bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and characterization of bleomycin-resistant clones of CHO cells
Authors: Brabbs Sylvia , Warr J. R. 
Published: September 2009

SUMMARYFive clones of Chinese hamster ovary cells with increased resistance to bleomycin have been isolated following ethylmethanesulphonate mutagenesis. Resistance was stable in three of the clones, but unstable in the other two. One of the stably resistant clones was cross resistant to unrelated drugs, and in contrast to the parental cells, its response to bleomycin was potentiated by tween 80. These two observations suggested a membrane alteration in the resistant clone. There was no significant difference in bleomycin-inactivating enzyme activity between the parental and resistant clones.
X-chromosomal heterosis inDrosophila melanogaster
Authors: Wilton A. N. , Sved J. A. 
Published: September 2009

SUMMARYPopulation cages were set up containing anX-chromosome balancer, and either a single wild-type chromosome(homozygous cages) or a mixture of wild-type chromosomes(heterozygous cages). The balancer chromosome was eliminated more rapidly from the heterozygous cages, indicating that chromosome heterozygotes are at an advantage over chromosome homozygotes. The disadvantage ofX-chromosome homozygosity in the female is estimated to be about 40%. From earlier studies it is known that the average disadvantage of homozygosity for either of the two major autosomes ofD. melanogasteris approximately 80%. Since these autosomes are both about twice as long as theXchromosome, the disadvantage per unit length is similar for both chromosomal types.BothX-chromosomal and autosomal heterosis can be explained by either dominance or overdominance at individual loci. However, a dominance model can only explain the similarity if many of theX-linked loci (about 50%) are limited in expression to the female.
Seasonal variation in the frequencies of the alcohol dehydrogenase isoalleles of Drosophila: correlation with environmental factors
Authors: Gionfriddo Maria A. , Vigue Charles L. , Weisgram Pierre A. 
Published: September 2009

SUMMARYDrosophila melanogaster adults were collected throughout the summers of 1976 and 1977 in Hartford, Connecticut. The frequencies of the Adh isoalleles were determined and seasonal variation demonstrated. Correlation coefficients were calculated between Adh frequencies and the seasonal variations in temperature, precipitation, relative humidity and barometric pressure. Although five correlations were significant it was concluded that these were due to chance.
Errata
Authors: Calleja G. B. , Zuker M. , Johnson Byron F. 
Published: September 2009

Estimation of meiosis and sporuiation efficiencies in the fission yeast by ascus analysisGenet. Res. (1979), 33, 109–119Page 113, line 9: formula should readPage 113, 4 lines from foot of page:‘pi’ should read ‘Pi’
Effective population size: the effects of sex, genotype, and density on the mean and variance of offspring numbers in the flour beetle,Tribolium castaneum
Authors: Wade Michael J. 
Published: September 2009

SUMMARYIn this paper I present the results of an experimental study of the effects of genotype and density on the mean and variance of offspring numbers in both sexes of the flour beetle,Tribolium castaneum. From the observed variance in offspring numbers the effective population size at several different densities is estimated using the methods of Crow & Morton (1955).I found that both the mean and variance of offspring numbers varied with genotype and density. In general, males were more variable in offspring numbers than females and this variability increased with density. Individuals homozygous for the black body colour mutant,b/b, were less variable in offspring numbers than + / + individuals, but the latter produced more offspring at most densities. As density increased, + / + individuals became more variable in offspring numbers whereasb/bindividuals were less sensitive in this regard. These findings are discussed in relation to the ecology of selection at the black and closely linked loci.
A transposing forked-duplication with position effect variegation in Drosophila
Authors: Shukla P. T. , Auerbach C. 
Published: September 2009

