bluuebunny/crossref_metadata_2025 huggingface dataset:
MUTATIONS AFFECTING SYNTHESIS OF β-GALACTOSIDASE ACTIVITY IN THE YEAST KLUYVEROMYCES LACTIS
Authors: Sheetz R Michael , Dickson Robert C
Published: April 2021

Fifty-one mutants of Kluyveromyces lactis that cannot grow on lactose (Lac-) were isolated and characterized. All of the mutations are in nuclear genes, are recessive in their wild-type allele and define seven complementation groups, which we designate lac3 through lac9. Strains bearing mutations in lac3,lac5, lac7, lac8 and lac9 are also unable to grow on galactose (Gal-). Since the Gal- and Lac- phenotype co-segregate, they are probably due to a single mutation. Strains bearing mutations in any of the seven complementation groups grow normally on glucose. However, strains bearing mutations in lac3, lac5 and lac6 do not grow on glucose if lactose is also present in the medium. Likewise, strains bearing mutations in lac3 and lac5 do not grow on glucose in the presence of galactose. Complementation groups lac4 and lac5 are loosely linked and map within a cluster of auxotrophic mutations on a chromosome that we designate Chromosome 2. The remaining five groups are unlinked. Thus, there is no evidence for clustering of Lac genes into an operon-like regulatory unit.—To further characterize the nature of the Lac- phenotype, the basal and inducible level of β-galactosidase activity were measured. All mutants had nearly normal basal enzyme levels, except those in lac4, which had barely detectable levels. Inducible enzyme levels varied from barely detectable levels in mutants bearing lac4 mutations up to four-fold inducible levels in strains bearing mutations in other complementation groups. In all cases, however, induction levels were below the 30-fold level obtained in wild-type cells. Three strains bearing lac5 mutations contain increased enzyme activity in the absence of inducer, indicating constitutive synthesis of β-galactosidase. In summary, these data indicate that several genes are necessary for synthesis of β-galactosidase activity.
MULTIPLE FORMS OF MAIZE ENDOSPERM ADP-GLUCOSE PYROPHOSPHORYLASE AND THEIR CONTROL BY SHRUNKEN-2 AND BRITTLE-2
Authors: Hannah L C , Tuschall D M , Mans R J
Published: April 2021

Heat-labile and heat stable forms of ADP-glucose pyrophosphorylase were identified in the maize endosperm. The heat-labile form is destroyed by normal electrophoretic conditions. The heat-stable form corresponds to pyrophosphorylase B. In wild type, 96% of the total activity is heat labile. Both forms are reduced in 11 brittle-2 (bt2) and 12 shrunken-2 (sh2) mutants. The heat-labile form is reduced to a greater extent than is the heat-stable form in each of the 23 mutants. Deletion of sh2 abolishes both forms. The original ratio of the two forms is restored after sh2 function is expressed via transposition of Dissociation from sh2. The possible roles of these genes in the control of ADP-glucose pyrophosphorylase are discussed.
NEW LOCI IN DICTYOSTELIUM DISCOIDEUM DETERMINING PIGMENT FORMATION AND GROWTH ON BACILLUS SUBTILIS
Authors: Morrissey James H , Wheeler Steven , Loomis William F
Published: April 2021

Seventeen independently isolated pigmentless (white) mutations in Dictyostelium discoideum are all recessive and fall into three complementation groups identifying two new whi loci in addition to the previously characterized whiA locus. whiB and whiC map to linkage groups III and IV, respectively. In addition, it was discovered that our laboratory stock of NC4, the wild-type strain from which these mutants were derived, has spontaneously lost the ability to grow on Bacillus subtilis. This new mutation, bsgB500, maps to linkage group VII and is not allelic to bsgA. bsgB500 is the first spontaneously derived mutation in D. discoideum that can be used to select heterozygous diploids, and for the first time allows genetic analysis to be routinely performed on strains derived from an unmutagenized background.
THE EFFECT OF GAMETOGENESIS REGIMES ON THE CHLOROPLAST GENETIC SYSTEM OF CHLAMYDOMONAS REINHARDTII
Authors: Sears Barbara B , Boynton John E , Gillham Nicholas W
Published: April 2021

In Chlamydomonas reinhardtii, gamete differentiation is induced by nitrogen deprivation. While cellular nitrogen content and amount of chloroplast DNA in cells of both mating types are reduced during gametogenesis, the spontaneous transmission of paternal (mt  -) chloroplast alleles in crosses is specifically affected by the stringency of the nitrogen starvation regime used for pregrowth and gametogenesis of the mt  - parent. In all cases, reciprocal crosses yielded biparental zygospores whose clones contain predominantly cells expressing only the chloroplast alleles from the maternal (mt  +) parent. No differences attributable to strain divergence were seen in chloroplast gene inheritance pattern, DNA content, or the relative frequency of transmission of paternal chloroplast alleles to progeny of biparental zygospores.
CORRELATION BETWEEN MAP POSITION AND PHENOTYPE OF CTI MUTANTS IN THE C CISTRON OF RHIZOBIUM MELILOTI PHAGE 16—3
Authors: Dudás Brigitta , Orosz László
Published: April 2021

