bluuebunny/crossref_metadata_2025 huggingface dataset:
THE GENETIC VARIABILITY OF THIRD CHROMOSOMES IN A LOCAL POPULATION OF DROSOPHILA MELANOGASTER
Authors: Watanabe Takao K , Yamaguchi Osamu , Mukai Terumi
Published: April 2021

Five hundred and two third chromosomes were extracted from a large cage population of Drosophila melanogaster initiated two months after collection of the progenitors near Raleigh, North Carolina in 1970.—Salivary gland chromosomes of 489 chromosome lines were examined and 54 chromosomes were found to carry inversions. The inversions were classified into three polymorphic types [In(3L)P, In(3R)P, and In(3R)C] and two unique types. The polymorphic inversions were found in frequencies of 0.012, 0.088, and 0.010, respectively.—Viabilities of homozygotes and heterozygotes were examined. Chromosomes with lethals occurred with a frequency of 0.495: 0.537 in the group of inversion-carrying chromosomes and 0.490 in the group of inversion-free chromosomes. The average homozygote viability computed on the basis of an average heterozygote viability of 1.0000 was 0.3235 if lethal lines were included and 0.6290 if they were excluded. The detrimental load to lethal load ratio (D:L ratio) was 0.70 (=0.4636-0.6650). The average viability of lethal heterozygotes was significantly larger than that of lethal-free heterozygotes. It appears, however, that lethal genes in heterozygotes have deleterious effects on fitness as a whole.—The average degree of dominance for viability polygenes was estimated to be about 0.3-0.4 in lethal-free individuals and nearly zero in lethal heterozygotes. Overdominance or some form of balancing selection was suggested at some loci. The difference between the values obtained for average degree of dominance due to genetic backgrounds and superior vibaility of lethal heterozygotes (but not fitness as a whole) suggests that some epistasis or coadaptation occurs.—The results described above are similar to those obtained for the second chromosomes (Mukai and Yamaguchi 1974).
COMPLEMENTATION ANALYSIS OF LINKED CIRCADIAN CLOCK MUTANTS OF NEUROSPORA CRASSA
Authors: Feldman Jerry F , Hoyle Marian N
Published: April 2021

A fourth mutant of Neurospora crassa, designated frq-4, has been isolated in which the period length of the circadian conidiation rhythm is shortened to 19.3 ± 0.3 hours. This mutant is tightly linked to the three previously isolated frq mutants, and all four map to the right arm of linkage group VII about 10 map units from the centromere. Complementation tests suggest, but do not prove, that all four mutations are allelic, since each of the four mutants is co-dominant with the frq  + allele—i.e., heterokaryons have period lengths intermediate between the mutant and wild-type—and since heterokaryons between pairs of mutants also have period lengths intermediate between those of the two mutants.
INHIBITION OF GROWTH BY AMBER SUPPRESSORS IN YEAST
Authors: Liebman Susan W , Sherman Fred
Published: April 2021

Strains of the yeast Saccharomyces cerevisiae that contain highly efficient amber (UAG) suppressors grow poorly on nutrient medium, while normal or nearly normal growth rates are observed when these strains lose the suppressors or when the suppressors are mutated to lower efficiencies. The different growth rates account for the accumulation of mutants with lowered efficiencies in cultures of strains with highly efficient amber suppressors. Genetic analyses indicate that one of the mutations with a lowered efficiency of suppression is caused by an intragenic mutation of the amber suppressor. The inhibition of growth caused by excessive suppression is expected to be exacerbated when appropriate suppressors are combined together in haploid cells if two suppressors act with a greater efficiency than a single suppressor. Such retardation of growth is observed with combinations of two UAA (ochre) suppressors (Gilmore 1967) and with combinations of two UAG suppressors when the efficiencies of each of the suppressors are within a critical range. In contrast, combinations of a UAA suppressor and a UAG suppressor do not affect growth rate. Apparently while either excessive UAA or excessive UAG suppression is deleterious to yeast, a moderate level of simultaneous UAA and UAG suppression is not.
A COMPUTER MODEL ALLOWING MAINTENANCE OF LARGE AMOUNTS OF GENETIC VARIABILITY IN MENDELIAN POPULATIONS. II. THE BALANCE OF FORCES BETWEEN LINKAGE AND RANDOM ASSORTMENT
Authors: Wills Christopher , Miller Charles
Published: April 2021

It is shown, through theory and computer simulations of outbreeding Mendelian populations, that there may be conditions under which a balance is struck between two factors. The first is the advantage of random assortment, which will, when multilocus selection is for intermediate equilibrium values, lead to higher average heterozygosity than when linkage is introduced. There is some indication that random assortment is also advantageous when selection is toward a uniform distribution of equilibrium values. The second factor is the advantage of linkage between loci having positive epistatic interactions. When multilocus selection is for a bimodal distribution of equilibrium values, an early advantage of random assortment is replaced by a later disadvantage. Linkage disequilibrium, which in finite populations is increased only by random or selective sampling, may hinder the movement of alleles to their selective equilibria, thus leading to the advantage of random assortment.—Some consequences of this approach to the structure of natural populations are discussed.
LAMBDA CIN-1, A NEW MUTATION WHICH ENHANCES LYSOGENIZATION BY BACTERIOPHAGE LAMBDA, AND THE GENETIC STRUCTURE OF THE LAMBDA CY REGION
Authors: Wulff Daniel L
Published: April 2021