SUMMARYIn the course of an X-ray experiment, the normal allele of forked was transposed to the second chromosome, where it acts as a suppressor of forked. In this position, which is near the centromere, the duplication (Dp-f+) is subject to a variegated position effect. This was studied in its dependence on the hetero-euchromatin balance; the results agree with and extend those found for other position effects. In addition, we found regional preferences for variegation in the individual flies. The most interesting aspect of Dp-f+ is its tendency to transpose either to the homologous second chromosome or to Chromosome IV. In the latter position, Dp-f+ acts as a dominant near-lethal, so that the apparent selectivity of insertion sites is at least in part due to deleterious effects at insertion sites other than its original one. In a new, and presumably, centromere-far position of Dp-f+ on Chromosome II the variegated position effect disappeared and transposition was reduced in frequency or wholly abolished. The frequency of losses of Dp-f+ approximately equalled that of transpositions. Since there is good evidence that transpositions occurred pre-meiotically, the apparent losses of Dp-f+ may have been due to meiotic segregation separating the loss from the new insertion.
Loss of Hfr DNA fromEscherichia colimerozygotes during inhibition of conjugation by nalidixic acid
Authors: Lloyd Robert G. , Hart Janet , Johnson Sandra 
Published: September 2009

SUMMARYThe effect of nalidixic acid on conjugal recombination was studied in matings with recipient strains carryingrecA200, a mutation which confers a thermosensitive Rec−phenotype. Addition of nalidixic acid to Hfr Nals× F−NalRrecA200matings at low temperature (35 °C) caused a sharp 10- to 20-fold decline in the yield of recombinants if plating on selective agar was delayed. Two separate processes were identified as being responsible for this decline. Those merozygotes in which the transferred DNA was free of the donor cell lost the ability to form recombinants through inactivation of this DNA, an effect which could be prevented by using exonuclease deficient (recB sbcB) recipients or by prior growth of exonuclease proficient recipients in medium containing 0·25 M sodium chloride. No more than 50% of the observed loss of recombinants could be attributed to this effect. The remaining merozygotes lost their ability for recombinant formation provided mating pairs, and presumably the displaced donor DNA strand, remained intact. This process was thought to involve withdrawal of transferred DNA (DeHaan & Gross, 1962) and was studied in isolation in matings withrecA+, orrecA200 recB sbcBrecipients. A mechanism involving re-annealing of the displaced Hfr DNA to the donor molecule as a result of nalidixic inhibition of gyrase activity in the donor causing relaxation of DNA supercoils is proposed to account for this withdrawal event.
Interpretation of intrinsic and extrinsic structural relations by path analysis: theory and applications to assortative mating
Authors: Cloninger C. Robert 
Published: September 2009

SUMMARYThe theory of path analysis is extended by considering a multivariate system of correlations from a dual perspective. Intrinsic factors exert a unidirectional influence on both the variance and covariance of dependent factors. In contrast, extrinsic factors have a bidirectional influence on the covariance structure of both antecedent and dependent factors and do not influence intrinsic variability. The mathematical model assumes a formally complete linear system of unitary factors. A coefficient is defined to quantify the influence of adventitious associations and is called a copath. Copaths are compared to path coefficients and to correlations due to common antecedents. The chain properties of these coefficients are derived along with a general formula and computational algorithm. The method is illustrated for multifactorial inheritance in extended pedigrees in the presence of different types of assortative mating.
Combining superior alleles from two homozygous populations in a cross-fertilizing species
Authors: Ho Y. T. , Comstock R. E. 
Published: September 2009

SUMMARYThe issue of incorporating the good alleles from two homozygous populations of a cross-fertilizing species into a single improved population was investigated assuming independent assortment, no epistasis, and either complete dominance (of the favourable or the unfavourable alleles) or additive genes. The selection limit in the foundation stock is a function of the effective population size (N), the proportion (x) contributed by the better source population (P1), the difference in relative fitness between single locus homozygotes and the proportion of loci (that will segregate in the foundation stock) fixed favourably in P1. In real life the last two of these are never known. We therefore focused on the response limits givenx= 0·5, 0·75, 0·875 or the optimum value ofx(which is a function of the other three parameters). Our general finding was that in situations whereNis large enough so that a major portion of the potential can be achieved, theF2population should be used as the foundation stock when the two source populations do not differ greatly in performance; but when one population performs considerably better than the other, the first backcross (but not second backcross) would be the choice.
Meso-tartrate resistance and phylogenetic relationships of biotypes ofSalmonella typhimurium
Authors: May Sandra G. , Old D. C. 
Published: September 2009

