bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of the macrophage alloantigenic marker (Mph-1) in inbred mice
Authors: Archer James R.
Published: September 2009

Improvements in cytotoxic technique allowed a determination to be made of the strain distribution and inheritance of Mph-1, the mouse peritoneal exudate cell alloantigen. Mph-lb, the allele in B10 lines, is inherited as a Mendelian co-dominant gene. In a 3-point backcross using the colour markers pink eye dilution (p) and chinchilla (cch) it was shown to map about 36 units from p in the order p-cch-Mph-l on chromosome 7. An alternative antigen, Mph-1.1, has been identified on strains F/St and I/StDa.
The maintenance of genetic variability by mutation in a polygenic character with linked loci
Authors: Lande Russell
Published: September 2009

It is assumed that a character under stabilizing selection is determined genetically bynlinked, mutable loci with additive effects and a range of many possible allelic effects at each locus. A general qualitative feature of such systems is that the genetic variance for the character is independent of the linkage map of the loci, provided linkage is not very tight. A particular detailed model shows that certain aspects of the genetic system are moulded by stabilizing selection while others are selectively neutral. With reference to experimental data on characters ofDrosophilaflies, maize, and mice, it is concluded that large amounts of genetic variation can be maintained by mutation in polygenic characters even when there is strong stabilizing selection. The properties of the model are compared with those of heterotic models with linked loci.
Mitotic mutants ofAspergillus nidulans
Authors: Morris N. Ronald
Published: September 2009

Forty-five temperature-sensitive mutants ofAspergillus nidulanswhich are defective in nuclear division, septation or distribution of nuclei along the mycelium have been isolated, and most have been subjected to complementation analysis and mapped to chromosome. Thirty-five of the mutants were unable to complete nuclear division at the restrictive temperature. Twenty-six of these mutants exhibited a co-ordinate drop in both spindle and chromosome mitotic indices at 42 °C, indicating that they fail to enter mitosis. These mutants have been assigned to the gene symbolnim. Nine mutants exhibited a co-ordinate rise in spindle and chromosome mitotic indices at 42 °C, indicating that they are arrested in mitosis. These mutants were assigned the gene symbolbim. Five mutants failed to form septa and were given the gene symbolsep; and five mutants had an abnormal nuclear distribution and were given the gene symbolnud. All of the mutations were recessive. Most of the mutants were in different complementation groups. Mutants in the same complementation groups were phenotypically similar, but phenotypically similar mutants were not necessarily or usually in the same complementation group. There was no evidence for genetic clustering of phenotypically similar mutants. The mutants were located on all eight chromosomes.
Tandem duplications inDrosophila melanogaster: III. Intrachromosomal exchange of a heterozygous tandem duplication
Authors: Kalisch Wolf-Ekkehard
Published: September 2009

During meiosis the two parts of a tandem duplication are able to pair in a double loop instead of pairing with the corresponding region of the homologous chromosome. The frequency of intrachromosomal exchange within this double loop was measured in heterozygous females of tandem duplicationDp(1; 1)Grby the phenotypes of the exceptional F1males. The intrachromosomal exchange frequency is increased significantly by both the ‘interchromosomal effect’ of heterozygous inversions in the autosomes and by a double inversion in the homologousXchromosome. Distribution of the exchange events depends on the pairing situation and its frequency within the double loop. The analysis of clusters of intrachromosomal recombinants observed favours the assumption that this exchange type is exclusively a meiotic event.
A genetic method for measuring non-disjunction in mice with Robertsonian translocations
Authors: Lyon Mary F. , Ward Hazel C. , Simpson Gillian M.
Published: September 2009

A high frequency of chromosomal non-disjunction occurs spontaneously in mice heterozygous for some Robertsonian translocations. If animals heterozygous for the translocation and homozygous for different alleles of a marker gene are mated together a few young homozygous for the marker arise through non-disjunction, and their frequency can be used as a measure. This method has been used with the Robertsonian translocation Rb(9.19)163H and the marker ruby ru (chr. 19); Rb(4.6)-2Bnr with brown (b) and misty (m) (chr. 4); and Rb(9.14)6Bnr with hairless (hr) and piebald (s) (chr. 14) respectively. The frequencies of marked young were: Rb163 0/5260 ruru; Rb2 21/1997 mm bb; and Rb6 19/1702 hrhr ss, and the corresponding calculated non-disjunction frequencies in each arm of the translocation were Rb163, <5 %; Rb2, 15%; Rb6, 15%. These figures show reasonably good agreement with values obtained by other methods. A search for genetic or environmental factors affecting the frequency of marked young in Rb2 and Rb6 revealed that in Rb2 the frequency increased with maternal age, whereas in Rb6 the maternal age of the marked young was non-significantly below that of the total progeny. The reasons for this discrepancy are not clear.
A recombination test to classify mutants ofBacillus subtilisof identical phenotype
Authors: Galizzi A. , Siccardi A. G. , Mazza G. , Canosi U. , Polsinelli M.
Published: September 2009

We have developed a recombination test inBacillus subtilisthat provides a tool for rapid genetic classification of mutants of identical phenotype. The test has been used to classify 25 ts mutants in nine recombination classes that have been proved by independent evidence to correspond to nine genetic loci.
The genetic control of protoperithecial production inSordaria brevicollis
Authors: Bond D. J. , MacDonald D. J.
Published: September 2009

