bluuebunny/crossref_metadata_2025_split huggingface dataset:
VALINE-RESISTANCE, A POTENTIAL MARKER IN PLANT CELL GENETICS. II. OPTIMIZATION OF UV MUTAGENESIS AND SELECTION OF VALINE-RESISTANT COLONIES DERIVED FROM TOBACCO MESOPHYLL PROTOPLASTS
Authors: Grandbastien M A , Bourgin J P , Caboche M 
Published: January 2021

ABSTRACT
The induction and selection of valine-resistant mutants from haploid tobacco (Nicotiana tabacum L.) mesophyll protoplast-derived cells have been studied. Using cells from an original mutant plant obtained previously, we performed reconstruction experiments in order to determine the best conditions for the recovery of resistant cells among a population of sensitive cells. Optimal selective conditions were shown to depend on various factors including cell density, time of addition of valine and seasonal variations affecting the mother plants.—Using cell densities of approximately 104 cells/ml, we defined efficient selective conditions: more than 25% of the putative mutant clones selected from UV-mutagenized protoplasts were reproducibly confirmed to be valine resistant. Further characterization of some regenerated mutant plants indicated that valine-resistance was associated with an uptake deficiency, as in the case of the original mutant plant of the Valr-2 line used for reconstruction experiments. Spontaneous mutation rates for valine-resistance were below accurately detectable levels, i.e., less than 10-6 per cell per generation. Induced mutation frequency varied nonlinearily with UV dose from 10-5 to 5 × 10-4 resistant clones per surviving colony. Two independent loci (vr2 and vr3) were previously shown to be involved in valine-resistance due to amino acid uptake deficiency. Haploid tobacco plants were produced through anther culture from an F1 double-heterozygous plant obtained from a cross between the original mutant plant and a wild-type plant. Study of the level of resistance to valine of protoplast-derived cells allowed the classification of these haploid plants in four types: sensitive, resistant and two intermediary resistant types believed to result from the presence of a mutant allele at only one of the two loci involved. The frequencies of UV-induced mutations in cells derived from haploid plants of one of the intermediary types were compared to those observed in wild-type cells. The results are considered in light of the amphidiploid structure of the tobacco genome.
MUTATIONS LEADING TO EXPRESSION OF THE CRYPTIC HMR
a LOCUS IN THE YEAST SACCHAROMYCES CEREVISIAE
Authors: Kassir Yona , Simchen Giora 
Published: January 2021

ABSTRACT
Mutations leading to expression of the silent HMR a information in Saccharomyces cerevisiae result in sporulation proficiency in mat a 1/MATα diploids. An example of such a mutation is sir5-2, a recessive mutation in the gene SIR5. As expected, haploids carrying the sir5-2 mutation are nonmaters due to the simultaneous expression of HMR a and HMLα, resulting in the nonmating phenotype of an a/α diploid. However, sir5-2/sir5-2 mat a 1/MATα diploids mate as α yet are capable of sporulation. The sir5-2 mutation is unlinked to sir1-1, yet the two mutations do not complement each other: mat a 1/MATα sir5-2/SIR5 SIR1/sir1-1 diploids are capable of sporulation. In this case, recessive mutations in two unlinked genes form a mutant phenotype, in spite of the presence of the normal wild-type alleles.—The PAS1-1 mutation, Provider of a Sporulation function, is a dominant mutation tightly linked to HMR a. PAS1-1 does not affect the mating ability of a strain, yet it allows diploids lacking a functional MAT a locus to sporulate. It is proposed that PAS1-1 leads to partial expression of the otherwise cryptic a1 information at HMR a.
MULTILOCUS POPULATION GENETICS WITH WEAK EPISTASIS. I. EQUILIBRIUM PROPERTIES OF TWO-LOCUS TWO-ALLELE MODELS
Authors: Hastings Alan 
Published: January 2021

ABSTRACT
Using perturbation techniques, I determine the equilibrium of two-locus two-allele models with overdominance and weak epistasis. To lowest order, the allele frequencies, the mean fitness and the covariance between heterokaryotic and homokaryotic flies arising in the Sturtevant experimental design are independent of the recombination rate, r. The disequilibrium varies as one divided by the recombination rate, in contrast to neutral models. Although the disequilibrium generated by weak epistasis is small, too small to be experimentally detected, it can be large enough to have biological importance.
ANIMAL MODEL STUDIES OF ALLELISM: CHARACTERIZATION OF ARYLSULFATASE B MUTATIONS IN HOMOALLELIC AND HETEROALLELIC (GENETIC COMPOUND) HOMOZYGOTES WITH FELINE MUCOPOLYSACCHARIDOSIS VI
Authors: McGovern Margaret M , Mandell Nadine , Haskins Mark , Desnick Robert J 
Published: January 2021

