bluuebunny/crossref_metadata_2025_split huggingface dataset:
SOME MODELS OF GENE CONVERSION FOR TREATING THE EVOLUTION OF MULTIGENE FAMILIES
Authors: Ohta Tomoko 
Published: January 2021

ABSTRACT
A simple model of gene conversion presented earlier has been compared with a more general model under the assumption of no bias. The former is based on a simple concept that, by conversion, a gene (or a segment of a gene) is transferred from one locus to another in a multigene family. Intrachromatid symmetric conversion may result in reciprocal exchange of genes within a multigene family, and the previous theory of identity coefficients needs modification when it occurs. The relationship of various parameters of the two models was made clear in formulating the transition equations of identity coefficients. As an example of extending the analyses, a model of preferential conversion that is relevant to the observed uneven polymorphisms of class I genes in the major histocompatibility complex has been investigated. It differs from the biased conversion, in that directional process is through location of genes on the chromosome. It is shown that the model satisfactorily explains the observed data, even though the effect of preferential conversion is difficult to distinguish from that of natural selection.
ISOLATION AND CHARACTERIZATION OF NEUROSPORA MUTANTS AFFECTED IN INVERTASE SYNTHESIS
Authors: Lee Deborah B , Free Stephen J 
Published: January 2021

ABSTRACT
We have outlined a procedure that allows the large-scale screening of mutagenized Neurospora crassa populations for invertaseless mutants. We have isolated and characterized three mutations, inv(DBL1), inv(DBL9) and inv(DBL14), which have been mapped at or near the invertase structural gene. One of these, inv(DBL1), is particularly interesting. Our experiments indicate that the reduced level of invertase activity in the inv(DBL1)-containing cell can be explained as the result of a reduced number of normal enzyme molecules. We also show that wild-type Neurospora is able to respond rapidly to a change of medium and can dramatically increase its production of invertase within 20 min after a transfer to a carbon-free medium.
MOLECULAR MAPPING OF A GENE CLUSTER FLANKING THE DROSOPHILA DOPA DECARBOXYLASE GENE
Authors: Gilbert Denise , Hirsh Jay , Wright T R F 
Published: January 2021

ABSTRACT
Nine lethal complementation groups flanking the Drosophila Dopa decarboxylase (Ddc) gene, have been localized within 100 kb of cloned chromosomal DNA. Six of these complementation groups are within 23 kb of DNA, and all ten complementation groups, including Ddc, lie within 78-82 kb of DNA. The potential significance of this unusually high gene density is discussed.
A TEST FOR RARE MALE MATING ADVANTAGE WITH DROSOPHILA PSEUDOOBSCURA KARYOTYPES
Authors: Anderson Wyatt W , Brown Celeste J 
Published: January 2021

ABSTRACT
Recent work has called into question the reality of the rare male mating advantage, pointing out that it could be a statistical artifact of marking flies for behavioral observation or of experimental bias in collecting males. We designed an experiment to test for rare male mating advantage that avoids these sources of bias. Large numbers of males of three Drosophila pseudoobscura karyotypes were allowed to mate with females of one karyotype in population cages. The females were then isolated before multiple mating occurred and their progeny used to diagnose the males that mated them. Populations were studied at five sets of male karyotypic frequencies. The mating success of the male homokaryotypes ST/ST and CH/CH, relative to that of the heterokaryotype ST/CH, was frequency dependent. Both ST/ST and CH/CH males displayed a statistically significant mating advantage at low frequency by comparision with their mating success in the midrange of karyotypic frequencies. Both male homokaryotypes also showed a significantly greater mating success at high homokaryotypic frequency than at intermediate frequencies, which is the same as saying that the heterokaryotype not only failed to show a rare male advantage but actually suffered a mating disadvantage at low frequency. We conclude that rare male mating advantage is not always an experimental or methodological artifact but does occur in laboratory populations of D. pseudoobscura. It may occur for some genotypes and not for others, however, and it may be only one of several forms of frequency-dependent mating behavior operating in a population.
IDENTIFICATION AND CHARACTERIZATION OF THE alc GENE PRODUCT OF BACTERIOPHAGE T4
Authors: Kutter Elizabeth , Drivdahl Rolf , Rand Keith 
Published: January 2021