Seven lambda cy mutants have been mapped within a small region located approximately halfway between the rightward boundary of the imm434 region and the lambda cII gene. The seven mutants lie at four sites separated by a total distance of about 12 nucleotide pairs, as estimated from recombination frequencies. Six of the seven mutants lie on the right side of the cy fine structure map, spanning a total distance of about 3-5 nucleotide pairs. Lying approximately 11-21 nucleotide pairs to the left of the leftmost cy mutant is a newly described mutation called cin-1, for c independent. The cin-1 mutation allows some lysogenization when coupled with any cy, cII or cIII mutant, but not when coupled with a defective cI gene. The cin-1 mutation, like cy mutants, has a cis-dominant action upon the cI gene in mixed infections. The observation that λimm434 cin-1 cy2001 lysogenizes efficiently, but not λimm434 cin-1 cy2001 cII68 nor any other λimm434 cin-1 cy derivative, is interpreted to mean that all of the cy mutants on the right side of the cy fine structure map inactivate a binding site for cII/cIII function, but that cy2001, the single mutant on the left side of the cyfine structure map, does not inactivate that binding site.
GENETICS OF MURINE LIVER AND KIDNEY ARYLSULFATASE B
Authors: Daniel William L
Published: April 2021

Mice from 12 inbred strains were surveyed for variation of kidney and liver arylsulfatase levels. Kidney variation was due to differences in the activity of arylsulfatase B. Twofold higher activities of arylsulfatase B in SWR/J kidney compared to A/HeJ kidney were determined by an autosomal gene which may be identical to the structural gene for arylsulfatase B since the SWR/J enzyme was more heat-stable than the A/HeJ enzyme. C57BL/6J mice possessed twofold higher liver arylsulfatase levels than did A/HeJ mice. The major portion of this variation could be attributed to differences in arylsulfatase B, and appeared to be inherited in autosomal fashion. Although some evidence supports the existence of a major locus influencing liver arylsulfatase activity, this must be substantiated by further studies. Whatever the nature of the genetic factors involved, they do not appear to involve structural genes since no differences were discernible between the enzymes of the two strains relevant to Km, heat stability, electrophoretic mobility, pH optimum, activation energy, or response to several inhibitors. Furthermore, the rank ordering of strains on the basis of kidney arylsulfatase activity differed markedly from that which pertained to liver activity. Kidney arylsulfatase levels, but not brain or liver arylsulfatase activities, appear subject to androgenic influences.
MORE ON NEI AND ROYCHOUDHURY'S SAMPLING VARIANCES OF HETEROZYGOSITY AND GENETIC DISTANCE
Authors: Mitra S
Published: April 2021

The inequality relationship between the expected values of (jx-g)2 and (ĝ-g)2, where jx is a biased and ĝ is an unbiased estimate of population homozygosity g, were examined earlier by Nei and Roychoudhury (1974) and later by Mitra (1975). The improvement in the inequality still left much to be desired. In this paper a lower boundary of g has been obtained which may be regarded as ultimate for ensuring a smaller expected value of (jx-g)2 than the corresponding value of (ĝ-g)2.
ON RECOMBINATION BETWEEN CLOSE AND DISTANT MARKERS IN PHAGE LAMBDA
Authors: Stahl Franklin W , Stahl Mary M
Published: April 2021

The contribution of parental DNA to progeny phages genetically recombinant for close markers, distant markers, or both simultaneously was studied in biparental and triparental replication-blocked crosses. The data are compatible with the previously proposed view that heterozygous overlaps at the sites of crossing over are sometimes about as long as the lambda chromosome. However, about half of the close marker recombinants have enjoyed triparental interactions, attenuating that conclusion and obscuring predictions of the long overlap model.
PHENOTYPIC DIVERSITY AMONG ALLELES AT THE PER-1 LOCUS OF NEUROSPORA CRASSA
Authors: Howe H Branch , Johnson T E
Published: April 2021

Comparison of 11 perithecial color mutants suggested that all were alleles at the per-1 locus but nonetheless separable into two groups because of phenotypic differences. Three of the mutant strains produced orange perithecia and black ascospores, and eight produced paler, yellow perithecia and white ascospores. Perithecial phenotype was dependent upon the genotype of the protoperithecial parent; ascospore phenotype, upon the genotype of the individual ascospore. No evidence was found that the white ascospores were due to chromosomal rearrangements. No separation of the perithecial and ascospore phenotypes by recombination was observed in a cross between one of the mutants and a per-1  + strain. However, apparent low levels of recombination in crosses between some of the mutants indicated possible genetic complexity at the per-1 locus. The phase specificity of the per-1 mutations and the possible nature and mode of expression of the orange and yellow perithecial pigments are discussed.
MITOCHONDRIAL GENETICS. XII. AN OLIGOMYCIN-RESISTANT MUTANT LOCALIZED AT A NEW MITOCHONDRIAL LOCUS IN SACCHAROMYCES CEREVISIAE
Authors: Clavilier Léa
Published: April 2021

Three antibiotic-resistance mutations were isolated from strain FL496–2B: two are independent Mendelian genes, one conferring both oligomycin and venturicidin resistance (oliR  496) and the other conferring cycloheximide resistance (cyhR  496). The third is a mitochondrial mutation, OR  9, and confers a low level of oligomycin resistance to cells (in vivo) but not to the extracted mitochondrial ATPase (in vitro). This mutation is located on the mitochondrial DNA at a new locus [OLI4] linked to [OLI2] and independent from [OLI1] and [OLI3] and from the other mitochondrial loci.

All three mutations (OR  9, oliR  496, cyhR  496) were found without any selection, in the same prototrophic haploid strain, which contained unknown resistances to antibiotics.