Mutations have been detected which affect the production of protoperithecia inSordaria brevicollis. These mutations have been calledperithecial-1andperithecial-2. Ascus analysis revealed that the former was a centromere unlinked gene, whilst the latter was very close to the mating-type locus. Theper 1−per 2− genotype was female sterile. Recovery of fertility by a sterile culture occurred and perithecial analysis revealed that this recovery was due to the accumulation of revertantper 1+nuclei in the mycelium.Per l−per 2+colonies were fertile and gave a cross of characteristic appearance.
Equivalence of the A genome of bread wheat and that ofTriticum urartu
Authors: Chapman Victor , Miller T. E. , Riley Ralph
Published: September 2009

Lines ofTriticum aestivumChinese Spring (2n= 6x= 42) which were ditelocentric or doubly ditelocentric, in turn, for the 14 chromosomes of the A and B genomes were pollinated byTriticum urartu(2n= 14). The behaviour of the marked telocentric chromosomes was scored in the 14 distinct hybrids obtained from these pollinations. In 6 of the hybrids in which different A genome chromosomes were marked by telocentrics there were from 50 to 80% of the pollen mother cells in which the telocentrics were paired. In the seven hybrids in which different B genome chromosomes were marked the telocentrics were never paired. It was concluded that the genome ofT. urartumatched very closely the A genome of hexaploid wheat and that it did not correspond, as had been proposed by Johnson, to the B genome. The pairing behaviour of the 14T. aestivum×T. urartuhybrids was compared with earlier results obtained from hybrids betweenT. aestivumandT. boeoticum. It was proposed that the higher trivalent frequencies seen in theT. boeoticumhybrids could be due to homoeologous pairing and that the genotype ofT. boeoticumhas the capacity partly to suppress the activity of thePhlocus of chromosome 5B of wheat, as a result of which homoeologous pairing is normally prevented.
Mitochondrial factors in the utilization of sugars inSaccharomyces cerevisiae
Authors: Evans I. H. , Wilkie D.
Published: September 2009

Cytoplasmic petite mutants, spontaneous and induced, show various patterns of ability υ. inability to utilize the sugars galactose, α-methylglucoside and maltose, depending on the strain from which they were isolated. Petites recombine and segregate their different sugar deficiencies among vegetative diploid progeny when crossed, indicating mitochondrial control. Crosses between petites and wild-type further indicate that mitochondrial factors may be interacting with nuclear factors in a complex regulatory system.
Oral morphogenesis during asexual reproduction in Paramecium tetraurelia
Authors: Jones Warren R.
Published: September 2009

Oral morphogenesis in stock 51 of Paramecium tetraurelia was investigated using the techniques of Chatton-Lwoff and protargol silver impregnation. During the stomatogenesis accompanying divisional morphogenesis a new oral anlage field and endoral kinety are formed and persist throughout the interfission period in both the proter and the opisthe. This previously overlooked fact is important for understanding the developmental origins and significance of the endoral kinety and the oral anlage field. Previously, the kinetosomes constituting the oral anlage field were thought to be formed just prior to the onset of stomatogenesis, being in some way derived from the kinetosomes of the endoral kinety. The demonstration of a permanent anlage field as an integral component of the oral assemblage suggests that the earliest stages of stomatogenesis might best be viewed as temporally controlled surfacing and/or ciliation of pre-existing kinetosomes rather than their de novo synthesis. The endoral kinety would thus have no contributory role in the formation of the anlage field used in the immediately ensuing stomatogenesis.
Are macronuclear subunits inParameciumfunctionally diploid?
Authors: Nyberg Dennis
Published: September 2009

The organization of the genetic material in the macronucleus of ciliates has been the subject of considerable controversy. Two of the four models of macronuclear structure predict assortment of the alternative phenotypes of heterozygotes during vegetative growth. Early studies of the phenotypic behaviour of heterozygotes after macronuclear regeneration (Sonneborn, 1947) had supported a diploid subunit model. The availability of quantitative predictions of the rate of assortment for the haploid and chromosomal models (Preer, this volume) and the existence of two alleles controlling a quantitative trait, copper tolerance, inParamecium tetraurelia, has provided an opportunity to test these models. The median tolerance limits to copper of unselected sublines were measured as a function of age. There was no increase in the variance among sublines, as the haploid and chromosomal models predict. Quantitative evaluation shows that subdiploid models with a kinetic complexity of 860 or less are not compatible with the results. This experiment was not sensitive enough, however, to exclude subdiploid models if the kinetic complexity is 2000 or greater. Selection on heterozygotes also failed to provide evidence in favour of assortment. All the results are consistent with and support the diploid subunit model of theParameciummacronucleus.
Macronuclear DNA in Stentor coeruleus: a first approach to its characterization
Authors: Pelvat B. , De Haller G.
Published: September 2009

The macronuclei of Stentor coeruleus were isolated on a discontinuous sucrose gradient and their DNA was purified by conventional methods. The GC content was 32 mole%. The DNA banded as a single peak on analytical ultracentrifugation at 1·691 g/cm3. The molecular weight of the DNA was 5 × 106 to 4 × 107 daltons. Genome size determined by DNA–DNA reassociation kinetics was 6 × 1010 daltons. The macronuclear genome was mostly simple, about 85% being made of non-repetitive sequences.
Non-randomness of nucleotide bases in mRNA codons
Authors: Nassar R. F. , Cook R. D.
Published: September 2009

