bluuebunny/crossref_metadata_2025 huggingface dataset:
Outcomes of surgical resection after neoadjuvant chemoimmunotherapy in locally advanced stage IIIA non-small-cell lung cancer
Authors: Romero Román Alejandra , Campo-Cañaveral de la Cruz Jose Luis , Macía Iván , Escobar Campuzano Ignacio , Figueroa Almánzar Santiago , Delgado Roel María , Gálvez Muñoz Carlos , García Fontán Eva M , Muguruza Trueba Ignacio , Romero Vielva Laura , Cano Garcia José Ramón , Martínez Téllez Elisabeth , Partida González Concepción , Jiménez López Marcelo Fernando , Jiménez Maestre Unai , Mongil Poce Roberto , Sánchez Lorente David , Álvarez Kindelán Antonio , Provencio Pulla Mariano
Published: January 2021

OBJECTIVES

This analysis aimed to evaluate perioperative outcomes of surgical resection following neoadjuvant treatment with chemotherapy plus nivolumab in resectable stage IIIA non-small-cell lung cancer.

METHODS

Eligible patients received neoadjuvant chemotherapy (paclitaxel + carboplatin) plus nivolumab for 3 cycles. Reassessment of the tumour was carried out after treatment and patients with at least stable disease as best response underwent pulmonary resection. After surgery, patients received adjuvant treatment with nivolumab for 1 year. Surgical data were collected from the NADIM database and patient charts were reviewed for additional surgical details.

RESULTS

Among 46 patients who received neoadjuvant treatment, 41 (89.1%) underwent surgery. Two patients rejected surgery and 3 did not fulfil resectability criteria. There were 35 lobectomies (85.3%), 3 of which were sleeve lobectomies (9.4%), 3 bilobectomies (7.3%) and 3 pneumonectomies (7.3%). Video-assisted thoracoscopy was the initial approach in 51.2% of cases, with a conversion rate of 19% (n = 4). There was no operative mortality at either 30 or 90 days. The most common complications were prolonged air leak (n = 8), pneumonia (n = 5) and arrhythmia (n = 4). Complete resection (R0) was achieved in all patients who underwent surgery, downstaging was observed in 37 patients (90.2%) and major pathological response in 34 patients (82.9%).

CONCLUSIONS

Surgical resection following induction therapy with chemotherapy plus nivolumab appears to be safe and offers appropriate oncological outcomes. Perioperative morbidity and mortality rates in our study were no higher than previously reported in this setting. A minimally invasive approach is, therefore, feasible.
ANALYSIS OF A MOUSE α-GLOBIN GENE MUTATION INDUCED BY ETHYLNITROSOUREA
Authors: Popp R A , Bailiff E G , Skow L C , Johnson F M , Lewis Susan E
Published: January 2021

A DBA/2 mouse treated with ethylnitrosourea sired an offspring whose hemoglobin showed an extra band following starch gel electrophoresis. The variant hemoglobin migrated to a more cathodal position in starch gel. Isoelectric focusing indicated that chain 5 of the mutant hemoglobin migrated to a more cathodal position than the normal chain 5 from DBA/2 mice and that the other α-globin, chain 1, was not affected. On focusing gels the phenotype of the mutant allele, Hbay  9, was expressed without dominance to normal chain 5, and Hbay  9  /Hbay  9 homozygotes were fully viable in the laboratory. The molecular basis for the germinal mutation was investigated by analyzing the amino acid sequence of chain 5y9, the mutant form of α-chain 5. A single amino acid substitution (His → Leu) at position 89 was found in chain 5y9. We propose that ethylnitrosourea induced an A → T transversion in the histidine codon at position 89 (CAC → CTC). This mutation has apparently not been observed previously in humans, mice or other mammals, and its novel occurrence may be indicative of other unusual mutational events that do not ordinarily occur in the absence of specific mutagen exposure.
GENETIC LOCALIZATION AND BIOCHEMICAL CHARACTERIZATION OF A TRANS-ACTING REGULATORY EFFECT IN DROSOPHILA
Authors: King Joseph J , McDonald John F
Published: January 2021

A region-specific, trans-acting regulatory gene that alters in vivo protein levels of α-glycerophosphate dehydrogenase (α-GPDH) has been mapped to position 55.4 on the third chromosome of Drosophila melanogaster. The gene has been found to affect the in vivo stability of α-GPDH in adult thoracic tissue but has no effect on α-GPDH levels in the abdomen. Although no other thoracic proteins were found to be influenced by the locus, it appears to modify the level of one additional abdominal protein. The action of the gene over development and its possible mode of control are discussed.
AN ANALYSIS OF HETEROSIS VS. INBREEDING EFFECTS WITH AN AUTOTETRAPLOID CROSS-FERTILIZED PLANT: MEDICAGO SATIVA L
Authors: Gallais A
Published: January 2021

Self-fertilization and crossing were combined to produce a large number of levels of inbreeding and of degrees of kinship. The inbreeding effect increases with the complexity of the character and with its supposed relationship with fitness. A certain amount of heterozygosity appears to be necessary for the expression of variability. With crossing of unrelated noninbred plants, genetic variance is mainly additive, but with inbreeding its major part is nonadditive. High additivity in crossing, therefore, coexists with strong inbreeding depression. However, even in inbreeding the genetic coefficient of covariation among relatives appears to be strongly and linearly related to the classical coefficient of kinship. This means that deviations from the additive model with inbreeding could be partly due to an effect of inbreeding on variances through an effect on means. An attempt to analyze genetic effects from a theoretical model, based upon the identity by descent relationship at the level of means and of covariances between relatives, tends to show that allelic interactions are more important and nonallelic interactions are less important for a character closely related to fitness. For a complex character, these results lead to the conception of a genome organized in polygenic complementary blocks integrating epistasis and dominance. Some consequences for plant breeding are also discussed.
THE EFFECTIVE PROPORTION OF SELF-FERTILIZATION WITH CONSANGUINEOUS MATINGS IN INBRED POPULATIONS
Authors: Ritland Kermit
Published: January 2021

