bluuebunny/crossref_metadata_2025 huggingface dataset:
MUTANTS OF THE BIOLOGICAL CLOCK IN CHLAMYDOMONAS REINHARDI
Authors: Bruce Victor G
Published: January 2021

A genetic analysis of the biological clock in Chlamydomonas reinhardi has been initiated. Of six wild-type strains tested (3 mt+ and 3 mt−), five had periods close to 24 hr whereas one had a 21-hr period. Mutants with altered clock period have been isolated. The periods of 3 of these variant strains are temperature compensated. Genetic crosses involving a long-period mutant suggest that a single gene confers the long-period character, and in general clock-period length seems to be a useful phenotypic measure of alterations in the clock due to genetic differences. One phase mutant was found but its behavior was variable and the phase of the rhythm, relative to a light–dark transition which initiates the rhythm, does not seem to be reliable as a parameter of clock differences. No markers have yet been mapped.
EXTRACHROMOSOMAL ELEMENT DELTA IN DROSOPHILA MELANOGASTER. VIII. INSEPARABLE ASSOCIATION WITH SENSITIVE SECOND CHROMOSOME
Authors: Minamori Sumio
Published: January 2021

The presence of delta is always accompanied by a sensitive second chromosome in Drosophila melanogaster or vice versa. The separability of delta and the chromosome line was investigated in experiments designed to eliminate delta or to suppress its multiplication for a number of generations. Cy/Sb-5 males which transmit a minute amount of delta b (retained by chromosome Sb, kills Sb/Sb and Sb/Sr zygotes) to their progeny were backcrossed for 61 generations to Cy/Pm females which carried no delta. After backcrossing 465 Cy/Sb-5 males were individually examined for retention of delta, and all were found to retain delta b in its latent state. A homozygous strain for the Sr-20B chromosome which retained a minute amount of delta r (retained by chromosome Sr, kills Sr/Sr zygotes) was obtained. 1,252 Cy/Sr-20B females derived from the homozygous strains at the 21st generation were tested individually for delta retention. All females tested were found to retain delta r in its latent state. The delta retention in Sb-5 chromosome lines isolated from Sr-Cy/Sb-5 heterozygous strains which carried delta r but not delta b was examined. The descendant Cy/Sb-5 lines from the heterozygous strains had accumulated their specific delta, delta b. These findings are consistent with those obtained in an earlier study, and lead to the conclusion that delta is associated inseparably with each specific sensitive chromosome.
FACTORS AFFECTING RECOGNITION AND DISJUNCTION OF CHROMOSOMES AT DISTRIBUTIVE PAIRING IN FEMALE DROSOPHILA MELANOGASTER. II. THE EFFECT OF A SECOND ARM
Authors: Moore Charleen M , Grell Rhoda F
Published: January 2021

The behavior of heterozygously inverted X chromosomes that were members of the distributive pool at least 70% of the time was studied when the other pool members were either two free 4's or one compound 4. The X's were structurally modified by additions or deletions of heterochromatin, so that the two homologues differed in both size and configuration or in size alone. In the noncompetitive situation, with two free 4's, recognition between the X's remained high despite the modifications, and primary X nondisjunction was low. In the competitive situation, with the compound 4, distributive nondisjunction of the X's increased approximately two orders of magnitude, and trivalent formation was indicated. Disjunction from the trivalent varied with X size and configuration. When both X's were acrocentric, the smaller X directed the larger X and the very small (see PDF) to the same pole; when the larger X carried a second arm, it assumed the directing role; when the size ratio of the smaller, one-armed X to the larger, two-armed X became less than ∼5/9, the smaller X again directed the other two.
INHERITANCE OF HAIR CONSTRICTIONS IN MICE
Authors: Mann Stanley J , Straile William E
Published: January 2021

The frequencies of multi-constricted hairs in the pelage is the same (75%) in the caudal mid-dorsum of C57BL/10 and CBA inbred mice, but there are more single-constricted hairs in C57BL mice (9.41%) than in CBA mice (0.13%). This structural feature is used as a basis for genetic analysis of the hair coat.—The frequency of single-constricted hairs (4.41%) in F1 mice is intermediate between the frequencies observed in the CBA and C57BL parent strains. Data from the F2 crosses and backcrosses to the respective parent strains indicate that the presence of numerous single-constricted hairs in the pelage is an inherited characteristic. The mode of inheritance is controlled primarily by a semi-dominant autosomal gene (single-constriction; Hct), without the involvement of maternal factors.
RATE OF DECREASE OF GENETIC VARIABILITY IN A TWO-DIMENSIONAL CONTINUOUS POPULATION OF FINITE SIZE
Authors: Maruyama Takeo
Published: January 2021

The rate of decay of genetic variability was investigated for two-dimensional continuous populations of finite size. The exact value of the rate involves a rather complicated expression (formula (4-1)). However, numerical examples indicate that in a population habitat size L × L and density D, the rate is approximately equal to (see PDF) where σ2 is the variance of dispersion distance assuming isotropical migration. The value given in (2) is equal to that of a panmictic population of size DL  2. It is remarkable that whether the rate assumes the value given by (1) or by (2) depends only on Dσ2 (a local property), which is independent of the habitat size. Since, in a one-dimensional population, this depends on both Dσ2 and the habitat size, there is an essential difference between the two types of population structure.—The function giving the probability of two homologous genes separated by a given distance being different alleles was also obtained, (formula (5-1)).
THE ANATOMY AND FUNCTION OF A SEGMENT OF THE X CHROMOSOME OF DROSOPHILA MELANOGASTER
Authors: Judd B H , Shen M W , Kaufman T C
Published: January 2021

