bluuebunny/crossref_metadata_2025_split huggingface dataset:
APHIDICOLIN-RESISTANT MUTANTS OF MOUSE LYMPHOMA L5178Y CELLS WITH A HIGH INCIDENCE OF SPONTANEOUS SISTER CHROMATID EXCHANGES
Authors: Tsuji Hideo , Shiomi Tadahiro , Tsuji Satsuki , Tobari Izuo , Ayusawa Dai , Shimizu Kimiko , Seno Takeshi 
Published: January 2021

ABSTRACT
Two aphidicolin-resistant cell mutants (AC 12 and AC 41) with a fourfold increase in spontaneous frequency of sister chromatid exchanges (SCEs) were obtained out of over 400 aphidicolin-resistant mutants isolated from mouse lymphoma L5178Y cells. They also exhibited three- to fourfold increases in spontaneous frequency of chromosome aberrations (CAs). To determine whether the high level of SCE frequency in AC 12 is caused by 5-bromodeoxyuridine (BrdUrd) used for visualizing SCEs, the effect of BrdUrd incorporated into DNA on SCE induction was analyzed. The SCE frequencies in AC 12 remained constant at BrdUrd incorporation levels corresponding to 2—90% substitution for thymidine in DNA. In addition, the small amount of BrdUrd incorporated into both daughter and parental DNA strands in AC 12 had minimal effect on SCE induction. Furthermore, AC 12 and AC 41 were slightly resistant to BrdUrd with respect to the induction of CAs, the inhibition of cell-cycle progression and the decrease in mitotic activity. These findings suggest that the high incidence of SCEs in AC 12 and AC 41 is formed by their intrinsic defects, not by the effects of BrdUrd used. The analysis of SCE frequencies in hybrid cells between these mutants and the parental L5178Y revealed that the genetic defects in AC 12 and AC 41 appear to be recessive, and that these two mutants belong to the same complementation group. Furthermore, AC 12 belonged to a different complementation group from ES 4, which was isolated previously from L5178Y as an SCE mutant with a twofold higher frequency of spontaneous SCEs. This finding indicates that at least two different genetic defects participate in the formation of the high incidence of spontaneous SCEs in mouse cells. These SCE mutants would provide valuable cell materials for studying the molecular mechanism of SCE formation.
MEIOSIS CAN INDUCE RECOMBINATION IN rad52 MUTANTS OF SACCHAROMYCES CEREVISIAE
Authors: Resnick Michael A , Nitiss John , Edwards Charles , Malone Robert E 
Published: January 2021

ABSTRACT
The RAD52 and RAD50 genes have previously been shown to be required for normal meiotic recombination and for various types of recombination occurring in mitotic cells. Recent evidence suggests that rad52 mutants might be defective in an intermediate recombination step; we therefore examined recombination during meiosis in several rad52 mutants at several different loci and in genetic backgrounds that yield efficient sporulation and synchronous meiosis. Similar to previous reports, spores from rad52 diploids are inviable and meiotic recombination is greatly reduced by rad52 mutations. However, intragenic recombinants were detected when cells were plated on selective media during meiosis; rad52 mutants experience induction of recombination between homologues under these special conditions. The frequencies of recombination at four loci were considerably greater than the mitotic controls; however, they were still at least 20 times lower than corresponding Rad+ strains. The prototrophs induced by meiosis in rad52 mutants were not typical meiotic recombinants because incubation in nutrient-rich medium before plating to selective medium resulted in the complete loss of recombinants. We propose that previously observed single-strand breaks that accumulate in rad52 mutants may be associated with recombinational intermediates that are resolved when cells are returned to selective mitotic media and that the meiosis-induced recombination in rad52 cells does not involve double-strand breaks.
ANALYSIS OF MEIOSIS-DEFECTIVE MUTATIONS IN YEAST BY PHYSICAL MONITORING OF RECOMBINATION
Authors: Borts Rhona H , Lichten Michael , Haber James E 
Published: January 2021