ABSTRACT
The identification of a second structural gene mutation at the feline arylsulfatase B locus (MPS VIb) provided the opportunity to investigate the expression of allelism by characterization of the residual enzymatic activity in feline mucopolysaccharidosis VI, an animal analogue of human Maroteaux-Lamy syndrome. Matings were designed to produce affected homozygotes who were homoallelic for the MPS VIa and MPS VIb mutations or heteroallelic genetic compounds (MPS VIa/VIb). The physicokinetic and immunological properties of the partially purified residual hepatic arylsulfatase B isozymes from the affected homoallelic and heteroallelic cats were compared to those of the normal feline enzyme. The residual hepatic arylsulfatase B activities from the inbred MPS VIa and MPS VIb homozygotes were distinguished by differences in physicokinetic and immunological properties. The newly identified mutant isozyme b had abnormal kinetic properties toward artificial and natural substrates, normal cryo- and thermostabilities, a normal molecular weight and an altered electrophoretic mobility. Polyacrylamide gel electrophoresis demonstrated that the mutant b subunits formed dimers with normal subunits in obligate heterozygotes (MPS VI +/b). In contrast, mutant isozyme a subunits from obligate MPS VIa /+ heterozygotes did not dimerize with the normal subunit, and the mutant and normal isozymes could be separated by anion exchange chromatography and polyacrylamide gel electrophoresis. Characterization of the partially purified residual hepatic arylsulfatase B activity from the heteroallelic homozygotes revealed the presence of both mutant isozymes a and b. The demonstration of two allelic mutations in the feline arylsulfatase B gene documented the occurrence of genetic heterogeneity in feline mucopolysaccharidosis VI and permitted characterization of the enzymatic defect in homoallelic and heteroallelic (genetic compound) homozygotes, providing a model for the study of allelism in human genetic disorders.
THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XIX. GENOTYPE-ENVIRONMENT INTERACTION IN VIABILITY
Authors: Tachida Hidenori , Mukai Terumi 
Published: January 2021

ABSTRACT
To investigate whether or not an excess of additive genetic variance for viability detected in southern natural populations of Drosophila melanogaster was created by diversifying selection, genotype-environment interaction was tested as follows. (1) Two karyotype chromosomes were used: 61 second chromosomes with the standard karyotype and 63 second chromosomes carrying In(2L)t. Their homozygote viabilities were larger than 50% of the average viability of random heterozygotes. (2) The effects of two factors (culture media and yeasts) were examined at three levels (the culture media: tomato, corn and banana; and the yeasts: sake, brewer's and baker's). The results of 16 three by three factorial experiments by the Cy method in the same karyotype groups for relative viabilities of homozygotes and heterozygotes elucidated the following findings: (1) there was no significant difference between the two karyotype groups, (2) the variance components of genotype-environment interaction were highly significant, (3) the variance component of heterozygotes was significantly smaller than that of homozygotes. From the experimental findings and previous results, diversifying selection in natural populations acting on viability polygenes to increase the additive genetic variance was suggested. The relation of the present result to protein polymorphism is also discussed.
DNA SEQUENCES OF FRAMESHIFT AND OTHER MUTATIONS INDUCED BY ICR-170 IN YEAST
Authors: Ernst Joachim F , Hampsey D Michael , Sherman Fred 
Published: January 2021

ABSTRACT
ICR-170-induced mutations in the CYC1 gene of the yeast Saccharomyces cerevisiae were investigated by genetic and DNA sequence analyses. Genetic analysis of 33 cyc1 mutations induced by ICR-170 and sequence analysis of eight representatives demonstrated that over one-third were frameshift mutations that occurred at one site corresponding to amino acid positions 29-30, whereas the remaining mutations were distributed more-or-less randomly, and a few of these were not frameshift mutations. The sequence results indicate that ICR-170 primarily induces G·C additions at sites containing monotonous runs of three G·C base pairs. However, some (see PDF) sites within the CYC1 gene were not mutated by ICR-170. Thus, ICR-170 is a relatively specific mutagen that preferentially acts on certain sites with monotonous runs of G·C base pairs.
NATURAL SELECTION VS. RANDOM DRIFT: EVIDENCE FROM TEMPORAL VARIATION IN ALLELE FREQUENCIES IN NATURE
Authors: Mueller Laurence D , Barr Lorraine G , Ayala Francisco J 
Published: January 2021

