bluuebunny/crossref_metadata_2025 huggingface dataset:
GENETIC VARIATION AFFECTING THE EXPRESSION OF CATALASE IN DROSOPHILA MELANOGASTER: CORRELATIONS WITH RATES OF ENZYME SYNTHESIS AND DEGRADATION
Authors: Bewley Glenn C , Laurie-Ahlberg Cathy C
Published: January 2021

Both second and third chromosome substitution lines isolated from natural populations of Drosophila melanogaster affect the expression of catalase (EC 1.11.1.6) at both the larval and adult stages of development. In each case, the level of catalase activity is strongly related to the level of catalase-specific cross-reacting material. Turnover studies employing the catalase inhibitor 3-amino-1,2,4-triazole were conducted on a selected number of lines. Although the variation in steady state levels of catalase protein was highly significant among lines, variation in intracellular degradation rate was not. These results suggest that the different steady state levels observed among lines largely reflect different rates of catalase synthesis.
GENETIC ANALYSIS OF BROWN ADIPOSE TISSUE, OBESITY AND GROWTH IN MICE
Authors: Saxton A M , Eisen E J
Published: January 2021

The hypothesis developed from single-gene mutant obese rodents that brown adipose tissue (BAT), through its thermogenic ability, is an important factor in the development of obesity, was tested in a randombred population of mice in which degree of adiposity is polygenically determined. Additive direct genetic parameters for measures of body size, lean, fatness and BAT at 6 wk of age were estimated under control and high-fat postweaning dietary regimens. Heritabilities were generally similar for the two diets. However, the lipid-free dry (LFD) component of BAT had a heritability estimate of 0.70 ± 0.26 on the control diet, but only 0.09 ± 0.20 on the high-fat diet. For all traits, genotype by diet interactions indicated that additive direct genetic rankings were not significantly different for the two diets. Based on estimates of genetic parameters in the control diet, selection for 6-wk body weight or 3- to 6-wk gain is expected to increase body size and adiposity. Selection for BAT weight is predicted to result in large, lean individuals. However, selection for the LFD content of BAT, generally believed to be a better indicator of thermogenic ability, is predicted to increase fatness as well as body size. Selection for LFD as a proportion of 6-wk body weight reduced the expected correlated response in fatness. It was concluded that BAT does not play a major role in determining the correlated response in obesity that is often found in populations selected for large body size.
PHOSPHOGLUCOSE ISOMERASE EXPRESSION IN SPECIES OF CLARKIA WITH AND WITHOUT A DUPLICATION OF THE CODING GENE
Authors: Gottlieb L D , Higgins R C
Published: January 2021

The duplication of the nuclear gene specifying the cytosolic isozyme of phosphoglucose isomerase (PGI; EC 5.3.1.9) arose within Clarkia, a genus of annual plants native to California, and now characterizes about half of the diploid species of this genus. Evidence obtained by immunological inhibition and titration of crude leaf extracts demonstrated that species with and without the duplication have the same levels of cytosolic to total PGI (the sum of the cytosolic and plastid PGI activities). The immunological studies were carried out with a specific anticytosolic PGI antiserum and were fully supported by a densitometric analysis of the electrophoretically separated isozymes. Densitometric examination of electrophoretically separated PGIs in 11 vegetable species revealed only two levels of cytosolic to total PGI activities, one of which was the same as in Clarkia. This suggests that only certain levels of the cytosolic isozyme are compatible with proper operation of the cytosolic PGI reaction and make it likely that some form of genic or metabolic regulation has evolved that compensates for the PGI duplication.
CHARACTERIZATION OF ALLOZYME NULL AND LOW ACTIVITY ALLELES FROM TWO NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Burkhart Barbara Dickson , Montgomery Elizabeth , Langley Charles H , Voelker Robert A
Published: January 2021

Null and low enzyme activity alleles recovered from two natural populations were analyzed for a number of genetic and biochemical properties. Analysis of 58 mutations at 14 loci showed that all but one allele were genetically viable and fertile, four alleles were associated with chromosome rearrangements, 28 alleles retained some enzyme activity, 13 alleles formed an active heterodimer with active alleles and five alleles showed partial interallelic complementation. Available evidence indicates that this sample includes mutations resulting from lesions in both coding and regulatory sequences. Certain mutations may be caused by transposable element insertions.
PLEIOTROPIC OVERDOMINANCE AND THE MAINTENANCE OF GENETIC VARIATION IN POLYGENIC CHARACTERS
Authors: Gillespie John H
Published: January 2021

A model of selection is described in which optimizing phenotypic selection is combined with pleiotropic overdominance. Thus, the role that mutation commonly plays in models of phenotypic evolution is replaced by balancing selection. Expressions are provided for the equilibrium genetic variance in phenotype and for the heterozygosity. An approximate analysis of the transient properties of the model shows that, in certain circumstances, the behavior is quite similar to that of models based on the interaction of mutation and selection.
CONSERVED LINKAGE WITHIN A 4-cM REGION OF MOUSE CHROMOSOME 9 AND HUMAN CHROMOSOME 11
Authors: Antonucci T K , Von Deimling O H , Rosenblum B B , Skow L C , Meisler M H
Published: January 2021