Maximum likelihood estimates of codon and base frequencies from observed amino acid composition of proteins were obtained based on models capable of revealing dependency between base arrangements in the three positions of a codon. Results showed that many of the proteins analysed revealed dependency between base arrangements in the first and second codon positions (first-order interaction). Also, in a number of proteins the interactions between base arrangements seemed to involve simultaneously more than one first order interaction and/or a second-order interaction (among base arrangements in the three codon positions). It was of interest to observe that the model of random base arrangements did not fit the observed amino acid data in almost all of the proteins that were analysed. More than ten amino acids contributed to this deviation from randomness.
Combined chromosomal and plasmid encoded control for the degradation of phenol inPseudomonas putida
Authors: Wong C. L. , Dunn N. W.
Published: September 2009

The TOL(M1) metabolic plasmid was transferred fromPseudomonas arvillamt-2 to a mutant ofPseudomonas putida. Although neither the donor nor the recipient could grow on phenol, the transconjugants could grow slowly on this carbon source. In these transconjugants phenol was converted to catechol by chromosomal encoded phenol hydroxylase followed by degradation of catechol by low uninduced levels of the plasmid encoded catecholmetacleavage pathway. A mutant, which grew well on phenol, was isolated from one of the transconjugants and it was found that phenol could now act as an inducer for themetacleavage pathway.
Genetic characterization ofrec-1, a mutant ofUstilago maydisdefective in repair and recombination
Authors: Holliday R. , Halliwell R. E. , Evans M. W. , Rowell V.
Published: September 2009

Detailed physiological and genetic studies of haploid and diploid strains have revealed a complex phenotype for therec-1 mutation inUstilago maydis. The mutant is defective in the repair of damage by UV light, ionizing radiation and nitrosoguanidine. Four alleles are all recessive and have the same sensitivity to UV, suggesting the loss of a single cellular function. A significant fraction of non-viable cells is formed during growth, and in diploid strains considerable variation in colony size and morphology is seen. The spontaneous frequency of mutation is greater than in wild-type cells, but there is little, if any, enhancement by irradiation.

rec-1 also has pleiotropic effects on genetic recombination. The spontaneous level of mitotic allelic or non-allelic recombination is abnormally high, but the relative increase after irradiation is much lower than in control diploids. Allelic recombination is strongly associated with the expression of a hetozygous recessive distal marker, and it is shown that this is often due to hemizygosity rather than to homozygosity of this marker. The results indicate that allelic recombination is due to crossing over rather than gene conversion, but that the cross over is often associated with a chromatid break.rec-1 interacts with other radiation sensitive mutants, such asrec-2. Diploids homozygous for both are totally deficient in allelic recombination. In crosses betweenrec-1 strains meiosis is defective, with a low viability of meiotic products and frequent production of aneuploids or diploids among the survivors. The overall phenotype ofrec-1 strains can best be explained in terms of the loss of a regulatory function, which leads to uncontrolled recombination during mitosis and meiosis, and the loss of a recombination repair pathway which is normally induced by agents which damage DNA.
On the estimation of probabilities of segregation from a bacterium carrying two incompatible plasmids
Authors: Baumberg S.
Published: September 2009

Equations are presented relating the number of generations elapsed to the fractions of bacteria carrying one or both plasmids in a clone derived from a cell containing two incompatible plasmids.
Genetic polymorphism and evolution in parthenogenetic animals: V. TriploidAdoxus obscurus(Coleoptera: Chrysomelidae)
Authors: Lokki Juhani , Saura Anssi , Lankinen Pekka , Suomalainen Esko
Published: September 2009

The genetic variability at 16 enzyme loci in 52 Scandinavian triploid parthenogenetic populations of the beetleAdoxus obscurushas been studied by starch-gel electrophoresis. The overall genotypes of different beetles have been compared with each other and with a sample from a diploid bisexual population from Canada. Eighty per cent of the parthenogenetic beetles have the same overall genotype. The remainder belong to six genotypes, three of which are found in only one population. The variability within and between parthenogenetic populations ofA. obscurusis much lower than in other comparable parthenogenetic insects studied by us. This is interpreted to be a consequence of the efficient migration of the genotypes with the highest fitness, leading to a replacement of less-adapted genotypes.A. obscurusis a flying insect, whereas the other parthenogenetic insects studied by us are sluggish flightless forms.
Aneuhaploids in bread wheat
Authors: Miller T. E. , Chapman Victor
Published: September 2009

Euploid and aneuploid plants ofTriticum aestivum, variety Chinese Spring were pollinated with, pollen ofHordeum bulbosum. Euhaploids and aneuhaploids of Chinese Spring were obtained from the crosses. Meiotic chromosome pairing was analysed in 25 different aneuhaploids and the results were compared with those obtained from euhaploids. The evidence provided by the meiotic studies was used to identify chromosomes whose activities affected the genetic control of chromosome pairing.