Allelic segregation at a single locus among offspring derived from matings, including those between inbred relatives, is a combination of two patterns, corresponding to self-fertilization and random outcrossing. The proportion of effective self-fertilization is termed the "effective selfing rate," and it is specified with identity coefficients. The description of the offspring genotypic distribution for a population with mating among relatives requires a set of three independent parameters of genetic and mating structure. One such set is the inbreeding coefficient of parents, the coefficient of kinship between mates and the effective selfing rate. The model used to derive the effective selfing rate distinguishes between the effective selfing rates of inbred vs. outbred parents; the mixed mating model does not distinguish between these two rates. As a result, the mixed mating model usually gives biased estimates of effective selfing, if there is mating among inbred relatives. The procedure for estimation of effective selfing, based upon progeny array data distributed according to the "effective selfing model," is presented, and an example is given.
HEALING OF BROKEN LINEAR DICENTRIC CHROMOSOMES IN YEAST
Authors: Haber James E , Thorburn Patricia C
Published: January 2021

In yeast, meiotic recombination between a linear chromosome III and a haploid-viable circular chromosome will yield a dicentric, tandemly duplicated chromosome. Spores containing apparently intact dicentric chromosomes were recovered from tetrads with three viable spores. The spore containing the dicentric inherited URA3 (part of the recombinant DNA used to join regions near the ends of the chromosome into a circle) as well as HML, HMR and MAL2 (located near the two ends of a linear but deleted from the circle). The Ura+ Mal+ colonies were highly variegated, giving rise to as many as seven distinctly different stable ("healed") derivatives, some of which were Ura+ Mal+, others Ura+ Mal- and others Ura- Mal+. The colonies were also sectored for five markers (HIS4, LEU2, CRY1, MAT and THR4) initially heterozygous in the tandemly duplicated dicentric chromosome.—Southern blot and genetic analyses have demonstrated that these stable derivatives arose from mitotic break-age of the dicentric chromosome, followed by one of several different healing events. The majority of the stable derivatives contained circular or linear chromosomes apparently resulting from homologous recombination between a broken chromosome end and a homologous region on the other end of the original dicentric duplicated chromosome. A smaller proportion of events resulted in apparently uniquely healed linear chromosomes in which the broken chromosome acquired a new telomere. In two instances we recovered chromosome III partially duplicated with a novel right end. We have also found one derivative that had also experienced rearrangement of repeated DNA sequences found adjacent to yeast telomeres.
CHOLINE ACETYLTRANSFERASE-DEFICIENT MUTANTS OF THE NEMATODE CAENORHABDITIS ELEGANS
Authors: Rand James B , Russell Richard L
Published: January 2021

We have identified five independent allelic mutations, defining the gene cha-1, that result in decreased choline acetyltransferase (ChAT) activity in Caenorhabditis elegans. Four of the mutant alleles, when homozygous, lead to ChAT reductions of>98%, as well as recessive phenotypes of uncoordinated behavior, small size, slow growth and resistance to cholinesterase inhibitors. Animals homozygous for the fifth allele retain approximately 10% of the wild-type enzyme level; purified enzyme from this mutant has altered K  m values for both choline and acetyl-CoA and is more thermolabile than the wild-type enzyme. These qualitative alterations, together with gene dosage data, argue that cha-1 is the structural gene for ChAT. cha-1 has been mapped to the left arm of linkage group IV and is within 0.02 map unit of the gene unc-17, mutant alleles of which lead to all of the phenotypes of cha-1 mutants except for the ChAT deficiency. Extensive complementation studies of cha-1 and unc-17 alleles reveal a complex complementation pattern, suggesting that both loci may be part of a single complex gene.
MUTATIONAL ANALYSIS OF THE REGION SURROUNDING THE 93D HEAT SHOCK LOCUS OF DROSOPHILA MELANOGASTER
Authors: Mohler Jym , Pardue Mary Lou
Published: January 2021

The region containing subdivisions 93C, 93D and 93E on chromosome 3 of Drosophila melanogaster has been screened for visible and lethal mutations. Treatment with three mutagens, γ irradiation, ethyl methanesulfonate and diepoxybutane, has produced mutations that fall into 20 complementation groups, including the previously identified ebony locus. No point mutations affecting the heat shock locus in 93D were detected; however, a pair of deficiencies that overlap in the region of this locus was isolated. Flies heterozygous in trans for this pair of deficiencies are capable of producing all of the major heat shock puffs (except 93D) and the major heat shock proteins. In addition, these flies show recovery of normal protein synthesis following a heat shock.
CHROMOSOMAL CONTROL OF FERTILITY IN DROSOPHILA MELANOGASTER. I. RESCUE OF T(Y;A)/bb
l-158 MALE STERILITY BY CHROMOSOME REARRANGEMENT
Authors: Lyttle Terrence W
Published: January 2021

