bluuebunny/crossref_metadata_2025_split huggingface dataset:
RECOMBINATION-DEFICIENT DELETIONS IN BACTERIOPHAGE Λ AND THEIR INTERACTION WITH CHI MUTATIONS
Authors: Henderson David , Weil Jon 
Published: January 2021

ABSTRACT
We have isolated a new class of deletion mutants of phage lambda that extend from the prophage attachment site, att, into the gam and cIII genes. In this respect they are similar to certain of the λpbio transducing phage, but they differ in having a low burst size and in forming minute plaques. Lytically grown stocks of the deletions contain a variable proportion of phage that produce large plaques. These have been shown to carry an additional point mutation. Similar mutations, called chi, have been described by Lam et al. (1974), who showed that they result in a hot-spot for recombination produced by the host recombination system (Rec). We show that chi mutations can occur at several sites in the lambda genome and produce a Rec-dependent increase in the burst size of the one deletion tested.—In addition to reducing burst size, the one deletion tested reduces synthesis of DNA and endolysin but increases production of serum blocking protein. A chi mutation partially restores DNA synthesis and endolysin production and reduces serum blocking protein to normal levels. Our results are consistent with the hypothesis put forward by Lam et al., that chi enhances the frequency of Rec-promoted recombination, which provides the only pathway for production of maturable DNA in a red- gam- infection. The mechanism of the differential effect on protein production is, however, unclear.—Chi mutations are found to occur in DNA other than that of λ. We show that, as has been suggested elsewhere (McMilin, Stahl and Stahl 1974), the λpbio transducing phages carry a chi mutation within the E. coli DNA substitution. A chi mutation also arose in a new substitution of unknown origin isolated in the course of this work.
AN ANALYSIS OF THE MODE OF GENE ACTION AFFECTING PUPA WEIGHT IN TRIBOLIUM CASTANEUM
Authors: Goodwill R 
Published: January 2021

ABSTRACT
Triple-testcross experiments (Kearsey and Jinks 1968) were employed to investigate the mode of gene action affecting pupa weight in Tribolium castaneum. Their experimental design involves two inbred lines, the F1 progeny and a segregating population derived from the cross of the inbred lines. In the present experiments, four segregating populations were used. These populations included the F2 generation, a select line (SEL) and two relaxed select lines (RSI and RSII). In addition, all possible reciprocal crosses were made among the RSI, RSII, and SEL populations. It was observed that: (1) additive, dominant and epistatic gene effects all made significant contributions to the pupa weight of the progeny from all four segregating populations; (2) there was no evidence of either accumulation of epistasis as a result of selection in the SEL population or decline in epistasis as a result of removing selection pressure from the RSI and RSII populations; and (3) significant negative heterosis and maternal effects contributed to the pupa weight of the crossbred progeny of the RSI, RSII and SEL populations.
GEOGRAPHICAL DISTRIBUTION OF TWELVE TRANSFERRIN ALLELES IN BLACK RATS OF ASIA AND OCEANIA
Authors: Moriwaki Kazuo , Kato Hatao , Imai Hirotami , Tsuchiya Kimiyuki , Yosida Tosihide 
Published: January 2021

ABSTRACT
About 450 black rats (Rattus rattus) were collected from 25 localities in Asia and Oceania. Their serum transferrins were analyzed by a newly developed thin layer acrylamide gel electrophoresis accompanied with acrinol pretreatment, exhibiting 12 transferrin bands. Generally, Asian type rats (2N=42) had fast-moving transferrins (R-series), Ceylon type (2N=40) moderately moving ones and Oceanian type (2N=38) slowly moving ones (C-series). Exceptionally, in northern India and Pakistan all Asian-type rats had C-series Tf. The possibility that divergence of R-series Tf and C-series Tf had preceded the karyotypic differentiation from 42 to 38 is proposed. In combination with the previous molecular data, the time of the divergence is roughly estimated between the order of a million years and ten thousand years.
STUDIES OF MUTATIONS IN T4 CONTROL GENES 33 AND 55
Authors: Horvitz H Robert 
Published: January 2021

