bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the sterility induced by the male recombination factor 31.1 MRF inDrosophila melanogaster
Authors: Yannopoulos George
Published: September 2009

The sterility which is associated with male recombination induced by 31.1 MRF was studied genetically and cytologically. In all crosses it was found that female sterility mainly involves failure of the heterozygous females to lay eggs because their ovaries are atrophic. Under the optical microscope, the atrophic ovaries were seen to contain only germaria in their ovarioles. It was also found that in some cases 31.1 MRF affects only one of the two ovaries of the same female. This observation suggests that defective development of atrophic ovaries is not due to influences from the rest of the body but should be attributed to the inability of the germ cells to differentiate. Moreover, various stocks as well as homologous chromosomes were found to react differently to 31.1 MRF with respect to female sterility. In their effect on male sterility it was observed that some strains behave as neutral and others as reactive when mated with 31.1/Cy L4males.
Effects of therexgene of phage λ on lysogeny
Authors: Campbell J. H. , Dykhuizen D. , Rolfe B. G.
Published: September 2009

Mutations in therexgene of phage λ affect lysogeny. λrex−phages have an increased probability of forming abortive lysogens instead of stable lysogens. In addition, established lysogens produce elevated levels of cured cells during anaerobic but not aerobic growth. It is suggested that the function of therexgene is related to excision or repressor function.
Naturally occurring strains ofSalmonella paratyphi Bunable to form adhesive (type-1) fimbriae
Authors: Old D. C.
Published: September 2009

The production of MSHA+(type-1 fimbriate) recombinants was observed in transductional crosses between different pairs of naturally occurring strains ofSalmonella paratyphi B. MSHA+recombinants were readily produced in transductions from MSHA+donor strains to MSHA−(type-2 fimbriate or non-fimbriate) recipient strains, and less frequently between some pairs of MSHA−strains. The genetic evidence suggests that there are at least three different clones among MSHA−strains ofS. paratyphi B. Relationships between the different strains and their possible origins are discussed.
Coordination on timing of gene expression inParamecium
Authors: Myohara Koji
Published: September 2009

InParamecium caudatum, syngen 3, cells become mature (i.e. capable of undergoing conjugation) by about 50 fissions after conjugation. Matingtype-instability, another mating characteristic, begins to occur between 80 and 120 fissions after conjugation in heterozygotes for the mating type locus (Myohara & Hiwatashi, 1975). Mating-type instability also occurs in dominant homozygotes, earlier than in heterozygotes. In two different early maturing mutants the homozygotes become mature 20 fissions earlier than in wild-type clones, and mating-type instabiliiy also begins earlier than in wild-type clones. The number of fissions from maturity to the occurrence of the mating type change does not differ.
A major autosomal gene effect on activity of glucose 6-phosphate dehydrogenase segregating between recombinant inbred lines of mice
Authors: Erickson Robert P. , Harper Kenneth
Published: September 2009

G6PD measurements (expressed per g haemoglobin) in both males and females of the parental lines C57BL/6J and C57L/J and four recombinant inbred (RI) lines between them showed segregation of G6PD levels as parental classes (one line showed the higher C57BL/6J activity, three lines were indistinguishable from C57L/J). Haemoglobin also varied significantly among the parental and RI lines but this variation did not explain the variation in G6PD. NADP levels (expressed per g wet wt of erythrocytes) correlated with G6PD levels but one RI line was intermediate in males while two RI lines were lower than either parental line in females. Thus, the major autosomal locus affecting G6PD levels which segregates between these two inbred lines probably does not act directly on NADP levels. The variation in the G6PD levels in the four RI lines co-segregated with the brown coat color locus but the association is not significant because of the small number of RI lines available.
Distribution of human chromosomes on the metaphase plate. Symmetrical arrangement in human male cells
Authors: Coll M. Dolores , Cuadras Carlos M. , Egozcue Jose
Published: September 2009

Two linear models have been devised and applied to the study of the distribution of human male chromosomes on the metaphase plate in preparations from lymphocyte cultures not treated with spindle poisons. Using these it has been found that the chromosomes are approximately distributed around a centre of symmetry and that the lines joining the centromeres of homologous chromosomes (i.e. segments) have the centre of symmetry approximately at their mid-point. Thus each chromosome mirrors the position of its homologue relative to the centre of symmetry. The position of each chromosome in the metaphase plate was found to be approximately constant relative to the centre of symmetry and the other chromosomes. The significance of these findings is discussed in relation to the hypothesis on the distribution of the chromosomes in interphase nuclei and to data on acrocentric associations, acrocentric-non-acrocentric associations and the frequency of the most common translocations.
Thymineless elimination of N group plasmids is Res−(RII)-dependent and determined by a different gene than the Uvp plasmid phenotype
Authors: Tribe M. J. , Pinney R. J.
Published: September 2009