A six-point cross was carried out to determine the gene order and distances among loci on mouse chromosome 9. Our results are consistent with the following arrangement: centromere - Lap-1 - (1.2 ± 0.8) - Es-17 - (3.0 ± 1.0) - Ups - (1.3 ± 0.7) - Alp-1 - (23.1 ± 3.4) - Mod-1 - (10.9 ± 2.6) - Acy-1. This study provides the first estimate of the distances between Es-17, Ups and Alp-1. Exceptions to the preferred association of alleles of Es-17 and Ups have been found in three feral populations and one inbred strain. Evidence is presented for the homology of this chromosome region with the ESA4 - UPS - APO-AI region on the long arm of human chromosome 11.
ISOLATION AND CHARACTERIZATION OF CONDITIONAL ALLELES OF BACTERIOPHAGE T4 GENES uvsX AND uvsY
Authors: Conkling Mark A , Drake John W
Published: January 2021

The bacteriophage T4 uvsW, uvsX and uvsY gene functions are required for wild-type levels of recombination and for normal survival and mutagenesis after treatments with ultraviolet (UV) and ionizing radiations. The ability of uvsX and uvsY mutations to suppress the lethality of gene 49 mutations was used to select temperature-sensitive and amber alleles of these two genes. (uvsW mutations do not suppress gene 49 mutations.) A simple and powerful complementation test was developed to assist in assigning uvs mutations to genes. The amber alleles of uvsX and uvsY behave as simple null alleles, fully suppressing a gene 49 defect, enhancing UV killing and abolishing UV mutagenesis. However, the properties of the ts alleles of uvsX and uvsY demonstrated that suppression of a gene 49 defect, sensitivity to UV-induced inactivation and UV mutability can be partially uncoupled. These results prompt the hypothesis that radiation mutagenesis occurs during DNA chain elongation past template damage within a recombinational intermediate rather than within a conventional replication fork.
DEVELOPMENTAL USE OF GENE PRODUCTS IN DROSOPHILA: THE MATERNAL-ZYGOTIC TRANSITION
Authors: Robbins Leonard G
Published: January 2021

Recent results suggest that activity of a large fraction of the Drosophila genome is needed at multiple developmental stages. The timing of the transition from dependence on maternally stored gene products to reliance on zygotically coded products has been examined for several zygotic-lethal mutations in the z-w region of the X chromosome. The mutants differ in zygotic sensitivity to reduced maternal activity, and they have a wide range of times of lethality. Nevertheless, both temperature shift experiments and clonal analysis indicate that all of the maternal-zygotic transitions occur around the time of blastoderm formation.
EVOLUTION AND VARIATION OF RENIN GENES IN MICE
Authors: Dickinson Douglas P , Gross Kenneth W , Piccini Nina , Wilson Carol M
Published: January 2021

Inbred strains of mice carry Ren-1, a gene encoding the thermostable Renin-1 isozyme. Ren-1 is expressed at relatively low levels in mouse submandibular gland and kidney. Some strains also carry Ren-2, a gene encoding the thermolabile Renin-2 isozyme. Ren-2 is expressed at high levels in the mouse submandibular gland and at very low levels, if at all, in the kidney. Ren-1 and Ren-2 are closely linked on mouse chromosome 1, show extensive homology in coding and noncoding regions and provide a model for studying the regulation of gene expression. An investigation of renin genes and enzymatic activity in wild-derived mice identified several restriction site polymorphisms as well as putative variants in renin gene expression and protein structure. The number of renin genes carried by different subpopulations of wild-derived mice is consistent with the occurrence of a gene duplication event prior to the divergence of M. spretus (2.75-5.5 million yr ago). This conclusion is in agreement with a prior estimate based upon comparative sequence analysis of Ren-1 and Ren-2 from inbred laboratory mice.
METAPHASE I ORIENTATION OF CHAIN-FORMING INTERCHANGE QUADRIVALENTS: A THEORETICAL CONSIDERATION
Authors: Koduru Prasad R K
Published: January 2021

The orientation behavior of chain forming interchange quadrivalents at metaphase I was studied in three interchange heterozygotes of pearl millet [Pennisetum americanum (L.) Leeke] which involve chromosomes 1, 3, 6 and 7 in various combinations. Of these, two combinations predominantly produced rings and the third was a chain-forming type. The chain quadrivalents derived from the two ring-forming interchanges, as well as the chain quadrivalent generated by the third interchange, all showed one adjacent orientation at metaphase I (adjacent-1 or -2, depending upon the formation or failure of chiasmata and their positions in the different segments of the pachytene cross). Homologous centromere co-orientation leading to adjacent-1 and alternate-1 occurs following chiasma failure in the noncentric arms of the pachytene cross, and nonhomologous centromere co-orientation leading to adjacent-2 and alternate-2 occurs following chiasma failure in the centric arms of the pachytene cross. Thus, it has been proposed that, unlike in ring quadrivalents, a specific chain quadrivalent will have only homologous or nonhomologous centromere co-orientations at metaphase I.
DIRECTED FORMATION OF DELETIONS AND DUPLICATIONS USING Mud(Ap, lac)
Authors: Hughes Kelly T , Roth John R
Published: January 2021