Some physiological, genetical and biochemical properties of the mitochondrial mutation are described.
CHARACTERIZATION OF T4 MUTANTS THAT PARTIALLY SUPPRESS THE INABILITY OF T4rII TO GROW IN LAMBDA LYSOGENS
Authors: Homyk Theodore , Rodriguez Angel , Weil Jon
Published: April 2021

In the course of isolating viable T4 deletions that affect plaque morphology (Homyk and Weil 1974), two closely linked point mutants, sip1 and sip2, were obtained. They map between genes t and 52, cause a reduction in plaque size and burst size, and partially suppress the lethality of rII mutants for growth in lambda lysogens. These characteristics demonstrate that sip1 and sip2 are similar to mutants previously reported by Freedman and Brenner (1972). In addition, D. Hall (personal communication) has shown that sip1 and sip2 are similar to the mutant farP85, which affects the regulation of a number of early genes (Chace and Hall 1975).—Sip suppression of rII mutants can be demonstrated in one-step growth experiments, even when both rII genes are completely deleted. This indicates that sip mutants do not simply reduce the level of rII gene products required for growth in a lambda lysogen. Instead, they alter the growth cycle so as to partially circumvent the need for any rII products.—Mutations at two other sites, designated L1 and L2, reverse the poor phage growth caused by sip and, in the one case tested, reverse the rII-suppressing ability of sip.
GENETICS OF ACETYLCHOLINESTERASE IN DROSOPHILA MELANOGASTER
Authors: Hall Jeffrey C , Kankel Douglas R
Published: April 2021

Genes in Drosophila melanogaster that control acetylcholinesterase (AChE) were searched for by segmental aneuploidy techniques. Homogenates of flies containing duplications or deletions for different segments were assayed for enzyme activity. A region on the third chromosome was found for which flies having one does consistently gave lower AChE activity than euploid flies, which were in turn had lower activity than flies with three doses. The activity differences were in the approximate ratio 1:2:3. Fine structure deletion mapping within this region revealed a very small segment for which one-dose flies have approximately half-normal activity. To obtain putative AchE-null mutations, lethal mutations within this region were assayed. Four allelic lethals have approximately half-normal activity in heterozygous condition. These lethals probably define the structural locus (symbol: Ace) for AChE.
IS THERE A GENE REGULATING THE SCUTE LOCUS ON THE THIRD CHROMOSOME OF D. MELANOGASTER?
Authors: Rendel J M
Published: April 2021

A section of the third chromosome of D. melanogaster some 25 to 40 centimorgans long including sr was transferred from a wild-type stock selected by Latter for high scutellar bristle number into a scute stock with a large number of scutellar bristles. This segment is shown to have a large effect on the bristle numbers of wild-type flies, to reduce the strength of canalization of the scute phenotype at 4 bristles, to have little, if any, effect on bristle numbers of scute flies with less than 4 bristles but to increase the number of flies with 5 and 6 scutellar bristles in scute stocks that normally have a large number of flies with 4 bristles. It is suggested that this segment in unselected chromosomes contains a gene that regulates bristle number by repressing the scute locus and that Latter has selected a mutant of the regulator which fails to repress the action of the scute locus.
MUTATORS IN SACCHAROMYCES CEREVISIAE: MUT1–1, MUT1–2 AND MUT2–1
Authors: Gottlieb Dorma J C , Von Borstel R C
Published: April 2021

The purpose of this study was to characterize two mutator stocks of yeast which were induced and selected on the basis of high spontaneous reversion rates of the suppressible "ochre" nonsense allele lys1-1. In the mutator stock VA-3, a single mutation, designated mut1-1, is responsible for the increase in the reversion rate of the ochre alleles lys1-1 and arg4-17. In stock VA-105, there are two separate mutator mutations. Tetrad analysis data showed these two loci are loosely linked. Based on complementation data, one of these mutations is at the same locus as mut1-1 and designated mut1-2. The second mutator of stock VA-105 was designated mut2-1. All three mutators are recessive. Both mut1-1 and mut1-2 give a high mutation rate for ochre nonsense suppressor (SUP) loci, but not for the ochre nonsense alleles. On the contrary, the mutation rates of the ochre alleles are greatly reduced. With the mutant mut2-1 there were mutations at both the lys1-1site and its suppressors; mut2-1 is as effective as mut1-2but not as effective as mut1-1 in inducing reversions of a missense mutant, his1-7. Neither mut1-1, mut1-2 nor mut2-1 were effective in inducing reversions of a putative frameshift mutation, hom3-10, or in inducing forward mutations to canavanine resistance.
GENE CONVERSION: A HITHERTO OVERLOOKED PARAMETER IN POPULATION GENETICS
Authors: Gutz Herbert , Leslie John F
Published: April 2021

Gene conversion causes deviations from the 2:2 segregation of allele pairs in meiosis. Thus, gene conversion is a potential cause for changes of allele frequencies in populations. Equations are derived for the effects of conversion in a large random-mating population. The influence of gene conversion on allele frequencies is compared with that of spontaneous mutation and meiotic drive.
SELECTION FOR RATE AND EFFICIENCY OF LEAN GAIN IN THE RAT
Authors: Notter David R , Dickerson G E , Deshazer J A
Published: April 2021