The wild-type N group plasmid RN3, which is phenotypically Res+Mod+(RII) is not eliminated by thymine starvation of its bacterial host. Derivatives of RN3 selected for the Res−phenotype are eliminated. The presence or absence of the RII modification specificity does not affect thymineless elimination of RN3 Res−plasmids. A Res−Mod(am) RN3 mutant is not eliminated by thymine starvation from either amber suppressing or non-suppressing hosts, suggesting that it carries a cryptic mutation in a novel genetic locus required for elimination. Thymineless elimination is shown to berecA+-dependent and the presence of the X group plasmid R6K significantly inhibits elimination of RN3 Res−Mod+. However, since R6K has no effect on two other plasmid-mediated functions of UV protection and UV-induced mutagenesis, which are alsorecA+-dependent, it would appear that elimination is determined by a separate plasmid gene than that encoding the UV functions. This is confirmed using derivatives of another N group plasmid R390, which eliminate but which have lost the ability to increase UV-induced mutagenesis in their host.
Genetic variation in varying environments
Authors: Mackay Trudy F. C.
Published: September 2009

In order to assess the relationship between genetic and environmental variability, a large natural population ofDrosophila melanogasterwas replicated as eight subpopulations, which were subjected to four different patterns of environmental variation. The environmental variable imposed was presence of 15% ethanol in the culture medium. Experimental treatments of the populations were intended to simulate constant environmental conditions, spatial heterogeneity in the environment, and two patterns of temporal environmental variation with different periodicity (long- and short-term temporal variation). Additive genetic and phenotypic variation in sternopleural and abdominal chaeta number, and body weight, were estimated in two successive years, and measurements were taken of the genotype–environment correlation of body weight and sternopleural bristle score with medium type.

Additive genetic variance of sternopleural chaeta number and of body weight was significantly greater in the three populations experiencing environmental heterogeneity than in the control population, but additive genetic variance of abdominal bristle score was not clearly affected by exposing populations to varying environments. Temporal environmental variation was equally, if not more, efficient in promoting the maintenance of genetic variation than spatial heterogeneity, but the cycle length of the temporal variation was of no consequence. Specific genotype–environment interactions were not present, therefore adaptation to heterogeneous environments is by selection of heterozygosityper se, rather than by differential survival of genotypes in the alternate niches.
Reduced pigmentation (rp), a new coat colour gene with effects on kidney lysosomal glycosidases in the mouse
Authors: Gibb S. , Håkansson E. M. , Lundin L.-G. , Shire J. G. M.
Published: September 2009

A spontaneous autosomal mutation in C57BL/Tb mice, provisionally called reduced pigmentation, symbolrp, has pronounced effects on three kidney lysosomal glycosidase activities. Homozygousrprpmice have significantly higher activities of β-galactosidase, β-glucuronidase andN-acetyl-β-hexosaminidase than their heterozygous litter-mates. Homozygotes have light ears and tails, diluted fur and dark eyes. The mutation is not allelic to any known to affect lysosomal functions, or to a number of pigmentation variants with similar phenotypic effects. The locus is on chromosome 7.
Spatio-temporal microdifferentiation of water-strider (Gerris) populations
Authors: Varvio-Aho Sirkka-Liisa , Pamilo Pekka
Published: September 2009

Spatial and temporal differentiation inGerris lacustrisandG. odontogaster(Heteroptera, Gerridae) were studied in restricted areas, where one population of each species was subdivided into several subpopulations. The aim of the study was to relate genetic population parameters to ecological population structure studied by mark-recapture methods in the same pond systems. Marked differentiation between the subpopulations and significant enzyme allele frequency changes between subsequent generations were found at several loci. It is suggested that non-selective forces are a sufficient explanation for the observed differences.
Comparative studies of two male recombination factors (MRF) isolated from a Southern GreekDrosophila melanogasterpopulation
Authors: Stamatis Nikos , Yannopoulos George , Pelecanos Michael
Published: September 2009

A comparative study of two male recombination factors (31. 1 MRF and 23. 5 MRF) isolated from the same Southern Greek natural population, revealed specific differences in their activities. 23. 5 MRF induces female sterility due to atrophie ovaries at a wide range of temperatures while 31. 1 MRF does so only at high temperatures. The gross morphology of the atrophie ovaries was the same and unilaterally affected pairs were found in the F1of crosses with both 23. 5 and 31. 1 MRF. Furthermore, 23. 5 MRF induces: (a) lower frequencies of abnormal anaphases I and II than 31. 1 MRF, (b) higher frequencies of ‘double crossovers’ resulting from deficiences or duplications, (c) large clusters of recombinants, suggesting premeiotic origin and (d) cases where one of the non-recombinant phenotypes was not produced. Such cases have never been observed with 31. 1 MRF. Moreover, the cytoplasm of theCy L4/Pmstrain that suppresses 31. 1 MRF does not affect the activities of 23. 5 MRF. Hypotheses to explain the different behaviour of the two factors are presented and discussed.
Galactosyltransferase activities on mouse sperm bearing multipletlethalandtviablehaplotypes of the T/t-complex
Authors: Shur Barry D.
Published: September 2009