Meiosis was abnormal in a 23-chromosome aneuhaploid and in the 22-chromosome sectors of a chimaeral plant. Both plants were thought to have resulted from the incomplete elimination of the genome ofH. bulbosumfrom hybrid embryos. It is suggested that the meiotic abnormalities in the two aneuhaploids were caused by the residual barley chromosomes.
The lactose system ofKlebsiella aerogenesV9A: 5. Lac-permease defective mutants of twoKlebsiellaLac plasmids and their apparent reversion to wild type
Authors: Reeve E. C. R.
Published: September 2009

The Lac plasmids in twoKlebsiellastrains, V9A and RE1544, give characteristic Lac-permease defective mutations which produce a lactose-negative (ML−) phenotype in the host strain, in spite of the presence of alacoperon on the chromosome. These ML−clones can revert to the wild-type (ML+) phenotype, and the mechanism of this reversion is examined. In V9A carrying its own Lac plasmid (FKlac), it is shown that reversion of ML−to ML+is usually the result of mutation to constitutivity of one of two galactoside permeases which are not induced by lactose but accumulate lactose when otherwise induced or made constitutive. However, in one out of the 51 ML+revertants tested the mechanism of reversion appeared to be a change back to wild type of the Lac plasmid's own permease gene. In V9A carrying the Lac plasmid (pRE6) from RE1544, successive changes of phenotype were obtained of ML+to ML−to ML+to ML−to ML+; these were all found to be the result of changes in the plasmid permease gene, and could be simply explained if an IS sequence could insert and excise from this gene.
Suppressor-specificity of antisuppressors in yeast
Authors: McCready Shirley J. , Cox Brian
Published: September 2009

Eighteen mutations ofSaccharomyces cerevisiae, at eight loci, isolated as antisuppressors ofSUPQ2, an ochre-suppressing allele ofSUP11, were crossed with three other suppressors.

They were found to abolish the ability ofSUP2(inserting tyrosine), to suppress the ochre mutationsade2.1andcan1.100, but not its ability, to suppresshis5.2orlys1.1.When coupled with any antisuppressor,SUPQ5, inserting serine, was also unable to suppressade2.1, but the suppression of other ochre mutations varied from oneasu-SUPQ5strain to another. No antisuppressor affected the ability ofSUP11-am, an amber-suppressing allele ofSUP11, to suppresstrp1.1, an amber mutation.
On the dynamics of activation of mammalian X chromosomes
Authors: Mukunda N. , Chandra H. Sharat , Gadgil Madhav , Rajagopal A. K. , Sudarshan E. C. G.
Published: September 2009

We have investigated a mathematical model of the process of activation of the X chromosomes in eutherian mammals. The model assumes that the activation is brought about over some definite time interval T by the complete saturation of N receptor sites on an X chromosome by M activating molecules (or multiples of M). The probability λ of a first hit on the receptor site is considered to be very much lower than that of subsequent hits; that is, we assume strong co-operative binding. Assuming further that an incomplete saturation of receptor sites is malfunctional, we can show that for proper activation of X chromosomes in normal diploid males and females, we must have λMT ≥ 3 and 0·96 ≤ N/M ≤ 1. An extension of this analysis for the triploid cases shows that under these conditions, we cannot explain the activation of two X's if the number of activating molecules is fixed at M. This suggests that there must be two classes of triploid embryos differing from each other in a step-wise manner in the number of activating molecules. In other words, triploids with two active X chromosomes would require 2M activating molecules as opposed to M molecules in triploids with a single active X. This interpretation of the two classes of triploids would be consistent with differing imprinting histories of the parental contributions to the triploid zygote.
The homoeologous relationships of rye chromosomes 4R and 7R with wheat chromosomes
Authors: Koller O. L. , Zeller F. J.
Published: September 2009

By means of rye chromosome CR from Imperial added to Chinese Spring wheat the alien substitutions 4A/CR, 4A/CRS, 4B/CR, 4D/CR, 4D/CRS, 7A/CRL, 7B/CR, 7B/CRL, 7D/CR and 7D/CRLwere isolated. Substitutions 4A/CRSand 4D/CRShad a better fertility and vegetative vigour than the corresponding substitutions with the complete chromosome CR. In substitutions the entire chromosome CR did not compensate for the absence of wheat chromosomes of group 7, whereas the substitutions 7A/CRL, 7B/CRLand 7D/CRLwere more fertile than the corresponding nullisomics 7A, 7B and 7D. It was shown that the short arm of CR is homoeologous to wheat telosomes 4Aα, 4BLand 4DS, whereas most of the long arm of CR is homoeologous to the wheat arms 7AS, 7BSand 7DS. Rye chromosome CR is designated 4R. Only three substitutions with rye chromosome DR were produced. The fertility of substitutions 7A/DR and 7B/DR were considerably lower than that of nulli-7A and nulli-7B. The 4B/DR substitution was sterile. Rye chromosome DR is believed to be a double interchanged chromosome in comparison to the correspondingSecale montanumchromosomes. Rye chromosome DR is designated 7R. On the basis of substitution ability of CR and DR and several homoeologous gene loci on these chromosomes an evolutionary scheme for the derivation of theSecale cerealegenome fromSecale montanumis outlined.
Inheritance of sperm head abnormality types in mice – the role of the Y chromosome
Authors: Krzanowska Halina
Published: September 2009