Full-sib family selection for rate (WP) or efficiency (WP/F) of protein gain in rats from 3 to 9 weeks of age was applied for five generations. Three rats per litter were killed to estimate carcass protein. Standardized response/cumulative selection for WP was.19±.10 for WP,.28±.10 for 3- to 9-week gain,.28±.08 for 9-week weight,.16±.08 for litter size,.22±.12 for skinning loss and -.07±.09 for fraction of protein in the live weight. Response from selection for WP/F was.18±.16 for WP/F,.20±.11 for WP,.21±.11 for weight gain,.16±.11 for 3-week weight,.21±.10 for 9-week weight, but negligible for skinning loss or body protein. Response to WP/F selection was extremely variable among generations, associated with generation differences in weight and composition at 9 weeks. Estimates of heritability from offspring-midparent regression were.20±.12 for WP and.24±.08 for WP/F. Estimates of genotype-generation environment interaction were large for growth, feed intake and skinning loss. Maternal effects were large for weaning weight, fraction of body protein and WP. Sire component genetic correlations were 1.08±.13 for WP with total gain,.92±.08 for WP/F with gross efficiency and.29±.25 for WP with WP/F. A partitional calorimeter was used to evaluate heat production of rats. Lines differed in average heat loss but not in heat loss per unit actual or metabolic weight. Response to selection has been steady for WP but probably could be improved by selecting for WP/F at a constant weight rather than a constant age.
A STUDY OF THE TRANSMISSION AND STRUCTURE OF DOUBLE STRANDED RNAs ASSOCIATED WITH THE KILLER PHENOMENON IN SACCHAROMYCES CEREVISIAE
Authors: Sweeney T Kevin , Tate Ann , Fink Gerald R
Published: April 2021

Killer strains contain two double stranded RNAs, L and M. The M dsRNA appears to be necessary for production of a toxin and for resistance to that toxin. Mutant strains have been found that are defective in their ability to kill and in their resistance to toxin. These sensitive, non-killer strains have altered dsRNA composition. One class has no M dsRNA. Another class of sensitive, non-killers called suppressives has no M dsRNA but instead has smaller dsRNAs called S. In diploids resulting from a cross of a wild-type killer by a suppressive the transmission of the M dsRNA is suppressed by the S dsRNA. When a suppressive is crossed by a strain with no M dsRNA, the diploids and all four meiotic spores have the S dsRNA characteristic of the parental suppressive strain. Suppressive strains do not suppress each other. Intercrosses between two different suppressives yields diploids with both parental S dsRNAs. These two S dsRNAs are transmitted to all 4 meiotic progeny. Another class of mutants has been found which is defective for one of the traits but retains the other. One type, temperature-sensitive killers, has a normal dsRNA composition but is unable to kill at 30°. The other type, immunity-minus, has a complex dsRNA pattern. The immunity-minus strain is extremely unstable during mitotic growth and segregates several different types of non-killers. Analysis of the dsRNAs from wild type and the mutants by electron microscopy shows that the L, M, and S dsRNAs are linear. All strains regardless of killer phenotype appear to have the same size L dsRNA.
THE LEWONTIN AND KRAKAUER TEST ON QUANTITATIVE CHARACTERS
Authors: Krimbas C B
Published: April 2021

It is shown that Lewontin and Krakauer's test could also be applied to quantitative characters that do not show important dominance and epistatic genetic variances. The design of experiments for this purpose and the error of the estimation of F are discussed.
MAPPING OF THE HOMOTHALLIC GENES, HMα AND HM
a, IN SACCHAROMYCES YEASTS
Authors: Harashima Satoshi , Oshima Yasuji
Published: April 2021

Two of the three homothallic genes, HMα and HM  a, showed direct linkage to the mating-type locus at approximately 73 and 98 stranes (57 and 65 centimorgans [cM]), respectively, whereas, the other, HO, showed no linkage to 25 standard markers distributed over 17 chromosomes including the mating-type locus. To determine whether the HMα and HM  a loci located on the left or right side of the mating-type locus, equations for three factor analysis of three linked genes were derived. Tetrad data were collected and were compared with expected values by X2 statistics. Calculations indicated that the HMα gene is probably located on the right arm at 95 stranes (65 cM) from the centromere and the HM  a locus at approximately 90 stranes (64 cM) on the left arm of chromosome III.
NONBEHAVIORAL SELECTION FOR PAWNS, MUTANTS OF PARAMECIUM AURELIA WITH DECREASED EXCITABILITY
Authors: Schein Stanley J
Published: April 2021

The reversal response in Paramecium aurelia is mediated by calcium which carries the inward current during excitation. Electrophysiological studies indicate that strontium and barium can also carry the inward current. Exposure to high concentrations of barium rapidly paralyzes and later kills wild-type paramecia. Following mutagenesis with nitrosoguanidine, seven mutants which continued to swim in the 'high-barium' solution were selected. All of the mutants show decreased reversal behavior, with phenotypes ranging from extremely non-reversing ('extreme' pawns) to nearly wild-type reversal behavior ('partial' pawns). The mutations fall into three complementation groups, identical to the pwA, pwB, and pwC genes of Kung et al. (1975). All of the pwA and pwB mutants withstand longer exposure to barium, the pwB mutants surviving longer than the pwA mutants. Among mutants of each gene, survival is correlated with loss of reversal behavior. Double mutants (A-B, A-C, B-C), identified in the exautogamous progeny of crosses between 'partial' mutants, exhibited a more extreme non-reversing phenotype than either of their single-mutant ('partial' pawn) parents.—Inability to reverse could be expected from an alteration in the calcium-activated reversal mechanism or in excitation. A normal calcium-activated structure was demonstrated in all pawns by chlorpromazine treatment. In a separate report (Schein, Bennett and Katz 1976) the results of electrophysiological investigations directly demonstrate decreased excitability in all of the mutants, a decrease due to an altered calcium activation. The studies of the genetics, the survival in barium and the electro-physiology of the pawns demonstrate that the pwA and pwB genes have different effects on calcium activation.
CHANGE IN STATE FOLLOWING TRANSPOSITION OF A REGULATORY ELEMENT OF THE ENHANCER SYSTEM IN MAIZE
Authors: Peterson Peter A
Published: April 2021