Many translocations between the Y chromosome and a major autosome have no effect on the fertility of Drosophila melanogaster males. However, when such translocation-bearing males also carry an X chromosome deficient for a large portion of the centric heterochromatin, they are generally sterile. This has been interpreted to be the result of an interaction between the deficiency and the subterminally capped autosome. Using this observation as a starting point, we have developed a selection scheme for radiation-induced translocation resealings that depends on the prediction that fertility in the presence of such a deficient X is restored whenever the displaced autosomal tip is brought back in association with an autosomal centromere. The observation and the prediction form the basis for what is referred to as the autosomal continuity model for male fertility.—Such a mutagenesis scheme offers several advantages. (1) It is efficient, producing upward of 1% resealings in some cases. (2) It is simple; since fertility is the basis for the selective screen, many males can be tested in a single vial. (3) It can be used to simultaneously generate both duplications and deficiencies specific for chromosomal material adjacent to the original translocation breakpoints. (4) The target for mutagenesis can be mature sperm.—Analysis of the pattern of male-fertile rearrangements obtained from several translocation lines using this protocol indicates that continuity of the autosomal tips and their centromeres is neither a necessary nor sufficient condition for male fertility in the presence of a bobbed-deficient X. Thus, the simple autosomal continuity model is not adequate to explain this complicated mechanism of chromosomal control of fertility and will have to be revised accordingly. Potential future lines of inquiry toward this goal are discussed.
CHLOROPLAST DNA VARIATION IN PEARL MILLET AND RELATED SPECIES
Authors: Clegg Michael T , Rawson James R Y , Thomas Karen
Published: January 2021

The evolution of specific regions of the chloroplast genome was studied in five grass species in the genus Pennisetum, including pearl millet, and one species from a related genus (Cenchrus). Three different regions of the chloroplast DNA were investigated. The first region included a 12-kilobase pair (kbp) EcoRI fragment containing the 23S, 16S and 5S ribosomal RNA genes, which is part of a larger duplicated region of reverse orientation. The second region was contained in a 21-kbp Sa/I fragment, which spans the short single-copy sequence separating the two reverse repeat structures and which overlaps the duplicated copies of the 12-kbp EcoRI fragment. The third region was a 6-kbp EcoRI fragment located in the large single-copy region of the chloroplast genome. Together these regions account for slightly less than 25% of the chloroplast genome. Each of these DNA fragments was cloned and used as hybridization probes to determine the distribution of homologous DNA fragments generated by various restriction endonuclease digests.—A survey of 12 geographically diverse collections of pearl millet showed no indication of chloroplast DNA sequence polymorphism, despite moderate levels of nuclear-encoded enzyme polymorphism. Interspecific and intergeneric differences were found for restriction endonuclease sites in both the small and the large single-copy regions of the chloroplast genome. The reverse repeat structure showed identical restriction site distributions in all materials surveyed. These results suggest that the reverse repeat region is differentially conserved during the evolution of the chloroplast genome.
A COMPARISON OF POSTMIGRATION AND MIGRATION-COUPLED MISMATCH CORRECTION MECHANISMS FOR BRANCH MIGRATION-MEDIATED GENE CONVERSION
Authors: Seed Brian
Published: January 2021

We examine several models for nonreciprocal recombination based on the formation of heteroduplex DNA by bidirectional branch migration. We show that the consistency of genetic maps resulting from postmigration mismatch correction is disrupted by the presence of a favored site for initiation of strand exchange, with local inversion of the genetic and physical maps a predicted consequence. We also examine models that allow mismatch correction to take place concurrently with the process of strand exchange and show that the genetic maps resulting from such migration-coupled conversions are substantially free of the anomalies expected of postmigration conversions.
GENETICAL ANALYSIS OF CHROMOSOMAL INTERACTION EFFECTS ON THE ACTIVITIES OF THE GLUCOSE 6-PHOSPHATE AND 6-PHOSPHOGLUCONATE DEHYDROGENASES IN DROSOPHILA MELANOGASTER
Authors: Miyashita Naohiko , Laurie-Ahlberg C C
Published: January 2021

By combining ten second and ten third chromosomes, we investigated chromosomal interaction with respect to the action of the modifier factors on G6PD and 6PGD activities in Drosophila melanogaster. Analysis of variance revealed that highly significant chromosomal interaction exists for both enzyme activities. From the estimated variance components, it was concluded that the variation in enzyme activity attributed to the intera ction is as great as the variation attributed to the second chromosome but less than attributed to the third chromosome. The interaction is not explained by the variation of body size (live weight). The interaction is generated from both the lack of correlation of second chromosomes for third chromosome backgrounds and the heterogeneous variance of second chromosomes for different third chromosome backgrounds. Large and constant correlation between G6PD and 6PGD activities were found for third chromosomes with any second chromosome background, whereas the correlations for second chromosomes were much smaller and varied considerably with the third chromosome background. This result suggests that the activity modifiers on the second chromosome are under the influence of third chromosome factors.
INTERACTION IN TRANSMISSION FREQUENCY BETWEEN THE SECOND AND THE THIRD CHROMOSOMES IN DROSOPHILA MELANOGASTER
Authors: Hiraizumi Yuichiro
Published: January 2021