Four inbred strains of mice were used, differing in the total percentages of spermatozoa with abnormal heads (KE, 22·1%; C57, 26·4%; KP, 7·7%; CBA, 5·5%) and in the frequency distribution of abnormality types, as divided into four arbitrary classes. The most variable class 2 (narrow heads with canals inside the nuclear material) accounted for 47% of all abnormalities in KE strain, was common in CBA (29%) and almost missing in KP and C57 strains. F1 hybrids from the diallel crosses of these strains exhibited highly significant heterosis effects and significant reciprocal differences in the total percentage of abnormalities. The relative frequency of class 2 ranked in F1 hybrids in a similar order as calculated from the mid-parental values. After seven generations of backcrosses performed to introduce the Y chromosome from CBA to the genetical background of the KE strain, the total percentage of abnormalities was significantly reduced, although the relative proportion of class 2 was similar to that in KE strain. Also the Y chromosome from C57 strain, introduced into the genetical background of KE strain, caused a significant reduction of total abnormalities, but again the relative frequency of class 2 was not affected. It is concluded that the Y chromosome plays an important role in determining the total percentage of sperm head abnormalities, but does not seem to be involved in influencing specific abnormality types.
Regressions between relatives
Authors: Bulmer M. G.
Published: September 2009

A metric character determined by a large number of loci without epistasis is normally distributed. In the absence of linkage the joint distribution in two or more relatives is multivariate normal, so that all regressions are linear and have constant residual variance. In the presence of linkage this is no longer true except in the case of parent and child; for all other types of relatives the regression line is unaffected by linkage but the residual variance about this line is no longer constant but increases away from the mean.
Inheritance of Scottish-type resistance to warfarin in the Norway rat
Authors: Greaves J. H. , Ayres P. B.
Published: September 2009

The inheritance of resistance to the rodenticide, warfarin, in the Norway rat, Rattus norvegicus, derived from a wild rat population in Scotland was studied in the backcross, intercross and testcross. The resistance was found to be due to a major gene with about the same map position in Linkage Group I as the warfarin-resistance gene, Rw2, which occurs in the wild rat population in Wales. In heterozygotes, the Scottish resistance gene, unlike the Welsh gene, is incompletely penetrant in expression, though the penetrance was found to increase markedly in response to selection. Differences between the Scottish and Welsh types of resistance suggest that the two resistance genes are allelic.
Parental age and recombination frequency in the house mouse
Authors: Wallace Margaret E. , MacSwiney Felicity J. , Edwards R. G.
Published: September 2009

The relationship between parental age and recombination frequency in the offspring of mice has been studied using backcrosses to heterozygous males or females. The mice were allowed to breed until they became infertile. Data for several chromosomes were analysed, mostly from a stock carrying five markers covering approximately three-quarters of the length of chromosome 2.

Analyses of two-point recombination ratios or of multi-point interference ratios revealed no consistent age-related heterogeneity in offspring of male or female heterozygotes. A significant age-related heterogeneity was detected in the offspring of female heterozygotes but not of males, when the number of offspring with no detectable recombination was compared to those with one or more. This difference between the sexes could be related to earlier cytological observations on chiasma frequency in oocytes and spermatocytes. The significance of these findings for the analysis of follicular growth in mammals and in the origin of human trisomic conditions is discussed.
New results on the genetic characteristics of the Far East race of Drosophila melanogaster
Authors: David J. , Bocquet C. , Pla E.
Published: September 2009

Recently collected strains from Malay peninsula, Taïwan and Japan proved to be similar to previously studied Japanese strains kept for long time under laboratory conditions. It is therefore possible to speak of a Far East race, characterized by slow growth, very high fresh weight and small ovariole number. High heterogeneity between laboratory strains founded from wild caught flies seems also typical. Among the three traits studied, a positive genetic correlation was observed only between duration of development and adult weight. No correlations were found between biometrical traits and the latitude of strain origin. The problem of the origin of the Far East race is discussed.
Distribution of crossing-over in mouse chromosomes
Authors: Lyon Mary F.
Published: September 2009

In devising maps of the positions of gene loci along chromosomes, by measurements of crossing-over, it is usual to assume that the chiasmata which give rise to the crossing-over are randomly located, unless there is evidence to the contrary. If chiasmata are in fact preferentially located at certain points or regions this not only affects mapping, but also is of interest for population genetics since it may favour the development during evolution of blocks of genes relatively undisturbed by crossing-over. Preferential localization of chiasmata is well known in a number of disparate organisms (Darlington 1965; John & Lewis, 1965), but has so far been little studied in mammals. Evidence is presented suggesting tha chiasmata are in fact non-randomly located in certain chromosomes of the mouse.
Characterization of the new osmotic mutants (os) which originated during genetic transformation inNeurospora crassa
Authors: Mishra N. C.
Published: September 2009

