared to males of the genotype car bb/Ybb- (CLARK, STRAUSBAUGH and KIEFER 1977; CLARK and KIEFER 1977). Experiments were designed to determine if the modulation of RNA metabolism by YbbSuVar-5 requires an rDNA deficiency on the X chromosome. Synthetic rates for 4S, 5S, and 18s + 28s RNA's were measured in the genotypes Sam+iso/Ybb- and Sam+iso/Ybbsuvar-5 by injecting adult males with 3H-uridine, allowing them to incorporate label for two hours, fractionating extracted RNA by polyacrylamide gel electrophoresis and determining the specific activities of RNA's (dpm/μgRNA). The results of these determinations showed that the synthetic rates for 4S, 5S, and 18s + 28S RNA's are the same in these two genotypes, demonstrating that the YbbSuVar-5 chromosome does not increase transcription when paired with an X chromosome that is wild type for rDNA. Saturation hybridization was used to measure the rDNA content in several genotypes. These results showed that Sam+iso/YbbSuVar-5 males and Sam+iso/Ybb- males have equivalent amounts of rDNA.—These results are consistent with the suggestion that the Ybb- and YbbSuVar-5 chromosomes have similar amounts of rDNA. The nature of compensatory strategies in rDNA-deficient genotypes is discussed.
INTERCHROMOSOMAL EFFECTS OF HETEROCHROMATIC DELETIONS ON RECOMBINATION IN DROSOPHILA MELANOGASTER
Authors: Yamamoto Masatoshi 
Published: April 2021

ABSTRACT
It is now known that partial deletions of the satellite sequences in X - chromosome heterochromatin result in a significant decrease in intrachromosoma1 recombination in the proximal region of the X chromosome of D. melanogaster (YAMAMOTO and MIKLOS 1978). It is important to ask then if the loss or gain of heterochromatin on the X also alters recombination in other chromosomes of the genome (interchromosomal effects). I have looked for such alterations by measuring recombination in chromosome 3. The results clearly indicate that the partial loss of X-chromosome heterochromatin not only decreases crossing over in the proximal region of the X chromosome itself, but also increases the frequency in chromosome 3. especially in the euchromatic regions around the centromere. Furthermore, the greater the deficiency of X heterochromatin, the higher is recombination in chromosome 3. This finding not only provides further evidence in support of the hypothesis that heterochromatin, in this case mainly composed of satellite DNA, regulates the recombination system, but it demonstrates that when the satellite content of one chromosome of the D. melanogasier genome is altered, there is an alteration in the crossover characteristics of other chromosomes in the same complement. If the amount of satellite DNA in a genome is being continuously altered, then one can predict that the recombination system is also being continually perturbed. Thus, the changing gene Combinations produced indirectly by increases or decreases of heterochromatin are among the components available to organisms to break up or form new gene combinations upon which se!ection can act.
FISSION MODELS OF POPULATION VARIABILITY
Authors: Thompson E A 
Published: April 2021

ABSTRACT
Most models in population genetics are models of allele frequency, making implicit or explicit assumptions of equilibrium or constant population size. In recent papers, we have attempted to develop more appropriate models for the analysis of rare variant data in South American Indian tribes; these are branching process models for the total number of replicates of a variant allele. The spatial distribution of a variant may convey information about its history and characteristics, and this paper extends previous models to take this factor into consideration. A model of fission into subdivisions is superimposed on the previous branching process, and variation between subdivisions is considered. The case where fission is nonrandom and the locations of like alleles are initially positively associated, as would happen were a tribal cluster or village to split on familial lines, is also analyzed. The statistics developed are applied to Yanomama Indian data on rare genetic variants. Due to insufficient time depth, no definitive new inferences can be drawn, but the analysis shows that this model provides results consistent with previous conclusions, and demonstrates the general type of question that may be answered by the approach taken here. In particular, striking confirmation of a higher-than-average growth rate, and hence smaller-than-previously-estimated age, is obtained for the Yan2 serum albumen variant.
ISOLATION AND CHARACTERIZATION OF TEMPERATURE-SENSITIVE RESPIRATORY MUTANTS OF NEUROSPORA CRASSA
Authors: Pittenger Thad H , West David J 
Published: April 2021