SUMMARYMeso-tartrate utilizing and resistant (mT+) recombinants were produced readily in transductions from an mT+donor strain to 42 naturally occurringmeso-tartrate non-utilizing and sensitive (mT−) recipient strains ofSalmonella typhimurium, and were produced, sometimes as frequently, in interbiotype crosses between different pairs of strains from the mT−biotypes 2, 18, 26 and of the FIRN group (biotypes 30 and 32). These findings suggested that the sites of themtamutations were independent in strains from the different mT−biotypes and were in agreement with their probable different lines of descent. Intrabiotype crosses indicated genetic homogeneity among strains of biotype 26 and among strains of biotype 30; on the other hand, they suggested that in each of the biotypes 2, 18 and 32, a minority of strains hadmtamutations present at different intragenic sites from those of the majority of strains. The derivations of the strains of the minority types are discussed.
The population genetics of theH-2polymorphism in European and North African populations of the house mouse (Mus musculusL.)
Authors: Nadeau J. H. , Wakeland E. K. , Götze D. , Klein J. 
Published: September 2009

SUMMARYTwo hundred and two house mice (Mus musculusL.) from 29 populations in Europe and North Africa were typed for 16 H-2K and 17 H-2D antigens, each antigen defining a different allele. Among the 13 best characterized populations, 1 to 4 common and 3 to 20 rare antigens were observed. However, an average of 37% of the H-2K and 39% of the H-2D antigens remain to be identified. Ninety-four percent of the 50 mice tested were heterozygous for H-2K antigens and 89% for H-2D antigens. In 4 of the 8 populations tested, the most common H-2K and H-2D antigens occurred in the same individual more often than if randomly associated. Associations between common H-2K and H-2D antigens and excess heterozygosities may be the consequence of the small size and instability of populations composed primarily of related individuals. Estimates of the genetic distances between populations revealed that Danish, Egyptian, and several of the Orkney Island populations were related. These were the only populations in which metacentric chromosomes were not found. In contrast, populations which were antigenically different were also karyotypically different, regardless of taxonomic status of allozymic similarity.
The influence of TOrl upon male fertility in t-bearing mice
Authors: Hammerberg Craig 
Published: September 2009

SUMMARYThe model of Lyon & Mason (1977) which defines three subregions of the t complex (T, tail-determining; A, abnormal transmission ratio; L, lethal) has been extended in an interpretation of male fertility data obtained from the combination of TOrl with different t haplotypes. The results demonstrate: (1) the T region of most t haplotypes (t12, t0, tw18 and tw2) possess gene(s) that interact with the L region to give quasisterility; (2) the T region of t6 lacks the allele(s) that result in quasisterility; and (3) the T region interacts with the A region to modify the transmission ratios of t haplotypes. The results were discussed in terms of an interacting genetic system controlling male fertility.
Genetic variation in small multigene families
Authors: Ohta Tomoko 
Published: September 2009

SUMMARYIn order to understand the evolution of genetic systems in which two genes are tandemly repeated (small multigene family) such as has been recently found in the haemoglobin α loci of primates, haemoglobin β loci of mouse and rarbit and other proteins, a population genetics approach was used. Special reference was made to the probarility of gene identity (identity coefficient), when unequal crossing-over is continuously occurring as well as random genetic drift, inter-chromosomal recombination and mutation. Two models were studied, cycle and selection models. The former assumes that unequal crossing-over occurs in cycles of duplication and deletion, and that the equilibrium identity coefficients were obtained. The latter is based on more realistic biological phenomena, and in this model it is assumed that natural selection is responsible for eliminating chromosomes with extra or deficient gene dose. Unequal crossing-over, inter-chromosomal recombination and natural selection lead to a duplication-deletion balance, which can then be treated as though it were a cycle model. The basic parameter is the rate of duplication-deletion which is shown to be approximately equal to 2(u+ 2β)X, whereuis the unequal crossing-over rate, 2β is the inter-chromosomal recombination rate andXis the frequency of chromosomes with three genes or of that with one gene. Genetic variation of the globin gene family, of which gene organization is known in most detail, is discussed in the light of the present analyses.
Gonosome-autosome translocations in fowl: the development of chromosomally unbalanced embryos sired by singly and doubly heterozygous cockerels
Authors: Blazak W. F. , Fechheimer N. S. 
Published: September 2009