ABSTRACT
We have obtained monthly samples of two species, Drosophila pseudoobscura and Drosophila persimilis, in a natural population from Napa County, California. In each species, about 300 genes have been assayed by electrophoresis for each of seven enzyme loci in each monthly sample from March 1972 to June 1975. Using statistical methods developed for the purpose, we have examined whether the allele frequencies at different loci vary in a correlated fashion. The methods used do not detect natural selection when it is deterministic (e.g., overdominance or directional selection), but only when alleles at different loci vary simultaneously in response to the same environmental variations. Moreover, only relatively large fitness differences (of the order of 15%) are detectable. We have found strong evidence of correlated allele frequency variation in 13-20% of the cases examined. We interpret this as evidence that natural selection plays a major role in the evolution of protein polymorphisms in nature.
CELLULAR GENES IN THE MOUSE REGULATE IN TRANS THE EXPRESSION OF ENDOGENOUS MOUSE MAMMARY TUMOR VIRUSES
Authors: Traina-Dorge Vicki L , Carr Jean K , Bailey-Wilson Joan E , Elston Robert C , Taylor Benjamin A , Cohen J Craig 
Published: January 2021

ABSTRACT
The transcriptional activities of the eleven mouse mammary tumor virus (MMTV) proviruses endogenous to two sets of recombinant inbred (RI) mouse strains, BXD and BXH, were characterized. Comparison of the levels of virus-specific RNA quantitated in each strain showed no direct relationship between the presence of a particular endogenous provirus or with increasing numbers of proviruses. Association of specific genetic markers with the level of MMTV-specific RNA was examined by using multiple regression analysis. Several cellular loci as well as proviral loci were identified that were significantly associated with viral expression. Importantly, these cellular loci associated with MMTV expression segregated independently of viral sequences.
DELETERIOUS MUTATIONS AS AN EVOLUTIONARY FACTOR. II. FACULTATIVE APOMIXIS AND SELFING
Authors: Kondrashov Alexey S 
Published: January 2021

ABSTRACT
A population with u deleterious mutations per genome per generation is considered in which only those individuals that carry less than a critical number k of mutations are viable. Besides a large number of loci subject to mutation and selection, the genome contains one or two special loci responsible for the mode of reproduction. Amphimixis vs. selfing are considered separately. In the first case, the genome degradation rate v (=u/√k) is found to play the decisive role, as in the case of recombination. When v &gt; 1.25, obligate amphimixis is established. If v decreases below this value, the alleles with first low and then larger penetrance are fixed, until alleles conferring obligate asexual reproduction become advantageous. The proportion of resources allocated to produce seeds also increases with decrease of v. These results are unlikely to depend on the genetic basis of the mode of reproduction. The result of competition between outcrossing and selfing depends on both u and k, as well as on whether the mutations are recessive. The alleles for selfing with low penetrance are selected against if the mutations are at all recessive. The fitness of alleles with high penetrance depends primarily on u, decreasing when u increases. There may exist conditions when only the alleles providing intermediate selfing rates can be fixed in a population. In other cases a population may exist with either obligate outcrossing or selfing at a high rate. Thus, truncation selection against deleterious mutations may be a factor supporting obligate or facultative sex despite the twofold advantage of apomixis or selfing.
MOLECULAR GENETICS OF THE ROSY-ACE REGION OF DROSOPHILA MELANOGASTER
Authors: Gausz Janos , Hall Lucinda M C , Spierer Anne , Spierer Pierre 
Published: January 2021