A genetic procedure is directed for the isolation of chromosomal deletions and duplications with predetermined endpoints. These rearrangements are generated in transduction crosses using a mixture of P22-transducing phage lysates grown on two strains, each carrying a Mud-lac insertion. The formation of duplications and deletions was demonstrated in the his operon using insertions of Mud1-8 (a transposition-defectiveMud-lac phage). This technique was also used to make larger chromosomal duplications between Mud1-8 insertions in the thr and leu biosynthetic operons and between Mud insertions in the thr and pyrB operons. Genetic evidence is presented that strongly suggests that inheritance of a single Mud prophage by P22-mediated crosses requires two transduced fragments; each carrying part of the Mud prophage. The two fragments must be involved in three recombinational exchanges; one exchange joins the donor Mud fragments and two exchanges occur between the composite fragment and the recipient chromosome, one on either side of the complete donor Mud element. Since duplications only occur between Mud insertions in the same orientation on the chromosome, the method of duplication formation provides a simple means of determining the orientation of Mud1-8 on the chromosome and, therefore, the direction of transcription of the gene into which Mud is inserted. This method was also used to construct recombinants between a Mud1-8 prophage and Casadaban's protein fusion vector Mud2 and, thereby, isolate Mud2-8, a Mud derivative containing the protein fusion ability of Mud2 and the defective transposition functions of Mud1-8.
MEIOTIC RECOMBINATION AND SPORULATION IN REPAIR-DEFICIENT STRAINS OF YEAST
Authors: Dowling Elizabeth L , Maloney Daniel H , Fogel Seymour
Published: January 2021

A genetic system designed to monitor recombination and sporulation in various repair-deficient yeast strains was constructed. Variously heterozygous at seven or eight sites distributed across the genome, the system facilitated sensitive detection of changes in frequency or pattern of meiotic recombination. Ten rad mutants sensitive primarily to UV-irradiation and without terminal blocks in the sporulation process were studied. Seven were defective in excision repair (rad1, rad2, rad3, rad4, rad10, rad14 and rad16), and three were defective in mutagenic repair (rad5, rad9 and rad18). Individually, each mutant displayed behavior consistent with an orthodox meiosis including a wild-type meiotic recombination profile with respect to gene conversion, PMS and intergenic map distances. Accordingly, we conclude that these mutants are without major effect on meiotic heteroduplex formation or correction. However, certain combinations of excision-defective mutants with rad18 exhibited marked ascosporal inviability. Tetraploids homozygous for rad1 and rad18 produce a large proportion of diploid spores containing a recessive lethal.
COMPLEMENTATION AND NONCOMPLEMENTATION AMONG NONALLELIC MUTATIONS ALTERING DEVELOPMENT IN SCHIZOPHYLLUM COMMUNE
Authors: Klein Keith K , Deppe Carol S
Published: January 2021

Mutations resistant to compounds that alter the development of Schizophyllum commune (cyclic adenosine monophosphate, caffeine and imidazole) were selected. These mutations defined four genes, car (cAMP resistance), caf-1 and caf-2 (caffeine resistance) and imr (imidazole resistance). The mutations were found to be noncomplementing in certain pairs when tested against each other and against two previously isolated developmental mutations, B-con and sep (septateless), in fully compatible, forced heterokaryons. The pattern of complementation in fully compatible diploids showed noncomplementation only between allelic mutations, except for one case, imr vs. car.
GENETIC MAPPING OF CAENORHABDITIS ELEGANS COLLAGEN GENES USING DNA POLYMORPHISMS AS PHENOTYPIC MARKERS
Authors: Cox George N , Carr Stephen , Kramer James M , Hirsh David
Published: January 2021

In Caenorhabditis elegans collagens comprise a dispersed family of 40—150 genes, the majority of which probably code for collagen proteins found in the animal's cuticle. The conserved (Gly-X-Y)n triple helix coding sequence of collagen genes has facilitated the isolation of a large number of C. elegans collagen genes by recombinant DNA methods. We have begun a study of the chromosomal organization of these genes by screening laboratory strains of C. elegans for DNA polymorphisms in the regions surrounding collagen genes. Polymorphisms near seven genes have been identified and have been used as phenotypic markers in genetic crosses to assign the genes to linkage groups II, III, IV, and X. Four genes are shown by multifactor crosses to map to a 2—3 map unit interval between unc-24 and unc-22 on chromosome IV.
VARIATION IN THE MAJOR URINARY PROTEIN MULTIGENE FAMILY IN WILD-DERIVED MICE
Authors: Sampsell Bonnie M , Held William A
Published: January 2021

The levels of expression and genomic organization of genes coding for the major urinary proteins (MUPs) were examined in several stocks of wild-derived mice. Levels of MUP mRNA in the liver varied considerably with M. musculusBrno and M. castaneus males having several-fold more MUP RNA than inbred C57BL/6 males, whereas M. hortulanus, M. caroli and M. cervicolor displayed levels much lower than C57BL/6. Analysis of RNA with MUP cDNAs specific to two different subfamilies of MUP genes revealed that M. caroli and M. cervicolor primarily expressed a MUP mRNA that was less abundant in C57BL/6, suggesting differential expression of subfamilies of genes within the MUP multigene complex. Although inbred males usually have five-fold more MUP mRNA than inbred females, male to female ratios for wild-derived stocks ranged from one to several hundred. Southern blots of genomic DNA hybridized to MUP subfamily probes revealed differences in restriction fragment sizes as well as possible variation in the number of MUP genes in some species. Analysis of urinary proteins from hybrids between C57BL/6 and M. spretus suggested that low MUP expression in M. spretus females was due to cis-acting genetic elements.
SELECTION WITH PARTIAL SELFING. I. MASS SELECTION
Authors: Wright A J , Cockerham C Clark
Published: January 2021