An average size chromomere of the polytene X chromosome of Drosophila melanogaster contains enough DNA in each haploid equivalent strand to code for 30 genes, each 1,000 nucleotides long. We have attempted to learn about the organization of chromosomes by asking how many functional units can be localized within a chromomere. This was done by 1) recovery of mutants representative of every cistron in the 3A2-3C2 region; 2) the characterization of the function of each mutant type and grouping by complementation tests; 3) the determination of the genetic and cytological position of each cistron by recombination and deletion mapping. The data clearly show one functional group per chromomere. It is postulated that a chromomere is one cistron within which much of the DNA is regulatory in function.
SEGMENTAL ANEUPLOIDY AND THE GENETIC GROSS STRUCTURE OF THE DROSOPHILA GENOME
Authors: Lindsley Dan L , Sandler L , Baker Bruce S , Carpenter Adelaide T C , Denell R E , Hall Jeffrey C , Jacobs Patricia A , Miklos George L Gabor , Davis Brian K , Gethmann R C , Hardy R W , Hessler A , Miller Steven M , Nozawa Hiroshi , Parry Dilys M , Gould-Somero M
Published: January 2021

By combining elements of two Y-autosome translocations with displaced autosomal breakpoints, it is possible to produce zygotes heterozygous for a deficiency for the region between the breakpoints, and also, as a complementary product, zygotes carrying a duplication for precisely the same region. A set of Y-autosome translocations with appropriately positioned breakpoints, therefore, can in principle be used to generate a non-overlapping set of deficiencies and duplications for the entire autosomal complement.—Using this method, we have succeeded in examining segmental aneuploids for 85% of chromosomes 2 and 3 in order to assess the effects of aneuploidy and to determine the number and location of dosage-sensitive loci in the Drosophila genome (Figure 5). Combining our data with previously reported results on the synthesis of Drosophila aneuploids (see Lindsley and Grell 1968), the following generalities emerge.—1. The X chromosome contains no triplo-lethal loci, few or no haplo-lethal loci, at least seven Minute loci, one hyperploid-sensitive locus, and one locus that is both triplo-abnormal and haplo-abnormal. 2. Chromosome 2 contains no triplo-lethal loci, few or no haplo-lethal loci, at least 17 Minute loci, and at least four other haplo-abnormal loci. 3. Chromosome 3 contains one triplo-lethal locus that is also haplo-lethal, few or no other haplo-lethal loci, at least 16 Minute loci, and at least six other haplo-abnormal loci. 4. Chromosome 4 contains no triplo-lethal loci, no haplo-lethal loci, one Minute locus, and no other haplo-abnormal loci.—Thus, the Drosophila genome contains 57 loci, aneuploidy for which leads to a recognizable effect on the organism: one of these is triplo-lethal and haplo-lethal, one is triplo-abnormal and haplo-abnormal, one is hyperploid-sensitive, ten are haplo-abnormal, 41 are Minutes, and three are either haplo-lethals or Minutes. Because of the paucity of aneuploid-lethal loci, it may be concluded that the deleterious effects of aneuploidy are mostly the consequence of the additive effects of genes that are slightly sensitive to abnormal dosage. Moreover, except for the single triplo-lethal locus, the effects of hyperploidy are much less pronounced than those of the corresponding hypoploidy.
LACK OF DNA HOMOLOGY BETWEEN THE LEGUME GLYCINE MAX AND ITS SYMBIOTIC RHIZOBIUM BACTERIA
Authors: Rake Adrian V
Published: January 2021

Any common genes of Glycine max and its symbiotic rhizobium bacteria 61A76 represent less than 0.6% of the bacterial genome. Thus, if any sizable exchange of DNA between host and symbiote occurs it must result in unstable DNA association which is lost with subsequent generations.
ON THE MECHANISM OF CHROMATIN LOSS INDUCED BY THE B CHROMOSOME OF MAIZE
Authors: Rhoades M M , Dempsey Ellen
Published: January 2021

Knobbed regions of the regular maize complement frequently are eliminated at the second microspore division in spores which have two or more B chromosomes. Evidence is presented that no or little loss occurs in spores with one B and that the rate is not increased in spores with more than two B's.—The B chromosomes from an unrelated strain proved as effective in inducing loss as did the B's of the original high loss stock.—Chromatin loss induced by B's is restricted to knobbed A chromosomes and occurs only at the second microspore division. Knobbed chromosomes 3, 5, and 9 have been tested and all interact with B's to give loss. Chromosomes with large knobs are more frequently broken than are those with smaller knobs and knobless chromosomes show negligible loss.—Although knobs and B's are essential for chromatin elimination, modifying genes can markedly affect the rate of loss.——Two knobbed heterologous chromosomes undergo simultaneous loss more frequently than expected from independent events. The data indicate that joint loss occurs in competent cells and that preferential assortment of the two deficient chromosomes to specific poles is unlikely.—B chromosomes and deficient chromosomes assort independently at the second microspore anaphase.—Genetic data from crosses with marker genes in both arms of chromosome 3 show that breakage of the postulated dicentric bridge does not occur solely at the centric region since a variety of deficient chromosomes were recovered.—Nondisjunction of B chromosomes and elimination of knobbed chromatin take place during the second microspore mitosis. The argument is advanced that the two phenomena result from faulty replication of heterochromatic segments. The position of the nonreplicating segment in the two kinds of chromosomes determines whether nondisjunction or breakage takes place.—Finally, it is suggested that all of the reported effects of the B chromosome can be accounted for if the B is a parasitic entity having no genetic function other than controlling the replication of its proximal heterochromatic knob and increasing the ability of B-containing sperm cells to compete successfully for fertilization of the egg.
MESODERM-ECTODERM INTERACTION IN THE PRODUCTION OF THE AGOUTI PIGMENTATION PATTERN IN MICE
Authors: Mayer Thomas C , Fishbane Jill L
Published: January 2021