ABSTRACT
Bacteriophage T4 infection rapidly and almost completely inhibits transcription of host and other phage DNAs. Two processes have been implicated to date in this inhibition: (1) ADP ribosylation of the α subunits of the RNA polymerase, involving gp alt (which is injected with the phage DNA) and, later, gp mod; and (2) the action of the T4 alc/unf gene product, synthesized immediately after infection. The latter unfolds the host genome and also blocks transcription of cytosine-containing DNA. Here, we describe the identification on two-dimensional polyacrylamide gels of gp alc/unf, the more precise mapping of the gene and the identification and analysis of the appropriate DNA sequence from an Unf+ alc mutant.
THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XVII. A POPULATION CARRYING GENETIC VARIABILITY EXPLICABLE BY THE CLASSICAL HYPOTHESIS
Authors: Kusakabe Shinichi , Mukai Terumi 
Published: January 2021

ABSTRACT
About 400 second chromosomes were extracted from the Aomori population, a northernmost population of D. melanogaster on Honshu in Japan, and the following experimental results were obtained. (1) The frequency of lethal chromosomes was 0.23. (2) The effective size of the population was estimated to be about 3000, from the allelism rate of lethal chromosomes and their frequency. (3) The detrimental and lethal loads for viability were 0.243 and 0.242, respectively, and the D/L ratio became 1.00. (4) The average degree of dominance for mildly deleterious genes was estimated to be 0.178 ± 0.056. (5) Additive (α2 A) and dominance (α2 D) variances of viability were estimated to be 0.00276 ± 0.00090 and 0.00011 ± 0.00014, respectively. (6) There was no significant difference in environmental variances between homozygotes and heterozygotes. Using these estimates, we discuss the maintenance mechanisms of genetic variability of viability in the population. The mutation-selection balance explained these experimental results.
POPULATION BOTTLENECKS AND NONEQUILIBRIUM MODELS IN POPULATION GENETICS. I. ALLELE NUMBERS WHEN POPULATIONS EVOLVE FROM ZERO VARIABILITY
Authors: Maruyama Takeo , Fuerst Paul A 
Published: January 2021

ABSTRACT
A simple numerical method was developed for the mean number and average age of alleles in a population that was initiated with no genetic variation following a sudden population expansion. The methods are used to examine the question of whether allele numbers are elevated compared with values seen in equilibrium populations having equivalent gene diversity. Excess allele numbers in expanding populations were found to be the rule. This was true whether the population began with zero variation or with low levels of variation in either of two initial distributions (initially an equilibrium allele frequency distribution or initially with loci occurring in only two classes of variation). Although the increase of alleles may persist for only a short time, when compared with the time which is required for approach to final equilibrium, the increase may be long when measured in absolute generation numbers. The pattern of increase in very rare alleles (those present only once in a sample) and the persistence of the original allele were also investigated.
COUPLING WITH PACKAGING EXPLAINS APPARENT NONRECIPROCALITY OF CHI-STIMULATED RECOMBINATION OF BACTERIOPHAGE LAMBDA BY RECA AND RECBC FUNCTIONS
Authors: Kobayashi Ichizo , Stahl Mary M , Fairfield Frederic R , Stahl Franklin W 
Published: January 2021

ABSTRACT
Chi (Χ, 5'-GCTGGTGG) is a recombinator in RecA- and RecBC-mediated recombination in Escherichia coli. In vegetative recombination between two bacteriophage lambda strains, one with and the other without Chi (a +Χ+ b - × a-Χob+), the Χ-containing recombinant (a -Χ+ b -) is less abundant than the non-Χ-containing recombinant (a+Χob+). Previously this was taken was evidence for nonreciprocality of Χ-stimulated exchange. This inequality, however, is now seen to result from an event at cos (λ's packaging origin) that both activates Chi and initiates DNA packaging. An event at rightward cos leads to activation of leftward Χ on the same chromosome for an exchange to its left. From the resulting circulating dimer (-cos-a+-Χo-b+-cos-a--Χ+-b—), the cos that activated Χ is more likely to be used for rightward packaging initiation than is the cos from the other parent. Consistent with this coupling model is "biased packaging" in λ carrying two cos sites per monomer genome. When their maturation is dependent on dimerization by Χ-stimulated exchange, the phage particles result more often from packaging from the cos that activates Χ than from packaging from the other cos. Since Chi activation and packaging can be uncoupled, we infer that some early and reversible step in packaging activates Χ. A strong candidate for this step is a double-strand break at cos that provides an oriented entry site for a recombinase.
ISOLATION AND GENETIC ANALYSIS OF CAULOBACTER MUTANTS DEFECTIVE IN CELL SHAPE AND MEMBRANE LIPID SYNTHESIS
Authors: Hodgson David A , Shaw Penny , Shapiro Lucille 
Published: January 2021