ABSTRACT
We have developed a method by which the extent of physical exchange of DNA molecules can be determined throughout meiosis in the yeast Saccharomyces cerevisiae. We have used this technique to analyze the effect of five meiosis-defective mutations (rad6, rad50, rad52, rad57 and spo11) on the physical exchange of DNA molecules. In the same experiments, we have also measured other meiotic parameters, such as premeiotic DNA synthesis, commitment to intragenic recombination, haploidization, ascus formation, and viability. rad50 and spo11 diploids make an undetectable amount of physically recombined DNA and &lt;1% of wild-type levels of viable intragenic recombinants. In contrast, diploids homozygous for rad52, rad6 or rad57 all yield significant amounts of novel restriction fragments which arise by recombination. rad57 diploids make nearly wild-type levels of the recombined restriction fragments, although they produce &lt;10% of the wild-type levels of viable intragenic recombinants. rad52 strains are also capable of a significant (33%) amount of exchange of DNA molecules, but make &lt;1% of wild-type levels of viable intragenic recombinants. rad6 diploids are also capable of undergoing a high level of exchange, as measured by the appearance of the recombined restriction fragment. In addition, rad6 diploids show an unusual allele- or locus-specific variability in the level of viable intragenic recombinants produced. Although rad6 diploids produce no viable spores, they are able to complete a significant amount of haploidization upon return to vegetative growth conditions.
THE SEARCH FOR MATING-TYPE-LIMITED GENES IN THE HOMOTHALLIC ALGA CHLAMYDOMONAS MONOICA
Authors: VanWinkle-Swift Karen P , Hahn Jang-Hee 
Published: January 2021

ABSTRACT
The non-Mendelian erythromycin resistance mutation ery-u1 shows bidirectional uniparental inheritance in crosses between homothallic ery-u1 and ery-u1 + strains of Chlamydomonas monoica. This inheritance pattern supports a general model for homothallism invoking intrastrain differentiation into opposite compatible mating types and, further, suggests that non-Mendelian inheritance is under mating-type (mt) control in C. monoica as in heterothallic species. However, the identification of genes expressed or required by one gametic cell type, but not the other, is essential to verify the existence of a regulatory mating-type locus in C. monoica and to understand its role in cell differentiation and sexual development. By screening for a shift from bidirectional to unidirectional transmission of the non-Mendelian ery-u1 marker, a mutant with an apparent mating-type-limited sexual cycle defect was obtained. The responsible mutation, mtl-1, causes a 1000-fold reduction in zygospore germination in populations homozygous for the mutant allele and, approximately, a 50% reduction in germination for heterozygous (mtl-1/mtl-1 +) zygospores. By next screening for strains unable to yield any viable zygospores in a cross to mtl-1, a second putative mating-type-limited mutant, mtl-2, was obtained. The mtl-2 strain, although self-sterile, mates efficiently with mtl-2 + strains and shows a unidirectional uniparental pattern of inheritance for the ery-u1 cytoplasmic marker, similar to that observed for crosses involving mtl-1. Genetic analysis indicates that mtl-1 and mtl-2 define unique unlinked Mendelian loci and that the sexual cycle defects of reduced germination (mtl-1) or self-sterility (mtl-2) cosegregate with the effect on ery-u1 cytoplasmic gene transmission. By analogy to C. reinhardtii, the mtl-1 and mtl-2 phenotypes can be explained if the expression of these gene loci is limited to the mt + gametic cell type, or if the wild-type alleles at these loci are required for the normal formation and/or functioning of mt + gametes only.
NONHOMOLOGOUS PAIRING IN MICE HETEROZYGOUS FOR A t HAPLOTYPE CAN PRODUCE RECOMBINANT CHROMOSOMES WITH DUPLICATIONS AND DELETIONS
Authors: Sarvetnick Nora , Fox Howard S , Mann Elizabeth , Mains Paul E , Elliott Rosemary W , Silver Lee M 
Published: January 2021