Inositol independent (inl+) strains were obtained either as transformants following treatment of the inositol requiring (inl) strains ofNeurospora crassawith the wild-type DNA or as revertants without any DNA treatment. A significant number of the inositol-independent transformants were also found to have acquired additional mutations called osmotics (os) which made them unable to grow on 1 m-NaCl medium. None of the inositol-independent revertants were found to possess such osmotic mutations and their growth remained unaffected by the presence of NaCl. Many of the osmotic mutants described here were found to be new alleles of the previously knownos–1mutation on the linkage group I ofNeurospora crassa. The remainder were found to map at two new genetic loci designated asos-6andos-7; these loci were found to be closely linked toos–1. Among the new osmotic mutants onlyos-1andos-6mutants showed intragenic complementation. The mechanism of DNA-induced mutation during transformation is discussed.
Superinfection inhibition by prophage B3 of some R plasmids inPseudomonas aeruginosa
Authors: Krishnapillai V.
Published: September 2009

The prophage of the phage B3 ofP. aeruginosaexhibits superinfection inhibition towards certain R plasmids such as R18-1 or R18-3 as shown by a severe depression (c. 10−6) in the conjugal transfer of these plasmids into B3 lysogens. The transfer of other R plasmids into such lysogens and the transfer of R18-1 or R18-3 into bacteria lysogenic for unrelated phages was unimpaired. R18-1 or R18-3 was non-transducible into B3 lysogens although transducible into non-lysogens. The interaction appeared to be reciprocally expressed since B3 lysogenization of bacteria R+for R18-1 or R18-3 was also reduced. Consistent with the failure of co-existence of the prophage and the plasmids was the observation that when the transconjugants from the cross R18-1 donor ×B3 lysogenic recipients were tested, transfer-deficient plasmid derivatives were encountered (about 40%). Other transconjugants were cured of prophage, or carried mutant B3 prophage with lytic, lysogenization or superinfection inhibition functions impaired.
Factors affecting the observed number of young resulting from adjacent-2 disjunction in mice carrying a translocation
Authors: Lyon Mary F. , Glenister P. H.
Published: September 2009

The frequency of adjacent-2 disjunction in mice carrying the reciprocal translocation T(9; 17)138Ca was studied by mating together animals heterozygous for the translocation and carrying different recessive marker genes, usingTtfor chromosome 17 andcwcwfor chromosome 9. The proportion of marked young arising from adjacent-2 disjunction varied according to the markers carried in the two parents. When the female carriedTtthe frequencies of marked young were always higher than when non-Tfemales were used, and whenTtandcwcwwere carried in the same parent there was a shortage of marked young obtaining both copies of the proximal region of chromosome 17 from the father. Both these effects were regarded as probably another example of the phenomenon discovered by Johnson, of inviability of young lacking a maternal homologue of a certain region of chromosome 17. There were other variations in frequency of marked young, among crosses using non-Tfemales, which may have been due to differences in transmission ratio of male gametes carrying varioust-haplotypes or to true variations in frequency of adjacent-2 disjunction.
The effect of random selection coefficients on populations of finite size – some particular models
Authors: Avery P. J.
Published: September 2009

The model of random selection coefficients is considered in the context of a finite population of diploids. The selection coefficients of the homozygotes are allowed to vary with equal variance while the fitness of the heterozygote is kept fixed. Steady-state solutions are found in the case of equal two-way mutation rates with particular reference to the expected heterozygosity. Increasing the variance of the selection coefficients of the homozygotes is found to uniformly increase the heterozygosity for all values of the average selection coefficients and its effect is largest when the selection coefficients of the homozygotes are fully correlated. The fate of mutant genes is also considered in the case of random selection coefficients by looking at the probability of ultimate fixation and the mean times to fixation and extinction. The errors in previous calculations (e.g. Kimura, 1954; Ohta, 1972) are pointed out. It is found that a small average heterozygote advantage together with a reasonable degree of variance in the coefficients can cause an unexpectedly large amount of heterozygosity to be maintained. It is also seen that probabilities of fixation and mean times to boundaries are usually increased by increasing the variance showing that it in fact helps to keep the population heterozygous for much longer than the non-random case. This is in contradiction to some conclusions of Karlin & Levikson (1974) because their haploid results are not easily extendable to the consideration of this sort of diploid model.
On the fixation probability of a gene under random fluctuations in selection intensities in small populations
Authors: Narain Prem , Pollak Edward
Published: September 2009

A population withNmonoecious individuals, and having two alleles, is considered. The problem of calculating the fixation probability of a particular allele under random fluctuation of selection intensities is re-examined, employing finite Markov chain methods. An approximate but general expression for this probability is obtained and the results obtained by previous workers are shown to be special cases of this result.
Resistance to meiotic drive at theMDlocus in an Indian wild population ofAedes aegypti
Authors: Suguna S. G. , Wood R. J. , Curtis C. F. , Whitelaw A. , Kazmi S. J.
Published: September 2009

Females from an Indian wild population ofAedes aegyptiwere crossed to males carrying the sex ratio distorter factorMDwhich shows meiotic drive. Progenies from F1males were tested for sex ratio distortion, i.e. the chromosomes from the wild females were screened for their resistance to the action ofMD. The distribution of sex ratio in the progenies of different F1males indicated a polymorphism in the wild population for resistant and sensitive variants of theXchromosome. Seven discrete categories ofXappear to exist, associated with sex ratios ranging from 50% ♀ to less than 1·25% ♀. The overall level of resistance varied slightly but significantly in different parts of a town. The results are discussed in relation to the use of sex ratio distortion for genetic control of mosquitoes.
Genetical and embryological comparison of two mutations which cause foetal blebs in mice
Authors: Center Elizabeth M.
Published: September 2009