From an original A2 allele (colored aleurone), a mutable allele, a2-m-4 1629, that changes from a2 to A2 is described. Mutability is expressed as a very distinct pattern limited to the last cell division.—The mutability of a2-m-4 1629 is autonomously controlled by an En at the a2 locus. This En, inactive on standard a testers for En, is partially active on a2-m-1, an a2 tester for En, and expresses varied levels of activity from limited to nearly full suppression of the a2-m-1 color phenotype.—When the En of the a2-m-4 1629 allele transposes from the a2 locus, it behaves, at the new position, like a standard En in triggering a2-m-1, a-m-1 and a-m(r), which express colored spots on a colorless background. The activity of En is therefore different following the change in chromosome location. This finding supports the "position" hypothesis that has been proposed to explain diverse patterns observed among controlling elements. In this case mutation is related to the terminal cell state and not to tissue differences as shown with some phase-variation regulatory elements.
ISOLATION AND CHARACTERIZATION OF X-LINKED MUTANTS OF DROSOPHILA MELANOGASTER WHICH ARE SENSITIVE TO MUTAGENS
Authors: Boyd J B , Golino M D , Nguyen T D , Green M M
Published: April 2021

Thirteen X-linked mutants have been isolated in Drosophila melanogaster which render male and homozygous female larvae sensitive to the mutagen methyl methanesulfonate. Their characterization and preliminary assignment to functional groups is described. Four of these mutants are alleles of mei-41 (Baker and Carpenter 1972). Like previously isolated alleles of this locus, these mutants reduce fertility and increase loss and nondisjunction of the X-chromosome in homozygous females. The remaining mutants have been tentatively assigned to six functional groups (two mutants to the mus(1)101 locus, two to mus(1)102, two to mus(1)103, and one each to mus(1)104, mus(1)105, and mus(1)106). Several of the complementation groups can be distinguished on the basis of nondisjunction and cross sensitivity to mutagens. Females homozygous for the mei-41, mus(1)101 and mus(1)102 mutants exhibit elevated levels of nondisjunction. Mutants belonging to complementation groups mei-41, mus(1)101, and mus(1)104 are sensitive to nitrogen mustard (HN2) in addition to their MMS sensitivity. Among these mutants there is currently a direct correlation between sensitivity to HN2, sensitivity to 2-acetylaminofluorene and a deficiency in post-replication repair (Boyd and Setlow 1976). Only the mei-41 mutants are hypersensitive to UV radiation, although several of the mutants exhibit sensitivity to Y-rays. Semidominance is observed in female larvae of the mei-41, mus(1)104, and mus(1)103 mutants after exposure to high concentrations of MMS. The properties of the mutants generally conform to a pattern which has been established for related mutants in yeast. Additional properties of these mutants are summarized in Table 9.
GENETIC HETEROGENEITY WITHIN ELECTROPHORETIC "ALLELES" OF XANTHINE DEHYDROGENASE IN DROSOPHILA PSEUDOOBSCURA
Authors: Singh R S , Lewontin R C , Felton A A
Published: April 2021

An experimental plan for an exhaustive determination of genic variation at structural gene loci is presented. In the initial steps of this program, 146 isochromosomal lines from 12 geographic populations of D. pseudoobscura were examined for allelic variation of xanthine dehydrogenase by the serial use of 4 different electrophoretic conditions and a heat stability test. The 5 criteria revealed a total of 37 allelic classes out of the 146 genomes examined where only 6 had been previously revealed by the usual method of gel electrophoresis. This immense increase in genic variation also showed previously unsuspected population differences between the main part of the species distribution and the isolated population of Bogotá, Colombia, in conformity with the known partial reproductive isolation of the Bogotá population. The average heterozygosity at the Xdh locus is at least 72% in natural populations. This result, together with the very large number of alleles segregating and the pattern of allelic frequencies, has implications for theories of genetic polymorphism which are discussed.
ROLE OF DNA SEQUENCES IN GENETIC RECOMBINATION IN THE ISO-1-CYTOCHROME c GENE OF YEAST. II. COMPARISON OF MUTANTS ALTERED AT THE SAME AND NEARBY BASE PAIRS
Authors: Moore Carol W , Sherman Fred
Published: April 2021

X-ray-induced mitotic recombination rates and spontaneous meiotic recombination rates have been determined in two-point crosses of various defined cyc1 mutants of the yeast Saccharomyces cerevisiae. All but one of the 17 cyc1 mutants chosen for this study contained either the addition, deletion or substitution of single base-pairs located within a defined segment of the gene that corresponds to the 11 amino acid residues at the amino terminus of iso-1-cytochrome c; approximately half of these mutants had alterations of the AUG initiation codon, some at the same base pair. Up to 66-fold differences in X-ray-induced recombination rates were observed when the same cyc1 mutant was crossed to cyc1 mutants having different alterations in the AUG initiation codon; over a ten-fold difference was observed in series of homologous crosses involving mutants with different changes at the same base-pair. Recombination rates that were associated with specific cyc1 mutants co-segregated with the particular alleles following meiosis, and comparable recombination patterns were also observed for independently isolated, identical mutations. With the mutants used in this study, the frequencies of meiotic recombination did not differ as markedly, suggesting a dissimilar dependence on specific DNA sequences for these two modes of recombination. These disproportionalities of recombination rates suggest that the nature of the mismatched bases influences the recombination process, but not in a way that can be simply interpreted.
DELAYED FORMATION OF CHROMOSOME ABERRATIONS IN MOUSE PACHYTENE SPERMATOCYTES TREATED WITH TRIETHYLENEMELAMINE (TEM)
Authors: Generoso W M , Krishna M , Sotomayor R E , Cacheiro N L A
Published: April 2021