ABSTRACT
We have investigated the structure and properties of a chromosomal product recovered from a rare recombination event between a t haplotype and a wild-type form of mouse chromosome 17. Our embryological and molecular studies indicate that this chromosome (twLub 2) is characterized by both a deletion and duplication of adjacent genetic material. The deletion appears to be responsible for a dominant lethal maternal effect and a recessive embryonic lethality. The duplication provides an explanation for the twLub 2 suppression of the dominant T locus phenotype. A reanalysis of previously described results with another chromosome 17 variant called TtOrl indicates a structure for this chromosome that is reciprocal to that observed for twLub 2. We have postulated the existence of an inversion over the proximal portion of all complete t haplotypes in order to explain the generation of the partial t haplotypes twLub 2 and TtOrl. This proximal inversion and the previously described distal inversion are sufficient to account for all of the recombination properties that are characteristic of complete t haplotypes. The structures determined for twLub 2 and TtOrl indicate that rare recombination can occur between nonequivalent genomic sequences within the inverted proximal t region when wild-type and t chromosomes are paired in a linear, nonhomologous configuration.
DNA SEQUENCE ANALYSIS OF MUTAGENICITY AND SITE SPECIFICITY OF ETHYL METHANESULFONATE IN Uvr+ AND UvrB- STRAINS OF ESCHERICHIA COLI
Authors: Burns Philip A , Allen Frances L , Glickman Barry W 
Published: January 2021

ABSTRACT
EMS-induced mutations within a 180 base pair region of the lacI gene of E. coli were cloned and sequenced. In total, 105 and 79 EMS-induced mutations from a Uvr+ and a UvrB- strain, respectively, were sequenced. The specificity of EMS-induced mutagenesis was very similar in the two strians; G:C → A:T transitions accounted for all but three of the mutants. The overall frequency of induced mutation was fivefold higher in the UvrB- strain compared to the Uvr+ strain. This demonstrates, at the DNA sequence level, that the presumed pre-mutagenic lesion, O 6-ethylguanine, is subject to repair by the uvrABC excision repair system of E. coli. An analysis of mutation frequencies with respect to neighboring base sequence, in the two strains, shows that O 6-ethylguanine lesions adjacent to A:T base pairs present better targets for the excision repair machinery than those not adjacent to A:T base pairs.
THE ABSENCE OF SOMATIC EFFECTS OF P-M HYBRID DYSGENESIS IN DROSOPHILA MELANOGASTER
Authors: McElwain M Catharine 
Published: January 2021

ABSTRACT
The wings and abdomens of dysgenic and nondysgenic control flies were scored for the presence of clones of cells mutant for first and third chromosome markers. These exceptional clones can arise from mitotic recombination, de novo mutation or deletion, and P-M hybrid dysgenesis has been shown to increase the frequency of parallel processes occurring in germ-line cells. Particular attention was given to careful genetic and molecular characterization of all stocks and to providing adequate and appropriate controls so that even very small increases in somatic clone frequency due to P-M hybrid dysgenesis would be detected. No difference was found in the frequency, size distribution or anatomical distribution of mutant somatic clones correlated to hybrid dysgenesis, confirming previous indications. The potential adaptive significance of a germ-line restriction of P-M hybrid dysgenesis is discussed.
AGROBACTERIUM-MEDIATED GENE TRANSFER RESULTS MAINLY IN TRANSGENIC PLANTS TRANSMITTING T-DNA AS A SINGLE MENDELIAN FACTOR
Authors: Budar F , Thia-Toong L , Van Montagu M , Hernalsteens J-P 
Published: January 2021