Mutants with abnormalities which were the consequence of the formation of haematomas during gestation were designated as ‘foetal haematomata’ (fh). Thefhhomozygotes were found to be morphologically and embryologically very similar to myelencephalic bleb (my) mice. It was also found, however, that thefhandmymutants were separate genetic entities due to two independently segregating recessive genes.
Long-term storage of mouse embryos at —196 °C: the effect of background radiation
Authors: Whittingham D. G. , Lyon Mary F. , Glenister P. H.
Published: September 2009

In order to test the feasibility of preservation, of genetic stocks of mice by storage in liquid nitrogen, mouse embryos at the 8-cell stage, were frozen and stored in liquid nitrogen at – 196 °C under increased radiation exposures of 1·8×, 9× and 84× background levels for periods of 6–8 months, 10–12 and 27–29 months, the 1·8 × level being regarded as a control. Their survival rates to the blastocyst stage, and after transfer to recipient females, to foetal or liveborn stages were then compared with those of unfrozen or short term frozen control embryos. The freezing processper secaused a marked loss of viability, in comparison with the unfrozen controls, but at the 1·8× radiation level there was then no further loss in viability even at the longest storage time (27–29 months). Similarly, at the 9× radiation level there was no loss of viability during storage up to 29 months, but at the 84× level the proportions of implanted embryos and live foetuses were slightly reduced. It was not clear if this was a true effect of radiation, since it was not related to time of storage. Considering all groups, about 20–30% of the embryos originally frozen were recovered as foetuses or liveborn young. It is concluded that the preservation of genetic stocks by storage in liquid nitrogen is a feasible proposition.
A new allele at the patch locus in the mouse
Authors: Truslove Gillian M.
Published: September 2009

Evidence is presented for the existence of a new allele at the patch locus called patch-extended (symbol Phe). Crosses of Phe with Ph, Wv and Rw produce double heterozygotes that are different from those resulting from the original patch allele. Besides the different coat colour in these mice, all the Wv + / + Phe animals that were tested resembled Wv + / Wv + and proved to be sterile. However, the two patch alleles interact to produce a split-face phenotype which resembles the presumed Ph/Ph.
Unifactorial inheritance of warfarin resistance in Rattus norvegicus from Denmark
Authors: Greaves J. H. , Ayres P. B.
Published: September 2009

Wild populations of the Norway rat, Rattus norvegicus, in Jutland have been known to be resistant to the anticoagulant rodenticide warfarin since 1962. The inheritance of the resistance was investigated in the F1, backcross and intercross. The results are consistent with the resistance being due to a major gene at the Rw locus. Resistant homozygotes, heterozygotes and susceptible homozygotes appeared to be distinguishable experimentally on the basis of differences in their susceptibility to vitamin K deficiency. The results are discussed in relation to previous studies of the inheritance of warfarin resistance in rats.
The detection, in unordered octads, of 6+:2mand 2+:6mratios with postmeiotic segregation, and of aberrant 4:4s, and their use in corresponding-site interference studies
Authors: Ghikas Aglaia , Lamb B. C.
Published: September 2009

Systems for the detection of postmeiotic segregation in unordered octads are described for 4:4(2), 6:2(2), 2:6(2), 5:3(3), 3:5(3) and 4:4(4) segregations, where the number in parentheses is the number of pairs of non-identical sister-spores. Linkage relations, centromere distances and phenotypic detectability of suitable combinations of markers for initial selective identification of such segregations, and subsequent confirmation tests, are discussed; correction formulae are given to allow for non-detection of certain classes in particular circumstances. Using one such system inAscobolus immersus, we detected 4:4(2), 6:2(2) and 2:6(2) segregations at thew-78 site: 2:6(2)swere previously unknown. Initial visual detection in this system was from octad phenotype ratios forw-78 (white ascospore) andgr-3 (granular ascospore pigmentation), with mating type and parafluorophenylalanine resistance as confirmatory markers after germination. Corresponding-site interference for wider ratio and – for the first time – narrower ratio unique classes was determined: it was moderately positive or moderately negative, depending on the cross and segregation class involved.
Genetic analysis of nystatin-resistant mutants ofSaccharomyces cerevisiae
Authors: Karunakaran V. , Johnston J. R.
Published: September 2009

Primary genes, designated asNYSA, NYSD, NYSE, NYSF(dominant) andnysB,nysC(recessive) are responsible for resistance to nystatin ranging from 30 to 80 u/ml. A dominant modifier gene increases the resistance conferred byNYSFfrom 80 to 140 u/ml and a recessive modifier gene enhances resistance due toNYSAby 20 u/ml (from 40 to 60 u/ml). One nystatin-resistant mutant is apparently cytoplasmic and this ‘mutation’ suppresses specifically the action of modifying factors which increase the level of resistance conferred by theNYSAgene. Interaction resulting in additive levels of resistance is shown by geneNYSDin combination with each of the genesnysB,nysCandNYSE. A model of step-wise increases in resistance due to polygenic primary genes and nuclear and cytoplasmic modifying factors is proposed.
The contribution of plasmid and host genes to plasmid-mediated interference with phage growth
Authors: Hughes Victoria , Meynell G. G.
Published: September 2009