ABSTRACT
Filtration-enrichment and inositol-less death methods of mutant isolation, coupled with a screen for cyanide-insensitive respiration, proved to be highly efficient methods for isolating temperature-sensitive (ts) nuclear Neurospora mutants having defective respiration. Eighteen different ts respiratory mutants have been isolated. Most of them are pleiotropic and defective in one or more of the following phenotypes: cytochrome aa3, b, and c (individual or multiple defects); oligomycin inhibition of ATPase activity; respiration and its inhibition by KCN and salicyl hydroxamic acid; and growth rates in liquid and solid media at 25° and 38°. Among these mutants are the first cytochrome c mutant of Neurospora and an extranuclear ts ATPase mutant. An added bonus was the fact that aver half of the mutants were affected either in ribosome assembly or in protein synthesis in the mitochondrion. We have yet to find any mutants completely lacking activities associated with the respiratory chain. However, the wide spectrum of mutants isolated here, along with those currently available, constitutes a considerable resource for investigating respiration in obligate aerobes.
GENETICS OF ARGININE BIOSYNTHESIS IN NEUROSPORA CRASSA
Authors: Davis Rowland H 
Published: April 2021

ABSTRACT
A large number of arginine-requiring mutants of Neurospora was isolated, using a strain already partially impaired in an enzyme of the pathway. Among the mutants, all previously described loci, except one, were represented, and several new loci were defined and mapped. Four groups of mutants were of particular interest. First, thc large group of arg-6 mutants, when tested for intragenic complementation, suggested a bifunctional gene, possibly controlling two steps in ornithine synthesis. This is consistent with the limited enzymic information about this locus. Second, the arg-13 locus was represented by 14 new mutants. All five tested were quite leaky. suggesting that the function controlled by this gene can be rarried out to a limited extent spontaneously or by another gene product. Third, a new locus, arg-14, was defined. It controls a step in ornithine synthesis. It lies in a 1 to 2 map-unit interval between arg-2 and pyr-3 on LG IVR, as shown by mapping in relation tG translocation breakpoints. Fourth, a second new locus whose mutants render the partial mutation in starting material auxotrophic was defined and mapped near the centromere of LG VIL. These new mutants are unable to derepress enzymes of the pathway and may qualify as regulatory mutants.
CYTOGENETIC BEHAVIOR OF SPORE KILLER GENES IN NEUROSPORA
Authors: Raju Namboori B 
Published: April 2021

ABSTRACT
Crosses heterozygous and homozygous for Sk–1, Sk–2 and Sk–3 were examined by light microscopy. All three Spore killers behave similarly. In heterozygoua killer x sensitive crosses, meiosis and ascospore development are normal until after the second postmeiotic mitosis when four of the eight ascospores in each ascus stop developing and degenerate. The four surviving ascospores carry the killer. Death of sensitives thus occurs only after killer and sensitive alleles, SkK and SkS, have segregated into separate ascospores. Homozygous killer x killer crosses do not show such a pattern of degeneration. Either all ascospores are normal or, if some fail to mature, they do not resemble the degenerating sensitive ascospores in heterozygous asci.——With Sk–2, it was shown that SkS nuclei do not abort when both SkK and SkS are present in the same ascospore. Mutants affecting ascus development were used to obtain large ascospores enclosing both SkK and SkS meiotic products in a common cytoplasm. SkS nuclei do not then undergo the degeneration that would be seen if they werc sequestered into separate ascospores, and viable SkS progeny are recovered in undiminished numbers when the mixed multinucleate large ascospores are germinated. In a four-spored mutant, where each ascospore encloses a single nucleus following meiosis, degeneration of SkS ascospores nevertheless occurs, even though the third nuclear division is omitted. Cycloheximide and temperature treatments do not affect: the expression of SkK.
MOLECULAR EVOLUTION AND POLYMORPHISM IN A RANDOM ENVIRONMENT
Authors: Gillespie John H 
Published: April 2021

ABSTRACT
A model of multi-allelic selection in a random environment, the SAS-CFF model, is examined for compatability with allele frequency and genetic distance data acquired by electrophoresis. The symmetric version of the model tends to predict higher than observed levels of polymorphism unless substantial positive autocorrelations in the environment are postulated. The actual allele frequency configurations observed in nature are in rough agreement with those predicted by the SAS-CFF model. An approximate analysis of the transient properties of the SAS-CFF model shows that, in broad outline, the behavior is quite similar to that of the neutral model.
EXCURSIONS ALONG THE INTERFACE BETWEEN DISRUPTIVE AND STABILIZING SELECTION
Authors: Felsenstein Joseph 
Published: April 2021

ABSTRACT
When a polygenic character is exposed to natural selection in which the curve giving fitness as a function of phenotype is a mixture of two Gaussian (normal) curves, the population may respond either by evolving to a specialized phenotype near one of the two optimum phenotypes, or by evolving to a generalized phenotype between them. Using approximate multivariate normal distribution methods, it is demonstrated that the condition for selection to result in a specialized phenotype is that the curve of fitness as a function of breeding value be bimodal. This implies that a specialized phenotype is more likely to result the higher is the heritability of the character. Numerical iterations of four-locus models and algebraic analysis of a symmetric two-locus model generally support the conclusions of the normal approximation.
THE SENSITIVITY OF GEL ELECTROPHORESIS AS A DETECTOR OF GENETIC VARIATION
Authors: Ramshaw John A M , Coyne Jerry A , Lewontin R C 
Published: April 2021