Nine temperature-sensitive clear mutations (Cti) in the C cistron (coding for the repressor protein) of Rhizobium meliloti temperate phage 16—3 were characterized according to the inductive temperature, the immunity of cells lysogenic for these mutant phages to superinfection by homoimmune weak virulent mutants, the phenotype of double-ti mutants and interallelic complementation. The results indicate that mutations of similar phenotypic expression are clustered on the genetic map. Furthermore, it seems probable that the C cistron of the original phage 16—3 is identical to that of the independently isolated phage strain 36.
TEMPERATURE-SENSITIVE MUTANTS BLOCKED IN THE FOLDING OR SUBUNIT ASSMBLY OF THE BACTERIOPHAGE P22 TAILSPIKE PROTEIN. I. FINE-STRUCTURE MAPPING
Authors: Smith Donna H , Berget Peter B , King Jonathan
Published: April 2021

As part of a study of protein folding, we have constructed a fine-structure map of 9 existing and 29 newly isolated UV- and hydroxylamine-induced temperature-sensitive (ts) mutations in gene 9 of Salmonella bacteriophage P22. Gene 9 specifies the polypeptide chain of the multimeric tail spikes, six of which form the cell attachment organelle of the phage. The 38 ts mutants were mapped against deletion lysogens with endpoints in gene 9. They mapped in 10 of the 15 deletion intervals. Two- and three-factor crosses between mutants within each interval indicated that at least 31 ts sites are represented among the 38 mutants. To determine the distribution of ts sites within the physical map, we identified the protein fragments from infection of su- hosts with 10 gene 9 amber mutants. Their molecular weights, ranging from 13,900 to 55,000 daltons, were combined with the genetic data to yield a composite map of gene 9. The 31 ts sites were distributed through most of the gene, but were most densely clustered in the central third.—None of the ts mutant pairs tested exhibited intragenic complementation. Studies of the defective phenotypes of the ts mutants (Goldenberg and King 1981; Smith and King 1981) revealed that most do not affect the thermostability of the mature protein, but instead prevent the folding or subunit assembly of the mutant chains synthesized at restrictive temperature. Thus, many of thes ts mutations identify sites in the polypeptide chain that are critical for the folding or maturation of the tail-spike protein.
MUTANTS AFFECTED IN ALKALINE PHOSPHATASE EXPRESSION: EVIDENCE FOR MULTIPLE POSITIVE REGULATORS OF THE PHOSPHATE REGULON IN ESCHERICHIA COLI
Authors: Wanner Barry L , Latterell Patrick
Published: April 2021

The expression of alkaline phosphatase (the product of the phoA gene) in Escherichia coli is believed to be subject to both positive control by the phoB gene product and negative control by the phoR gene product. We have isolated a large number of PhoA- mutants in the phoR  - genetic background. Among mutants altered in the positive control of alkaline phosphatase, some were phoB mutants; others had a mutation in a new gene, designated phoM. We believe that the phoM gene codes for a positive regulator that acts together with the phoB gene product in phoA gene expressions.—The PhoM phenotype was found to be masked in phoR  + strains. This and other evidence support a positive regulatory role for the phoR gene product as well.—Our experiments demonstrate that phoA is under positive control by three different positive regulators: the products of the phoB, phoM and phoR genes. The phoB gene product is always needed together with either the phoR or phoM gene product. In addition, the phoR gene product acts as a negative regulator.—We describe a model for phoA gene expression consistent with this new evidence.
MEIOSIS IN NEUROSPORA CRASSA. II. GENETIC AND CYTOLOGICAL CHARACTERIZATION OF THREE MEIOTIC MUTANTS
Authors: DeLange A M , Griffiths A J F
Published: April 2021

Three recessive meiotic mutants, asc(DL95), asc(DL243) and asc(DL879), were detected by the abortion of many of their ascospores and were analyzed using both cytological and genetic methods. Even though asc(DL95), asc(DL243) and the previously studied meiotic mutant, mei-1 (Smith 1975; Lu and Galeazzi 1978), complement one another in crosses, they apparently do not recombine (DeLange and Griffiths 1980). Thus, they may represent alleles of the same gene or comprise a gene cluster. Ascospore abortion in these mutants is caused by abnormal disjunction of meiotic chromosomes. In crosses homozygous for asc(DL95), asc(DL879) or mei-1, both pairing of homologs and meiotic recombination frequencies are reduced. In each case, this primary defect is followed by the formation of univalents at metaphase I and their irregular segregation. The mutant asc(DL243) has a defect in ascus formation, and later in disjunction during the second meiotic and post-meiotic divisions. The first-acting defect before or during karyogamy results in the abortion of most cells. Some cells manage to proceed past this block. During the second meiotic division, most chromosomes of the few resulting asci are attached to only one of the two spindle-pole bodies. Disjunction at the postmeiotic division is also highly irregular. This mutant appears to be defective in the attachment of one spindle-pole body to a set of chromosomes. The defect may involve either a centromere-associated product or a spindle-pole body.
TWO-LOCUS PROBLEMS IN TRANSMISSION GENETICS OF MITOCHONDRIA AND CHLOROPLASTS
Authors: Ohta Tomoko
Published: April 2021