The expected responses to mass selection carried out before or after reproduction in a population whose members all have a fixed probability of self pollination (s) are formulated using covariances of relatives and their component quadratic functions for a model with arbitrary additive and dominance effects. The response measured in the first generation offspring after selection (immediate gain) can differ from that retained when the population has regained equilibrium (permanent gain). The population mean behaves in a predictable manner during the return to equilibrium, and its value at any time can be predicted from earlier generations. The permanent gain from selection after reproduction is always (1 + s)/2 times as large as that from selection before reproduction, but the relationship of the immediate gains depends on the genetic model assumed.—Numerical analysis applied to a model with two alleles per locus and varying allele frequencies, dominance ratios and numbers of loci showed that the proportion of the immediate gain retained at equilibrium was reduced with the large inbreeding depression associated with increasing dominance levels and numbers of loci and was generally lower for selection after reproduction than before. In the absence of information as to the magnitude of genetic variances and inbreeding depression in species reproducing by partial selfing, the importance of this phenomenon is unknown.
THE SAMPLING DISTRIBUTION OF LINKAGE DISEQUILIBRIUM UNDER AN INFINITE ALLELE MODEL WITHOUT SELECTION
Authors: Hudson Richard R
Published: January 2021

The sampling distributions of several statistics that measure the association of alleles on gametes (linkage disequilibrium) are estimated under a two-locus neutral infinite allele model using an efficient Monte Carlo method. An often used approximation for the mean squared linkage disequilibrium is shown to be inaccurate unless the proper statistical conditioning is used. The joint distribution of linkage disequilibrium and the allele frequencies in the sample is studied. This estimated joint distribution is sufficient for obtaining an approximate maximum likelihood estimate of C = 4Nc, where N is the population size and c is the recombination rate. It has been suggested that observations of high linkage disequilibrium might be a good basis for rejecting a neutral model in favor of a model in which natural selection maintains genetic variation. It is found that a single sample of chromosomes, examined at two loci cannot provide sufficient information for such a test if C < 10, because with C this small, very high levels of linkage disequilibrium are not unexpected under the neutral model. In samples of size 50, it is found that, even when C is as large as 50, the distribution of linkage disequilibrium conditional on the allele frequencies is substantially different from the distribution when there is no linkage between the loci. When conditioned on the number of alleles at each locus in the sample, all of the sample statistics examined are nearly independent of λ = 4Nμ, where μ is the neutral mutation rate.
STATISTICS OF NATURAL POPULATIONS. II. ESTIMATING AN ALLELE PROBABILITY IN FAMILIES DESCENDED FROM CRYPTIC MOTHERS
Authors: Arnold Jonathan , Morrison Melvin L
Published: January 2021

In population studies, adults are frequently difficult or inconvenient to identify for genotype, but a family profile of genotypes can be obtained from an unidentified female crossed with a single unidentified male. The problem is to estimate an allele frequency in the cryptic parental gene pool from the observed family profiles. For example, a worker may wish to estimate inversion frequencies in Drosophila; inversion karyotypes are cryptic in adults but visible in salivary gland squashes from larvae. A simple mixture model, which assumes the Hardy-Weinberg law, Mendelian laws and a single randomly chosen mate per female, provides the vehicle for studying three competing estimators of an allele frequency. A simple, heuristically appealing estimator called the Dobzhansky estimator is compared with the maximum likelihood estimator and a close relative called the grouped profiles estimator. The Dobzhansky estimator is computationally simple, consistent and highly efficient and is recommended in practice over its competitors.
MAPPING CDC MUTATIONS IN THE YEAST S. Cerevisiae BY RAD52-MEDIATED CHROMOSOME LOSS
Authors: Hanic-Joyce Pamela J
Published: January 2021

Using the chromosome loss-mapping method of Schild and Mortimer, I have mapped several new temperature-sensitive mutations that define five CDC genes. Modified procedures were used to facilitate mapping temperature-sensitive mutations in general, and these modifications are discussed. The mutations were assigned to specific chromosomes by chromosome loss procedures, and linkage relationships were determined subsequently by standard tetrad analysis. Four of the mutations define new loci. The fifth mutation, cdc63-1, is shown to be allelic to previously known mutations in the PRT1 gene.
FURTHER CHARACTERIZATION OF GENETIC ELEMENTS ASSOCIATED WITH THE SEGREGATION DISTORTER PHENOMENON IN DROSOPHILA MELANOGASTER
Authors: Sharp Cecil B , Hilliker Arthur J , Holm David G
Published: January 2021

Segregation Distorter, SD, associated with the second chromosome of Drosophila melanogaster, is known to cause sperm bearing the non-SD homologue to dysfunction in heterozygous males. In earlier studies, using different, independently derived, SD chromosomes, three major loci were identified as contributing to the distortion of segregation ratios in males. In this study the genetic components of the SD-5 chromosome have been the subjects of further investigation, and our findings offer the following information. Crossover analysis confirms the mapping of the Sd locus to a position distal to but closely linked with the genetic marker pr. Spontaneous and radiation-induced recombinational analyses and deficiency studies provide firm support to the notion that the Rsp(Responder) locus lies within the proximal heterochromatin of chromosome 2, between the genetic markers lt and rl and most likely in the heterochromatin of the right arm. The major focus of this study, however, has been on providing a better definition of the genetic properties of the Enhancer of SD [E(SD)]. Our findings place this locus within the region of the two most proximal essential genes in the heterochromatin of the left arm of chromosome 2. Moreover, our analysis reveals a probable association of the E(SD) locus with a meiotic drive independent of that caused by Sd.
DEVELOPMENTAL GENETICS OF THE 2C-D REGION OF THE DROSOPHILA X CHROMOSOME
Authors: Perrimon Norbert , Engstrom Lee , Mahowald Anthony P
Published: January 2021