Segregation-distortingt-sperm show a specific increase inN-acetylglucosamine: galactosyltransferase activity over wild-type (+/+) due to a deficiency of a wild-type galactosyltransferase inhibitor (Shur & Bennett, 1979). Eight other enzymic activities are indistinguishable between +- andt-sperm suspensions. In this study, three additional points are analysed. First, galactosyltransferases are assayed on sperm homozygous for a semilethal haplotype (tW2/tW2), relative to heterozygous (+ /tw2) and wild-type (+/+) controls.tW2/tW2assays circumvent the +-sperm inhibition oft-sperm galactosyltransferases that occurs in heterozygous + /t-assays and show thatt-sperm are actually four times as active as wild-type. Second, sperm which are compound heterozygotes for two complementing lethalt-haplotypes (tlx/tly), have nearly twice the theoretical enzyme level oftlx/tlysperm. Thus, in either homozygous (tW2/tW2) or double heterozygous (tlx/tly) formt-haplotypes act synergistically on sperm galactosyltransferase activity.

Third, and most interesting, sperm bearing either recombinant, viablet-haplotypes (+/tv,tvx/tvy), or one of three dominantT/t-complex mutations, were assayed to determine which portions of theT/t-complex are responsible for elevated galactosyltransferase activity. Results show that sperm bearing recombinant, non-segregation-distorting, viabletv-haplotypes no longer show elevated transferase activity. Therefore, the elevatedt1-sperm galactosyltransferase activity strictly correlates with the increased transmission frequency oft1-sperm. These studies strengthen further the hypothesis that sperm surface galactosyltransferases are involved in egg binding during fertilization, and thatt1-sperm segregation-distortion results, at least in part, from increased galactosyltransferase activity.
Rapid detection of allelic recombination at thegalllocus in yeast by assay of the recombinant gene product
Authors: Johnston Leland H.
Published: September 2009

A diploid heteroallelic at thegal1locus and producing little residual galactokinase activity was chosen. Following either γ- or UV-irradiation, recombination occurred leading to the formation of wild-typeGAL1 genes and an increase in detectable galactokinase. An enhanced level of enzyme was first detectable 2 h after irradiation and reached a maximum within 12–14 h. With increasing doses of irradiation, more enzyme was produced and this increase superficially resembled that obtained for plated recombinants. However, far more enzyme was actually synthesized than expected from the number of viable recombinants in the cells assayed. This suggests that recombination must have occurred in cells without colony-forming ability, indeed it may have occurred more frequently in these cells than in viable cells.
The effects of thet-complex upon male reproduction are due to complex interactions between its several regions
Authors: Hammerberg Craig
Published: September 2009

The three major regions (T, tail-determining; A, abnormal transmission ration; L, embryonic lethality) of thetcomplex on the murine seventeenth chromosome can interact to influence male reproduction (Lyon & Mason, 1977; Hammerberg, 1981). Evidence is presented here that suggests: (1) the presence of a polymorphic system within the T region that influences quasi-sterility in the male; (2) the existence of enhancing factors of transmission ratio distortion; and (3) that preferential interactions betweent-haplotypes are found to occur bothcisandtranswhich influence transmission ratio distortion.
Time until fixation of a mutant belonging to a multigene family
Authors: Ohta Tomoko
Published: September 2009

Time until fixation of a mutant that occurs in one copy of a multigene family was investigated from the standpoint of population genetics. Because of the complexity of the double process of random drift (on the chromosome and in the population), an approximate method based on the rate of steady decay of genetic variability is applied. The simple model of gene conversion with constant gene family size is also used. The expectation based on the approximate method is shown to be valid by extensive Monte Carlo simulations, and the results are useful for understanding the mechanisms of turnover of multigene families, when comparison is available between closely related species.
Biochemical genetics of Neurospora nuclease I: Isolation and characterization of nuclease (nuc) mutants
Authors: Forsthoefel A. M. , Mishra N. C.
Published: September 2009