Alleles at the agouti locus in the mouse determine the synthesis of either phaeomelanin or eumelanin by follicular melanocytes by altering the hair follicle environment. The method of dermal-epidermal recombination of mouse skin from C57BL/6J a/a and C57BL/6J Aw-J/Aw-J embryos was used in this study to establish the precise site of agouti gene action within the hair follicle. The pigmentary pattern of hairs formed in the recombination skin grafts was specific for the genotype of the dermal (mesodermal) component of the hair follicle. The genotype of the epidermal (ectodermal) component had no influence on the type of hair pigmentary pattern. These results indicate that future studies on gene mechanisms should focus on the dermis as the determining factor in altering the hair follicle environment.
TANDEM DUPLICATIONS OF THE rII REGION OF BACTERIOPHAGE T4D
Authors: Parma David H , Ingraham Laura J , Snyder Marlene
Published: January 2021

Genetic analyses of ten duplication strains of bacteriophage T4D isolated from an rJ101 × rl589 cross reveal that all ten duplications segregate structurally normal chromosomes (r segregants); six of the duplications have been shown to segregate inviable particles, presumed triplications, with the same frequency that they yield r segregants; viable triplication segregants have been isolated from four of the duplications; the rII region from the r1589 parent maps to the left of that from the rJ101 parent in nine of the duplications, while the tenth exhibits the reverse order. These observations are consistent with the hypothesis that the duplications are tandem duplications of a portion of the genome which includes the rII region. The evidence for triplications segregated from the duplications is not readily compatible with stabilized terminal redundancies as the basis of the duplications. Evidence is presented that the length of the duplication is compensated by a deletion of non-essential information elsewhere in the phage genome.
FECUNDITY AND LONGEVITY OF F1 FEMALES OF HABROBRACON FROM SPERM X-RAYED WITH 3000r
Authors: Heidenthal Gertrude , Nelson Wayne , Clark Leonard
Published: January 2021

Our purpose was to compare with respect to fecundity and longevity two groups of F1 diploid virgins of Habrobracon the fathers of which had been X-rayed with 3000r. Sorting of wasps into two groups was based on low or high hatchability of their F2 haploid eggs. Wasps with low hatchability (below 60%) are heterozygous for induced embryonic lethals such as recessives and translocations; wasps with high hatchability (100–60%) are free of lethals or possibly heterozygous for mild detrimentals. The F1s showing high hatchability laid significantly more eggs on the average; the average difference in lifespan was almost statistically significant (7% level). A more sensitive analysis by regression indicated a highly significant linear regression of survival of all F1s on hatchability of their eggs: F1s whose eggs showed 100% hatchability lived 1.84 days longer on the average than those whose eggs showed no hatchability. Furthermore, the former laid 4.99 more eggs on the average than the latter. The data also showed a very highly significant positive correlation coefficient between eggs laid and survival of mothers (0.122***) and a very highly significant positive partial correlation coefficient (0.105***) with hatchability held constant. The latter indicates that the F1s which laid more eggs also live longer, regardless of the hatchability of their eggs and hence of the heterozygosity of the mothers for lethals and other detrimentals.
SALMONELLA TYPHIMURIUM-ESCHERICHIA COLI HYBRIDS FOR THE TRYPTOPHAN REGION
Authors: Mojica-A T , Middleton R B
Published: January 2021

Fifty-eight hybrids were analyzed for their phenotypic stability, presence and nature of cryptic trp alleles and by P22-mediated transduction to yield percent homologies. The hybrids fall into 5 distinguishable classes: a haploid class in which selected E. coli genes replace equivalent sites in the S. typhimurium chromosome; three merodiploid classes in which the selected E. coli genes are integrated at novel sites in the S. typhimurium chromosome—on the same transducing fragment as the female genes selected against, with or without cryptic damage to a nearby gene, or not on the same transducing fragment; and one class in which recombination has not taken place and the E. coli DNA is presumed to be an exogenote. The homology values are heterogeneous and do not permit an accurate determination of the relative frequency of incorporation of the integrated male genetic material. A further study of 20 hybrids indicates that genetic rearrangements can occur in the hybrids.
CHROMOSOMAL RECOMBINATION IN HAEMOPHILUS INFLUENZAE
Authors: Stuy Johan H , Hoffmann Joan F , Duket Lea H
Published: January 2021

Haemophilus influenzae cultures doubly lysogenic for defective phage HP1, with a prophage marker sequence +b+/a+c, always contained some free wild-type phage. Single ultraviolet-irradiated cells produced either no wild-type phage or large numbers of them. This suggested that the phage was not released by the original double lysogen but by internal recombinants, i.e., by double lysogens with altered prophage marker sequence such as +++/abc or +b+/++c. Thirty-one wild-type phage-producing clones have been isolated independently from cultures of this double lysogen and identified. They fell in five classes. Two classes, still possessing all three prophage markers, can be explained by Campbell's (1963) prophage recombination model. The other classes had lost one or more markers. They can be explained by interchromosomal double-strand DNA breakage and rejoining. A single-DNA-strand gene conversion model is discussed in view of the fact that genetic transformation involves single-DNA-strand exchanges. A number of potentially interesting mutants has been analyzed of which only the derivatives of rec1 mutant DB117 (obtained from Dr. J. Setlow) were incapable of internal recombination.
PRELIMINARY CHARACTERIZATION OF "SEX RATIO" AND REDISCOVERY AND REINTERPRETATION OF "MALE SEX RATIO" IN DROSOPHILA AFFINIS
Authors: Voelker Robert A
Published: January 2021