We have conducted a genetic and developmental analysis of genes within the 2C-D area of the X chromosome. Phenotypes of 33 mutations representing nine adjacent complementation groups including eight recessive lethals and one visible homeotic mutation (polyhomeotic) are described. Germline clonal analysis of the eight zygotic lethals has revealed three types of gene requirements: (1) normal activity at two pupal lethal loci (corkscrew and C204) and one larval lethal locus (ultraspiracle) is required for normal embryogenesis; (2) normal activity at three larval lethal loci (DF967, VE651 and Pgd) is required for normal oogenesis; and (3) activity at only one locus (EA82), a larval lethal, appears to have no maternal requirement. Ambiguous results were obtained for the GF316 lethal complementation group. Analysis of mitotic figures of the pupal lethals indicates that C204 disrupts an essential mitotic function. This result correlates with the preblastoderm arrest observed among embryos derived from germline clones of C204. Embryos derived from germline clones of corkscrew (csw) exhibit a "twisted" phenotype. The recessive lethal ultraspiracle (usp) disrupts the organization of the posterior tip of the larva both zygotically and maternally: second instar usp/Y larvae derived from heterozygous usp/+ mothers possess an extra set of spiracles, whereas usp/Y embryos derived from females possessing a germline clone (usp/usp) exhibit a localized ventral defect in the ninth or posterior eighth abdominal segment. Analysis of the phenotypes of deficiency-hemizygous embryos indicates the presence of an embryonic zygotic lethal locus, as yet unidentified, which produces central nervous system and ventral hypoderm degeneration. Additional information on the genetic organization of loci within the adjacent 2E area are also described. The implications of this analysis to our understanding of the maternal of zygotic lethal loci in development are discussed.
NATURAL SELECTION WITH NUCLEAR AND CYTOPLASMIC TRANSMISSION. II. TESTS WITH DROSOPHILA FROM DIVERSE POPULATIONS
Authors: Clark Andrew G
Published: January 2021

Observations of intraspecific variation in organelle DNA have prompted a renewed interest in the evolutionary consequences of cytoplasmically transmitted factors. Attempts to quantify the significance of cytoplasmic effects are frequently limited by the difficulty in partitioning the cause of reciprocal cross differences among a series of possibilities. In the experiment reported here the nuclear genomes of a set of six lines of Drosophila melanogaster from diverse geographic locations were replaced in a series of cytoplasms. The segregation of the SM5 balancer chromsome was scored in a factorial design, and the data allowed a partitioning of variance such that cytoplasmic effects were distinguished from maternal effects and meiotic drive. An attempt was made to avoid the confounding problem of hybrid dysgenesis by performing the entire experiment (including chromosomal extractions) in a P cytotype. Results indicated a significant contribution of cytoplasm to the variance in SM5 segregation. Error variance showed an increasing trend as the experiment proceeded, and additional tests indicated that this was due to an accumulation of chromosomal mutations. These findings are interpreted in light of the population genetic theory that addresses the maintenance of cytoplasmic polymorphism.
LOCALIZATION OF ACTION OF THE IS50-ENCODED TRANSPOSASE PROTEIN
Authors: Phadnis Suhas H , Sasakawa Chihiro , Berg Douglas E
Published: January 2021

The movement of the bacterial insertion sequence IS50 and of composite elements containing direct terminal repeats of IS50 involves the two ends of IS50, designated O (outside) and I (inside), which are weakly matched in DNA sequence, and an IS50 encoded protein, transposase, which recognizes the O and I ends and acts preferentially in cis. Previous data had suggested that, initially, transposase interacts preferentially with the O end sequence and then, in a second step, with either an O or an I end. To better understand the cis action of transposase and how IS50 ends are selected, we generated a series of composite transposons which contain direct repeats of IS50 elements. In each transposon, one IS50 element encoded transposase (tnp  +), and the other contained a null (tnp  -) allele. In each of the five sets of composite transposons studied, the transposon for which the tnp  + IS50 element contained its O end was more active than a complementary transposon for which the tnp  - IS50 element contained its O end. This pattern of O end use suggests models in which the cis action of transposase and its choice of ends is determined by protein tracking along DNA molecules.
ANALYSIS OF THE DOSAGE COMPENSATION OF A SPECIFIC TRANSCRIPT IN DROSOPHILA MELANOGASTER
Authors: Breen Thomas R , Lucchesi John C
Published: January 2021

The amount of steady-state level RNA complementary to the X-linked salivary gland secretion polypeptide gene Sgs-4 was measured in male and female third-instar larvae carrying one or two doses of a wild-type allele of the gene. RNA levels were found to be compensated in normal one-dose males and two-dose females and to be dosage-dependent within each sex. The presence of mutant alleles of male-less (mle) was found to reduce the level of Sgs-4 transcripts in males. These results support the contentions that dosage compensation is mediated by regulating the level of X-linked gene transcripts and that a product of the mle  + gene is involved in this process.
TEMPORAL AND MICROGEOGRAPHIC VARIATION IN ALLOZYME FREQUENCIES IN A NATURAL POPULATION OF DROSOPHILA BUZZATII
Authors: Barker J S F , East P D , Weir B S
Published: January 2021