Isolation and characterization of five new nuclease (nuc) deficient mutants ofNeurosporahave been described. The new mutants are unable to utilize nucleic acids as the sole phosphorus source and possess growth characteristics similar to thosenuc(nuc-1andnuc-2) mutants described previously. Two new mutants (nuc-4andnuc-5) were able to use RNA or predigested DNA (but not intact DNA) as phosphorus source and showed temperature sensitive growth at 37 °C. Based on the data from complementation and genetic analyses the five new nuc mutants (nuc-3, nuc-4, nuc-5, nuc-6andnuc-7) were found nonallelic to each other and to previously describednuc(nuc-1andnuc-2) mutants; the newnucmutants mapped to the right ofarg-12on linkage group II. On biochemical analyses, thesenucmutants were found to possess a lower level of extracellular nucleases and alkaline phosphatase as compared to the wild type strain. The ds DNase activity of the new mutants was only about 2–12% of that of the wild type strain; thus, the low level of these extracellular enzymes in thenucmutants causes their inability to utilize nucleic acids as the sole phosphorus source. Wild type levels of these enzymes were restored in the complementing heterokaryons capable of full growth on the DNA medium. Data from intercrosses, mutagen sensitivity and spontaneous mutation-frequency studies (as discussed in a subsequent paper) indicated the involvement of thenucgenes in DNA repair and recombination.
Steroid sulphatase in the mouse
Authors: Lam S. T. S. , Polani P. E. , Fensom A. H.
Published: September 2009

A form of the human skin disease, ichthyosis, results from a mutation at the steroid sulphatase locus (STS) on the X chromosome. This locus appears to escape inactivation in the XX female, resulting in the expression of two doses of the STS gene (Shapiro et al. 1978; Crawfurd, 1982). The scurfy mutation in the mouse is thought to be homologous to the human disease (McKusick, 1978), and so should also be due to a steroid sulphatase (STS) deficiency. Our findings in male and female mice suggest that, in contrast to the human, the murine ‘STS’ locus is subject to X chromosome inactivation. However, another interpretation of the results is possible, namely that STS may be coded for by an autosomal gene.
Chromosome rearrangements resulting in increased aneuploid production inSordaria brevicollis
Authors: Bond D. J. , Broxholme S. J.
Published: September 2009

Two spontaneously arising chromosome rearrangements were isolated inSordaria brevicollisfrom one perithecium. These were detected through increased production of black spores in intercrosses of complementing buff spore colour mutants. One was a reciprocal translocation between linkage groups I and II; the other a reciprocal translocation between linkage groups II and VI. In the former case the translocation resulted in frequent non-disjunction generating black spores which were either tertiary or interchange disomics. The frequency of premature centromere division was also increased. In the case of the translocation involving linkage groups II and VI the black spores were formed as a result of adjacent-1 segregation and were probably duplication/deficiency products.

In both rearrangements the breakpoint in linkage group II was, as far as could be judged, in an identical place. This and the fact that they were isolated from a single fruiting body, suggests that the chromosome breakage event arose as a potential lesion, which replicated before the potential break was either restituted, to restore a normal chromosome, or opened, to form the rearrangements.
Segregation of centricY-autosome translocations inDrosophila melanogaster: II. Segregation determinants in females
Authors: Falk Raphael , Rahat Ana , Baker Shula
Published: September 2009

This is a study of the chromosomal segregation patterns in females of 15 Experimental stocks ofDrosophila melanogaster, each carrying one element of a T (Y; 2) with a centric break-point. In each Experimental stock the relative frequency of all eight possible meiotic configurations of four relevant chromosomal elements was followed: an attached-Xchromosome, a multiply-inverted chromosome 2, a free arm of chromosome 2, and a half-translocation element. Although the 15 translocation elements were broken at different sites, there were no basic differences among the Experimental stocks in their segregation patterns. The three two-by-two configurations were the most common. Comparison of this pattern with that of the segregation pattern of stocks similar but for an inversion-free chromosome 2, showed that in the Experimental stocks exchange pairing did not play a significant role in the determination of the segregation pattern.

The results of these experiments, together with the analysis of results from other published studies provide evidence against the model that had been forwarded by Grell. According to this model, chromosomes that did not participate in exchange pairing undergo another pairing cycle, in which total chromosome length is a factor in the determination of segregation.

We support a modified version of Novitski's model of premetaphase chromocenter-like chromosome aggregation. Disjunction of non-exchange chromosomes is regulated by determinants located in the proximal heterochromatin of the sex chromosomes and the autosomes. However, the specificity, especially that of the autosomal determinants, is not high. Thus, if an autosome and a sex chromosome are available, their determinants may interact-to-disjoin by default. More frequently, the determinants of the left-arm autosomal element may interact-to-disjoin with those of the right-arm chromosomal element.
Expression and amplification of the genes for ribosomal RNA in bobbed mutants ofDrosophila melanogaster
Authors: Dutton F. Lee , Krider Hallie M.
Published: September 2009