ABSTRACT
Forty-four independent transformed tobacco plants were obtained from a cocultivation experiment with Agrobacterium tumefaciens strains carrying modified Ti-plasmids. The transformed plants were either self-fertilized or crossed with nontransformed plants or with other transformed plants. The segregation of a phenotypic marker (kanamycin resistance) in the progenies of these plants was determined. In 40 cases out of 44, the segregation of the kanamycin resistance marker is consistent with Mendelian genetics. Among these 40 clones, 35 contain a single kanamycin resistance locus. The five others segregate two independent resistance loci. In two of the single insert clones, the segregation ratio after selfing indicates that the T-DNA insertion may have caused a recessive lethal mutation.
RECESSIVE NONSENSE SUPPRESSORS IN SACCHAROMYCES CEREVISIAE : ACTION SPECTRA, COMPLEMENTATION GROUPS AND MAP POSITIONS
Authors: Ono Bun-Ichiro , Ishino-Arao Yumiko , Tanaka Masahiro , Awano Ikuko , Shinoda Sumio 
Published: January 2021

ABSTRACT
Three genes SUP111, SUP112 and SUP113 of Saccharomyces cerevisiae have been identified that can mutate to give recessive omnipotent nonsense suppressors. Alleles of these loci can also act as allosuppressors; that is, different phenotypes, due apparently to different efficiencies of suppression, can result from different alleles at a given locus. The SUP111, SUP112 and SUP113 loci map to the right arms of chromosomes VIII, VII and XIII, respectively.
INDUCTION OF INTRACHROMOSOMAL RECOMBINATION IN YEAST BY INHIBITION OF THYMIDYLATE BIOSYNTHESIS
Authors: Kunz B A , Taylor G R , Haynes R H 
Published: January 2021

ABSTRACT
The biosynthesis of thymidylate in the yeast Saccharomyces cerevisiae can be inhibited by antifolate drugs. We have found that antifolate treatment enhances the formation of leucine prototrophs in a haploid strain of yeast carrying, on the same chromosome, two different mutant leu2 alleles separated by Escherichia coli plasmid sequences. That this effect is a consequence of thymine nucleotide depletion was verified by the finding that provision of exogenous thymidylate eliminates the increased production of Leu+ colonies. DNA hybridization analysis revealed that recombination, including reciprocal exchange, gene conversion and unequal sister-chromatid crossing over, between the duplicated genes gave rise to the induced Leu+ segregants. Although gene conversion unaccompanied by crossing over was responsible for the major fraction of leucine prototrophs, events involving reciprocal exchange exhibited the largest increase in frequency. These data show that recombination is induced between directly repeated DNA sequences under conditions of thymine nucleotide depletion. In addition, the results of this and previous studies are consistent with the possibility that inhibition of thymidylate biosynthesis in yeast may create a metabolic condition that provokes all forms of mitotic recombination.
ONE-STEP AND STEPWISE MAGNIFICATION OF A BOBBED LETHAL CHROMOSOME IN DROSOPHILA MELANOGASTER
Authors: Endow Sharyn A , Komma Donald J 
Published: January 2021

ABSTRACT
Bobbed lethal (bbl) chromosomes carry too few ribosomal genes for homozygous flies to be viable. Reversion of bbl chromosomes to bb or nearly bb + occurs under magnifying conditions at a low frequency in a single generation. These reversions occur too rapidly to be accounted for by single unequal sister chromatid exchanges and seem unlikely to be due to multiple sister strand exchanges within a given cell lineage. Analysis of several one-step revertants indicates that they are X-Y recombinant chromosomes which probably arise from X-Y recombination at bb. The addition of ribosomal genes from the Y chromosome to the bbl chromosome explains the more rapid reversion of the bbl chromosome than is permitted by single events of unequal sister chromatid exchange. Analysis of stepwise bbl magnified chromosomes, which were selected over a period of 4-9 magnifying generations, shows ribosomal gene patterns that are closely similar to each other. Similarity in rDNA pattern among stepwise magnified products of the same parental chromosome is consistent with reversion by a mechanism of unequal sister strand exchange.
LINKAGE RELATIONSHIPS IN WILD EMMER WHEAT, TRITICUM DICOCCOIDES
Authors: Golenberg Edward M 
Published: January 2021