Temporal variation in allozyme frequencies at six loci was studied by making monthly collections over 4 yr in one population of the cactophilic species Drosophila buzzatii. Ten sites were defined within the study locality, and for all temporal samples, separate collections were made at each of these sites. Population structure over microgeographic space and changes in population structure over time were analyzed using F-statistic estimators, and multivariate analyses of allele and genotype frequencies with environmental variables were carried out.—Allele frequencies showed significant variation over time, although there were no clear cyclical or seasonal patterns. A biplot analysis of allele frequencies over seasons within years and over years showed clear discrimination among years by alleles at four loci. During the 4 yr, three alleles showed directional changes which were associated with directional changes in environmental variables. Significant associations with one or more environmental variables were found for allele frequencies at every locus and for both expected and observed heterozygosities (except those for Est-1 and Est-2). Thus, variation in allele frequencies over time cannot be attributed solely to drift. Significant linkage disequilibria were detected among three loci (Est-2, Hex and Aldox), but there was no evidence for spatial or temporal patterns.—The F-statistic analyses showed significant differentiation among months within years for all loci, but the statistic used (coancestry) was heterogeneous among loci. Estimates of F (inbreeding) for all loci were significantly different from zero, with the loci in four groups, Adh-1 (negative), Pgm (small positive), Est-2 and Hex (intermediate) and Est-1 and Aldox (high positive). The correlation of genes within individuals within populations (f) for each locus in each month by site sample differed among loci, as did the patterns of change in f over time (seasons). Heterogeneity in the F-statistic estimates indicates that natural selection is directly or indirectly affecting allele and genotype frequencies at some loci. However, the F-statistic analyses showed essentially no microgeographic structure (i.e., among sites), although there was significant heterogeneity in allele frequencies among flies emerging from individual rots.—Thus, microspatial heterogeneity probably is most important at the level of individual rots, and coupled with habitat selection, it could be a major factor promoting diversifying selection and the maintenance of polymorphism. Resolution of the nature of this selection and of the apparent inbreeding detected at all loci except Adh-1 will require detailed study of the breeding structure of the population at the microhabitat level (individual rots) and of gene flow within the population.
ENZYME ACTIVITY IN EMS-INDUCED NULL MUTATIONS OF DUPLICATED GENES ENCODING PHOSPHOGLUCOSE ISOMERASES IN CLARKIA
Authors: Jones T W A , Pichersky E , Gottlieb L D
Published: January 2021

The duplication of the nuclear gene encoding the cytosolic isozyme of phosphoglucose isomerase (PGI; EC 5.3.1.9) originated within Clarkia, a genus of annual plants native to California. Previous immunological studies showed that species with and without the duplication have the same levels of cytosolic PGI activity (relative to that of the plastid PGI isozyme), as well as similar levels of cytosolic PGI protein. In the present study, we characterized seven EMS-induced null activity mutations in both duplicate PGI genes. The mutations reduced PGI activity levels in direct proportion to the normal contribution of each gene. Homozygous mutants at Pgi-3 had 64% of wild-type activity, whereas those at Pgi-2 had only 36%. The effects of the mutations at the two loci were additive, as shown by further reductions in activity in certain progeny classes in F2 progenies between them. The homozygous double null mutant class was not recovered and is presumably lethal. All of the mutants appear to be CRM+. The results account for the previously observed differences in in vivo accumulation of the duplicate isozymes in numerous Clarkia species. The results further show that PGI activity is not directly regulated by metabolic factors and suggest that the reduced PGI levels in Clarkias with the duplication probably evolved by regulatory changes in transcription or translation. The study also demonstrates a novel method to evaluate whether a particular enzyme activity is essential.
GENEALOGY OF PRINCIPAL STRAINS OF THE YEAST GENETIC STOCK CENTER
Authors: Mortimer Robert K , Johnston John R
Published: January 2021

We have constructed a genealogy of strain S288C, from which many of the mutant and segregant strains currently used in studies on the genetics and molecular biology of Saccharomyces cerevisiae have been derived. We have determined that its six progenitor strains were EM93, EM126, NRRL YB-210 and the three baking strains Yeast Foam, FLD and LK. We have estimated that approximately 88% of the gene pool of S288C is contributed by strain EM93. The principal ancestral genotypes were those of segregant strains EM93-1C and EM93-3B, initially distributed by C. C. Lindegren to several laboratories. We have analyzed an isolate of a lyophilized culture of strain EM93 and determined its genotype as MAT  a/MAT? SUC2/SUC2 GAL2/gal2 MAL/MAL mel/mel CUP1/cup1 FLO1/flo1. Strain EM93 is therefore the probable origin of genes SUC2, gal2, CUP1 and flo1 of S288C. We give details of the current availability of several of the progenitor strains and propose that this genealogy should be of assistance in elucidating the origins of several types of genetic and molecular heterogeneities in Saccharomyces.
A VISIBLE ALLELE OF THE MUSCLE GENE sup-10 X OF C. ELEGANS
Authors: Greenwald Iva , Horvitz H Robert
Published: January 2021