We have employed stocks bearing clonally derivedXchromosomes to investigate several features of the bobbed mutant syndrome, and the amplification of rDNA genes inD. melanogaster. We report that posterior macroscutellar bristle length correlates well with the rDNA content (i.e. dose ofivs–, or uninterrupted genes) in clonedXderivative strains.X/Omales andX/Xfemales with statistically indistinguishable rDNA contents have virtually identical bristle lengths. This indicates that (with respect to this phenotypic character) the rDNAs in these two genotypes are expressed equally, without apparent sexual dimorphism or dosage compensation. However, the severity of bobbed phenotype in terms of bristle morphology, turgite etching, and delayed eclosion is greater in theXbb/XNO−female than in theXbb/Omale genotype for the alleles examined. We estimate the minimum dose of functioning rRNA genes required for viability at 26 δC to be 70 genes per diploid genome. We have examined the capacity of severalXchromosomes which bear bobbed mutant alleles to compensate inX/Omales, and find that disproportionate replication of these rDNAs does not take place. In contrast, at least one of the non-compensating bobbed alleles does appear to undergo rDNA magnification.
New ara-C resistant mutants of the Chinese hamster ovary cells
Authors: Mishra N. C. , Hinnant Kathryn , Cason Emily
Published: September 2009

Mutants of Chinese hamster ovary (CHO) cell resistant to cytosine arabinoside (ara-C), an inhibitor of DNA synthesis and antitumour drug, have been isolated and characterized both biochemically and genetically. Mutants occurring spontaneously and those induced by treatment with N-methyl-N′-Nitro-N-nitrosoguanidine (MNG), were obtained at a frequency of 0·24 × 10−6 and 3·4 10−6 respectively. The mutants showed a stable ara-C resistant phenotype which was inherited as a dominant trait in genetic crosses. The wild type (CHO K-1) and the mutant (103, 002 and 003) cells showed no differences in the levels of the uptake of ara-C or of its degradation. Results of biochemical studies further excluded the involvement of deaminase, kinase and ribonucleotide reductase as the possible factor(s) in conferring drug resistance to the mutant cells. However, the wild type and mutant DNA polymerases differed in the level of the in vitro incorporation of specific dNMP in the presence of ara-CTP. These data suggested that the wild-type DNA polymerase which becomes error prone in the presence of ara-CTP may cause the drug sensitivity of the wild-type cells and that a change in the mutant enzyme making it resistant (or less prone) to ara-CTP induced errors in dNMP incorporation may control the drug resistance of the mutant cells.
Crossover frequencies within paracentric inversions in maize: the implications for homologue pairing models
Authors: Maguire Marjorie P.
Published: September 2009

Crossover frequencies within three overlapping heterozygous paracentric inversions of differing length in the long arm of chromosome 1 of maize were estimated from cytological data. These frequencies were found to be close to normal for the regions involved and directly proportional to the respective physical lengths of these inversions. It is suggested that if pairs of centres which are specialized to regulate homologous pairing of the region between them exist in this part of the maize genome, they are most probably numerous and widely distributed.
A new allele of microphthalmia induced in the mouse: microphthalmia - defective iris (midi)
Authors: West John D. , Fisher Graham , Loutit John F. , Marshall Michael J. , Nisbet Norman W. , Perry V. Hugh
Published: September 2009

A new allele of microphthalmia (mi) in the mouse was discovered among the progeny of a male that had been treated with the potent mutagen ethylnitrosourea. Homozygotes have white coats, mildly defective bone resorption and small eyes (about 60% of the normal size) with very little pigmentation. The iris and retina are abnormal, there is no vitreous body and iris pigmentation is restricted to a rim around the pupil. No haematopoietic defect was detected. Genetic studies showed that the mutation is linked to lurcher (Lc) on chromosome 6 and crosses withMiwh/ + andmi/ + mice indicate that the mutation is allelic with these two alleles of the microphthalmia (mi) locus. We designate the new allele microphthalmia-defective iris (midi). Somemidi/+ heterozygotes (including the original mutant animal showed a bright ‘red-reflex’ when light was shone directly into the eye and this may have been caused by reduced choroidal pigmentation. Otherwisemidi/ + mice appeared normal. Themidi/micompound heterozygotes had white coats, small eyes, and small teeth; bone resorption was more severely defective than inmidi/mihomozygotes. The osteopetrosis was corrected by treatment ofmidi/mimice with parentalmi/ + bone marrow which suggests that the defect is intrinsic tomidi/mimarrow cells. The coats ofmidi/Miwhcompound heterozygotes were white; the irises were more symmetrical and iris pigmentation was less severely reduced than inmidi/midihomozygotes but pupil dilation appeared to be restricted. Partial complementation occurred in themidi/Miwhcompound heterozygotes with respect to eye size, which was usually near normal.
Preferential transmission in wild common shrews (Sorex araneus), Heterozygous for Robertsonian rearrangements
Authors: Searle J. B.
Published: September 2009