Wild second and third chromosomes from isofemale lines established from wild-inseminated females captured in natural populations of Drosophila melanogaster in Hawaii, New York, North Carolina and Texas were made heterozygous in males with marked second and third chromosomes from a laboratory strain, and the transmission frequencies of the wild second (= k  2) and the third (= k  3) chromosomes from the heterozygous male parents were measured. Based upon the preliminary tests of k  2, the isofemale lines were classified into two groups; group A included those lines showing average k  2 values considerably smaller than the Mendelian expectation of 0.5, and group B included those lines showing average k  2 values close to 0.5. Effects of the wild second chromosomes on k  2 in group A were suppressed (the average k  2 values increased) by the presence of the wild third chromosomes, whereas the wild second chromosomes in this group, in turn, caused a decrease in k  3 of the wild third chromosomes. The intensities of the observed effects were more or less comparable in their absolute values, and these phenomena do not appear to be due to differential viabilities of zygotes. No such interaction was observed between the wild second and third chromosomes in group B. An extention of the model of the Segregation Distorter system of D. melanogaster, as well as a model based upon the P-M system of hybrid dysgenesis, may explain the observed results.
MUTATION RATES FOR ENZYME AND MORPHOLOGICAL LOCI IN BARLEY (HORDEUM VULGARE L.)
Authors: Kahler A L , Allard R W , Miller R D
Published: January 2021

Spontaneous mutation rates were estimated by assaying 84,126 seedlings of a highly homozygous barley line (isogenic line 2025) for five enzyme loci. No mutants were observed in 841,260 allele replications. This result excludes, at probability level 0.95, a spontaneous mutation rate larger than 3.56 x 10-6/locus/gamete/generation for these enzyme loci. Isogenic line 2025 also was scored for mutants at four loci governing morphological variants. No mutants were observed in 3,386,850 allele replications which indicates that the upper bound for the mutation rate for these loci is 8.85 x 10-7. It was concluded that, even though spontaneous mutation has been important in creating variability in the barley species at the loci scored, the rate is too low to have much affect on the short-term dynamics of barley populations.
ARYL HYDROCARBON HYDROXYLASE INDUCTION BY BENZO[a]ANTHRACENE: REGULATORY GENE LOCALIZED TO THE DISTAL PORTION OF MOUSE CHROMOSOME 17
Authors: Legraverend Catherine , Kärenlampi Sirpa O , Bigelow Sanford W , Lalley Peter A , Kozak Christine A , Womack James E , Nebert Daniel W
Published: January 2021

Aryl hydrocarbon (benzo[a]pyrene) hydroxylase inducibility by benzo[a]anthracene was studied in 29 somatic cell hybrid clones, developed by fusing mouse spleen or peritoneal cells from four different inbred strains with hypoxanthine phosphoribosyltransferase-deficient Chinese hamster E36 cells. Karyotype analysis plus 25 markers assigned to 16 autosomes and the X chromosome were examined. In 28 of the 29 clones, the presence or absence of inducibility is associated with the presence or absence, respectively, of mouse chromosome 17.—Liver microsomal aryl hydrocarbon hydroxylase induction by 3-methylcholanthrene or benzo[a]anthracene was assessed in appropriate backcrosses with the Mus musculus molossinus, M. m. castaneus, MOR/Cv, PL/J, SM/J and DBA/2J inbred strains and in 13 NX8 recombinant inbred lines. Twenty-seven biochemical genetic markers representing all but four autosomes were tested for possible linkage with the hydroxylase inducibility, and no linkage was found. The hepatic Ah receptor was quantitated in 26 BXD recombinant inbred lines; the Ah phenotype did not match exactly any of the more than 70 genes with established strain distribution patterns representing 12 autosomes and at least five unlinked markers.—It is concluded that a major gene controlling aryl hydrocarbon hydroxylase inducibility by benzo[a]anthracene is located on chromosome 17. Because there is no significant linkage with any of three biochemical markers in the upper third of the chromosome, we conclude that the inducibility gene is located in the distal 40% of mouse chromosome 17. Whether this trait represents the Ah locus, i.e., the gene encoding the cytosolic Ah receptor, will require further study.
NATURAL SELECTION WITH NUCLEAR AND CYTOPLASMIC TRANSMISSION. I. A DETERMINISTIC MODEL
Authors: Clark Andrew G
Published: January 2021

A deterministic model allowing variation at a nuclear genetic locus in a population segregating two cytoplasmic types is formulated. Additive, multiplicative and symmetric viability matrices are analyzed for existence and stability of equilibria. The protectedness of polymorphisms in both nuclear genes and cytoplasmic types is also investigated in the general model. In no case is a complete polymorphism protected with this deterministic model. Results are discussed in light of the extensive variation in mtDNA that has recently been reported.
GENETIC ANALYSIS OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER IN JAPAN. III. GENETIC VARIABILITY OF INDUCING FACTORS OF AMYLASE AND FITNESS
Authors: Yamazaki Tsuneyuki , Matsuo Yoshinori
Published: January 2021

"Inducibility" of amylase in Drosophila melanogaster was defined and investigated in a natural population from Japan. Inducibility represents the effects of factors remote from the structural gene that control the amount of enzyme produced. Inducibility of an isogenic line is measured as the ratio of the enzyme's specific activity in two different inducing environments. There was considerable genetic variability with respect to inducibility of amylase in 44 isogenic lines derived from a natural population of D. melanogaster . Net fitness and its components in these isogenic lines were also measured. The results indicated that, although the inducibility of the enzyme was positively correlated with the net fitness (rg = 0.63 ± 0.2), the enzyme activities in the normal medium were not (rg = 0.12 ± 0.37). The analysis of the data shows that the differences in inducing factors are mainly responsible for the differences in the fitness of lines and are the genetic materials for the adaptive evolution of organisms.
CAENORHABDITIS ELEGANS DEFICIENCY MAPPING
Authors: Sigurdson D Christine , Spanier Gail J , Herman Robert K
Published: January 2021