A problem in transmission genetics was studied theoretically by regarding a cell as a population of organelle chromosomes. A hybrid cell of the two strains is assumed to consist initially of equal numbers of the two types of nucleoids, each containing an equal number of chromosomes. The two parent strains have different alleles at the two loci, and the two-locus dynamics of the hybrid cell line was analyzed. Within each nucleoid, stochastic matching and gene conversion are assumed to occur between the chromosomes, and at a certain rate fusion and division are assumed to take place between the nucleoids within the cell. Under this model, the changes of average genotype frequencies at the two loci within a nucleoid and within a cell were formulated, and the final frequencies of recombinant chromosomes were obtained. Random segregation of nucleoids at cell division was incorporated into the analyses; in addition, the increase of homozygosity in the cell was formulated. The results may be useful for interpreting the observed data on organelle genetics of some species of algae and yeast.
SELECTIVE NEUTRALITY OF 6PGD ALLOZYMES IN E. COLI AND THE EFFECTS OF GENETIC BACKGROUND
Authors: Dykhuizen Daniel , Hartl Daniel L
Published: April 2021

We have used gluconate-limited chemostats to study selective differences between isogenic strains of Escherichia coli K12 into which four naturally occurring alleles coding for allozymes of 6-phosphogluconate dehydrogenase (6PGD) had been transferred. The limit of detectability of selection with our procedures is a selection coefficient of 0.5%. In the normal E. coli K12 genetic background, all alleles are selectively neutral or nearly neutral. The absence of detectable selection does, however, depend on genetic background and on such environmental factors as cell density. In a genetic background containing a mutation that cuts off the alternative metabolic route for 6-phosphogluconate, selection between allozymes can be detected, and the selection is in the direction expected from the measured apparent Km values of the allozymes. Even when the alternative metabolic route is not blocked by mutation, one of the 6PGD allozymes has a detrimental, but density-dependent, interaction with a mutation conferring resistance to bacteriophage T5. In all cases, the observed selection is due to the allozymes themselves (or to associated regulatory elements), as the selection disappears when the chemostats are limited by a different carbon source (ribose plus succinate). Nevertheless, the four alleles do seem to be selectively neutral or nearly neutral in the normal E. coli K12 genetic background. Moreover, the distribution of allele frequencies in natural populations of E. coli is in accord with the expectations of selective neutrality.

I am inclined to suspect that we see, at least in some [cases], variations which are of no service to the species, and which consequently have not been seized on and rendered definite by natural selection…. Variations neither useful nor injurious would not be affected by natural selection, and would be left either a fluctuating element, as perhaps we see in certain polymorphic species, or would ultimately become fixed…. We may easily err in attributing importance to characters, and in believing that they have been developed through natural selection;… many structures are now of no direct use to their possessors, and may never have been of any use to their progenitors…. [On the other hand,] we are much too ignorant in regard to the whole economy of any organic being to say what slight modifications would be of importance or not.
BEHAVIORAL AND BIOCHEMICAL DEFECTS IN TEMPERATURE-SENSITIVE ACETYLCHOLINESTERASE MUTANTS OF DROSOPHILA MELANOGASTER
Authors: Hall Jeffrey C , Alahiotis Stamatis N , Strumpf David A , White Kristin
Published: April 2021

Temperature-sensitive (ts) mutants of the Ace gene, which codes for acetylcholinesterase (AChE) in Drosophila melanogaster, were analyzed for defects in viability, behavior and function of the enzyme. The use of heat-sensitive and cold-sensitive mutations permited the function of AChE in the nervous system to be analyzed temporally. All ts mutations were lethal, or nearly so, when animals expressing them were subjected to restrictive temperatures during late embryonic and very early larval stages. Heat treatments to Ace-ts mid- and late larvae had little effect on the behavior of these animals or on the viability or behavior of the eventual adults. Heat-sensitive mutants exposed to nonpermissive temperatures as pupae, by contrast, had severe defects in phototaxis and locomotor activity as adults. AChE extracted from adult ts mutants that had developed at a permissive temperature were abnormally heat labile, and they had reduced substrate affinity when assayed at restrictive temperatures. However, enzyme activity did not decline during exposure of heat-sensitive adults to high temperatures even though such treatments caused decrements in phototaxis (29°) and, eventually, cessation of movement (31°). The cold-sensitive mutant also produced readily detectable levels of AChE when exposed to a restrictive temperature during the early developmental stage when this mutation causes almost complete lethality. We suggest that the relationship among the genetic, biochemical and neurobiological defects in these mutants may involve more than merely temperature-sensitive catalytic functions.
LACK OF GENIC VARIATION IN THE ABUNDANT PROTEINS OF HUMAN KIDNEY
Authors: Smith Sandra C , Racine Robert R , Langley Charles H
Published: April 2021

Abundant proteins of 25 human kidneys were surveyed for genic variation by means of two-dimensional electrophoresis. Eighty-three (83) proteins were scored, and no genic variation was detected. This reduction in genic heterozygosity corroborates results determined with two-dimensional electrophoresis in mice and flies. These results suggest that previous estimates of electrophoretic variation may have been in error because of biased selection of loci.
A RARE-MALE ADVANTAGE IN THE HOUSEFLY INDUCED BY WING CLIPPING AND SOME GENERAL CONSIDERATIONS FOR DROSOPHILA
Authors: Bryant Edwin H , Kence Aykut , Kimball Kay T
Published: April 2021