Data from foetal and weanling studies suggest that Oxford race metacentrics kq and no, but not pr, are transmitted preferentially from Robertsonian heterozygote common shrews collected from the Oxford area. These results suggest a possible mechanism for the maintenance of the Robertsonian polymorphism in that area.
A restriction and modification model for the initiation and control of recombination inNeurospora
Authors: Catcheside D. E. A.
Published: September 2009

It is hypothesized that the products of Neurosporarec+genes mask recombinators such ascogby modifying DNA and that unmodified recombinators act as recognition sites for an endonuclease with scission properties like those of the type I restriction enzymes found inE. coli. These cut the DNA in both strands at some variable distance from a recognition site. Repair of a two strand gap initiated in this way would require DNA synthesis using the information contained in the homologous DNA duplex, leading to gene conversion. Crossing over could follow from resolution of two Holliday structures formed during gap repair. The hypothesis explains the polarity in the frequency of conversion events across genetic loci, the observation that chromosomes carrying recombinators are more often converted than is the homologue, and how recombinators can initiate conversion at a distance, as suggested by the pattern of conversion events in thehis-3locus in crosses heterozygous for the translocation TM429.
An assessment of the homoeology of six Agropyron intermedium chromosomes added to wheat
Authors: Forster B. P. , Reader S. M. , Forsyth S. A. , Koebner R. M. D. , Miller T. E. , Gale M. D. , Cauderon Y.
Published: September 2009

Six wheat/Agropyron intermedium addition lines are described on the basis of their phenotype and biochemical markers. An assessment of homoeology of each addition chromosome is made. Chromosome morphology, plant phenotype, isozyme and protein studies are compared with similar data for other wheat/alien addition lines and other members of the Triticeae. These comparisons give consistent results and it is concluded that addition lines L1, L2, L3, L4, L5 and L7 carry Agropyron chromosomes of homoeologous groups 7, 3, 1, 4, 5 and 6 respectively. This agrees with previously published work with one exception: the L5 chromosome belongs to homoeologous group 5 and not group 2 as proposed by Figueiras et al. (1986).
The influence of mutations on chromosome 17 upon the segregation of homologues in female mice heterozygous for Robertsonian translocations
Authors: Ruvinsky A. O. , Agulnik S. I. , Agulnik A. I. , Belyaev D. K.
Published: September 2009

The influence of mutations in chromosome 17 upon the segregation of the metacentric and acrocentric homologues in the progeny of female mice heterozygous for Robertsonian translocations Rb(8.17)11em and Rb(16.17)7Bnr was studied. Genetic analysis indicated that the portion of non-Rb (normal karyotype) progeny from mothers heterozygous for mutations tf, qk, t12 was weakly different from the 50% Mendelian expected level (55–57%). Introduction of mutations T, FuKi, Fu, t6 into the female genotype caused a stronger segregation distortion and an increase in the portion of progeny with normal karyotype (63–67%). From the data on embryonic mortality and cytogenetic observations it is concluded that a distortion of equal transmission arises before M II of meiosis. Consequently, the preferential distribution of the metacentric chromosome to the polar body during the first meiotic division is relevant to the observed segregation distortion.
Heritability of body size in a natural population of the Great Tit (Parus major) and its relation to age and environmental conditions during growth
Authors: Noordwijk A. J. Van , Balen J. H. Van , Scharloo W.
Published: September 2009

We have analysed data on weight and tarsus length collected during a long-term study of natural populations of Great Tits to evaluate the relative importance of genetic variation in body size. Some of our data were collected over a 25-year period, and therefore include a relatively large sample of naturally occurring environmental conditions. An overall heritability estimate calculated from the uncorrected mean weights of breeding birds amounts to 0·5. This estimate is unlikely to be influenced by resemblance in environmental conditions between relatives. Heritability estimates based on the size of fledglings vary between zero and the value for adults, depending on the environmental conditions during growth. If the feeding conditions for the nestlings are poor, no resemblance between parents and offspring is observed. Selection against small nestlings acts strongly on the environmental variance. This is concluded from the higher heritability estimates in the same cohorts after survival for at least three months after fledging, compared to measurements on nestlings. Such selection acting differentially on the genetic and environmental components of the phenotypic variance has important consequences for our ability to make predictions of phenotypic change from measured natural selection. Nevertheless, the amount of genetic variation would allow rapid response should selection on adult size occur.
Cytogenetic analysis of theechinoid (ed), dumpy (dp)andclot (cl)region inDrosophila melanogaster
Authors: Szidonya János , Reuter Gunter
Published: September 2009