Six schemes were used to identify 80 independent recessive lethal deficiencies of linkage group (LG) II following X-ray treatment of the nematode Caenorhabditis elegans. Complementation tests between the deficiencies and ethyl methanesulfonate-induced recessive visible, lethal and sterile mutations and between different deficiencies were used to characterize the extents of the deficiencies. Deficiency endpoints thus helped to order 36 sites within a region representing about half of the loci on LG II and extending over about 5 map units. New mutations occurring in this region can be assigned to particular segments of the map by complementation tests against a small number of deficiencies; this facilitates the assignment of single-site mutations to particular genes, as we illustrate. Five sperm-defective and five oocyte-defective LG II sterile mutants were identified and mapped. Certain deficiency-by-deficiency complementation tests allowed us to suggest that the phenotypes of null mutations at two loci represented by visible alleles are wild type and that null mutations at a third locus confer a visible phenotype. A segment of LG II that is about 12 map units long and largely devoid of identified loci seems to be greatly favored for crossing over.
CONDITIONAL POLYGENIC EFFECTS IN THE STERNOPLEURAL BRISTLE SYSTEM OF DROSOPHILA MELANOGASTER
Authors: Schnee Fred B , Thompson James N
Published: January 2021

The chromosomal architecture of genotype × environment interactions was investigated in lines of Drosophila melanogaster selected for increased or decreased sternopleural bristle number at 18°, 25° and 29°. In general, interactions were found to have a stabilizing effect upon the bristle phenotype, in the sense that the genotype × environment interaction tended to increase bristle number under conditions in which temperature alone reduced bristle number and vice versa. The polygenic modifiers of mean bristle number were often separable from modifiers of the response to temperature both at the chromosomal level and intrachromosomally. In one of the low selection lines, a temperature-dependent polygenic locus was mapped on chromosome 3. It is suggested that genotype × environment interactions be thought of in terms of conditional polygenic expression. Such conditionality may be one of the ways in which polygenic variation is maintained in a population in the face of selection for an optimum phenotype.
THE GENETIC ANALYSIS OF QUANTITATIVE TRAIT DIFFERENCES BETWEEN TWO HOMOZYGOUS LINES
Authors: Elston R C
Published: January 2021

Previous maximum likelihood methods to analyze quantitative data on two inbred parental strains, their F1 and backcross generations are extended in three directions: (1) a method is suggested to transform the data to better satisfy the assumptions of normality and homoscedasticity; (2) the likelihoods are modified to allow for litter correlations and heteroscedasticity and (3) allowance is made for the incorporation of F2 data. The problem of making a choice among a set of simple genetic hypotheses is further discussed.
SPECIFIC DELETION OCCURRING IN THE DIRECTED EVOLUTION OF 6-PHOSPHOGLUCONATE DEHYDROGENASE IN ESCHERICHIA COLI
Authors: Miller Raymond D , Dykhuizen Daniel E , Green Louis , Hartl Daniel L
Published: January 2021

A novel genetic change leading to increased activity of 6-phosphogluconate dehydrogenase (6PGD) in E. coli has been observed. The mutation is a deletion of approximately 0.4 kilobase pairs occurring between the structural gene of 6PGD (gnd) and one copy of an insertion element (IS 5) found normally in E. coli K12 a few hundred base pairs upstream (counterclockwise) from gnd at 44 minutes on the conventional genetic map. The deletion is associated with a threefold higher activity of 6PGD and a 57% increase in the maximum growth rate when cells are grown in gluconate.
RING CHROMOSOMES AND rDNA MAGNIFICATION IN DROSOPHILA
Authors: Endow Sharyn A , Komma Donald J , Atwood K C
Published: January 2021

Tartof showed that ribosomal gene magnification in Drosophila was inhibited in a ring Χ chromosome. The present studies extend this observation by showing that ring Χ chromosomes are lost meiotically in male Drosophila undergoing ribosomal gene magnification as evidenced by the recovery of a lower number of ring-bearing progeny under magnifying conditions compared with nonmagnifying conditions. Associated with ring chromosome loss is a highly significant increase in the number of double-sized dicentric ring chromosomes in meiotic cells from magnifying males. These observations explain the failure of ring Χ chromosomes to magnify and imply that magnification in rod chromosomes occurs via a mechanism of unequal sister chromatid exchange. Our results support the hypothesis that the primary event of magnification is a sister chromatid exchange in the rDNA, that the frequency of sister strand exchanges is increased in magnifying flies, that a significant number of exchanges in magnifying flies occurs meiotically and that some of the exchanges are nonreciprocal. We have also found that autosomal mutations can affect both the frequency of abnormal ring structures and the ability of ring Χ chromosomes to magnify.
ASSOCIATION OF ISOZYMES WITH A RECIPROCAL TRANSLOCATION IN CULTIVATED RYE (SECALE CEREALE L.)
Authors: Figueiras Ana M , Gonzalez-Jaen Maria T , Salinas Julio , Benito Cesar
Published: January 2021