ABSTRACT
In this paper we report the isolation, characterization and genetic analysis of several C. crescentus mutants altered in membrane lipid synthesis. One of these, a fatty acid bradytroph, AE6002, was shown to be due to a mutation in the fatA gene. In addition to the presence of the fatA506 mutation, this strain was found to contain two other mutations, one of which caused the production of a water-soluble brown-orange pigment (pigA) and another which caused formation of helical cells (hclA). Expression of the latter two phenotypes required complex media and both were repressed by glucose. However, the lesions were mapped to loci that are separated by a substantial distance. The hclA and the fatA genes mapped close together, possibly implying that comutation had occurred in AE6002. Data are presented that allow the unambiguous identification of a second Fat gene (fatB) in C. crescentus. The map position of another mutation in membrane lipid biogenesis, the glycerol-3-PO4 auxotroph gpsA505, was also determined. During this study the flaZ gene was fine-mapped and the positions of proC and rif changed from the previously reported location.
GENETIC ANALYSIS OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER IN JAPAN. IV. NATURAL SELECTION ON THE INDUCIBILITY, BUT NOT ON THE STRUCTURAL GENES, OF AMYLASE LOCI
Authors: Matsuo Yoshinori , Yamazaki Tsuneyuki 
Published: January 2021

ABSTRACT
To test the validity of previous results the inducibility of amylase as well as other biochemical parameters was measured using 45 homozygous strains of Drosophila melanogaster from Akayu, Japan. Only the inducibility (but not protein contents or specific activity of the enzyme) was highly correlated with productivity measured using a starch food regime (rp = 0.41, P &lt; 0.005, rg = 0.73 ± 0.21). Inducibility was also negatively correlated with developmental time using starch food; namely, the one with high inducibility developed the fastest. Population cage experiments using 1600 genomes from the same natural population showed that the inducibility responded positively to natural selection (1.6-fold increase in inducibility in cages using starch food relative to those using normal food), but little frequency change of allozymes was observed. All of these results were consistent and indicated that polymorphisms of inducing factors or regulatory genes were major determinants of fitness differences in a particular environment and may be the genetic materials responsible for the adaptive evolution of organisms, at least in amylase loci.
REARRANGEMENT OF THE GENETIC MAP OF CHROMOSOME VII OF SACCHAROMYCES CEREVISIAE
Authors: Celenza John L , Carlson Marian 
Published: January 2021

ABSTRACT
The genetic map of the right arm of chromosome VII of Saccharomyces cerevisiae includes markers on a distal segment for which meiotic linkage to the centromere-proximal marker cly8 has not previously been demonstrated. According to the currently accepted map, SUF4 is the most distal marker on the right arm. We have shown by tetrad analysis that SUF4 is linked to cly8 and ade6. The genetic distance between SUF4 and cly8 is 29 cM. These data indicate that the genetic map of the right arm of chromosome VII should be revised by inverting the orientation of the distal segment so that SUF4 is located near cly8, and SUC1 and MAL1 are the most distal markers. With this revision, all of the polymeric fermentation markers that have been mapped are located at the ends of chromosomes.
INTERACTING GENES CONTROL GLYCEROL-3-PHOSPHATE DEHYDROGENASE EXPRESSION IN DEVELOPING CEREBELLUM OF THE MOUSE
Authors: Kozak Leslie P 
Published: January 2021