The chromosomal region surrounding theed, dpandclgenes has been studied cytogenetically (24–26 on 2L chromosome). It contains threeMinutesand a haplo-sterile function. For isolation of deficiencies and mutations these haplo-insufficient functions were covered by an insertional translocation of 24D4-25F2 into the X chromosome, or by tandem duplications. 112 lethal and visible mutations induced by EMS and X-rays have been localized by deficiency mapping to 20 subregions. They specify 42 loci in a 48 band interval consistent with the notion that most of the bands encode a single lethal function. Thedp, DTS, tkvand suppressor/enhancer loci for position-effect variegation were studied in detail. A dominant suppressor function was localized within the structural part of thedpcomplex. New non-conditional lethals have been isolated for theDTSlocus. Complementation analysis with the previously identified dominant heat-sensitive alleles places the site for heat sensitivity in the middle of the locus. Two haplo-abnormal enhancers of position-effect variegation were localized in the region 25F2–26A1. A triplo-abnormal suppressor function maps to 26B2–5; 26B9. The dose-dependent functions of these loci were studied by the use of deficiencies and duplications.
Contribution of recombinants produced by female flies heterozygous forEst-α alleles to genie variation ofDrosophila virilis
Authors: Tsuno Kendo
Published: September 2009

With 12 alleles at theEst-α locus ofDrosophila virilis, 44 genotypes of females heterozygous for a pair of them were constructed, and about 4 × 104of their F1progenies per genotype were electrophoretically examined. Eighty-three variants different from both of their parental alleles were obtained from a total of 2·0 × 106progenies. Statistical analysis suggested most of their variants to be recombinants. And no null or inactive allele, of which frequency is several percent in natural populations, appeared in 11·6 × 104progenies from females heterozygous for active alleles. These results suggest that the high variation of theEst-α locus in this species is generated by recombinants from female heterozygotes.
Fertility of sperm from t/ + mice: evidence that + − bearing sperm are dysfunctional
Authors: Olds-Clarke Patricia , Peitz Betsy
Published: September 2009

Male mice carrying one complete t haplotype transmit it to virtually all offspring. This implies that either the sperm carrying the t haplotype have an advantage in fertilization, or that the sperm not carrying a t haplotype are dysfunctional. To distinguish between these possibilities, epididymal sperm from tw32/ + and congenic + / + males were artificially inseminated into the uterus of T / + females, and the transmission ratio determined from the phenotype of the offspring. After artificial insemination (AI) of sperm from tw32/ + males, the mean ratio was 0·95 (3 experiments, 5 litters), demonstrating that the transmission ratio remains high after AI into the uterus. After AI of a mixture of equal numbers of motile sperm from tw32/ + and congenic + / + males, the mean ratio was 0·22 (6 experiments, 8 litters). These results suggest that sperm carrying a t haplotype from t/ + males are not superior to sperm from + / + males, and therefore imply that sperm not carrying a t haplotype from t/ + males are dysfunctional.
Chromosomal location of peptidase, PEPT-1, genes in Triticum aestivum var. Chinese Spring
Authors: Golenberg Edward M.
Published: September 2009

Ditelocentric accessions of the Chinese Spring cultivar of Triticum aestivum were analysed electrophoretically for peptidase (PEPT) and amino peptidase (AMP = LAP) activity. Isozymic activity was missing in the accessions CSDT6AS and CSDT6BS when stained for PEPT. This was taken as evidence that the structural genes encoding these isozymes are located on the long arms of chromosomes 6A and 6B. These genes have been named Pept-A1 and Pept-B1, respectively. Isozymic activity was missing in the CSDT6BL accession when stained for AMP. This result reconfirms the previously published location of the gene Amp-B1 on the short arm of chromosome 6B and demonstrates that the two sets of loci are clearly different.
Persistence of a lethal t haplotype in a laboratory stock of outbred mice
Authors: Silver Lee M. , Lukralle Deborah , Garrels James I. , Willison Keith R.
Published: September 2009

A cryptic, lethal t haplotype (named tLmb) has been discovered in the non-inbred MF1 laboratory stock of mice. Detailed genetic and molecular studies demonstrate a close relationship between tLmb and a well-studied t haplotype, t6, previously extracted also from a laboratory stock. It appears likely that t6 is an aberrant t haplotype derived by recombination from a tLmb-like ancestral chromosome. The persistence of tLmb through 40 years of random breeding in a laboratory stock indicates that high transmission ratio distortion is sufficient to overcome the deleterious effect of a recessive lethal gene in a mouse population.
The tabby locus (Ta) in the mouse: its site of action in tail and body skin
Authors: Pennycuik Pamela R. , Raphael Kathryn A.
Published: September 2009

By means of grafting skin in which the epidermis of one genotype was combined with dermis of another to a nude host, we have shown that the effect of the mutant at the tabby (Ta) locus on follicle initiation in tail skin was not confined to either the epidermis or the dermis, that the effect ofTaon the morphology of body hairs was determined by the epidermis but that the close proximity of epidermis of a different genotype also affected body hair morphology.
Protein and amino acid composition of hair from mice carrying the naked (N) gene
Authors: Raphael Kathryn A. , Marshall R. C. , Pennycuik Pamela R.
Published: September 2009