In this paper, we extend our previous analyses of a set of genes in Caenorhabditis elegans that are involved in muscle structure and function: unc-93 III, sup-9 II, sup-10 X and sup-11 I. We describe an unusual, visible allele of sup-10, examine how this allele interacts genetically with mutations in other genes of this set and propose that the wild-type products of the unc-93 and sup-10 loci may be components of a protein complex. We also describe a new gene of this set, sup-18 III, and the interaction of sup-18 alleles with mutations in the other genes.
MAIZE MITOCHONDRIAL PLASMID S-1 SEQUENCES SHARE HOMOLOGY WITH CHLOROPLAST GENE psbA
Authors: Sederoff Ronald R , Ronald Pamela , Bedinger Patricia , Rivin Carol , Walbot Virginia , Bland Molly , Levings C S
Published: January 2021

The linear, 6397-base pair (bp), mitochondrial S-1 DNA molecule from maize contains a 420-bp segment that is homologous with the chloroplast gene (psbA) that codes for the quinone binding protein of photosystem II. This is the first report of a chloroplast sequence in a naturally occurring viral-like or plasmid DNA. The complete sequence of the S-1 chloroplast segment has been compared with homologous regions of six different chloroplast genes. The S-1 segment has diverged from the other genes both by length mutation and base substitution. Several of the length mutations are exact adjacent tandem duplications of 4 and 5 bp similar to "footprints" left after excision of transposable elements in maize nuclear DNA.
VARIATION AND GENOMIC LOCALIZATION OF GENES ENCODING DROSOPHILA MELANOGASTER MALE ACCESSORY GLAND PROTEINS SEPARATED BY SODIUM DODECYL SULFATE-POLYACRYLAMIDE GEL ELECTROPHORESIS
Authors: Whalen Michael , Wilson Thomas G
Published: January 2021

Accessory gland proteins from Drosophila melanogaster males have been separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis into nine major bands. When individual males from 175 strains were examined, considerable polymorphism for nearly one-half of the major protein bands was seen, including null alleles for three bands. Variation was observed not only among long-established laboratory strains but also among stocks recently derived from natural populations. There was little difference in the amount of variation between P and M strains, indicating that P element mutagenesis is not a factor producing the variation. Codominant expression of variants for each of five bands was found in heterozygotes, suggesting structural gene variation and not posttranslational modification variation. Stocks carrying electrophoretic variants of four of the major proteins were used to map the presumed structural genes for these proteins; the loci were found to be dispersed on the second chromosome. Since males homozygous for variant proteins were fertile, the polymorphism seems to have little immediate effect on successful sperm transfer. We propose that a high degree of polymorphism can be tolerated because these proteins play a nutritive rather than enzymatic role in Drosophila reproduction.
MOLECULAR LOCALIZATION, DEVELOPMENTAL EXPRESSION AND NUCLEOTIDE SEQUENCE OF THE ALPHA-METHYLDOPA HYPERSENSITIVE GENE OF DROSOPHILA
Authors: Marsh J Lawrence , Erfle Mary P , Leeds Carol A
Published: January 2021

The region surrounding the dopa decarboxylase gene of Drosophila contains a cluster of functionally related genes, many of which affect cuticle development and/or catecholamine metabolism. In this report we describe the molecular mapping and sequencing of a full-length cDNA copy of a transcript that maps to the alpha-methyldopa hypersensitive region. Developmental RNA blots show stage-specific patterns of transcription and multiple RNA transcripts. A 2-kb transcript is most abundant at about 12 hr of embryogenesis, and lower levels are detected throughout most of embryogenesis. Lower levels of this transcript are also detected in adults. Smaller stage-specific transcripts are detected in late third-instar larvae. This pattern of transcription is consistent with the known lethal phases and phenotypes of the alpha-methyldopa hypersensitive gene (amd). Based on map position, pattern of transcription, homology with dopa decarboxylase and association with altered DNA in mutants, we conclude that this transcript represents the amd gene.
NONRANDOM ASSOCIATION BETWEEN STRUCTURAL Amy AND REGULATORY map VARIANTS IN DROSOPHILA MELANOGASTER
Authors: Klarenberg A J , Scharloo W
Published: January 2021

Populations of Drosophila melanogaster were investigated for variation in structural Amy genes, coding for different electrophoretic variants, and regulatory genes that determine the tissue-specific production patterns of α-amylase in the midguts of adults and larvae. Analysis of strains homozygous for second chromosomes extracted from three cage populations of different geographical origin revealed a consistent nonrandom association between Amy and midgut activity pattern (map) variants of α-amylase in adults and third-instar larvae. The origin and maintenance of the linkage disequilibrium between Amy and map genes are discussed.
MOLECULAR POPULATION GENETICS OF THE ALCOHOL DEHYDROGENASE GENE REGION OF DROSOPHILA MELANOGASTER
Authors: Aquadro Charles F , Desse Susan F , Bland Molly M , Langley Charles H , Laurie-Ahlberg Cathy C
Published: January 2021