ABSTRACT
Three experiments based on an idea of YOUDERIAN have been performed to determine the proportions and kinds of amino acid substitutions that are detected by gel electrophoresis when applied to surveys of protein variation in populations. The experiments involved applying the sequential method of electrophoresis under sereral conditions of pH and gel concentration to a large sample of human hemoglobins with known amino acid substitutions. In the first experiment, a random sample of 20 different hemoglobin variants was studied, and these were separated into 17 distinct electrophoretic classes by three sequential gel conditions, thus giving a detectability of 85%. A single pass under standard conditions detected eight classes. The second experiment compared groups of substitutions that were chemically identical, but in different positions in the α and β chains, while the third experiment compared pairs of substitutions that were charge equivalent. but chemically different at the same chain position. The sequential method distinguished 90% of all chemically identical substitutions when they were at different chain locations, and four out of five charge equivalent but chemically different substitutions at the same site. Examination of the location of each substitution in the three-dimensional structure of hemoglobins showed that interior substitutions usually are less different from HbA than are surface substitutions and that local interactions with chain and spatial neighbors are sufficient to distinguish substitutions in very similar positions on the outside of the molecule. The "charge ladder" model of electrophoretic classes is clearly incorrect, and it appears that sequential gel electrophoresis as practiced in our Drosophila surveys has detected a substantial fraction of amino acid substitutions if hemoglobin is regarded as a model. This estimate may be modified as other molecules beside hemoglobin are subjected to similar calibration experiments.
RESTORATION OF NUCLEO-MITOCHONDRIAL COMPATIBILITY IN PARAMECIUM
Authors: Sainsard-Chanet Annie , Knowles Jonathan 
Published: April 2021

ABSTRACT
In Paramecium, as previously described, the nuclear mutation cl1 is incompatible with wild-type mitochondria (M+); however, all cl1,/cl1,M+ cells eventually overcome this incompatibility (SAINSARD, CLAISSE and BALME-FREZOL 1974). We have studied the kinetics and genetic basis of the spontaneous restoration of harmony between nucleus and mitochondria. We also studied the modification of these kinetics following microinjection of compatible mutant mitochondria into cl1/cl1M+ cells. We demonstrate that nucleo-mitochondrial readjustment is always achieved by mitochondrial changes that fall into two classes. The first class corresponds to spontaneous mitochondrial mutations affecting the amount of cytochrome aa3 and is similar to the previously described Mcl and Msu mutations (SAINSARD-CHANET 1978; SAINSARD 1975). The nature of the second class of modification is not yet understood; it may correspond either to a mitochondrial "adaptation" or to an unusual type of mutation arising and reverting at high frequency.
CYTOGENETICS OF THE SOUTH AMERICAN DROSOPHILA MULLERI COMPLEX: THE MARTENSIS CLUSTER. MORE INTERSPECIFIC SHARING OF INVERSIONS
Authors: Wasserman Marvin , Koepfer H Roberta 
Published: April 2021

ABSTRACT
Three Drosophila mulleri complex species have been found to be endemic to the cactus regions of northern South America. The three species are morphologically distinct, and no hybridization between species has been found in either the laboratory or nature. An analysis of their salivary gland chromosomes revealed that they evolved from a single cytological population, subspecies F of the ancestor of the D. mulleri complex, and comprise a cluster of sister species that are homozygous for inversions not found elsewhere. Within the martensis cluster are also found several inversions that are unique for these species, but have segregated out among the three species. Thus 2f2 is found in martensis and starmeri, but not in uniseta, while 2t6, 3v and 3w are found in starmeri and uniseta, but not in martensis. This is analogous to the situation found within the remainder of the mulleri complex species, all the members of which share homozygosity for six other inversions. An interpretation of the cytological evolution of the martensis cluster is proposed.
EFFECT OF TERMINAL ANEUPLOIDY ON EPIDERMAL CELL VIABILITY IN DROSOPHILA MELANOGASTER
Authors: Ripoll Pedro 
Published: April 2021

ABSTRACT
In Drosophila melanogaster, individuals heterozygous for translocations between chromosomes Y and 3 can generate, by means of mitotic recombination, somatic cells bearing duplications and deletions. Using translocations with different breakpoints, I have studied the behavior of clones ofcells with increasing degrees of aneuploidy in the abdominal cuticle. Both hyper- and hypoploid cells can survive being duplicated or deficient even for large chromosome 3 fragments. While hyperploidy does not severely affect cell viability, the recovery of hypoploid clones decreases linearly as a function of the size of the deleted fragment. In this report, the quantitative and qualitative aspects of thiseffect are discussed.