In D. affinis "sex ratio" (sr), a form of meiotic drive characterized by the production of mostly or only female progeny by certain males, is associated with two different X chromosome sequences, XS-I XL-II and XS-II XL-IV. The behavior of the two sequences differed, depending on the Y chromosome constitution, being either Y  L or 0. Males with sequence XS-II XL-IV and Y  L produced progenies with nearly normal sex ratios; males with the same X chromosome sequence but in the absence of a Y chromosome in some cases gave progenies with nearly normal sex ratios but in other cases gave progenies which tended toward phenotypic sr. Males with sequence XS-I XL-II and Y  L gave progenies which were characteristically sr (0.97–0.98 females); in the absence of a Y chromosome males with this sequence produced progenies which were virtually all-male. This latter finding is presumably identical to Novitski's (1947) "male sex ratio" (msr). The interpretation offered here attributes msr to an interaction between sr sequence XS-I XL-II and the 0 condition. A general consideration of the available data on sr in D. affinis is presented.
QUINACRINE FLUORESCENT CHROMOSOME ANALYSIS OF THE SNELL TRANSLOCATION IN THE MOUSE
Authors: Miller D A , Allderdice P W , Kouri R E , Dev V G , Grewal M S , Miller O J , Hutton J J
Published: January 2021

The chromosomes involved in the T(2;4)Sn (formerly designated T(5;8) Sn) or Snell translocation in the mouse have been identified as numbers 2 and 4 by analysis of the fluorescent banding patterns of quinacrine mustard-stained chromosomes in primary cultures from heterozygous and homozygous embryos.
MULTIPLE MEIOTIC DRIVE SYSTEMS IN THE DROSOPHILA MELANOGASTER MALE
Authors: Miklos George L Gabor , Yanders Armon F , Peacock W J
Published: January 2021

The behaviour of two "meiotic drive" systems, Segregation-Distorter (SD) and the sex chromosome sc4sc8 has been examined in the same meiocyte. It has been found that the two systems interact in a specific way. When the distorting effects of SD and sc4sc8 are against each other, there is no detectable interaction. Each system is apparently oblivious to the presence of the other, gametes being produced according to independence expectations. However when the affected chromosomes are at the same meiotic pole an interaction occurs; the survival probability of the gamete containing both distorted chromosomal products is increased, rather than being decreased by the combined action of two systems.
CLONAL VARIATION IN PARAMECIUM II. A COMPARISON OF STABLE AND UNSTABLE CLONES OF THE SAME SEROTYPE
Authors: Finger Irving , Onorato Fred , Heller Carol , Dilworth Linda
Published: January 2021

Paramecium generally expresses only one antigen on its surface from among an array of antigens. This mutual exclusion of antigens now has been shown in certain instances to be illusory. Unstable clones which will give rise to subclones with new serotypes possess several antigens. Unstable clones, even though they manifest only one serotype, continually manufacture an antigen other than the surface antigen characteristic of the serotype.
EVIDENCE FOR POST-CLEAVAGE FERTILIZATION AMONG MOSAICS IN HABROBRACON JUGLANDIS
Authors: Clark Arnold M , Gould Adair B
Published: January 2021

Habrobracon females homozygous for the mutant ebony produce about 5% mosaic progeny among fertilized eggs. The present experiment demonstrates by means of a test-cross method that in the production of these mosaics only one pronucleus is involved, and that this nucleus cleaves before union of one of its daughter nuclei with the sperm nucleus.
VARIATION ASSOCIATED WITH AN AEGILOPS UMBELLULATA CHROMOSOME SEGMENT INCORPORATED IN WHEAT. II. PEROXIDASE AND LEUCINE AMINOPEPTIDASE ISOZYMES
Authors: Macdonald T , Smith H H
Published: January 2021

Zymograms were analyzed of a number of Triticum aestivum derivatives which incorporated a segment of the Aegilops umbellulata chromosome bearing resistance to leaf rust. Evidence has been presented which suggests that genes involved in the production of two peroxidases and a single peptidase are located on the short arm of wheat chromosome 6B. One peroxidase isozyme, attributed to the presence of the Aegilops segment, was seen in only one of the resistant lines (Transfer) and it was postulated that this peroxidase band was present in a suppressed state in a number of lines. Possible differences in the A and B genomes of T. aestivum and T. dicoccum were discussed.
DEVELOPMENTAL ANALYSIS OF THE WING DISC IN THE MUTANT ENGRAILED OF DROSOPHILA MELANOGASTER
Authors: Garcia-Bellido A , Santamaria P
Published: January 2021

The engrailed (en) mutation leads to the transformation of the posterior structures of the dorsal mesothoracic disc into those characteristic of the anterior region of the same disc. Similar posterior-anterior duplications have been detected in dorsal as well as ventral structures of all the thoracic segments. —Genetic combinations of en with other pattern mutants have shown their synergistic effect on the posterior wing pattern.—A clonal analysis of the en wing disc shows that en affects its development in a characteristic way. The genetic change, by induced mitotic recombination, of en+ into en cells is followed by the corresponding transformation, except when it takes place some cell divisions prior to differentiation.—The en posterior wing disc cells show positive affinities with normal anterior wing disc cells in aggregates.—The mode of action of the en+ locus controlling wing disc development is discussed.
A DOMINANT CONSTITUTIVE phoR MUTATION IN ESCHERICHIA COLI
Authors: Pratt Charles , Gallant Jonathan
Published: January 2021