Multiple-choice crosses among five geographic strains of the housefly, Musca domestica L., were carried out in equal (10:10) and low-frequency (4:16) ratios. Initially, a low-frequency-male mating advantage was apparent, but further analyses related this minority advantage to a reduction of male mating success during marking by wing clipping. When there are fluctuating differences in the level of sexual vigor between competing male types over replicate trials of a cross, a mating advantage will accrue to the minority type. Even if males from the two competing strains are equally vigorous, such fluctuating differences will occur during sampling of flies. Harming the flies during marking will serve to enhance this effect and make significant departures toward greater mating success of rare males highly likely. This statistical bias in favor of minority males was substantiated in simulations of the Kence-Bryant model of mating success and compared with our results of a minority advantage in the housefly and with published results of a minority advantage in Drosophila. Our evidence, though circumstantial, that an advantage to minority males could have been induced by such an experimental bias suggests that a re-examination of existing data, as well as new experimentation, is necessary to discern whether or not a real rare-male advantage exists.
SUPPRESSORS OF MUTATIONS IN THE rII GENE OF BACTERIOPHAGE T4 AFFECT PROMOTER UTILIZATION
Authors: Hall Dwight H , Snyder Ronald D
Published: April 2021

Homyk, Rodriguez and Weil (1976) have described T4 mutants, called sip, that partially suppress the inability of T4rII mutants to grow in λ lysogens. We have found that mutants sip1 and sip2 are resistant to folate analogs and overproduce FH2 reductase. The results of recombination and complementation studies indicate that sip mutations are in the mot gene. Like other mot mutations (Mattson, Richardson and Goodin 1974; Chace and Hall 1975; Sauerbier, Hercules and Hall 1976), the sip2 mutation affects the expression of many genes and appears to affect promoter utilization. The mot gene function is not required for T4 growth on most hosts, but we have found that it is required for good growth on E. coli CTr5X. Homyk, Rodriguez and Weil (1976) also described L mutations that reverse the effects of sip mutations. L2 decreases the folate analog resistance and the inability of sip2 to grow on CTr5X. L2 itself is partially resistant to a folate analog, and appears to reverse the effects of sip2 on gene expression. These results suggest that L2 affects another regulatory gene related to the mot gene.
A TWO-SEX POLYGENIC MODEL FOR THE EVOLUTION OF PREMATING ISOLATION. I. DETERMINISTIC THEORY FOR NATURAL POPULATIONS
Authors: Sved J A
Published: April 2021

It is proposed that mating behavior is normally determined by independent genetic systems in the male and female. A specific model is put forward in which mating behavior is determined by additive gene contributions in both sexes, and the strength of mating attraction is maximized when mating "scores" in the two sexes are equalized. This type of model, which may be described as a "facilitation" model, is related to models proposed by a number of authors. It is pointed out that a second class of models exists, "avoidance" models, and that these, although less tractable analytically, could be more realistic. —An organism is assumed to be divided into two strains, and selection is introduced through lethality or sterility of the hybrid (postmating isolation). The selective tendency for divergence of mating behavior in one sex is then shown to be proportional to the amount of divergence that already exists in the opposite sex, multiplied by a quantity that can be described as the heritability of mating attraction. The situation in which no initial divergence exists in either sex constitutes an equilibrium that is unstable, but one that requires substantial deviations before any selective progress can be made. Thus, the evolution of premating isolation to reinforce postmating isolation may be an inefficient process. The process would occur much more efficiently if some initial chance divergence in mating behavior occurred during the period in which postmating isolation evolved.
A TWO-SEX POLYGENIC MODEL FOR THE EVOLUTION OF PREMATING ISOLATION. II. COMPUTER SIMULATION OF EXPERIMENTAL SELECTION PROCEDURES
Authors: Sved J A
Published: April 2021

A Monte-Carlo simulation program is described for a polygenic mating model introduced in the first paper in this series (Sved 1981). The program is used to simulate the situation in laboratory experiments in which two strains are allowed to mass-mate, hybrids are artificially eliminated and the establishment of mating isolation is studied. It is shown that, if mating choice is sufficiently precise, a combination of chance fluctuation and selection can lead to divergence in mating behavior. However, for small population sizes, the variability would usually be considerably reduced by the time some divergence is established, leading to low eventual levels of isolation. For larger population sizes, on the other hand, it may take many generations for any divergence to be established. —A dissection of the selective forces involved in the divergence shows that the major force potentially responsible for initial selective response is the tendency for divergent females and males to reject mates from the wrong strain. However, this is nullified in mixed-strain matings by the tendency of such individuals equally to reject mates from the correct strain. To overcome this problem, it is suggested that the usual mixed-strain mating procedure be replaced by procedures specifically designed to select for rejection of interstrain matings. Two procedures are suggested for this, and computer simulation shows that one or other of the procedures will work under the assumptions of the mating model. Other possible outcomes of selection, including asymmetrical divergence, are discussed for cases in which the assumptions of the mating model are invalid.
THE ISOLATION OF MMS- AND HISTIDINE-SENSITIVE MUTANTS IN NEUROSPORA CRASSA
Authors: Delange A M , Mishra N C
Published: April 2021

A simple method of replica plating has been used to isolate mutants of Neurospora crassa that have increased sensitivity to methyl methanesulfonate (MMS) and/or to histidine. Twelve mutants with increased sensitivity to MMS and one mutant with increased sensitivity to histidine showed Mendelian segregation of the mutant phenotypes. Three mutants were mapped to loci not previously associated with MMS sensitivity. Two others were allelic to the UV- and MMS-sensitive mutant, mei-3. Survival curves indicate that conidia (mutant or wild-type) survive on much higher concentrations of MMS at 25° than at 37°. In contrast, mycelial growth is more resistant to MMS at 37°. The possibility of qualitatively different repair processes at these two temperatures is discussed.
INSERTIONS OF THE TRANSPOSON Tn1 INTO THE PSEUDOMONAS AERUGINOSA CHROMOSOME
Authors: Krishnapillai V , Royle Pamela , Lehrer Joanna
Published: April 2021