ABSTRACT
The cerebellum of BALB/cJ mice has approximately 2.5 times as much glycerol-3-phosphate dehydrogenase (GPDH) as that of C57BL/6J mice. This difference in enzyme levels, which positively correlates with similar differences in the levels of hybridizable GPDH mRNA, is controlled by at least two unlinked regulatory loci and the structural gene, Gdc-1, located on chromosome 15. These regulatory loci, which act predominantly during the second and third weeks of postnatal cerebellar development and differentiation, have been separated from each other in the CXB recombinant inbred strains of mice. One regulatory locus, Gdcr-1, although unlinked to the structural gene, has an allele in BALB/c mice that preferentially enhances expression of the BALB/c structural allele at Gdc-1. The other locus, Gdcr-2, which may or may not be single, enhances GPDH expression at Gdc-1 irrespective of the allele present, as is commonly observed for loci acting from a distance. Measurements of GPDH mRNA in the recombinant inbred mice suggest that these regulatory genes act by modulating mRNA levels. Accordingly, the regulation of GPDH expression in the cerebellum of mice depends on a complex interaction of unlinked regulatory elements with regulatory elements near the structural gene. Furthermore, since the Gdc-1 locus is expressed in virtually every tissue of the mouse except blood and since the observed genetic variation is restricted to the cerebellum, it is likely that other tissues will have their own distinctive genetic mechanisms for modulating Gdc-1 expression.
BACTERIOPHAGE T4 GENE 32 PARTICIPATES IN EXCISION REPAIR AS WELL AS RECOMBINATIONAL REPAIR OF UV DAMAGES
Authors: Mosig Gisela 
Published: January 2021

ABSTRACT
Gene 32 of phage T4 has been shown previously to be involved in recombinational repair of UV damages but, based on a mutant study, was thought not to be required for excision repair. However, a comparison of UV-inactivation curves of several gene 32 mutants grown under conditions permissive for progeny production in wild-type or polA - hosts demonstrates that gene 32 participates in both kinds of repair. Different gene 32 mutations differentially inactivate these repair functions. Under conditions permissive for DNA replication and progeny production, all gene 32 mutants investigated here are partially defective in recombinational repair, whereas only two of them, P7 and P401, are also defective in excision repair. P401 is the only mutant whose final slope of the inactivation curve is significantly steeper than that of wildtype T4. These results are discussed in terms of interactions of gp32, a single-stranded DNA-binding protein, with DNA and with other proteins.
RESOLUTION OF DICENTRIC CHROMOSOMES BY TY-MEDIATED RECOMBINATION IN YEAST
Authors: Surosky Richard T , Tye Bik-Kwoon 
Published: January 2021

ABSTRACT
We have integrated a plasmid containing a yeast centromere, CEN5, into the HIS4 region of chromosome III by transformation. Of the three transformant colonies examined, none contained a dicentric chromosome, but all contained a rearranged chromosome III. In one transformant, rearrangement occurred by homologous recombination between two Ty elements; one on the left arm and the other on the right arm of chromosome III. This event produced a ring chromosome (ring chromosome III) of about 60 kb consisting of CEN3 and all other sequences between the two Ty elements. In addition, a linear chromosome (chromosome IIIA) consisting of sequences distal to the two Ty elements including CEN5, but lacking 60 kb of sequences from the centromeric region, was produced. Two other transformants also contain a similarly altered linear chromosome III as well as an apparently normal copy of chromosome III. These results suggest that dicentric chromosomes cannot be maintained in yeast and that dicentric structures must be resolved for the cell to survive.—The meiotic segregation properties of ring chromosome III and linear chromosome IIIA were examined in diploid cells which also contained a normal chromosome III. Chromosome IIIA and normal chromosome III disjoined normally, indicating that homology or parallel location of the centromeric regions of these chromosomes are not essential for proper meiotic segregation. In contrast, the 60-kb ring chromosome III, which is homologous to the centromeric region of the normal chromosome III, did not appear to pair with fidelity with chromosome III.
A MODEL OF DUPLICATIVE TRANSPOSITION AND GENE CONVERSION FOR REPETITIVE DNA FAMILIES
Authors: Ohta Tomoko 
Published: January 2021

ABSTRACT
A model of duplicative transposition and gene conversion for the evolution of repetitive DNA families was studied. In this model, transposition and conversion (both unbiased) are assumed to occur both within and between the genomes in a diploid cell, and any degree of linkage intensity is incorporated. The transition equations for allelic and nonallelic identity coefficients have been formulated by using the previous results. The results are widely applicable to many repetitive sequences, from dispersed families like transposons to tightly linked multigene families. It has been shown through extensive numerical studies on equilibrium properties that duplicative transposition and gene conversion have very similar effects on nonallelic identity coefficients, but that allelism and allelic identity are greatly influenced by the relative rates of occurrence of the two processes.
MEIOTIC GENE CONVERSION MUTANTS IN SACCHAROMYCES CEREVISIAE. I. ISOLATION AND CHARACTERIZATION OF pms1-1 AND pms1-2
Authors: Williamson Marsha S , Game John C , Fogel Seymour 
Published: January 2021