In rye (Secale cereale L. cv. "Ailés") the progeny of a cross between a structural heterozygote for a reciprocal translocation (involving the 1R chromosome) and a homozygote for the standard chromosome arrangement were analyzed for the electrophoretic patterns of eight different leaf isozymes and also for their meiotic configuration at metaphase I.—The Got-3 and Mdh-2b loci are linked to each other and also to the reciprocal translocation. The Mdh-2b locus is located in the interstitial segment of the 3Rq chromosome arm, with an estimated distance of 8 cM to the breakpoint. Therefore, the reciprocal translocation involves the 1R and 3R chromosomes.—Also, the Mdh-1 and 6-Pgd-2 loci are linked (16 ± 3 cM) and have been located on the 2Rq arm. Finally, the Per-3 and Per-4 loci are located on the 2Rp chromosome arm at an estimated distance of 26 ± 4 cM.
CHLOROPLAST DNA VARIATION AND EVOLUTION IN PISUM: PATTERNS OF CHANGE AND PHYLOGENETIC ANALYSIS
Authors: Palmer Jeffrey D , Jorgensen Richard A , Thompson William F
Published: January 2021

Variation in 30 chloroplast DNAs, representing 22 wild and cultivated accessions in the genus Pisum, was analyzed by comparing fragment patterns produced by 16 restriction endonucleases. Three types of mutations were detected. First, an inversion of between 2.2 kilobase pairs (kb) and 5.2 kb distinguished a population of P. humile from all other Pisum accessions examined. Second, deletions and insertions of between 50 and 1200 base pairs produced small restriction fragment length variations in four regions of the 120-kb chloroplast genome. Two of these regions—one of which is located within the sequence that is inverted in P. humile—showed a high degree of size polymorphism, to the extent that size differences were detected between individuals from the same accession. Finally, a total of only 11 restriction site mutations were detected among the 165 restriction sites sampled in the 30 DNAs. Based on these results and previous data, we conclude that the chloroplast genome is evolving very slowly relative to nuclear and mitochondrial DNAs. The Pisum chloroplast DNA restriction site mutations define two major lineages: One includes all tested accessions of P. fulvum, which is known to be cytogenetically quite distinct from all other Pisum taxa. The second includes 12 of 13 cultivated lines of the garden pea (P. sativum) and a wild population of P. humile from northern Israel. These observations strongly reinforce an earlier conclusion that the cultivated pea was domesticated primarily from northern populations of P. humile. A 13th P. sativum cultivar has a chloroplast genome that is significantly different from those of the aforementioned lines and somewhat more similar to those of P. elatius and southern populations of P. humile. This observation indicates that secondary hybridization may have occurred during the domestication of the garden pea.
FOUR SIMULTANEOUSLY STABLE POLYMORPHIC EQUILIBRIA IN TWO-LOCUS TWO-ALLELE MODELS
Authors: Hastings Alan
Published: January 2021

The existence of four simultaneously stable equilibria with both loci polymorphic is shown for the Lewontin-Kojima version of the two-locus two-allele symmetric viability model, using bifurcation theory. This exceeds the previously claimed bound of two stable polymorphisms. Biological implications of the result are discussed.
TEMPORAL ACTION OF MUTATIONS INHIBITING THE ACCOMPLISHMENT OF QUIESCENCE OR DISRUPTING DEVELOPMENT IN THE FUNGUS PODOSPORA ANSERINA
Authors: Durrens Pascal , Bernet Jean
Published: January 2021

Two Podospora mutants carrying mutations modE and modF were persumed to be quiescent defective, because, when grown under glucose limitation, they differed from the wild-type strain in an excess of dry weight production and a reduction of cell survival. New insight on the action of modE and modF mutations was provided by the study of double mutants resulting from the association of modE or modF mutations with unrelated developmental mutations.—ModE and modF were first coupled to three allelic mutations (modC) that inhibit production of all hyphal cell derivatives (late ramifications, aerial hyphae and protoperithecia). Suppression in the double mutants of the excess of proliferation associated with modE and modF and restoration of normal cell survival indicated that modE and modF result in an uncontrolled production of hyphal cell derivatives in which deregulation is presumed to be responsible for the reduction of cell survival following glucose exhaustion.—ModE and modF were associated with mutations of two genes (modD and modG) which abolish production of hyphal cell derivatives (like modC mutations) but also inhibit the renewal of growth of cells situated in the center of colonies. Investigations of eight of these double mutants showed that modE and modF mutations suppress the inhibitory action of modD and modG on production of hyphal cell derivatives and on growth renewal.—Taken together these results lead to the suggestion that the accomplishment of a quiescent state for cell survival under glucose starvation is the final stage in the differentiation of hyphal cells and prerequisite for the production of derivatives of hyphal cells and for a control of their development.
TARGETED SELECTION EXPERIMENTS AND ENZYME POLYMORPHISM: NEGATIVE EVIDENCE FOR OCTANOATE SELECTION AT THE G6PD LOCUS IN DROSOPHILA MELANOGASTER
Authors: Eanes Walter F , Bingham Brendan , Hey Jody , Houle David
Published: January 2021

Published studies have reported significant selection with respect to the G6pd locus for Drosophila melanogaster reared on Na-octanoate food. We have reexamined the selective effects of Na-octanoate on egg to adult viability with respect to the G6pd polymorphism using specially constructed X chromosomes. Four experiments were carried out using different 6Pgd backgrounds in two recombinant sets of chromosomes segregating for the G6pd locus but constructed so as to minimize variation over most of the X chromosome. In addition, two measures of viability were used, and the size of the experiments and their associated degrees of freedom are approximately double those reported in the former studies. Our results find no evidence for differential selection on G6pd genotypes (males and females) by Na-octanoate and, therefore, do not corroborate the positive results of selection reported by other investigators. The reasons for our different results are discussed.
VALINE-RESISTANCE, A POTENTIAL MARKER IN PLANT CELL GENETICS. I. DISTINCTION BETWEEN TWO TYPES OF VALINE-RESISTANT TOBACCO MUTANTS ISOLATED FROM PROTOPLAST-DERIVED CELLS
Authors: Bourgin J P , Goujaud J , Missonier C , Pethe C
Published: January 2021