ABSTRACT
Three hundred and fifteen kilobases of DNA from the rosy-Ace region on chromosome 3R of D. melanogaster have previously been cloned and extensively characterized. We describe the isolation of nine new deficiency mutants that break within the 315-kb interval. The position of these breakpoints on the DNA map was determined by in situ and Southern hybridization. Further, we more precisely mapped the breakpoints of several deletions previously analyzed. The results permit us to delimit sequences essential to the known complementation groups in the region within approximately 20 kb in most cases. However, one gene, B16-1, is shown to contain essential sequences that span about 50 kb. Also, we demonstrate by overlapping deficiencies that a 45-kb DNA segment from the region, which includes one known complementation group, allows limited survival when deleted.
THE EVOLUTION OF SELF-REGULATED TRANSPOSITION OF TRANSPOSABLE ELEMENTS
Authors: Charlesworth B , Langley C H 
Published: January 2021

ABSTRACT
This paper examines the conditions under which self-regulated rates of transposition can evolve in populations of transposable elements infecting sexually reproducing hosts. Models of the evolution of both cis-acting regulation (transposition immunity) and trans-acting regulation (transposition repression) are analyzed. The potential selective advantage to regulation is assumed to be derived from the deleterious effects of mutations associated with the insertion of newly replicated elements. It is shown that both types of regulation can easily evolve in hosts with low rates of genetic recombination per generation, such as bacteria or bacterial plasmids. Conditions are much more restrictive in organisms with relatively free recombination. In haploids, the main selective force promoting regulation is the induction of lethal or sterile mutations by transposition; in diploids, a sufficiently high frequency of dominant lethal or sterile mutations associated with transpositions is required. Data from Drosophila and maize suggest that this requirement can sometimes be met. Coupling of regulatory effects across different families of elements would also aid the evolution of regulation. The selective advantages of restricting transposition to the germ line and of excising elements from somatic cells are discussed.
POLYMORPHISMS FOR PURELY CYTOPLASMICALLY INHERITED TRAITS IN BISEXUAL PLANTS
Authors: Gregorius Hans-Rolf 
Published: January 2021

ABSTRACT
It is shown that cytoplasm polymorphisms transmitted only by the ovules can be maintained without gene-cytoplasmic interactions. The necessary prerequisites are asymmetry of the plasmotypes in production of ovules and pollen (sexual asymmetry), incomplete and frequency-dependent fertilization efficiency and differential selfing rates. These factors can generate the negative frequency dependence of cytoplasmic fitnesses required for a stable polymorphism. The model considered allows also for facultative fixation of either of two plasmotypes and, thus, may produce all of the dynamical characteristics known for nuclear selection with two alleles at one locus.
Strong sexual asymmetry, which probably occurs frequently in bisexual plants, may facilitate stable cytoplasmic polymorphisms. However, these polymorphisms may also endanger survival of the whole population in the absence of nuclear interactions. Gene-cytoplasmic interactions avoid this risk and, at the same time, utilize the advantages of sexual asymmetry in maintaining genetic polymorphisms.
A MATERNAL-EFFECT SEX-TRANSFORMATION MUTANT OF THE HOUSEFLY, MUSCA DOMESTICA L
Authors: Inoue Hiroaki , Hiroyoshi Toshiki 
Published: January 2021

ABSTRACT
A maternal-effect sex-transformation mutant, transformer(tra), of the housefly is described. It is located on autosome 4 in close linkage with the Ba locus. Normally, the sex of Musca domestica is determined by the presence or absence of an epistatic factor, M. When produced by tra/tra mothers, a large fraction of the tra/tra genotypic female progeny carrying no M factors are transformed to develop into intersexes or fertile phenotypic males. The tra/+ progeny are also transformed, but less frequently. Aging of the mothers increases the frequency of sex-transformed flies. When produced by tra/+ mothers, tra/tra progeny (but not +/tra) occasionally undergo sex transformation. Thus, tra + is active both maternally and zygotically. Genotypic males carrying the M factor are not affected by the tra mutant. It is concluded that the tra + gene product is required for female determination and/or differentiation. A model is proposed to explain actions of all the known sex-determination genes in M. domestica, and it is discussed in relation to sex-determination mechanisms in several other insect species.
SUPPRESSORS OF snf
2 MUTATIONS RESTORE INVERTASE DEREPRESSION AND CAUSE TEMPERATURE-SENSITIVE LETHALITY IN YEAST
Authors: Neigeborn Lenore , Rubin Kenneth , Carlson Marian 
Published: January 2021