ABSTRACT
Available mutations in transcriptional control genes 33 and 55 of coliphage T4 have been examined. By complementation analysis and map position, 15 mutants (13 in T4D, 2 in T4B) have been shown to lie in gene 33 and 6 (5 in T4D, 1 in T4B) in gene 55. According to patterns of suppression and recombination, these mutants define three distinct amber sites in gene 33 and also three distinct amber sites in gene 55. All of these mutations are true amber mutations, in apparent contrast to some traditional T4 "amber" mutants which grow in su+ E. coli CR63 but not in su- E. coli B because of a strain difference other than the su+ determinant. Evidence is presented that, contrary to previous suggestions (Bolle et al. 1968; Pulitzer and Geiduschek 1970), the gene 33 product is absolutely essential for T4 development.
A GENETIC AND BIOCHEMICAL STUDY OF HISTIDINE BIOSYNTHESIS IN MICROCOCCUS LUTEUS
Authors: Kane-Falce Caroline , Kloos Wesley E 
Published: January 2021

ABSTRACT
Histidine auxotrophs of Micrococcus luteus strain ATCC 27141 were induced by treatment of the parent strain with N-methyl-N′-nitro-N-nitro-soguanidine. Auxotrophs were biochemically characterized by examining culture accumulations of histidine intermediates, using paper chromatography and the Bratton-Marshall test, and growth responses to L-histidinol. his(IG) mutants failed to accumulate Pauly-positive imidazoles; his(EAHF) mutants accumulated 5-amino-1-ribosyl-4-imidazole carboxamide; hisB mutants accumulated imidazoleglycerol; hisC mutants accumulated imidazoleacetol; hisD mutants accumulated histidinol. L-histidinol failed to stimulate the growth of hisD mutants, but did stimulate all other histidine mutants, blocked at earlier steps in the biosynthetic pathway. In addition, imidazoleglycerol phosphate dehydrase activity was assayed in representative mutants of each class. hisB mutants lacked activity for this enzyme.—Two-point, three-point, and cotransformation analyses resolved linkage relationships of histidine genes and in two gene clusters aided in determining their sequences. Histidine biosynthetic genes exist in at least four separate, unlinked regions of the chromosome. One histidine gene cluster is closely linked to a tryptophan gene cluster and appears to be contiguous in the sequence his(IG)-his(EAHF)-trpE-trpC-trpB-trpA. A second and unlinked histidine cluster has the tentative gene sequence his(EAHF)-hisB-hisC-his(EAHF). The hisD gene and an unclassified mutant site his-94 are not linked to any of the other histidine genes examined in this study or to each other.
MITOTIC CHROMOSOME LOSS IN A DISOMIC HAPLOID OF SACCHAROMYCES CEREVISIAE
Authors: Campbell D A , Fogel S , Lusnak K 
Published: January 2021

ABSTRACT
Experiments designed to characterize the incidence of mitotic chromosome loss in a yeast disomic haploid were performed. The selective methods employed utilize the non-mating property of strains disomic for linkage group III and heterozygous at the mating type locus. The principal findings are: (1) The frequency of spontaneous chromosome loss in the disome is of the order 10-4 per cell; this value approximates the frequency in the same population of spontaneous mitotic exchange resulting in homozygosity at the mating type locus. (2) The recovered diploids are pure clones, and thus represent unique events in the disomic haploid. (3) Of the euploid chromosomes recovered after events leading to chromosome loss, approximately 90% retain the parental marker configuration expected from segregation alone; however, the remainder are recombinant for marker genes, and are the result of mitotic exchanges in the disome, especially in regions near the centromere. The recombinant proportion significantly exceeds that expected if chromosome loss and mitotic exchange in the disome were independent events. The data are consistent with a model proposing mitotic nondisjunction as the event responsible for chromosome loss in the disomic haploid.
ROLE OF DNA SEQUENCES IN GENETIC RECOMBINATION IN THE ISO-1-CYTOCHROME c GENE OF YEAST. I. DISCREPANCIES BETWEEN PHYSICAL DISTANCES AND GENETIC DISTANCES DETERMINED BY FIVE MAPPING PROCEDURES
Authors: Moore Carol W , Sherman Fred 
Published: January 2021