SUMMARYCockerels singly or doubly heterozygous (t1/ +, t2/ + and tl/t2, respectively; collectively heterokaryotypic, HTK) for two different Z-autosome translocations (t1, t2) produce an array of chromosomally balanced and unbalanced spermatozoa owing to adjacent segregation and nondisjunction at the first meiotic division. This study addresses the developmental capacity of embryos derived from matings of control ( + / + ) and HTK (tl/ +, t2/ +, tl/t2) cockerels with hens bearing normal chromosome complements (+ /W).Estimates of the hatchability of fertile eggs sired by + / +, tl/ +, t2/ + and tl/t2 cockerels were 82·8%, 43·0%, 41·3% and 10·9%, respectively. Approximately 75% of the mortality observed in embryos sired by HTK cockerels occurred by four days of incubation. Developmental arrest generally occurred earlier in embryos sired by t2/+ and tl/t2 cockerels than in those by tl/ + cockerels. These differences reflect variation in the degree of embryonic chromosome unbalance expected among embryos of the different sire groups. The pattern of mortality after three days was similar in embryos sired by HTK cockerels. In control embryos, mortality was highest on days 20–21 of incubation.Chromosome analysis of 16/18 h embryos, day 1/5 embryos and hatched chicks sired by HTK cockerels revealed that most, if not all, chromosomally unbalanced embryos died during development; the majority before three days of incubation. Partial monosomy for chromosome one was found to be more deleterious to embryonic development than partial trisomy.
Isolation and characterization of deficiencies exposing therudimentarylocus ofDrosophila melanogaster
Authors: Naguib Fardos N. M. , Jarry Bruno 
Published: September 2009

SUMMARYTherudimentarylocus ofDrosophila melanogastercontains the structural information for the first three enzymes of thede novopyrimidine pathway. Two newrudimentary (r)mutants have been isolated following mutagenesis with ICR-170. From complementation analysis and cyto-genetical observation both were shown to be deficiencies which expose therlocus.Df(1)r19is deleted from band 14D1 to 15D1 andDf(1)r1Dfrom band 14B6 to 15A2. These deficiencies were combined with several characterizedralleles each giving a single enzymatic defect in one of the first three enzymes of the pyrimidine pathway. An unusual semilethaltranseffect was observed in some but not all the combinations. The effect was not observed with a third smaller deficiency which also exposes therudimentarylocus.
Chromosomal distribution of the major insert inDrosophila melanogaster28S rRNA genes
Authors: Peacock W. J. , Appels R. , Endow S. , Glover D. 
Published: September 2009

SUMMARYThe major type I insert sequence for the 28S rRNA genes ofDrosophila melanogasterhas been mapped within the chromosomes using a probe synthesized from a cloned sequence containing the entire 5·4 kb segment. The genomic distribution was shown to be complex in that the insert sequence occurred next to many different types of sequences, in addition to occurring as an insert in the 28S rRNA genes of theXchromosome.In situhybridization of mitotic chromosomes showed most of the insert units not contained in the ribosomal genes to be located near the ribosomal gene cluster on theXchromosome. Additional sites were detected in polytene chromosomes in region 102C, 8–12 and in the hetero-chromatin of the autosomes.
A semilethal t-haplotype in the Orkney Islands
Authors: Dooher G. B. , Berry R. J. , Artzt K. , Bennett D. 
Published: September 2009

SUMMARYBreeding tests of wild house mice, trapped from an isolated population from Sanday in the Orkney Islands, have demonstrated the presence of a semilethal t-haplotype designated tw106. Microscopic examination of sperm and testes from a sterile male obtained from this population revealed the histological characteristics typical for homozygotes for semilethal t-haplotypes. This report is the first description of the recovery of a t-haplotype from an island population of wild mice.
Inbreeding for isogeneity by backcrossing to a fixed parent in haploid and diploid eukaryotes
Authors: Leslie John F. 
Published: September 2009