A dominant constitutive mutation of the phoR locus controlling alkaline phosphatase synthesis in Escherichia coli is described. Its phenotype can be explained by the production of a poisonous subunit of the phoR gene product. The phoR gene product is inferred to consist of at least 3 or 4 subunits.
THE EFFECT OF OXYGEN ON THE FREQUENCY OF SOMATIC RECOMBINATION IN DROSOPHILA MELANOGASTER
Authors: Stauffer H H
Published: January 2021

The influence of oxygen on the frequency of somatic recombination in the yellow singed system on the X chromosome of Drosophila melanogaster was studied under a variety of experimental conditions. Flies raised from egg to adult in atmospheres containing 70-90% oxygen were found to have significantly more mosaic spots on their abdominal tergites than were observed in flies which developed in air. First instar larvae X-rayed in from 0 to 100% oxygen demonstrated the existence of an oxygen effect for somatic recombination in the cells which form the abdominal hypoderm. The mosaic spot counts, beginning with the lowest numbers which were found in flies X-rayed in nitrogen, increased rapidly with rising oxygen tensions until the percentage in air was reached, then leveled off at the higher concentrations. Post-treatment with nitrogen of larvae X-rayed in air or oxygen created a substantially higher number of mosaic spots than were found when larvae, after being similarly irradiated, were instead placed into air or oxygen.
STUDIES ON THE SAL LOCUS IN DROSOPHILA PSEUDOOBSCURA. I. THE BANDING PATTERN OF THE TIP OF SALIVARY CHROMOSOME 3 IN LARVAE HOMOZYGOUS AND HETEROZYGOUS FOR SAL
Authors: Gersh Eileen Sutton
Published: January 2021

In the mutant sal the banding pattern at the tip of chromosome 3 is changed. Certain bands are compacted instead of being partially puffed. In sal+/sal heterozygotes, when the chromosome tips are paired they both show the sal+ pattern or are intermediate; but when unpaired, each shows the pattern characteristic of its own genotype.
BACTERIAL CONJUGATION: AN ANALYSIS OF MIXED RECOMBINANT CLONES
Authors: Lotan Dafna , Yagil Ezra , Bracha Moshe
Published: January 2021

A fraction of recombinant colonies resulting from conjugation is heterogenetic for unselected markers. Constitutivity for alkaline phosphatase synthesis (phoR) is studied as the unselected marker. The frequency of phoR heterogeneity depends on the genetic distance between phoR and the selected marker. Various models are considered which explain the formation of heterogenetic colonies (mixed clones), and experiments are described which test these models. It is concluded that the Hfr fragment can replicate and participate more than once in recombination thus yielding heterogenetic colonies.
SUSCEPTIBILITY TO SPONTANEOUS PNEUMONITIS IN AN INBRED STRAIN OF BEIGE AND SATIN MICE
Authors: Lane Priscilla W , Murphy Edwin D
Published: January 2021

Among mice of strain SB/Le, homozygous for the mutant genes beige (bg), satin (sa), and white-bellied agouti (Aw), 70% developed progressive pneumonitis by 6 months of age. Among backcross offspring from an outcross to C57BL/6J-Aw-J, 49% of homozygous beige and 11% of nonbeige genotypes developed pneumonitis by 6 months of age. The evidence indicates that a specific action of the beige gene increases susceptibility to progressive pneumonitis. Lymphadenopathy, including reticulum cell neoplasms and atypical lymphoproliferative lesions, was observed in high incidence in sa+/sa bg males, suggesting a closer association with satin than with beige. Beige mice show giant lysosomal granules in the leukocytes and pigment dilution closely analogous to the Chediak-Higashi syndrome in man and similar disorders in mink and cattle. Strain SB/Le provides a convenient model in a laboratory animal for study of the increased susceptibility to infection analogous to that of the Chediak-Higashi syndrome.
ALLOZYME GENOTYPE-ENVIRONMENT RELATIONSHIPS. I. VARIATION IN NATURAL POPULATIONS OF DROSOPHILA PACHEA
Authors: Rockwood-Sluss E S , Johnston J S , Heed W B
Published: January 2021

Remarkable geographic and seasonal uniformities in gene and genotype frequencies were found for four enzyme loci. Principal component analysis revealed two patterns of allele frequency changes in three of the allozyme loci (Est-b, Est-c and Acph) and one pattern in the Mdh-d locus. These patterns accounted for 90% to 100% of the variability at these loci. Significant positive correlations were obtained between several of the components and the variability in the non-saponifiable and alkaloid fractions of the senita cactus host plant. The genetic variance within a single locality (Guaymas, Mexico) was as great as the variance between all localities sampled. This is interpreted as a local founder effect. The temporary nature of the rotting cactus breeding site, the delayed maturation and the differential maturation rate of females and males are three factors proposed to cause forced outbreeding and counter the local founder effect. A combination of selection resulting from a direct interaction of the genotype and the environment, in addition to migration, is proposed to maintain the uniform gene frequencies.
GENETIC CONTROL OF MITOCHONDRIA IN PARAMECIUM
Authors: Beisson J , Sainsard A , Adoutte A , Beale G H , Knowles J , Tait A
Published: January 2021