The transposon Tnl has been translocated to the chromosome of Pseudomonas aeruginosa from plasmid R18, iollowing hydro,xylamine mutagenesis of the plasmid. Twelve insertions were mapped to six distinct sites distal to 55 min of the origin of chromosome transfer by the plasmid FP2. These map locations were confirmed by host chromosome mobilization tests mediated by plasmids RI8 or R91-5, due to Tni homology between plasmid and host chromosome. All the Tnl chromosomal inserts were retransposable to other plasmids (Sa, R931 and R38). The behavior of Tnl in P. aemginosa was very similar to its behavior in Escherichia coli with respect to regional specificity, orientation of insertion and in serving as regions of homology for host chromosome mobilization by plasmids. This last property has permitted the demonstration that Tnl on RI8 and R91-5 is in opposite orientation with respect to the origin of transfer (oriT) of the two plasmids.
THE GENETIC BASIS OF DOSAGE COMPENSATION OF ALCOHOL DEHYDROGENASE-1 IN MAIZE
Authors: Birchler James A
Published: April 2021

The levels of alcohol dehydrogenase (ADH) do not exhibit a structural gene-dosage effect in a one to four dosage series of the long arm of chromosome one (1L) (BIRCHLER19 79). This phenomenon, termed dosage compensation, has been studied in more detail. Experiments are described in which individuals aneuploid for shorter segments were examined for the level of ADH in order to characterize the genetic nature of the compensation. The relative ADH expression in segmental trisomics and tetrasomics of region IL 0.72–0.90, which includes the Adh locus, approaches the level expected from a strict gene dosage effect. Region IL 0.20–0.72 produces a negative effect upon ADH in a similar manner to that observed with other enzyme levels when IL as a whole is varied (BIRCHLEF1I9 79). These and other comparisons have led to the concept that the compensation of ADH results from the cancellation of the structural gene effect by the negative aneuploid effect. The example of ADH is discussed as a model for certain other cases of dosage compensation in higher eukaryotes.
FITNESS AND DENSITY-DEPENDENT POPULATION GROWTH IN DROSOPHILA MELANOGASTER
Authors: Mueller Laurence D , Ayala Francisco J
Published: April 2021

The density-dependent rates of population growth were determined for 26 populations of Drosophila melanogaster maintained in the serial transfer system. Twenty-five populations were homozygous for an entire chromosome 2 sampled from nature; the other was a random heterozygous population. Rates of population growth around the carrying capacity cannot explain the large fitness depression of these lines. However, the homozygous lines show large differences in rates of population growth at low densities relative to the random heterozygous standard. The average relative fitness of the homozygous lines, as determined from the growth rates at the lowest density, is 0.51.
IDENTIFICATION OF A GENETIC ELEMENT THAT CONTROLS THE ORGAN-SPECIFIC EXPRESSION OF Adh1 IN MAIZE
Authors: Woodman James C , Freeling Michael
Published: April 2021

Allozyme balances serve as markers of quantitative behavior of electrophoretically distinguishable alleles. By the use of ADH Set I allozyme balances, it is demonstrated that all Adh1-S/Adh1-F individuals from more than 20 diverse S/F families exhibit a reciprocal correlation between Adh1 quantitative behavior in two maize organs: the scutellum and primary root. Within an electrophoretic mobility class, the Adh1 allele that is relatively underexpressed in the scutellum is relatively overexpressed in the primary root, and vice versa. Segregation tests prove that this "reciprocal effect" is the property of a cis-acting site that is closely linked to or within the Adh1 structural gene, and it is not affected by diverse genetic backgrounds. Immunological and [3H]-leucine incorporation experiments establish that Adh1 quantitative variants differ in ADH1·ADH1 synthetic rates in the anaerobic primary root. The reciprocal-effect phenomenon suggests that the cis-acting loci controlling Adh1 quantitative expression in each respective organ are at least in close proximity, or may share common DNA sequences. We discuss the possibility that the reciprocal-effect locus is a regulatory component of the Adh1 cistron.
THE GENETIC AND CYTOLOGICAL ORGANIZATION OF THE Y CHROMOSOME OF DROSOPHILA MELANOGASTER
Authors: Kennison James A
Published: April 2021

Cytological and genetic analyses of 121 translocations between the Y chromosome and the centric heterochromatin of the X chromosome have been used to define and localize six regions on the Y chromosome of Drosophila melanogaster necessary for male fertility. These regions are associated with nonfluorescent blocks of the Y chromosome, as revealed using Hoechst 33258 or quinacrine staining. Each region appears to contain but one functional unit, as defined by failure of complementation among translocations with breakpoints within the same block. The distribution of translocation breakpoints examined appears to be nonrandom, in that breaks occur preferentially in the nonfluorescent blocks and not in the large fluorescent blocks.
GENETIC VARIABILITY OF FLIGHT METABOLISM IN DROSOPHILA MELANOGASTER. I. CHARACTERIZATION OF POWER OUTPUT DURING TETHERED FLIGHT
Authors: Curtsinger James W , Laurie-Ahlberg Cathy C
Published: April 2021