Variation in the DNA restriction map of a 13-kb region of chromosome ll including the alcohol dehydrogenase structural gene (Adh) was examined in Drosophila melanogaster from natural populations. Detailed analysis of 48 D. melanogaster lines representing four eastern United States populations revealed extensive DNA sequence variation due to base substitutions, insertions and deletions. Cloning of this region from several lines allowed characterization of length variation as due to unique sequence insertions or deletions [nine sizes; 21-200 base pairs (bp)] or transposable element insertions (several sizes, 340 bp to 10.2 kb, representing four different elements). Despite this extensive variation in sequences flanking the Adh gene, only one length polymorphism is clearly associated with altered Adh expression (a copia element approximately 250 bp 5′ to the distal transcript start site). Nonetheless, the frequency spectra of transposable elements within and between Drosophila species suggests they are slightly deleterious. Strong nonrandom associations are observed among Adh region sequence variants, ADH allozyme (Fast vs. Slow), ADH enzyme activity and the chromosome inversion ln(2L)t. Phylogenetic analysis of restriction map haplotypes suggest that the major twofold component of ADH activity variation (high vs. low, typical of Fast and Slow allozymes, respectively) is due to sequence variation tightly linked to and possibly distinct from that underlying the allozyme difference. The patterns of nucleotide and haplotype variation for Fast and Slow allozyme lines are consistent with the recent increase in frequency and spread of the Fast haplotype associated with high ADH activity. These data emphasize the important role of evolutionary history and strong nonrandom associations among tightly linked sequence variation as determinants of the patterns of variation observed in natural populations.
Hybrid Dysgenesis in Drosophila melanogaster: Evidence from Sterility and Southern Hybridization Tests that P Cytotype Is Not Maintained in the Absence of Chromosomal P Factors
Authors: Sved John A
Published: January 2021

A two-generation crossing program was used to replace the entire chromosome complement of P strains by M strain chromosomes, the maternal contribution being from the P strain. The cytotype of chromosomally substituted females was indistinguishable from M strain cytotype, judged by the sterility of offspring from the cross of such females to P strain males. In addition, following replacement of the chromosomes, the level of DNA homologous to the P factor was sufficiently low to be explicable by low levels of P factor transposition. These results are consistent with immediate chromosomal control for the switching from P to M cytotype. However, the reverse chromosome substitution, replacing all chromosomes of an M strain with P chromosomes, did not usually lead to immediate change of cytotype properties, showing that there is a true maternal effect in the M to P direction.—The absence of true maternal inheritance for P cytotype argues against models of P factor repression which depend on autonomous replication of a nonchromosomal element. The repression could still be explained by nonchromosomal copies of the P factor, provided that these are replenished from chromosomal P factors. A model is put forward in which P cytotype is due to the presence of circular P factors carrying a P factor target sequence, leading to preferential transposition of chromosomal P factors to nonchromosomal target sites.
Genetic Mapping of the Amino-Terminal Domain of Bacteriophage T4 DNA Polymerase
Authors: Hughes Melanie B , Yee Arthur M F , Dawson Myra , Karam Jim
Published: January 2021

The DNA polymerase of bacteriophage T4 is a multifunctional enzyme that harbors DNA-binding, DNA-synthesizing and exonucleolytic activities. We have cloned in bacterial plasmids about 99% of the structural gene for this enzyme (T4 gene 43). The gene was cloned in six contiguous 5'-terminal DNA fragments that defined seven intragenic mapping regions. Escherichia coli hosts harboring recombinant plasmids carrying the gene 43 subsegments were used in marker-rescue experiments that assigned a large number of ts and nonsense polymerase mutations to different physical domains of the structural gene. Conspicuously, only one missense mutation in a large collection of mutants mapped in the 5'-terminal 450 base-pair segment of the approximately 2700 base-pair gene. To test if this indicated a DNA polymerase domain that is relatively noncritical for biological activity, we mutagenized a recombinant plasmid carrying this 5'-terminal region and generated new conditional-lethal mutations that mapped therein. We identified five new ts sites, some having mutated at high frequency (nitrosoguanidine hot spots). New ts mutations were also isolated in phage genes 62 and 44, which map upstream of gene 43 on the T4 chromosome. A preliminary examination of physiological consequences of the ts gene 43 mutations showed that they exhibit effects similar to those of ts lesions that map in other gene 43 segments: some were mutators, some derepressed gene 43 protein synthesis and they varied in the severity of their effects on T4-induced DNA synthesis at nonpermissive temperatures. The availability of the gene 43 clones should make it possible to isolate a variety of lesions that affect different activities of the T4 DNA polymerase and help to define the different domains of this multifunctional protein.
A New Epistasis Group for the Repair of DNA Damage in Bacteriophage T4: Replication Repair
Authors: Wachsman Joseph T , Drake John W
Published: January 2021

The gene 32 mutation amA453 sensitizes bacteriophage T4 to the lethal effects of ultraviolet (UV) irradiation, methyl methanesulfonate and angelicin-mediated photodynamic irradiation when treated particles are plated on amber-suppressing host cells. The increased UV sensitivity caused by amA453 is additive to that caused by mutations in both the T4 excision repair (denV) and recombination repair (uvsWXY) systems, suggesting the operation of a third kind of repair system. The mutation uvs79, with many similarities to amA453 but mapping in gene 41, is largely epistatic to amA453. The mutation mms1, also with many similarities to amA453, maps close to amA453 within gene 32 and is largely epistatic to uvs79. Neither amA453 nor uvs79 affect the ratio of UV-induced mutational to lethal hits, nor does amA453 affect spontaneous or UV-enhanced recombination frequencies. Gene 32 encodes the major T4 ssDNA-binding protein (the scaffolding of DNA replication) and gene 41 encodes a DNA helicase, both being required for T4 DNA replication. We conclude that a third repair process operates in phage T4 and suggest that it acts during rather than before or after DNA replication.