SUMMARYThe consequences of repeated backcrossing to a fixed parent are examined for haploid eukaryotes having a transitory diploid phase. The isogenicity attained in the absence of selected markers depends on the number of chromosomes and the total genetic map length, while the isogenicity of a chromosome carrying a selected marker increases more slowly and depends on the size of the chromosome. As inbreeding proceeds, the remaining non-isogenic material is not distributed evenly to all of the progeny. Instead, the majority of the progeny are completely isogenic with the fixed parent (with the exception of a region surrounding each selected marker), while the non-isogenic material is concentrated in a minority of the progeny. Even when the average isogenicity of the progeny and the fixed parent exceeds 99%, a significant proportion of the progeny will contain tracts of non-isogenic material which average several map units in length. Minor modifications enable these results to be applied to diploide. Examples show how to determine the degree of isogenicity produced by a given number of backcrosses in several specific situations.
New prime plasmids fromPseudomonas aeruginosa
Authors: Royle P. L. , Holloway B. W. 
Published: September 2009

SUMMARYpMO1111, a derivative of FP110 carrying a Tn1insert, has been used to generate two plasmid primes carryingPseudomonas aeruginosachromosome. pMO1112 has been shown to carry thepro-82+gene and pMO1113 carriesargH+andlys-12+. pMO1112 is considerably more stable than pMO1113 in arecA+background.
Gametic selection and the selection component analysis
Authors: Nadeau Joseph H. , Dietz Klaus , Tamarin Robert H. 
Published: September 2009

SUMMARYThe selection component analysis developed by Christiansen & Frydenberg (1973, 1976) is a method to study the components of natural selection and is based on an analysis of population samples which include mothers and their progeny (mother–offspring combinations). Because only one progeny per mother–offspring combination is analysed, gametic selection and the reproductive components of selection in males are poorly characterized. We investigated the information which can be gained by analysing all progeny in each combination and showed that analysis of entire litters enables detection of gametic selection. Testing and estimation procedures are derived for this purpose. Sexual selection in males and mate preferences remain poorly characterized because the only information about the reproductive components in males is contained in the sample of male gametes and is insufficient to reconstruct the breeding structure of the male population. The format and interpretation of a selection component analysis is presented which takes these results into account.
A mathematical model of extranuclear genes and the genetic variability maintained in a finite population
Authors: Takahata Naoyuki , Maruyama Takeo 
Published: September 2009

SUMMARYA mathematical theory of population genetics accounting for the genes transmitted through mitochondria or chloroplasts has been studied. In the model it is assumed that a population consists ofNmmales andNffemales, the genetic contribution from a male is β and that from a female 1 – β, and each cell line containsneffective copies of a gene in its cytoplasm. Assuming selective neutrality and an infinite alleles model, it is shown that the sum (H) of squares of allelic frequencies within an individual and the corresponding sum (Q) for the entire population are, at equilibrium, given byandwhere ρ = 2β(1−β),Ne= {β2/Nm+(1−β)2/Nf}−1, λ is the number of somatic cell divisions in one generation, andvis the mutation rate per cell division. If the genes are transmitted entirely through the female the formulae reduce to Ĥ ≃ 1/(1 + 2nv) andQ^≃ 1/{1 + (2Neλ+ 2n)υ}. Non-equilibrium behaviours ofHandQ^are also studied in the case of a panmictic population. These results are extended to geographically structured models, and applied to existing experimental data.
Exchange between the ribosomal RNA genes ofXandYchromosomes inDrosophila melanogastermales
Authors: Maddern R. H. 
Published: September 2009

SUMMARYThe genes coding for the 18s and 28s ribosomal RNA (rRNA) are present on both theXandYchromosomes ofD. melanogasterat a site known as thebobbedlocus. Exchange was observed in males between a normally orientatedXandYchromosome (Dp(1; 1)scv1andBSY y31d) with a frequency of 0·079%. One-quarter (7 in 27) of these exchange products between two + chromosomes which both carried sufficient rRNA genes for abb+phenotype exhibited abbphenotype. Evidence is presented that one-half, and possibly all, of the exchanges involved the repetitivebbgenes. These results together with those reported by Palumbo, Caizzi & Ritossa (1973) imply that the repeatedbbgenes of either (or both) theXorYchromosome are not arranged with uniform polarity and, further, that spermatogonial exchange between theXandYchromosomes may be restricted to thebbloci.