ABSTRACT
The linkage relationships in wild emmer wheat, Triticum dicoccoides, between nine enzymatic loci (Mdh-1, Ipo, β-Glu, Pept-1, Pept-3, Est-5, Est-1, 6Pgdh-2 and Hk) and a coleoptile pigment locus (Rc) were investigated. Chromosome locations of genes were inferred from analysis of ditelocentric lines of Triticum aestivum, cultivar Chinese Spring. The loci Mdh-B1 and Hk are linked (lambda = 0.1869) and are most likely located on the chromosome 1B. The loci Pept-B1 and Rc are linked (lambda = 0.2758) and are located on the 6Bq chromosomal arm. Rc also has significant interactions with the loci Pept-3 and Ipo, although there is no significant linkage detectable. The interactions may be a result of epigenetic interactions. Est-1 has only one active product in T. dicoccoides and is most likely located on the 3Ap chromosome arm. No significant interactions were found for the remaining loci.
THYMIDINE UTILIZATION BY tut MUTANTS AND FACILE CLONING OF MUTANT ALLELES BY PLASMID CONVERSION IN S. CEREVISIAE
Authors: Sclafani Robert A , Fangman Walton L 
Published: January 2021

ABSTRACT
Plasmid pJM81 contains a Herpes simplex virus thymidine kinase (TK) gene that is expressed in yeast. Cells containing the plasmid utilize thymidine (TdR) and the analogue 5-bromodeoxyuridine (BUdR) for specific incorporation into DNA. TdR auxotrophs, harboring plasmid pJM81 and a mutation in the yeast gene TMP1 require high concentrations of TdR (300 μg/ml) to support normal growth rates and the wild-type mitochondrial genome (ρ+) cannot be maintained. We have identified a yeast gene, TUT1, in which recessive mutations allow efficient utilization of lower concentrations of TdR. Strains containing the mutations tmp1 and tut1, as well as plasmid pJM81, form colonies at 2 μg/ml TdR, grow at nearly normal rates and maintain the ρ+ genome at 50 μg/ml TdR. These strains can be used to radiolabel DNA specifically and to synchronize DNA replication by TdR starvation. In addition, the substitution of BUdR for TdR allows the selective killing of DNA-synthesizing cells by 310-nm irradiation and allows the separation of replicated and unreplicated forms of DNA by CsCl equilibrium density banding. We also describe a unique, generally applicable system for cloning mutant alleles that exploits the fact that Tk+ yeast cells are sensitive to 5-fluorodeoxyuridine (FUdR) and that gene conversions can occur between a yeast chromosome and a TK-containing plasmid.
THE EVOLUTIONARY HISTORY OF DROSOPHILA BUZZATII. XII. THE GENETIC BASIS OF STERILITY IN HYBRIDS BETWEEN D. BUZZATII AND ITS SIBLING D. SERIDO FROM ARGENTINA
Authors: Naveira Horacio , Fontdevila Antonio 
Published: January 2021

ABSTRACT
The genetic basis of hybrid sterility has been investigated in backcross segmental hybrids between two sibling species, Drosophila buzzatii and D. serido. Asynapsis of homologous bands in hybrid polytene chromosomes has been used to identify the D. serido chromosome segments introgressed into the D. buzzatti genome. All the investigated chromosomes contain male sterility factors. For autosomes, sterility is produced when an introgressed D. serido chromosome segment, or combination of segments, reaches a minimum size. On the other hand, any introgressed X chromosome segment from D. serido, irrespective of its size, produces either male hybrid sterility or inviability.
THE CIS-TRANS TEST SHOWS NO EVIDENCE FOR A FUNCTIONAL RELATIONSHIP BETWEEN TWO MOUSE t COMPLEX LETHAL MUTATIONS: IMPLICATIONS FOR THE EVOLUTION OF t HAPLOTYPES
Authors: Mains Paul E 
Published: January 2021