Induction of chromosome aberrations in pachytene spermatocytes of mice by 2 mg/kg TEM was compared with induction by 400 R X rays. These doses induced comparably high dominant lethal effects in pachytene spermatocytes of mice. Cytological analysis at diakinesis-metaphase I stage showed that whereas 76.4% of the cells treated with X rays at pachytene stage had aberrations, the frequencies observed in two TEM experiments were only 0.8 and 2.2%. On the other hand, 5% of the progeny from TEM-treated pachytene spermatocytes were found to be translocation heterozygotes. This is the first report on the recovery of heritable translocations from treated spermatocytes of mice. The aberration frequencies observed for TEM in diakinesis-metaphase I were much too low to account for all the lethal mutations and heritable translocations. Thus, the formation of the bulk of aberrations induced by TEM in pachytene spermatocytes was delayed-a marked contrast to the more immediate formation of X-ray-induced aberrations. It is postulated that the formation of the bulk of TEM-induced aberrations in pachytene spermatocytes and in certain postmeiotic stages occurs sometime during spermiogenesis, and not through the operation of postfertilization pronuclear DNA synthesis.
GENETIC ANALYSIS OF PHOTOTACTIC BEHAVIOR IN DROSOPHILA SIMULANS
Authors: Ann Markow Therese , Smith Weber L
Published: April 2021

Phototaxis mazes have been employed to select photopositive and photonegative strains of Drosophila simulans. The results suggest that phototactic behavior in D. simulans, as in other Drosophila species, is a polygenic trait. Hybridization using divergent strains revealed that the genes controlling negative phototactic behavior in D. simulansare autosomal, as opposed to D. melanogaster in which negative phototactic behavior is known to be very strongly sex-linked.
DISTRIBUTION OF NUCLEOTIDE DIFFERENCES BETWEEN TWO RANDOMLY CHOSEN CISTRONS IN A FINITE POPULATION
Authors: Li Wen-Hsiung
Published: April 2021

Watterson's (1975) formula for the steady-state distribution of the number of nucleotide differences between two randomly chosen cistrons in a finite population has been extended to transient states. The rate for the mean of this distribution to approach its equilibrium value is 1/2 N and independent of mutation rate, but that for the variance is dependent on mutation rate, where N denotes the effective population size. Numerical computations show that if the heterozygosity (i.e., the probability that two cistrons are different) is low, say of the order of 0.1 or less, the probability that two cistrons differ at two or more nucleotide sites is less than 10 percent of the heterozygosity, whereas this probability may be as high as 50 percent of the heterozygosity if the heterozygosity is 0.5. A simple estimate for the mean number (d) of site differences between cistrons is d = h/(1 - h) where h is the heterozygosity. At equilibrium, the probability that two cistrons differ by more than one site is equal to h  2, the square of heterozygosity.
A COMPARATIVE STUDY OF THE ESTERASE-5 LOCUS IN DROSOPHILA PSEUDOOBSCURA, D. PERSIMILIS AND D. MIRANDA
Authors: Cobbs Gary , Prakash Satya
Published: April 2021

Electrophoretic phenotypes of the esterase-5 locus were examined in the sibling species D. pseudoobscura, D. persimilis and D. miranda. D. persimilis alleles were found to have uniformly higher charge on monomers than corresponding alleles of either D. pseudoobscura or D. miranda. Consequently, D. persimilis shares no alleles in common with either D. pseudoobscura or D. miranda, while the latter two species share a number of alleles. It was discovered that by increasing the concentration of acrylamide gel and increasing the length of migration, more allelic differences could be distinguished. Also more alleles were discovered by examining monomer mobility in addition to dimer mobility. In D. persimilis and D. miranda it was found that the previously known high frequency allelic classes broke down into several allelic classes. A test of goodness-of-fit to the infinite alleles model was done and a rough agreement with the model was found.
MUTANTS OF THE FORMYLTETRAHYDROFOLATE INTERCONVERSION PATHWAY OF SACCHAROMYCES CEREVISIAE
Authors: McKenzie K Q , Jones Elizabeth W
Published: April 2021

Thirteen mutants of Saccharomyces cerevisiae that lack one or more of the three enzyme activities of the pathway for interconversion of tetrahydrofolate coenzymes at the formate level of oxidation have been isolated. They do not require adenine. All fail to complement mutations in the ade3 locus. Mutations that greatly reduce activity for one enzyme also reduce activity for the other two interconversion enzymes. The three enzyme activities cochromatograph on TEAE-cellulose columns. A mutation that eliminates synthetase activity also alters the chromatographic behavior of the remaining cyclohydrolase and dehydrogenase activities. It is suggested that the three activities reside in an enzyme complex encoded by the ade3 locus.
MUTATIONS CAUSING TRANSFORMATION OF SEXUAL PHENOTYPE IN THE NEMATODE CAENORHABDITIS ELEGANS
Authors: Hodgkin Jonathan A , Brenner Sydney
Published: April 2021