The mechanical power imparted to the wings during tethered flight of Drosophila melanogaster is estimated from wing-beat frequency, wing-stroke amplitude and various aspects of wing morphology by applying the steady-state aerodynamics model of insect flight developed by Weis-Fogh (1972, 1973). Wing-beat frequency, the major determinant of power output, is highly correlated with the rate of oxygen consumption. Estimates of power generated during flight should closely reflect rates of ATP production in the flight muscles, since flies do not acquire an oxygen debt or accumulate ATP during flight. In an experiment using 21 chromosome 2 substitution lines, lines were a significant source of variation for all flight parameters measured. Broadsense heritabilities ranged from 0.16 for wing-stroke amplitude to 0.44 for inertial power. The variation among lines is not explained by variation in total body size (i.e., live weight). Line differences in flight parameters are robust with respect to age, ambient temperature and duration of flight. These results indicate that characterization of the power output during tethered flight will provide a sensitive experimental system for detecting the physiological effects of variation in the structure or quantity of the enzymes involved in flight metabolism.
A MODEL OF EVOLUTIONARY BASE SUBSTITUTIONS AND ITS APPLICATION WITH SPECIAL REFERENCE TO RAPID CHANGE OF PSEUDOGENES
Authors: Takahata Naoyuki , Kimura Motoo
Published: April 2021

A model of evolutionary base substitutions that can incorporate different substitutional rates between the four bases and that takes into account unequal composition of bases in DNA sequences is proposed. Using this model, we derived formulae that enable us to estimate the evolutionary distances in terms of the number of nucleotide substitutions through comparative studies of nucleotide sequences. In order to check the validity of various formulae, Monte Carlo experiments were performed. These formulae were applied to analyze data on DNA sequences from diverse organisms. Particular attention was paid to problems concerning a globin pseudogene in the mouse and the time of its origin through duplication. We obtained a result suggesting that the evolutionary rates of substitution in the first and second codon positions of the pseudogene were roughly 10 times faster than those in the normal globin genes; whereas, the rate in the third position remained almost unchanged. Application of our formulae to histone genes H2B and H3 of the sea urchin showed that, in each of these genes, the rate in the third codon position is tremendously higher than that in the second position. All of these observations can easily and consistently be interpreted by the neutral theory of molecular evolution.
MUTATIONAL SPECIFICITY OF ULTRAVIOLET LIGHT IN ESCHERICHIA COLI WITH AND WITHOUT THE R PLASMID pKM101
Authors: Fowler R G , McGinty L , Mortelmans K E
Published: April 2021

Plasmid pKM101 provides UV protection and increases the frequency of spontaneous and UV-induced mutations in Escherichia coli. By analyzing reversion patterns of defined trpA alleles, we showed that pKM101 altered the mutational specificity of UV-induced mutations. Certain UV-induced base-pair substitutions were strongly enhanced, while others were decreased in frequency in the presence of pKM101. This result suggests an interaction between cellular misrepair and an error-prone repair function(s) provided by pKM101. We have also examined UV mutational specificity in the absence of pKM101 and found the following: (1) UV preferentially enhances missense, as well as nonsense, intergenic suppressor mutations; (2) UV causes all possible base-pair substitutions as well as frameshift mutations; (3) G·C base pairs are more susceptible to UV mutagenesis than A·T base pairs at the same nucleotide positions; and (4) UV-induced mutations can occur at nucleotide positions that are not part of pyrimidine-pyrimidine sequences.
LINKAGE OF MUTATIONS AFFECTING MINUS FLAGELLAR MEMBRANE AGGLUTINABILITY TO THE mt
- MATING-TYPE LOCUS OF CHLAMYDOMONAS
Authors: Hwang Carol J , Monk Brian C , Goodenough Ursula W
Published: April 2021

Two independently isolated mutant strains, imp-10 and imp-12, were obtained by UV irradiation of wild-type mating-type minus (wt-). Each fails to agglutinate sexually with gametes of either mating type, but mating and zygote formation can be elicited by agglutinating either strain to wt+ gametes by means of anti-flagellar antiserum. Tetrad analysis of the resultant zygotes shows that both imp-10 and imp-12 are very closely linked to mt  -, with no recombinants observed. Diploid strains constructed between imp-10 or imp-12 and wt+ gametes are wt-, that is, they agglutinate and fuse like normal minus cells. Tetrad analysis of triploids from imp-10 diploid x wt+ haploid crosses shows that only imp-10 and wt+ products are recovered. A model is proposed to account for these results.
PARASEXUAL GENETIC ANALYSIS OF CELL PROPORTIONING MUTANTS OF DICTYOSTELIUM DISCOIDEUM
Authors: Morrissey James H , Loomis William F
Published: April 2021

Eight independently isolated mutants of Dictyostelium discoideum that differentiate exclusively into stalk cells make up one complementation group and carry single recessive mutations at the stalky locus, stkA, located on linkage group II. KY19, a previously described strain that differentiates into spores, but not stalk cells, was found to possess a recessive mutation defining the stalkless locus, stlA, located on linkage group VI. An analysis of the properties of these mutants, together with the phenotype of a haploid double mutant carrying stkA and stlA indicates that stlA results in poorly organized stalk tubes and incomplete stalk cell differentiation, while stkA causes all of the cells to differentiate into stalk cells, even when not enclosed in the stalk tube. The significance of these results is discussed in relation to current theories of pattern formation in D. discoideum.
EVIDENCE THAT TWO LOCI PREDOMINANTLY DETERMINE THE DIFFERENCE IN SUSCEPTIBILITY TO THE HIGH PRESSURE NEUROLOGIC SYNDROME TYPE I SEIZURE IN MICE
Authors: McCall R D , Frierson D
Published: April 2021