Mitochondrial mutations for resistance to various antibiotics (erythromycin, chloramphenicol, spiramycin, mikamycin) have been obtained in Paramecium aurelia and their properties are reviewed. Using these mitochondrial markers, the interactions between nucleus and mitochondria have been studied in two ways: by microinjection of mitochondria from one stock or species into other stocks and species of P. aurelia and by a genetic study of a nuclear mutation affecting mitochondrial multiplication. Both types of experiments show: (1) that there may exist incompatibility between a given type of mitochondria and the cell into which they are introduced and (2) that through multiplication in the host cell, mitochondrial properties can be modified. The possible basis for incompatibility and host-induced modifications is discussed.
PHYSIOLOGICAL STUDIES OF SALMONELLA HISTIDINE OPERATOR-PROMOTER MUTANTS
Authors: Ely Bert
Published: January 2021

S. typhimurium hisO mutations are cis dominant and trans recessive and occur in a regulatory segment separate from but adjacent to the first structural gene of the histidine operon, hisG. Strains containing hisO mutations singly and in combination with other regulatory mutations were examined for their content of L-histidinol phosphate phosphatase when grown on limiting and on excess L-histidine. HisO mutations classed as "constitutive" (high enzyme levels) or as "promoter-like" (low enzyme levels) cause a variety of sub-phenotypes. A model is proposed that accounts for the phenotypes found as well as for the interspersion of constitutive and promoter-like mutations on the genetic map (Ely, Fankhauser and Hartman 1974). In this model we suggest that the his operator-promoter DNA is a functional unit that assumes alternate conformations including: (a) the classic linear duplex, active in transcription, and (b) a looped structure that is transcriptionally closed and susceptible to the binding of repressor.
GENETIC ANALYSIS OF A DOUBLE MALE STRAIN OF ESCHERICHIA COLI K12
Authors: Falkinham Joseph O , Clark A J
Published: January 2021

The behavior of a double male strain of Escherichia coli K12 has been compared to that of its parents and a primary F' strain carrying F14 in order to determine whether the genome of the double male, responsible for the double origin mode of gene transmission, is composed of one or two linkage groups. F-prime plasmids carrying leu and pyrB and argG and metC have been detected following mating an F-  recA  - recipient with the double male. Their existence strongly supports the contention that the double male is composed of a single linkage group with two integrated sex factors. Data from acridine orange curing experiments places the frequency of double male cells in the population of growing cells in the two-chromosome configuration as less than one percent. Evidence for a unique origin and terminus of DNA replication deduced by the density labelling and transduction of double male DNA supports the contention that the double male is best considered a cell with a single chromosome carrying two integrated F plasmids.
PHASE-SPECIFIC GENES FOR MACROCONIDIATION IN NEUROSPORA CRASSA
Authors: Selitrennikoff Claude P , Nelson Robert E , Siegel Richard W
Published: January 2021

Two new mutant genes in Neurospora crassa prevent the formation of free macroconidia from proconidial chains. These genes, called conidial separation-1 and conidial separation-2, are phase-specific, playing no role in either the sexual life cycle or other aspects of the asexual life cycle. A cell-wall-associated autolytic activity was found to increase in wild-type cultures at the time of active formation of free conidia from proconidial chains; no such increase was detected in mutant cultures. It appears that the products of these genes are both essential for and unique to macroconidiation.
INDUCTION BY MUTAGENS OF TANDEM GENE DUPLICATIONS IN THE glyS REGION OF THE ESCHERICHIA COLI CHROMOSOME
Authors: Straus Daniel S
Published: January 2021

Four mutagens (ultraviolet light, nitrous acid, the acridine half mustard ICR 372, and niridazole) have been found to increase the frequency of tandem gene duplications in the glyS region of the Escherichia coli chromosome. This result was obtained by quantitating the spontaneous and mutagen-induced reversion frequency of a glycyl-tRNA synthetase (glyS) mutant. Following mutagenesis, as many as 0.2% of the survivors were obszrved to contain duplications in the glyS region. In addition, several classes of stable revertants of the glyS mutant have been identified.
RIBOSOMAL GENE MAGNIFICATION IN DROSOPHILA: A CHROMOSOMAL CHANGE
Authors: Harford A Gayler
Published: January 2021

The sex-linked mutant "bobbed" can undergo a rapid phenotypic reversion during a prescribed series of outcrosses. The experiments reported here distinguish between two general genetic models. The first is that the phenotypic change results from the changing genetic background brought about by the outcrosses. The second is that the phenotypic change results from an alteration of the X chromosome in the germ line. The data support the second model. It is shown that both the bobbed and reverted phenotypes segregate from the same female. In addition, the reverted phenotype maps in or near the proximal heterochromatin of the X chromosome, which is the standard map position of both bobbed and the nucleolus organizer.
LINKAGE DISEQUILIBRIUM IN NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Langley Charles H , Tobari Yoshiko N , Kojima Ken-Ichi
Published: January 2021

Two large, stable populations (Texas and Japan) of Drosophila melanogaster were surveyed at 21 allozyme loci on the second and third chromosomes and for chromosomal gene arrangements on those two chromosomes. Over 220 independent gametes were sampled from each population. The types and frequencies of the surveyed genetic variation are similar to those observed previously and suggest only slight differentiation among geographically distant populations. Linkage disequilibrium among linked allozymes loci is only slightly, if at all, detectable with these sample sizes. Linkage disequilibrium between linked inversions and allozymes loci is common especially when located in the same arm. These disequilibria appear to be in the same direction for most comparisons in the two population samples. This result is interpreted as evidence of similar selective environments (ecological and genetic) in the two populations. It is also noted that the direction of these linkage disequilibria appears to be oriented with respect to the gene frequencies at the component loci.
GENETIC ANALYSIS IN THE COLONIA STRAIN OF PHYSARUM POLYCEPHALUM: HETEROTHALLIC STRAINS THAT MATE WITH AND ARE PARTIALLY ISOGENIC TO THE COLONIA STRAIN
Authors: Adler Paul N , Holt Charles E
Published: January 2021