In previous experiments, seven lines of valine-resistant plants were regenerated from protoplast-derived haploid tobacco mesophyll cells which had been UV mutagenized and submitted to selection by toxic concentrations of valine. In this study we described the transmission of valine-resistance to progeny and a preliminary phenotypical and biochemical characterization of the resistant plants.—Two types were thus distinguished among the seven mutant lines. Valine-resistance of the mutants of the first type (three lines) was transmitted as a single Mendelian dominant character (Vr1), whereas valine-resistance of the second type (four lines) was transmitted as a digenic recessive character (vr2 and vr3). Allelism tests revealed that the four recessive mutant lines yielded resistant progeny when intercrossed and, therefore, bear recessive mutant alleles at the same two unlinked loci.—When cultured at a density of 100 cell/ml, protoplast-derived cells of mutants of the first type had a low level of resistance to valine, whereas protoplast-derived cells of mutants of the second type displayed a high level of resistance to valine and to other amino acids.—According to the results of 14 C-labelled amino acid uptake experiments, the amino acid resistance of mutants of the second type, but not valine-resistance of the first type, could be accounted for by reduced uptake of several amino acids. Possible uses of valine-resistance as a marker in plant cell genetics are discussed.
SELECTION WITH GENE-CYTOPLASM INTERACTIONS. II. MAINTENANCE OF GYNODIOECY
Authors: Ross M D , Gregorius H R
Published: January 2021

Gynodioecy is apparently frequently inherited through gene-cytoplasm interactions. General conditions for the protectedness of gene-cytoplasm polymorphisms for a biallelic model with two cytoplasm types were obtained previously, and these are applied to seven special cases of gene-cytoplasm interactions controlling gynodioecy and involving dominance. It is assumed that nuclear polymorphisms cannot be maintained in one cytoplasm type only. It is held that pure cytoplasmic inheritance of gynodioecy without nuclear interactions is unlikely, and it is shown that gynodioecy with gene-cytoplasm interactions is easier to establish than purely nuclear gynodioecy, for monogenic biallelic dominant or recessive inheritance. For three special cases, a resource-allocation model with simple assumptions always leads to conditions for protectedness of gynodioecy.
INVESTIGATION OF THE NATURE OF P-INDUCED MALE RECOMBINATION IN DROSOPHILA MELANOGASTER
Authors: Sinclair Donald A R , Grigliatti Thomas A
Published: January 2021

The present study consists of an investigation of P-induced male recombination in Drosophila melanogaster from a number of perspectives. In an initial set of experiments, male recombination induced by several different P strains was examined on both major autosomes. The ability of these P strains to evoke recombination is striking; in many cases it exceeded that of radiation treatment. Also of interest is the apparent nonrandom chromosomal distribution of P-exchange breakpoints. The data suggest that both recombinagenic capacity and distribution pattern of exchange breakpoints may be P-strain specific. In addition to these findings, we have confirmed previous indications that P-induced exchange is reasonably symmetrical and that it frequently occurs during premeiotic stages of spermatogenesis. Moreover, we have established that radiation and P background act additively with regard to the induction of male recombination. The second part of the work involved an analysis of heterochromatic vs. euchromatic recombination induced by several recombinagenically potent P strains. Results of these experiments have confirmed our earlier findings concerning the recombinagenic capacity of P strains. More importantly, it would appear that P-induced exchange in heterochromatin is rare. The induction of various kinds of mutations was also monitored in several of these experiments. The results indicate that the mutagenic potential of the P strains is substantial and of particular interest, that certain types of mutations are P-strain specific. For example, rare heterochromatic lesions were recovered exclusively in the experiment using the h12 strain, whereas a novel pleiotropic mutation occurred at a high frequency only in the T-007 experiment. Our findings are discussed within the context of a model of P-induced exchange.
MOLECULAR CLONING OF α-AMYLASE GENES FROM DROSOPHILA MELANOGASTER. II. CLONE ORGANIZATION AND VERIFICATION
Authors: Levy Jack N , Gemmill Robert M , Doane Winifred W
Published: January 2021

Restriction maps of an α-amylase structural gene clone, λDm65, and of four putative α-amylase pseudogene clones are presented. Two α-amylase structural genes, inverted with respect to each other, are contained in λDm65. Subregions of internal DNA sequence homology within λDm65 and of cross-homology between the presumptive pseudogene clones and λDm65 were determined. Subregions of cross-homology between the Drosophila clones and the mouse α-amylase cDNA clone, pMSa104, were also determined. The presence of functional α-amylase structural genes in λDm65 was verified by injection of appropriate subclones into the germinal vesicle of Xenopus oocytes, followed by incubation of the oocytes under conditions that allowed coupled transcription and translation of injected genes to occur. Subclones of the 3.8- and 5.6- kb EcoRI fragments of λDm65 were shown to code for α-amylase isozymes 1 and 3, respectively, of Drosophila melanogaster Canton-S. Both subclones are homologous to RNA of a size sufficient to accommodate the α-amylase-coding information. No RNA species homologous to other subcloned EcoRI fragments of λDm65 was detected.
THE GLN1 LOCUS OF SACCHAROMYCES CEREVISIAE ENCODES GLUTAMINE SYNTHETASE
Authors: Mitchell Aaron P
Published: January 2021