Most mammals tested, when exposed to increasing pressure in helium/oxygen atmospheres, exhibit progressive motor disturbances culminating in two, usually successive, well-differentiated convulsive seizures. The seizures are highly reproducible components of the constellation of events that collectively constitute the High Pressure Neurologic Syndrome (HPNS). In the present study, we present evidence that the mean difference in seizure threshold pressures of the first seizure to occur (HPNS Type I) between inbred mouse strains DBA/2J and C57BL/6J is predominantly determined (> 60%) by the expression of a major locus—possibly linked to the H-2 locus on chromosome 17—and a minor locus, probably unlinked. This outcome is derived from applications of the maximum likelihood modeling procedure of Elston and Stewart (1973) and Stewart and Elston (1973) to eleven models of genetic determinacy and tests (including breeding tests) of "preferred" models so derived using BXD recombinant inbred strains that show the following: The major locus exhibits conditional dominance characteristics depending upon compression rate and minor locus genotype. At a constant mean compression rate of 100 atm hr-1, the major locus manifests strong, though incomplete, dominance apparently independent of minor locus genotype. Its expression is, however, highly sensitive to compression rate, losing its dominance altogether at a linear rate of 1,000 atm hr-1. The major locus interacts with the weakly dominant and relatively compression-rate-insensitive minor locus to retain dominance at fast compression only when the dominant alleles of both loci are present. A principal finding of this study is that employing two compression rates permits fuller genetic characterization of murine high-pressure seizure susceptibility differences than could be achieved by use of a single compression rate.
DYNAMICS OF THE LINKAGE DISEQUILIBRIUM FUNCTION UNDER MODELS OF GENE-FREQUENCY HITCHHIKING
Authors: Asmussen Marjorie A , Clegg Michael T
Published: April 2021

The dynamic behavior of the linkage disequilibrium (D) between a neutral and a selected locus is analyzed for a variety of deterministic selection models. The time-dependent behavior of D is governed by the gene frequency at the selected locus (p) and by the selection (s) and recombination (r) parameters. Thomson (1977) showed numerically that D may increase under certain initial conditions. We give exact conditions for D to increase in time, which require that the selection intensity exceed the recombination fraction (s > r) and that p be near zero or one. We conclude from this result that gene frequency hitchhiking is most likely to be important when a new favorable mutant enters a population. We also show that, for what can be a wide range of gene frequencies, D will decay at a faster rate than the neutral rate. Consequently, the hitchhiking effect may quickly diminish as the selected gene becomes more common.—The method of analysis allows a complete qualitative description of the dynamics of D as a function of s and r. Two major findings concern the range of gene frequencies at the selected locus for which D either increases over time or decays at a faster rate than under neutrality. For all models considered, the region where D increases (i) first enlarges then shrinks as selection intensifies, and (ii) steadily shrinks as r increases. In contrast, the region of accelerated decay constantly enlarges as the selection intensity increases. This region will either shrink or enlarge as r increases, depending upon the form of selection in force.
MUTATION AT THE am LOCUS OF NEUROSPORA CRASSA
Authors: Kinsey John A , Hung Bao-Shin T
Published: April 2021

Forty-eight new mutations at the am locus of Neurospora crassa have been characterized. Nineteen mutations were induced by UV; of these, eight were missense, two were frameshifts, two were nonsense, three were deletions and four were unidentified. Twenty-nine mutations were induced with nitrous acid; of these, twenty-one were missense, three were frameshifts, one was nonsense, two were deletions and one was genetically unstable.
THE GENETIC ANALYSIS OF A RECIPROCAL TRANSLOCATION, eT1(III; V), IN CAENORHABDITIS ELEGANS
Authors: Rosenbluth Raja E , Baillie David L
Published: April 2021

The Caenorhabditis elegans mutation e873, which results in a recessive uncoordinated phenotype (formerly named Unc-72) and which had been isolated after 32P t reatment (BRENNER1 974), has now been found to act as a crossover suppressor and to be associated with a translocation between linkage groups (LG's) IIIand V. The translocation has been named, eTl(ZI1; V); eT1acts as a dominant crossover suppressor for both the right half of LGIIIand the left half of LGV,providing a balancer for a total of 39 map units. The uncoordinated e873phenotype has been shown to be a consequence of Eminactive unr- 36111gene. It was possible to demonstrate that, in translocation heterozygotes, eT1chromosomes marked with either sma-3or dpy-11segregate from normal LGIII,while those marked with bli-5, sm-2or unc-42segregate from normal LGV.Since bli-5and sma-2are normally on LGIII,and dpy-11is normally on LGV,it is concluded that: (a) eT1is a reciprocal translocation; (b) there is a breakpoint between sma-3and sma-2in LGIII(the region containing unc- 36)and one between dpy-11and unc-42in LGV;(c) thera is no dominant centromere between sma-2and bli-5on LGIII,since in eT1these genes are not linked to a LGIIIcentromere. Similarly, it is highly unlikely that there is a centromere to the left of dpy-11on LGV.The new gene order in eT1was determined by measuring recombination rates between markers in eT1homozygotes. It is concluded that the new order is: dpy-1 sma-3 (break) dpy-11 unc-60,and bli-5 sma-2 (break) unc-42 unc-51.——Thisis the first analysis of a C. eleganstranslocation with respect to reciprocity, breakpoints and new gene order.
Mortality, Falls, and Fracture Risk Are Positively Associated With Frailty: A SIDIAP Cohort Study of 890 000 Patients
Authors: Middleton Robert , Poveda Jose Luis , Orfila Pernas Francesc , Martinez Laguna Daniel , Diez Perez Adolfo , Nogués Xavier , Carbonell Abella Cristina , Reyes Carlen , Prieto-Alhambra Daniel
Published: April 2021

Background

Frail subjects are at increased risk of adverse outcomes. We aimed to assess their risk of falls, all-cause mortality, and fractures.