Amoebae of the Colonia (CL) strain, which normally produce plasmodia in clones, are shown to cross with mt3 and mt4 amoebae under appropriate conditions. Strains carrying mt3 and mt4 in a CL genetic background were constructed and used in the genetic analysis of mutants isolated in CL.
ESTERASES OF DROSOPHILA II. BIOCHEMICAL STUDIES OF ESTERASE-5 in D. pseudoobscura
Authors: Berger Edward M
Published: January 2021

In vitro enzyme hybridization was carried out with combinations of six allozymic variants of Esterase-5 from Drosophila pseudoobscura. Studies on heat stability and specific activity changes accompanying hybridization were done to examine the possible expression of overdominance at the biochemical level. In 11 of 15 combinations no significant change in specific activity was found following hybridization. In two cases hybridization resulted in a decrease in activity in the mixture, while in two cases esterase activity was elevated. Heat stability studies, in several cases, revealed reduced rates of inactivation in in vitro and in vivo heterozygotes compared with homozygotes. From these and other data a model for the molecular mechanism of heterosis is presented.
THE RESPONSE OF DOPA DECARBOXYLASE ACTIVITY TO VARIATIONS IN GENE DOSAGE IN DROSOPHILA: A POSSIBLE LOCATION OF THE STRUCTURAL GENE
Authors: Hodgetts Ross B
Published: January 2021

A location of the structural gene(s) for dopa decarboxylase (EC 4.1.1.26) is proposed on the basis of enzyme determinations in a set of duplication-bearing aneuploids, which revealed only one dosage-sensitive region in the Drosophila genome. This region lies between 36EF and 37D on the left arm of chromosome 2.
FITNESS OF ALLOZYME VARIANTS IN DROSOPHILA PSEUDOOBSCURA. I. SELECTION AT THE PGM-1 AND ME-2 LOCI
Authors: Marinković Dragoslav , Ayala Francisco J
Published: January 2021

We have studied in Drosophila pseudoobscura the effect of allozyme variation on seven fitness components: female fecundity, egg hatchability, egg-to-adult survival under near-optimal and under competitive conditions, rate of development under near-optimal and under competitive conditions, and mating capacity of males. Three genotypes at each of two loci, Pgm-1 and Me-2, have been studied in various combinations. These two loci are highly polymorphic in natural populations of D. pseudoobscura. Statistically significant differences involving one or more genotypes exist for all components of fitness. No single genotype is best for all fitness components; rather the relative fitnesses of genotypes are reversed when different parameters are considered, or when they are studied in different environmental conditions. Also, the average egg-to-adult survival and rate of development are better when different genotypes are reared together than when they occur in pure culture. Four different modes of selection have been uncovered by our experiments. These forms of selection may account for the persistence of the two allozyme polymorphisms in nature, and for previously observed seasonal fluctuations of the allelic frequencies in natural populations.
GENETIC ORGANIZATION AND ADAPTIVE RESPONSE OF ALLOZYMES TO ECOLOGICAL VARIABLES IN FUNDULUS HETEROCLITUS
Authors: Mitton Jeffry B , Koehn Richard K
Published: January 2021

Populations of Fundulus heteroclitus, (Cyprinodontidae) a widespread coastal marine fish, were studied in control and artificially heated environments on the North Shore of Long Island, New York to determine (1) patterns of variation in biochemical phenotypes and (2) the extent to which this variation reflected adaptation to environmental characteristics.—Variation at three of twelve polymorphic isoenzyme loci from the warm water population was beyond the range of variation among control populations, and resembled those determined for populations living at more southern latitudes. Hence, these differences were interpreted as adaptations to warm environments. Significant differences in allele frequencies and zygotic proportions at ten of twelve isoenzyme loci were found associated with differences in environments, sexes, and/or age classes. These data strongly support the view that protein polymorphisms are adaptive.—Several observations suggested that selection acts upon multilocus phenotypes rather than upon those of single loci. Several di-locus phenotypic distributions were demonstrated to be nonrandom, and those that exhibited similar patterns of dependence over years were postulated to be maintained by selection. Highly heterozygous fish exhibited superior viability when cohorts were compared over successive years.—The consequences of the polygynous mating system in this species for maintaining genetic variation and for allowing rapid evolutionary response to a variable environment are discussed.
POPULATION SIZE AND SELECTION INTENSITY EFFECTS ON LONG-TERM SELECTION RESPONSE IN MICE
Authors: Eisen E J
Published: January 2021

Long-term response to within full-sib family selection for increased postweaning gain was evaluated in lines having different effective population sizes (Ne) and selection intensities (i). Line designations were I4(4), I8(2), I16(2), M4(4), M8(2) and M16(2), where I and M indicate selection of the top 50% and 25%, respectively; 4, 8 and 16 represent the number of parental pairs per replicate and number of replicates is given in parentheses. Realized within full-sib family heritabilities (hR  2) in the first phase of selection (0-14 generations) were larger in 16-pair lines than in 4- and 8-pair lines. In the second phase of selection (>14 generations), hR  2 declined significantly (P<.01) in all lines, and only the I16 and M16 lines had hR  2 values significantly (P<.01) greater than zero. Realized genetic correlations involving number born, 12-day litter weight, weaning weight and six-week weight tended to decline in the second phase of selection. The I16, M16 and control (C16) replicates were crossed in all combinations at generation 14. Crosses were then selected within litters for high postweaning gain. The hR  2 values in the crossbred lines were all larger than those in the second selection phase for M16-1, M16-2 and I16-1, but not for I16-2. Within each Ne level, total response was significantly (P<.01) less for I lines compared with M lines. Total response increased as Ne increased, within each level of i. Relatively small differences in realized i values among Ne lines could not account for this result. The difference in total response among the Ne lines at a given selection intensity may be due to inbreeding depression and a combination of interactions involving "drift" and selection. By crossing replicates of the M lines with the C16 control, the effects of inbreeding depression were removed. Inbreeding depression and genetic drift, as defined herein, were equally important in accounting for differences among Ne lines in total response.
ENZYME POLYMORPHISMS: GENE FREQUENCY DISTRIBUTIONS WITH MUTATION AND SELECTION FOR OPTIMAL ACTIVITY
Authors: Latter B D H
Published: January 2021