Among 41 yeast glutamine auxotrophs, complementation analysis defined a single gene, GLN1, on chromosome 16 between MAK3 and MAK6. Half of the alleles fell into two intragenic complementation classes. No clustering of complementing alleles was found in a fine structure map. Altered glutamine synthetase subunits, including nonsense fragments and charge variants, were identified in several of the mutants, indicating that GLN1 is the structural gene for this enzyme. Negative complementation was observed for almost every allele associated with a protein product and all gln1/+ heterozygotes displayed reduced susceptibility to ammonia repression of the remaining glutamine synthetase activity. This latter observation is explained by the hypothesis that ammonia represses the enzyme only through its metabolism to glutamine. A basis for the two gln1 complementation classes is proposed.
TRANSPOSITION OF PLASMID-BORNE Tn10 ELEMENTS DOES NOT EXHIBIT SIMPLE LENGTH-DEPENDENCE
Authors: Way J C , Kleckner N
Published: January 2021

The transposition frequencies of Tn10 elements from the bacterial chromosome to an F epitome decrease 40% for every kilobase increase in transposon length. The basis for this relationship is not known. We have now examined complemented transposition of defective Tn10 elements off small multicopy plasmids. We find that length dependence in this situation is either reduced or absent, depending on the specific class of transposition events involved. These observations can be interpreted as evidence against the model that chromosomal length dependence occurs because of decay of a transposition-associated replicative complex. This interpretation is consistent with unrelated experiments suggesting that Tn10 transposition is normally nonreplicative. Alternative explanations of length dependence phenomena are discussed.
NONRANDOM MATING IN AN OPEN-POLLINATED MAIZE POPULATION
Authors: Bijlsma R , Allard R W , Kahler A L
Published: January 2021

Randomness of fertilization was studied in an open-pollinated population of maize (Zea mays L.) through allozyme assays of seedlings from open-pollinated seeds produced on both tasseled and detasseled plants. Mixed-mating-model estimates of the amount of outcrossing (t) were not significantly different from t = 1.00 for four enzyme loci (Adh1, Idh2, Got1 and Acp1), indicating that fertilizations were at random in the population. However, for loci Prx1 and Est4, estimates of t were significantly smaller than unity-0.80 and 0.70 for tasseled plants and 0.81 and 0.80 for detasseled plants. The excesses of homogametic fertilizations detected on the detasseled plants could not have been due to selffertilization, s = 1 - t, because the detasseled plants shed no pollen. Analyses of allelic frequencies in the pollen that produced seed on the detasseled plants established that different maternal plants sampled genetically different populations of pollen from the outcross pollen pool. It was suggested that the causes of the differential sampling were temporal variation in the pollen pool, and/or gametophytic selection, correlated with marker-locus genotype. Two-, three- and four-locus interactions among the marker loci were often statistically significant, indicating that the factors responsible for the nonrandom gametic unions observed in the maize population studied were complexly interactive.
MONTE CARLO STUDIES OF PLANT MATING SYSTEM ESTIMATION MODELS: THE ONE-POLLEN PARENT AND MIXED MATING MODELS
Authors: Schoen Daniel J , Clegg Michael T
Published: January 2021

Estimation of mating system parameters in plant populations typically employs family-structured samples of progeny genotypes. These estimation models postulate a mixture of self-fertilization and random outcrossing. One assumption of such models concerns the distribution of pollen genotypes among eggs within single maternal families. Previous applications of the mixed mating model to mating system estimation have assumed that pollen genotypes are sampled randomly from the total population in forming outcrossed progeny within families. In contrast, the one-pollen parent model assumes that outcrossed progeny within a family share a single-pollen parent genotype. Monte Carlo simulations of family-structured sampling were carried out to examine the consequences of violations of the different assumptions of the two models regarding the distribution of pollen genotypes among eggs. When these assumptions are violated, estimates of mating system parameters may be significantly different from their true values and may exhibit distributions which depart from normality. Monte Carlo methods were also used to examine the utility of the bootstrap resampling algorithm for estimating the variances of mating system parameters. The bootstrap method gives variance estimates that approximate empirically determined values. When applied to data from two plant populations which differ in pollen genotype distributions within families, the two estimation procedures exhibit the same behavior as that seen with the simulated data.
THE TRANSPOSABLE ELEMENT Ds AFFECTS THE PATTERN OF INTRAGENIC RECOMBINATION AT THE bz AND R LOCI IN MAIZE
Authors: Dooner H K , Kermicle J L
Published: January 2021

Insertion of the transposable element Ds into either the bz or R locus affects intragenic recombination in various ways. We have examined here one aspect of this problem; namely, the distribution of flanking markers among intragenic recombinations produced by different types of heterozygotes carrying Ds insertion mutations. Heteroallelic combinations of a Ds insertion mutation and a mutation borne on a structurally normal chromosome generate a majority of intragenic recombinants of a crossover type. In contrast to this, most intragenic recombinants obtained from heterozygotes between two different Ds insertion mutations have a parental arrangement of outside markers. Therefore, the resolution of the recombination intermediate would appear to depend on the nature of the mutations in the heterozygote.