ABSTRACT
Recombination rates have been examined in two-point crosses of various defined cyc1 mutants using five mapping methods. Nucleotide sequences of mutant codons were identified in previous studies from alterations in functional iso-1-cytochromes c produced by intragenic revertants. Heteroallelic diploids were analyzed for rates of mitotic recombination that occurred spontaneously and that were induced with X-rays, ultraviolet light and the near-ultraviolet light emitted by sunlamps, as well as rates of meiotic recombination that occur after sporulation. Frequencies of both mitotic and meiotic recombination do not necessarily correspond with physical distances separating altered nucleotides. The most extreme discrepancy involved two adjacent intervals of thirteen base pairs which differed approximately thirtyfold in their spontaneous and X-ray-induced recombination rates. Marked disproportions between genetic and physical distances appear to be due to the interaction of the two nucleotide sequences in the heteroallelic combination and not to the sequences of the mutant codons alone. Recombination values that were obtained by all five methods could not be used to establish the correct order of mutant sites. Relationships of the recombination rates for the various pairwise crosses are different after mitosis from those after meiosis, suggesting that these two recombinational processes are to some extent different in their dependence on particular nucleotide configurations. On the other hand, the relationships of the rates induced by UV-, sunlamp- and X-irradiation were identical or very similar. In addition to the intrinsic properties of the alleles affecting frequencies of mitotic and meiotic recombination rates, two- to threefold variations in recombination rates could be attributed to genetic backgrounds.
LETHAL EFFECTS OF LOW AND "NULL" ACTIVITY ALLELES OF 6-PHOSPHOGLUCONATE DEHYDROGENASE IN DROSOPHILA MELANOGASTER
Authors: Bewley Glenn C , Lucchesi John C 
Published: January 2021

ABSTRACT
EMS-induced "null" and low activity alleles for 6-phosphogluconate dehydrogenase were characterized with respect to enzymatic activity, relative viability, fertility, and the effective lethal phase. It was determined that flies hemizygous and homozygous for the low activity allele, Pgd -, possessed a depressed developmental rate, diminished viability, and loss of female fertility. Heterozygotes for Pgd - and a deficiency for Pgd + were lethal. The "null" activity allele demonstrated a lethal phenotype in both the hemizygous and homozygous condition. The effective lethal phase for the "null" allele occurs during late embryonic development (20-22 hr).
A POSSIBLE ROLE OF REPETITIOUS DNA IN RECOMBINATORY JOINING DURING CHROMOSOME REARRANGEMENT IN DROSOPHILA MELANOGASTER
Authors: Lee C S 
Published: January 2021

ABSTRACT
It is postulated that certain repetitious DNA components play a role in the recombination processes during chromosome rearrangements. When the distribution of silver grain densities after the in situ hybridization of repetitious DNA (Rudkin and Tartof 1973) and the distribution of chromosome breaks due to X-irradiation (Kaufmann 1946) are compared, a strong correlation is found for the euchromatic portion of the D. melanogaster salivary X chromosome. These observations justify the postulate above that certain repetitious DNA provides homologous regions in the DNA of broken chromosome ends necessary for proper recombinatory joining.
NATURAL SELECTION AND AGE-STRUCTURED POPULATIONS
Authors: Demetrius Lloyd 
Published: January 2021

ABSTRACT
This paper studies the properties of a new class of demographic parameters for age-structured populations and analyzes the effect of natural selection on these parameters. Two new demographic variables are introduced: the entropy of a population and the reproductive potential. The entropy of a population measures the variability of the contribution of the different age classes to the stationary population. The reproductive potential measures the mean of the contribution of the different age classes to the Malthusian parameter. The Malthusian parameter is precisely the difference between the entropy and the reproductive potential. The effect of these demographic variables on changes in gene frequency is discussed. The concept of entropy of a genotype is introduced and it is shown that in a random mating population in Hardy-Weinberg equilibrium and under slow selection, the rate of change of entropy is equal to the genetic variance in entropy minus the covariance in entropy and reproductive potential. This result is an information theoretic analog of Fisher's fundamental theorem of natural selection.
PARAMETERS OF MITOTIC RECOMBINATION IN MINUTE MUTANTS OF DROSOPHILA MELANOGASTER
Authors: Ferrus A 
Published: January 2021