ABSTRACT
Mutations in the SNF2 gene of Saccharomyces cerevisiae prevent derepression of the SUC2 (invertase) gene, and other glucose-repressible genes, in response to glucose deprivation. We have isolated 25 partial phenotypic revertants of a snf2 mutant that are able to derepress secreted invertase. These revertants all carried suppressor mutations at a single locus, designated SSN20 (suppressor of snf2). Alleles with dominant, partially dominant and recessive suppressor phenotypes were recovered, but all were only partial suppressors of snf2, reversing the defect in invertase synthesis but not other defects. All alleles also caused recessive, temperature-sensitive lethality and a recessive defect in galactose utilization, regardless of the SNF2 genotype. No significant effect on SUC2 expression was detected in a wild-type (SNF2) genetic background. The ssn20 mutations also suppressed the defects in invertase derepression caused by snf5 and snf6 mutations, and selection for invertase-producing revertants of snf5 mutants yielded only additional ssn20 alleles. These findings suggest that the roles of the SNF2, SNF5 and SNF6 genes in regulation of SUC2 are functionally related and that SSN20 plays a role in expression of a variety of yeast genes.
A DIPHENOL OXIDASE GENE IS PART OF A CLUSTER OF GENES INVOLVED IN CATECHOLAMINE METABOLISM AND SCLEROTIZATION IN DROSOPHILA. II. MOLECULAR LOCALIZATION OF THE Dox-A2 CODING REGION
Authors: Pentz Ellen Steward , Wright Theodore R F 
Published: January 2021

ABSTRACT
Mutations at the Dox-A2 (2-53.9) locus alter the A2 component of diphenol oxidase, an enzyme having an important role in cuticle formation. This locus is in the dopa decarboxylase, Df(2L)TW130 region, which contains a cluster of at least 14 genes involved in catecholamine metabolism and the formation, sclerotization and melanization of cuticle in Drosophila. The region is subdivided by deficiencies, and localization of breakpoints in cloned DNA reveals a dense subcluster of six genes in the 23 kb proximal to Ddc. Five lethal loci distal to Ddc comprise a second such subcluster. The proximal breakpoints of deficiencies Df(2L)hk18 and Df(2L)OD15 define a 14.3- to 16.8-kb region containing Dox-A2 and l(2)37Bb, and those of Df(2L)OD15 and Df(2L)TW203 define a 9.3- to 12.1-kb region containing l(2)37Ba, l(2)37Bc and l(2)37Be.—Southern blots show two of the Dox-A2 mutations are small deletions (0.1 and 1.1 kb). The Dox-A2 locus mRNA is 1.7 kb. cDNA clones indicate that the 3' end is centromere proximal and that the coding region contains at least one small intron. The Dox-A2 locus is within 3.4 to 4.4 kb of the Df(2L)OD15 breakpoint, placing four of the vital loci within a maximum of 15.5 kb. The location of Dox-A2 in a cluster of genes affecting cuticle formation is discussed.
SELECTION FOR INCREASED MUTATION RATES WITH FERTILITY DIFFERENCES BETWEEN MATINGS
Authors: Holsinger K E , Feldman M W , Altenberg L 
Published: January 2021

ABSTRACT
Previous studies of mutation modification have considered models in which selection is a result of viability differences that are sex symmetric. The results of a numerical study of a model in which selection is a result of fertility differences between mated pairs demonstrate that the type of selection to which a population is subject can have a significant impact on the evolution of various parameters of the genetic system. When the fertility of matings between individuals with different genotypes exceeds the fertility of at least some of the matings between individuals with the same genotype, selection may favor increased rates of mutation, in contrast to the results from all existing constant viability models with random mating and infinite population size. Increased mutation rates are most frequently favored when forward and back mutation occur at approximately equal rates and when the modifying locus is loosely linked to the selected locus. We present one example in which selection favors increased rates of mutation even though the selection scheme is reducible to one of differential viability between the sexes.
AN INVESTIGATION OF THE GENETICS OF "MALE SEX-RATIO" PHENOTYPE IN DROSOPHILA PSEUDOOBSCURA
Authors: Cobbs Gary 
Published: January 2021

ABSTRACT
A laboratory strain of Drosophila pseudoobscura (L116) is studied that, when crossed to sex-ratio homozygous females, produces sons that exhibit varying levels of the male sex-ratio (msr) phenotype. The msr phenotype occurs only in sex-ratio males and is due to the production of a high frequency of nullo-XY sperm. The level of the msr phenotype is variable, and new variability is generated in one father-son transmission. Pedigree studies indicate the genes for msr reside on the Y chromosome or the autosomes of the L116 stock.