The R factors, R56 and R64, interfere with the growth of several otherwise unrelated phages, including λ, P22 and T7. In addition, λviris inhibited more strongly in λ lysogens carrying either R factor when the prophage has an intact O – P region. Interference does not occur in certainstr AR+hosts but may reappear if they also carry other mutations affecting ribosomal proteins. Host mutants not permitting interference were isolated but were notstrA. Non-interfering plasmid mutants were also isolated, of which some also failed to cause interference after transfer to a different host genus.
Allosuppressors in yeast
Authors: Cox B. S.
Published: September 2009

Five loci have been identified inSaccharomyces cerevisiaewhose function reduces suppressor activity in strains carrying ochre super-suppressor mutations. Recessive mutations which allow an increased level of suppression occur at these loci. In such mutants, termed allosuppressors, the serine-inserting suppressorSUPQ5suppresses ochre mutations in a [psi−] background and Class I tyrosine-inserting suppressors are lethal or have a reduced viability. Mutations at two allosuppressor loci,sal3 andsal4, have a lethal interaction with one another and with the extrachromosomal determinant [psi+]. This interaction is expressed in the absence of any suppressor mutation. All the mutant alleles of one allosuppressor locussal3 are cold sensitive. One allosuppressor mutation,sal4.2, is temperature-sensitive for growth, as well as for other aspects of its phenotypic expression; namely the expression ofSUPQ5and the lethal interactions with Class I super-suppressors, with [psi+] and withsal3. At low temperature (24 °C),sal3-sal4.2 double mutants weakly suppress the ochre mutationade2.1, but do not suppresshis5.2 orlys1.1. It is argued that the site of function of the products of these loci is ribosomal and that they are involved in chain termination at UAA codons. It is inferred that the [psi+] factor or its product affects protein synthesis by interaction with the ribosome.
Continuous variation of genic dosage inPhycomyces
Authors: Medina Juan Ramon
Published: September 2009

A computer simulation of the genetic analysis of the asexual life cycle ofPhycomyces' heterokaryons has been carried out. We have studied experimentally the relationship between the nuclear proportion in heterokaryotic mycelia containing prototrophic and auxotrophic nuclei and their growth rates. We discuss possible evolutionary implications of heterokaryosis in coenocytic fungi and the genetic applications of the quantitative complementation technique.
Polymorphism at the G6PD and 6PGD loci inDrosophila melanogaster: I. Evidence for selection in experimental populations
Authors: Bijlsma R. , van Delden W.
Published: September 2009

Gene frequency changes were followed in 17 experimental cage populations ofDrosophila melanogasterpolymorphic for the two loci G6PD and 6PGD. From these cages it was observed that selection was favouring theFalleles of both loci when the cages were started with low frequencies of these alleles (0·20Fand 0·50F). A viability experiment and an extinction experiment also provided evidence that theFalleles of both loci were favoured. It is argued that the observed selection is not due to selective differences in genetic background of the different alleles, but is acting on the isozyme loci themselves.
A plasmodial colour mutation in the MyxomycetePhysarum polycephalum
Authors: Anderson R. W.
Published: September 2009

A spontaneous mutation conferring white plasmodial colour on the MyxomycetePhysarum polycephalumhas been analysed. The mutantwhi-1 allele is recessive towhi+in both heterokaryotic and heterozygous plasmodia. Thewhilocus is unlinked tomt, npfA, fusAandleu.
Theoretical study on genetic variation in multigene families
Authors: Ohta Tomoko
Published: September 2009

Genetic variation contained in a multigene family was theoretically investigated from the standpoint of population genetics. Unequal crossover is assumed to be responsible for the coincidental evolution of mutant genes in a chromosome. When the allowed latitude of the duplicated or deleted number of gene units at unequal crossover is 10 ˜ 15% of the total gene number in a chromosome, the arrangement of gene lineage in a chromosome is shown to be roughly random. The equilibrium properties of genetic variation or the probability of identity of two genes within a family (clonality) were studied under mutation, unequal crossover, interchromosomal crossover and sampling of gametes. The clonality of a multigene family withina chromosomeis shown to be approximately

in which α = 2k/n2withk= effective number of cycles of unequal crossover and withn= number of gene units in a family,vis the mutation rate per gene unit, β is the rate of interchromosomal crossover per family andNeis the effective size of the population, all measured by the rate per generation. The clonality of a gene family betweentwo different chromosomesbecomes approximatelyC1=C0/(l + 4Neν). Some models of natural selection which lowers the clonality or increases genetic variation in a multigene family were investigated. It was shown that natural selection may be quite effective in increasing genetic variation in a gene family.
Skeletal polymorphism and genetic drift in a Delhi frog, Rana cyanophlictis – a follow-up study
Authors: Grewal Manjit Singh
Published: September 2009

Four isolated populations of the skipper frog, Rana cyanophlictis were first studied in 1965 and then again in 1975. The genetical changes were measured by the incidence of 19 non-metrical skeletal variants. It was found that these populations have changed very little in 10 years, although the inter-population diversity, as judged by the estimates of divergence, is less now than previously. This could be due to the similar environmental conditions prevailing in Delhi and its neighbourhood from where these frog populations were collected.