ABSTRACT
A sample of 16 Minutes, representing 12 loci distributed over all the chromosome arms and including 3 pairs of alleles and 4 deficiencies, has been studied with respect to several developmental and recombinational parameters. Cell marker mutants located in most of the chromosome arms were used to assess (1) spontaneous and X-ray-induced mitotic recombination frequencies of each Minute, and (2) clone sizes of the different cell marker clones. These parameters were analyzed both in the wing disc and in the abdominal histoblasts.—Whereas spontaneous frequencies are not affected by the presence of the Minutes studied, the different Minutes characteristically increase the frequency of recombination clones arising after X-irradiation. The recombinant clones which are M +/M + are significantly larger than clones in the same fly which retain the M +/M condition. This is particularly striking in clones in the wing disc, slightly so in clones in the tergites. The occurrence of mitotic recombination in the fourth chromosome is reported for the first time.—Chaeta length and developmental delay correlates with the recombinational parameters in different ways. Possible causal interrelationships of the different traits of the Minute syndrome are discussed.
POLYALLELIC MUTATIONAL EQUILIBRIA
Authors: King Jack Lester , Ohta Tomoko 
Published: January 2021

ABSTRACT
A new deterministic formulation is derived of the equilibrium between mutation and natural selection, which takes into account (a) the possibility of many allelic mutation states, (b) selection coefficients of the order of magnitude of the mutation rate and (c) the possibility of further mutation of already mutant alleles. The frequencies of classes of alleles 0, 1, 2, n mutant steps removed from the type allele are shown to form a Poisson distribution, with a mean and variance of the mutation rate divided by the coefficient of selection against each incremental mutational step. — This formulation is interpreted in terms of the expected frequencies of electromorphs, defined as classes of alleles characterized by common electrophoretic mobilities of their protein products. Electromorph frequencies are predicted to form stable unimodal distributions of relatively few phenotypic classes. Common electromorph frequencies found throughout the ranges of species with large population sizes are interpreted as being a uniquely electrophoretic phenomenon; band patterns on starch and acrylamide gels are phenotypes, not genotypes. It is predicted that individual electromorphs are highly heterogeneous with regard to amino acid sequence.
Perceived Types, Causes, and Consequences of Financial Exploitation: Narratives From Older Adults
Authors: Nguyen Annie L , Mosqueda Laura , Windisch Nikki , Weissberger Gali , Axelrod Jenna , Han S Duke 
Published: January 2021

Abstract

Objectives
The goal of this study was to investigate the perception of financial exploitation and its causes and consequences by older adults who have firsthand experience of being exploited.

Method
Thirty-one cognitively healthy older adult participants aged 50 or older were drawn from the Finance, Cognition, and Health in Elders Study. In-depth, one-on-one interviews were conducted. Interview transcripts were analyzed using an iterative, data-driven, thematic coding scheme and emergent themes were summarized.

Results
Categories of financial exploitation included (a) investment fraud, (b) wage theft/money owed, (c) consumer fraud, (d) imposter schemes, and (e) manipulation by a trusted person. Themes emerged around perceived causes: (a) element of trust, (b) promise of financial security, (c) lack of experience or awareness, (d) decision-making, and (e) interpersonal dynamics. Perceived consequences included negative and positive impacts around (a) finances, (b) financial/consumer behaviors (c) relationships and trust, (d) emotional impact, and (e) future outlook.

Discussion
These narratives provide important insights into perceived financial exploitation experiences.
Maximizing Home Health Aide Retention: The Impact of Control and Support on the Job
Authors: Gleason Hayley P , Miller Edward Alan 
Published: January 2021

Abstract

Background and Objectives
This study examined relationships between the level of control and support and home health aides (HHAs) job satisfaction and intent to leave the job.