ABSTRACT
Mouse t haplotypes often carry embryonic lethal mutations. Sixteen complementation groups are known, but the viability of the heterozygotes between them is often less than 100%. It has been reported that cis heterozygotes of two lethal mutations showed better viability than trans heterozygotes. This could indicate that the mutations were part of the same functional unit, even though they map up to 15 cM apart. However, the tw5 and tw12 haplotypes in our colony did not show a statistically significant decrease in viability when combined in trans. The cis-trans analysis was repeated using two independent chromosomes, derived by recombination between the tw5 and the tw12 haplotypes to provide the two lethal mutations in cis. Two independent chromosomes, representing the reciprocal recombination event, supplied the corresponding wild-type alleles in cis. These chromosomes were combined in the four pairwise combinations, and male/female reciprocal crosses were done. The cis heterozygotes showed a decrease, rather than an increase, in viability in seven of the eight cases. These results probably reflect effects of unrelated background genes. The lethal mutations, instead of being functionally related, may have occurred in a random, unrelated set of genes and may confer a selective advantage to t haplotypes found in wild populations.
REARRANGEMENT OF GENES LOCATED ON HOMOLOGOUS CHROMOSOMAL SEGMENTS IN MOUSE AND MAN: THE LOCATION OF GENES FOR ALPHA-AND BETA-INTERFERON, ALPHA-1 ACID GLYCOPROTEIN-1 AND -2, AND AMINOLEVULINATE DEHYDRATASE ON MOUSE CHROMOSOME 4
Authors: Nadeau Joseph H , Berger Franklin G , Kelley Kevin A , Pitha Paula M , Sidman Charles L , Worrall Neil 
Published: January 2021

ABSTRACT
Gene mapping studies to determine the order of alpha- and beta-interferon (Ifa, Ifb), aminolevulinate dehydratase(Lv), and alpha-1 acid glycoprotein-1 and -2 (Orm-1, Orm-2) relative to each other and to the reference genes brown (b), B-cell maturation factor responsiveness (Bmfr-1), and major urinary protein-1 (Mup-1) are reported. The most likely order was Mup-1—Lv—b—Orm-1, Orm-2—Ifa, Ifb—Bmfr-1. This order suggested that two chromosomal segments located on chromosome 4 in the mouse and chromosome 9 in man have been conserved since divergence of lineages leading to man and mouse; these segments are marked by soluble aconitase-1 (Aco-1) and galactose-1 phosphate uridyl transferase (Galt) and by Lv and Orm-1. This order also demonstrated that, although genes located on opposite arms of chromosome 9 in man remain syntenic in the mouse, gene order has not been conserved; Ifa and Ifbare not located in their expected locations near Aco-1 and Galt. The position of Ifa and Ifb between Orm-1and Bmfr-1 could not be determined with certainty because of apparent heterogeneity in recombination frequencies between crosses involving conventional laboratory strains of mice and crosses involving interspecific matings between laboratory mice and Mus spretus. This result suggests that caution must be exercised when using M. spretus in linkage crosses.
POSSIBLE DERIVATION OF THE LABORATORY MOUSE GENOME FROM MULTIPLE WILD MUS SPECIES
Authors: Blank R D , Campbell G R , D′Eustachio P 
Published: January 2021

ABSTRACT
Laboratory strains of mice are thought to be derived from wild populations of Mus domesticus. Many instances of non-domesticus genetic information fixed in these strains have been described, however, and the amount of strain-to-strain genetic variation exceeds that found in wild domesticus populations. In order to estimate the extent of the non-domesticus contribution to laboratory mouse genomes, and to determine whether it could account for observed variation, we have used computer simulations to investigate the properties of genetically marked chromosomal segments and the distribution of residual allogenicity at various times during inbreeding. A locus or chromosomal segment is allogenic if it is unfixed within a lineage at a given time. The odds of fixation of a foreign chromosome segment are predicted to be an exponentially decreasing function of its length. The median segment length is predicted to be 17 centimorgans. Available data for markers of chromosomes 1, 9 and 12 in recombinant inbred strain sets conform to these predictions. Together, the results suggest that introgression of non-domesticus chromosomes and segregation of residual allogenicity are sufficient to account for the genetic diversity observed among inbred mouse strains and substrains.