ABSTRACT
The pms1 mutants, isolated on the basis of sharply elevated meiotic prototroph frequencies for two closely linked his4 alleles, display pleiotropic phenotypes in meiotic and mitotic cells. Two isolates carrying recessive mutations in PMS1 were characterized. They identify a function required to maintain low postmeiotic segregation (PMS) frequencies at many heterozygous sites. In addition, they are mitotic mutators. In mutant diploids, spore viability is reduced, and among survivors, gene conversion and postmeiotic segregation frequencies are increased, but reciprocal exchange frequencies are not affected. The conversion event pattern is also dramatically changed in multiply marked regions in pms1 homozygotes. The PMS1 locus maps near MET4 on chromosome XIV. The PMS1 gene may identify an excision-resynthesis long patch mismatch correction function or a function that facilitates correction tract elongation. The PMS1 gene product may also play an important role in spontaneous mitotic mutation avoidance and correction of mismatches in heteroduplex DNA formed during spontaneous and UV-induced mitotic recombination. Based on meiotic recombination models emphasizing mismatch correction in heteroduplex DNA intermediates, this interpretation is favored, but alternative interpretations involving longer recombination intermediates in the mutants are also considered.
RAD52-INDEPENDENT MITOTIC GENE CONVERSION IN SACCHAROMYCES CEREVISIAE FREQUENTLY RESULTS IN CHROMOSOMAL LOSS
Authors: Haber James E , Hearn Mark 
Published: January 2021

ABSTRACT
We have examined spontaneous, interchromosomal mitotic recombination events between his4 alleles in both Rad+ and rad52 strains of Saccharomyces cerevisiae. In Rad+ strains, 74% of the His+ prototrophs resulted from gene conversion events without exchange of flanking markers. In diploids homozygous for the rad52-1 mutation, the frequency of His+ prototroph formation was less than 5% of the wild-type value, and more than 80% of the gene conversion events were accompanied by an exchange of flanking markers. Most of the rad52 intragenic recombination events arose by gene conversion accompanied by an exchange of flanking markers and not by a simple reciprocal exchange between the his4A and his4C alleles. There were also profound effects on the kinds of recombinant products that were recovered. The most striking effect was that RAD52-independent mitotic recombination frequently results in the loss of one of the two chromosomes participating in the gene conversion event.
ESCHERICHIA COLI RHO FACTOR IS INVOLVED IN LYSIS OF BACTERIOPHAGE T4-INFECTED CELLS
Authors: Linder Claës H , Carlson Karin 
Published: January 2021

ABSTRACT
A Rid (Rho interaction deficient) phenotype of bacteriophage T4 mutants was defined by cold-sensitive restriction (lack of plaque formation) on rho + hosts carrying additional polar mutations in unrelated genes, coupled to suppression (plaque formation) in otherwise isogenic strains carrying either a polarity-suppressing rho or a multicopy plasmid expressing the rho + allele. This suggests that the restriction may be due to lower levels of Rho than what is available to T4 in the suppressing strains.—Rid394×4 was isolated upon hydroxylamine mutagenesis and mapped in the t gene; other t mutants (and mot, as well as dda dexA double mutants) also showed a Rid phenotype. In liquid culture in strains that restricted plaque formation Rid394×4 showed strong lysis inhibition (a known t - phenotype) but no prolonged phage production (another well-known t - phenotype). This implies that when Rho is limiting the t mutant shuts off phage production at the normal time. Lysis inhibition was partially relieved, and phage production prolonged to varying extents depending on growth conditions in strains that allowed plaque formation. No significant effects on early gene expression were found. Apparently, both mutant (polarity-suppressing) and wild-type Rho can function in prolonging phage production and partially relieving lysis inhibition of Rid394×4 when present at a sufficiently high level, and Rho may play other role(s) in T4 development than in early gene regulation.