Gene frequency distributions observed in large-scale surveys of species of Drosophila are shown to be incompatible with a genetic model involving neutral mutations and genetic drift alone. The data are, however, qualitatively similar to predictions based on an alternative model of natural selection for an optimal level of enzyme activity in addition to drift and mutation. The intensity of selection detected reduces the mean rate of gene substitution to less than one-quarter that expected on the neutral-allele hypothesis.
GENETIC CONTROL OF PHOSPHATE-METABOLIZING ENZYMES IN NEUROSPORA CRASSA: RELATIONSHIPS AMONG REGULATORY MUTATIONS
Authors: Littlewood Barbara S , Chia William , Metzenberg Robert L
Published: January 2021

In Neurospora crassa, the phosphate-metabolizing enzymes are made during phosphate starvation, but not under phosphate sufficiency. The synthesis of these enzymes is controlled by three regulatory genes: pcon-nuc-2, preg and nuc-1. pcon-nuc-2 and preg are closely linked. A model of the hierarchical relationships among these regulatory genes is presented. Studies of double mutants and revertants confirm several predictions of the model. It has been found that nuc-2 (null) and pconc (constitutive) mutations reside in the same cistron. pregc (constitutive) mutations are epistatic to nuc-2 mutations. nuc-1 (null) mutations are epistatic to all others.
RESOLUTION OF AN EQUIVOCAL GENETIC ELEMENT IN DROSOPHILA MELANOGASTER: ORGANIZATION OF THE MAROON-LIKE LOCUS
Authors: Duck Peter , Chovnick Arthur
Published: January 2021

Despite extensive prior study, an understanding of the genetic organization of the maroon-like locus (ma-l:1-64.8) has been elusive. A large-scale, three-point fine structure recombination experiment is described, whose results provide documentation for an inescapable argument that maroon-like is a single element rather than a polycistronic system.
GENIC HETEROZYGOSITY AND VARIATION IN PERMANENT TRANSLOCATION HETEROZYGOTES OF THE OENOTHERA BIENNIS COMPLEX
Authors: Levy Morris , Levin Donald A
Published: January 2021

Genic heterozygosity and variation were studied in the permanent translocation heterozygotes Oenothera biennis I, Oe. biennis II, Oe. biennis III, Oe. strigosa, Oe. parviflora I, Oe. parviflora II, and in the related bivalent formers Oe. argillicola and Oe. hookeri. From variation at 20 enzyme loci, we find that translocation heterozygosity for the entire chromosome complex is accompanied by only moderate levels of genic heterozygosity: 2.8% in Oe. strigosa, 9.5% in Oe. biennis and 14.9% in Oe. parviflora. Inbred garden strains of Oe. argillicola exhibited 8% heterozygosity; neither garden nor wild strains of Oe. hookeri displayed heterozygosity and only a single allozyme genotype was found. The mean number of alleles per locus is only 1.30 in Oe. strigosa, 1.40 in Oe. biennis, and 1.55 in Oe. parviflora, compared to 1.40 in Oe. argillicola. Clearly, the ability to accumulate and/or retain heterozygosity and variability has not been accompanied by extraordinary levels of either. Clinal variation is evident at some loci in each ring-former. A given translocation complex may vary geographically in its allozymic constitution. From gene frequencies, Oe. biennis I, II, and III, Oe. strigosa and Oe. hookeri are judged to be very closely related, whereas Oe. argillicola seems quite remote; Oe. parviflora is intermediate to the two phylads. Gene frequencies also suggest that Oe. argillicola diverged from the Euoenothera progenitor about 1,000,000 years ago, whereas most of the remaining evolution in the complex has occurred within the last 150,000 years.
RECESSIVE LETHAL AMBER SUPPRESSORS IN YEAST
Authors: Brandriss Marjorie C , Soll Larry , Botstein David
Published: January 2021

Recessive lethal amber suppressor mutations have been isolated in a diploid strain of Saccharomyces cerevisiae. Diploids carrying these suppressors upon sporulation yield asci with only two live spores, both lacking the suppressor. At least two classes of recessive lethal suppressors exist. Aneuploid strains carrying one wild type and one suppressor locus have been isolated and used in mapping studies; one suppressor maps on chromosome III, the other does not.
EVIDENCE OF PREFERENTIAL PAIRING OF CHROMOSOMES AT MEIOSIS IN ANEUPLOID YEAST
Authors: James A P , Inhaber Elizabeth R
Published: January 2021

Meiotic pairing in homothallic S. cerevisiae was studied by tetrad analysis, using strains that were trisomic or tetrasomic for chromosome I. The disomic segregants of these strains produce tetrasomic spore colonies that can be distinguished by their phenotype. Results indicated the existence of preferential pairing and nonrandom assortment of chromosomes at meiosis I. The frequency of crossing over is apparently normal in at least some regions when non-preferred pairing occurs.