Ten mutations are described that transform genotypic hermaphrodites of the nematode Caenorhabditis elegans into phenotypic males. These fall into three autosomal complementation groups, termed tra-1, tra-2, and tra-3. Two alleles of tra-1 produce almost complete transformation, to a fertile male phenotype; such transformed animals are useful for analyzing sex-linked genes. All alleles of tra-1 and tra-2 are recessive; the one known allele of tra-3 is both recessive and maternal in effect. Where tested, both XX and XXX hermaphrodites are transformed into males, but XO males (true males) are unaffected by these mutations. It is suggested that these genes are actually involved in hermaphrodite development and have no role in male development.
THE INFLUENCE OF THE MATING SYSTEM ON THE MAINTENANCE OF GENETIC VARIABILITY IN POLYGENIC CHARACTERS
Authors: Lande Russell
Published: April 2021

The traditional models of the effect of assortative mating and inbreeding on the genetic variance of polygenic characters (Fisher 1918; Wright 1921) presume that there is no natural selection or mutation. In a large population, the genetic variance determined by additive genes may then increase by up to a factor of two with local inbreeding, and even more with assortative mating. The classical models are still used to interpret data from natural populations. But contrary to their assumptions, most metrical characters in natural populations are usually thought to be under a type of selection which depletes polygenic variation. Mutation is then necessary to maintain genetic variation. The present models show that with the additional features of mutation and selection, in a large population, the mating system has no influence on the amount of genetic variability maintained by additive genes.
ACCUMULATION OF DELETERIOUS GENES IN A CAGE POPULATION OF DROSOPHILA MELANOGASTER
Authors: Lee Won Ho , Watanabe Takao K
Published: April 2021

Lethal and sterility mutations were accumulated in a cage population which was initiated with lethal- and sterility-free second chromosomes of D. melanogaster. It took about 2,000 days for the frequencies of these genes to reach equilibrium levels, i.e., 18% lethal and 9% male-sterile chromosomes. Two other cage populations which were initiated with random chromosomes sampled from natural populations and kept for more than eleven years in the laboratory showed 19-20% lethal content. The elimination rates of lethals by homozygosis in these populations were smaller than the mutation rate. By using Nei's formulae, the deleterious effect of a lethal gene in heterozygous condition (h) was estimated to be 0.035. The effective population number in the cage populations was estimated to be 1,000-2,900, while the actual population number was 3,500-7,800.
Amino acid digestibility and digestible indispensable amino acid score-like values of black soldier fly larvae fed different forms and concentrations of calcium using the precision-fed cecectomized rooster assay
Authors: Do Sungho , Koutsos Elizabeth A , Utterback Pamela L , Parsons Carl M , de Godoy Maria R C , Swanson Kelly S
Published: April 2021

Black soldier fly larvae (BSFL) are an alternative protein source for animals, including dogs and cats. Dietary calcium source is an essential nutrient for BSFL development in the pupal stage. Calcium carbonate (CaCO3) and calcium chloride (CaCl2) are common calcium sources but differ in solubility, acid-binding capacity, and calcium concentration. A high calcium concentration in BSFL may affect how well nitrogen and amino acids (AA) are digested by animals consuming them, thereby affecting feed conversion efficiency. Our objective was to determine the effects of dietary calcium form and concentration on nutrient composition, AA digestibility, and digestible indispensable amino acid score (DIAAS)-like values of BSFL intended for use in animal feeds using the precision-fed cecectomized rooster assay. All BSFL tested in this study were harvested at 18 d after hatch. Industry standard rearing conditions were maintained and a commercial layer ration was fed to all BSFL until 11 d post-hatch. From day 11 to 18, BSFL were fed a combination of distiller’s dried grains with solubles from a distillery, bakery byproduct meal, and varied calcium sources. All BSFL diets contained 0.2% calcium in the basal diet plus additional calcium in the following amounts and forms: BSFLA: 1.2% CaCl2, BSFLB: 1.2% CaCO3, BSFLC: 0.75% CaCO3, and BSFLD: 0.6% CaCO3 + 0.6% CaCl2. On day 18, BSFL were washed and frozen. Prior to the rooster assay, BSFL were lyophilized and ground. In total, 16 cecectomized roosters (4 roosters per substrate) were randomly assigned to test substrates. After 24 h of feed withdrawal, roosters were tube-fed 20 g of test substrates. Following crop intubation, excreta were collected for 48 h. Endogenous corrections for AA were made using five additional cecectomized roosters. All data were analyzed using a completely randomized design and the GLM procedure of SAS 9.4. Nutrient and AA digestibilities were not different among substrates. DIAAS-like values were calculated to determine protein quality according to the Association of American Feed Control Officials nutrient profiles and National Research Council recommended allowances for dogs and cats. Although AA digestibilities did not differ, those containing CaCO3 generally had higher DIAAS-like reference values than the diet containing CaCl2 alone (BSFLA). Aromatic AA (Phe + Tyr) and sulfur AA (Met + Cys) were often first-limiting AA. Our results suggest that calcium sources fed to BSFL did not affect AA digestibility and protein quality.
Comparison of digestible and metabolizable energy and digestible phosphorus and amino acid content of corn ethanol coproducts from Brazil and the United States produced using fiber separation technology for swine
Authors: Paula Vinicius R C , Milani Natália C , Azevedo Cândida P F , Sedano Anderson A , Souza Leury J , Mike Brian P , Shurson Gerald C , Ruiz Urbano S
Published: April 2021