Research Design and Methods
Data derive from a survey of 512 HHAs in Massachusetts. Logistic regression using generalized estimating equations was employed for the analysis. Dependent variables included satisfaction and intent to leave the job as a home care aide generally and satisfaction and intent to leave the job at the aide’s current agency.

Results
The findings showed that greater control and support on the job were important predictors of positive work outcomes, controlling for job demands and other covariates. The odds of HHAs being satisfied with their job as a home care aide increased with the degree of control, whereas the odds of HHAs being satisfied with their job at their current agency increased with the extent of support. Control was negatively associated with HHAs’ intent to leave the job as an aide; no relationship was found between control or support and HHAs’ intent to leave their current agency.

Discussion and Implications
The results from this study illustrate the importance for HHAs of having control and autonomy in their work, as well as the benefit of support from supervisors and the home care agency, on satisfaction and intent to leave. Expanding HHA’s ability to maintain control over their day-to-day work, as well as enhancing the supports available to them, is likely to benefit home care workers, clients, and agencies through increased retention.
Dimethyl fumarate dose-dependently increases mitochondrial gene expression and function in muscle and brain of Friedreich’s ataxia model mice
Authors: Hui Chun Kiu , Dedkova Elena N , Montgomery Claire , Cortopassi Gino 
Published: January 2021

Abstract
Previously we showed that dimethyl fumarate (DMF) dose-dependently increased mitochondrial gene expression and function in cells and might be considered as a therapeutic for inherited mitochondrial disease, including Friedreich’s ataxia (FA). Here we tested DMF’s ability to dose-dependently increase mitochondrial function, mitochondrial gene expression (frataxin and cytochrome oxidase protein) and mitochondrial copy number in C57BL6 wild-type mice and the FXNKD mouse model of FA. We first dosed DMF at 0–320 mg/kg in C57BL6 mice and observed significant toxicity above 160 mg/kg orally, defining the maximum tolerated dose. Oral dosing of C57BL6 mice in the range 0–160 mg/kg identified a maximum increase in aconitase activity and mitochondrial gene expression in brain and quadriceps at 110 mg/kg DMF, thus defining the maximum effective dose (MED). The MED of DMF in mice overlaps the currently approved human-equivalent doses of DMF prescribed for multiple sclerosis (480 mg/day) and psoriasis (720 mg/day). In the FXNKD mouse model of FA, which has a doxycycline-induced deficit of frataxin protein, we observed significant decreases of multiple mitochondrial parameters, including deficits in brain mitochondrial Complex 2, Complex 4 and aconitase activity, supporting the idea that frataxin deficiency reduces mitochondrial gene expression, mitochondrial functions and biogenesis. About 110 mg/kg of oral DMF rescued these enzyme activities in brain and rescued frataxin and cytochrome oxidase expression in brain, cerebellum and quadriceps muscle of the FXNKD mouse model. Taken together, these results support the idea of using fumarate-based molecules to treat FA or other mitochondrial diseases.
Evolutionary genetics of skin pigmentation in African populations
Authors: Feng Yuanqing , McQuillan Michael A , Tishkoff Sarah A 
Published: January 2021

Abstract
Skin color is a highly heritable human trait, and global variation in skin pigmentation has been shaped by natural selection, migration and admixture. Ethnically diverse African populations harbor extremely high levels of genetic and phenotypic diversity, and skin pigmentation varies widely across Africa. Recent genome-wide genetic studies of skin pigmentation in African populations have advanced our understanding of pigmentation biology and human evolutionary history. For example, novel roles in skin pigmentation for loci near MFSD12 and DDB1 have recently been identified in African populations. However, due to an underrepresentation of Africans in human genetic studies, there is still much to learn about the evolutionary genetics of skin pigmentation. Here, we summarize recent progress in skin pigmentation genetics in Africans and discuss the importance of including more ethnically diverse African populations in future genetic studies. In addition, we discuss methods for functional validation of adaptive variants related to skin pigmentation.