Method

We used a retrospective cohort study using the Sistema d’Informació per al Desenvolupament de l’Investigació en Atenció Primària database (>6 million residents). Subjects aged 75 years and older with ≥1 year of valid data (2007–2015) were included. Follow-up was carried out from (the latest of) the date of cohort entry up to migration, end of the study period or outcome (whichever came first). The eFRAGICAP classified subjects as fit, mild, moderate, or severely frail. Outcomes (10th revision of the International Classification of Diseases) were incident falls, fractures (overall/hip/vertebral), and all-cause mortality during the study period. Statistics: hazard ratios (HRs), 95% CI adjusted (per age, sex, and socioeconomic status), and unadjusted cause-specific Cox models, accounting for competing risk of death (fit group as the reference).

Results

A total of 893 211 subjects were analyzed; 54.4% were classified as fit, 34.0% as mild, 9.9% as moderate, and 1.6% as severely frail. Compared with the fit, frail had an increased risk of falls (adjusted HR [95% CI] of 1.55 [1.52–1.58], 2.74 [2.66–2.84], and 5.94 [5.52–6.40]), all-cause mortality (adjusted HR [95% CI] of 1.36 [1.35–1.37], 2.19 [2.16–2.23], and 4.29 [4.13–4.45]), and fractures (adjusted HR [95% CI] of 1.21 [1.20–1.23], 1.51 [1.47–1.55], and 2.36 [2.20–2.53]) for mild, moderate, and severe frailty, respectively. Severely frail had a high risk of vertebral (HR of 2.49 [1.99–3.11]) and hip fracture (HR [95% CI] of 1.85 [1.50–2.28]). Accounting for competing risk of death did not change results.

Conclusion

Frail subjects are at increased risk of death, fractures, and falls. The eFRAGICAP tool can easily assess frailty in electronic primary care databases in Spain.
Regional tongue deformations during chewing and drinking in the pig
Authors: Olson Rachel A , Montuelle Stéphane J , Curtis Hannah , Williams Susan H
Published: April 2021

As a muscular hydrostat, the tongue undergoes complex deformations during most oral behaviors, including chewing and drinking. During these behaviors, deformations occur in concert with tongue and jaw movements to position and transport the bolus. Moreover, the various parts of the tongue may move and deform at similar timepoints relative to the gape cycle or they may occur at different timepoints, indicating regional biomechanical and functional variation. The goal of this study is to quantify tongue biomechanics during chewing and drinking in pigs by characterizing intrinsic deformations of the tongue across multiple regions simultaneously. Tongue deformations are generally larger during chewing cycles compared to drinking cycles. Chewing and drinking also differ in the timing of regional length and width, but not total length, deformations. This demonstrates functional differences in the temporal dynamics of localized shape changes whereas the global properties of jaw-tongue coordination are maintained. Finally, differences in the trade-off between length and width deformations demonstrate that the properties of a muscular hydrostat are observed at the whole tongue level, but biomechanical variation (e.g., changes in movements and deformations) at the regional level exists. This study provides new critical insights into the regional contributions to tongue deformations as a basis for future work on multidimensional shape changes in soft tissues.
Ecomorphometric Analysis of Diversity in Cranial Shape of Pygopodid Geckos
Authors: Gurgis George P , Daza Juan D , Brennan Ian G , Hutchinson Mark , Bauer Aaron M , Stocker Michelle R , Olori Jennifer C
Published: April 2021

Synopsis

Pygopodids are elongate, functionally limbless geckos found throughout Australia. The clade presents low taxonomic diversity (∼45 spp.), but a variety of cranial morphologies, habitat use, and locomotor abilities that vary between and within genera. In order to assess potential relationships between cranial morphology and ecology, computed tomography scans of 29 species were used for 3D geometric morphometric analysis. A combination of 24 static landmarks and 20 sliding semi-landmarks were subjected to Generalized Procrustes Alignment. Disparity in cranial shape was visualized through Principal Component Analysis, and a multivariate analysis of variance (MANOVA) was used to test for an association between shape, habitat, and diet. A subset of 27 species with well-resolved phylogenetic relationships was used to generate a phylomorphospace and conduct phylogeny-corrected MANOVA. Similar analyses were done solely on Aprasia taxa to explore species-level variation. Most of the variation across pygopodids was described by principal component (PC) 1(54%: cranial roof width, parabasisphenoid, and occipital length), PC2 (12%: snout elongation and braincase width), and PC3 (6%: elongation and shape of the palate and rostrum). Without phylogenetic correction, both habitat and diet were significant influencers of variation in cranial morphology. However, in the phylogeny-corrected MANOVA, habitat remained weakly significant, but not diet, which can be explained by generic-level differences in ecology rather than among species. Our results demonstrate that at higher levels, phylogeny has a strong effect on morphology, but that influence may be due to small sample size when comparing genera. However, because some closely related taxa occupy distant regions of morphospace, diverging diets, and use of fossorial habitats may contribute to variation seen in these geckos.