Three experiments (exp.) were conducted to determine and compare the digestibility of nutrients and energy of corn distillers dried grains with solubles (DDGS) from the United States (USDDGS), a dried mixture of corn bran with solubles (CBS) from Brazil (BRCBS), and high protein corn distillers dried grains (HP-DDG) from the United States (USHPDG) and Brazil (BRHPDG) in growing pigs. The feed ingredients were evaluated for apparent total tract digestibility (ATTD) of gross energy (GE), dry matter (DM), crude protein (CP), ether extract, neutral and acid detergent fiber (NDF and ADF, respectively), and digestible and metabolizable energy (DE and ME, respectively) using the total collection and index methods in exp. 1; ATTD and standardized total tract digestibility (STTD) of phosphorus (P) in exp. 2; and apparent (AID) and standardized (SID) ileal digestibilities of CP and amino acids (AA) in exp. 3. Fifty crossbred barrows (32.4 ± 6.9, 38.3 ± 5.2, and 46.2 ± 5.3 kg body weight [BW], in exp. 1, 2, and 3, respectively) were fed a corn basal diet in exp. 1, a P-free diet in exp. 2, and an N-free diet in exp. 3 or diets with 40% inclusion of test ingredients to provide 10 replications per treatment. Pigs were housed individually in metabolism cages (exp. 1) or in pens (exp. 2 and 3) and fed at 2.8 times the maintenance DE requirement (110 kcal/kg BW0.75) based on their BW at the beginning of each experiment. Except for ATTD of NDF, which tended (P = 0.058) to be greater by the index method compared with the total collection method, no difference between the total collection and index methods was observed for ATTD of remaining nutrients and DE. The ATTD of DM, GE, NDF, and DE content of BRHPDG were greater (P < 0.001) than USHPDG, BRCBS, and USDDGS. The AID of CP, Arg, His, Ile, Leu, Lys, Thr, and Val and the SID of His, Leu, Lys, and Val of BRHPDG were 8% to 36% greater (P < 0.05) than those from USHPDG. Except for Trp, all AID and SID AA values were greater (P < 0.05) in BRHPDG than in USHPDG. The ATTD of DM, GE, NDF, and ADF; DE and ME content; AID of CP, Arg, Ile, Leu, Phe, Thr, and Trp; and SID of CP, Arg, Phe, and Thr of USDDGS were 9% to 45% greater (P < 0.05) than those in BRCBS. The ATTD and the STTD of P in USHPDG and USDDGS were 26% to 42% greater (P < 0.05) compared with BRHPDG and BRCBS. In conclusion, BRHPDG had a greater digestibility of energy and most of the AA than USHPDG, while the BRCBS evaluated had lower nutritional value than the USDDGS source.
An Annotated Draft Genome for the Andean Bear,Tremarctos ornatus
Authors: Saremi Nedda F , Oppenheimer Jonas , Vollmers Christopher , O’Connell Brendan , Milne Shard A , Byrne Ashley , Yu Li , Ryder Oliver A , Green Richard E , Shapiro Beth
Published: April 2021

The Andean bear is the only extant member of the Tremarctine subfamily and the only extant ursid species to inhabit South America. Here, we present an annotated de novo assembly of a nuclear genome from a captive-born female Andean bear, Mischief, generated using a combination of short and long DNA and RNA reads. Our final assembly has a length of 2.23 Gb, and a scaffold N50 of 21.12 Mb, contig N50 of 23.5 kb, and BUSCO score of 88%. The Andean bear genome will be a useful resource for exploring the complex phylogenetic history of extinct and extant bear species and for future population genetics studies of Andean bears.
Prolonged patient survival after implementation of a continuous quality improvement programme empowered by digital transformation in a large dialysis network
Authors: Garbelli Mario , Ion Titapiccolo Jasmine , Bellocchio Francesco , Stuard Stefano , Brancaccio Diego , Neri Luca
Published: April 2021

Background

Treatment of end-stage kidney disease patients is extremely challenging given the interconnected functional derangements and comorbidities characterizing the disease. Continuous quality improvement (CQI) in healthcare is a structured clinical governance process helping physicians adhere to best clinical practices. The digitization of patient medical records and data warehousing technologies has standardized and enhanced the efficiency of the CQI’s evidence generation process. There is limited evidence that ameliorating intermediate outcomes would translate into better patient-centred outcomes. We sought to evaluate the relationship between Fresenius Medical Care medical patient review CQI (MPR-CQI) implementation and patients’ survival in a large historical cohort study.

Methods

We included all incident adult patients with 6-months survival on chronic dialysis registered in the Europe, Middle East and Africa region between 2011 and 2018. We compared medical key performance indicator (KPI) target achievements and 2-year mortality for patients enrolled prior to and after MPR-CQI policy onset (Cohorts A and B). We adopted a structural equation model where MPR-CQI policy was the exogenous explanatory variable, KPI target achievements was the mediator variable and survival was the outcome of interest.

Results

About 4270 patients (Cohort A: 2397; Cohort B: 1873) met the inclusion criteria. We observed an increase in KPI target achievements after MPR-CQI policy implementation. Mediation analysis demonstrated a significant reduction in mortality due to an indirect effect of MPR-CQI implementation through improvement in KPI target achievement occurring in the post-implementation era [odds ratio 0.70 (95% confidence interval 0.65–0.76); P < 0.0001].

Conclusions

Our study suggests that MPR-CQI achieved by standardized clinical practice and periodic structured MPR may improve patients’ survival through improvement in medical KPIs.