The protein and amino acid compositions of hair from mice carrying the naked (N) gene were compared with those of wild-type (+ / +) mouse hair using two-dimensional polyacrylamide gel electrophoresis and amino acid analysis. In samples obtained from N /+ mice, the numbers of positions of the low-sulphur (LS), high-sulphur (HS) and high tyrosine (HT) protein spots were indistinguishable from those observed in + / + samples but the amount of HT protein was reduced in N / + hair. In samples obtained from N /N mice the protein spots were fewer than, and perhaps different from, those in samples from the other two genotypes; all protein classes were represented but the HS and HT protein content appeared to be less than that in + / + and N / + hair. Amino acid analyses of hair samples showed that the HS contents of + / + and N / + hair were approximately the same, whereas the HT protein content of N / + hair was about half that in + / + hair. N / N hair contained less half-cystine and tyrosine than + / + and N / + hairs, but because the contents of proline, threonine and glycine were unexpectedly high, it appears that protein components of unusual composition are present in N / N hair. It was concluded that the gene at the N locus is involved only indirectly in the synthesis of the structural proteins found in mouse hair.
A model of extranuclear genomes and the substitution rate under within-generation selection
Authors: Takahata Naoyuki
Published: September 2009

A single locus model of extranuclear genomes is developed under the assumption of the complete action of within-generation drift which is caused by random transmission of multiple copy genomes during cell division in a generation. Within-generation drift segregates different copy genomes in a cell into different cells, resulting in homoplasmic cells. Under some conditions, the present model reduces to that for haploid nuclear genomes. A point overlooked in previous models is that the multiplicity also admits of the possibility of selection occurring within a cell or between cells in an individual (within-generation selection). If there is selection mediated by, for instance, differential proliferation of genomes, then a haploid model no longer explains the dynamics of extranuclear genomes. Rather a model analogous to biased gene conversion at a single locus (Nagylaki, 1983; Walsh, 1983) is more appropriate. An application of this model to either the fixation probability or substitution rate of new mutations shows that strictly maternal inheritance does not allow the fullest use of mutations, as it obscures the effect of within-generation selection. But if there is appreciable paternal contribution, within-generation selection could be a strong evolutionary force to which nuclear genomes are never exposed.
Genetic analysis of the sexual dimorphism of glass inDrosophila melanogaster
Authors: Birchler James A.
Published: September 2009

A modifier locus is described that alters the level of phenotypic expression of the third chromosome mutant glass in a sex specific manner. Alternative alleles either confer a sexually dimorphic level of pigment in glass mutants, with the male being greater, or cause similar expression in the two sexes. The alleles are indistinguishable in females but produce the respective phenotypes in males. The gene maps to the tip of theXchromosome at position 0·96 ± 0·11. Cytologically, the locus is present between polytene bands 3A6–8 and 3C2–3 as determined by its inclusion in translocatedXsegments inw+Y,Dp(l;2)w70h31andDp(l;3)w67k27The dimorphic allele is dominant to the nondimorphic condition in males heterozygous for an insertional translocation carrying the dimorphic allele and a normal chromosome carrying the nondimorphic form. The dimorphic allele in two doses in males does not exhibit a dosage effect. The modifier phenotype is unaffected in twoXflies by the presence of the transformer mutation.
Antagonism between novobiocin and coumermycin A1inBacillus subtilis
Authors: Gadó István , Széll Valéria , Büki Kálmán , Szvoboda György
Published: September 2009

When combinations of inhibitors acting on the subunit B of DNA gyrase were tested inBac.subtilisstrains, the growth-inhibiting effect of novobiocin was specifically antagonized by subinhibitory concentrations of coumermycin A1. An antagonism in the opposite direction was not observed.

Two alternative models are proposed, where the supercoiling decrease caused by novobiocin is antagonized by coumermycin.

This phenomenon seems to be characteristic of theBac.subtilisspecies.
The genetic correlation between characters maintained by selection, linkage and inbreeding
Authors: Lande Russell
Published: September 2009

Mutation is modelled in two quantitative characters under separate genetic control in a large population. A bivariate pattern of selection acts to correlate the characters and, without pleiotropy, their genetic correlation is due entirely to linkage disequilibrium. Data on spontaneous mutation, the effective number of genes, and the intensity of natural selection on quantitative characters are used to evaluate the models. It is concluded that, even when selection favors a high correlation between the characters, with random mating and no linkage between loci influencing different traits the genetic correlation between characters is likely to be small in magnitude. A genetic correlation of large magnitude can be maintained only if the loci influencing different characters are tightly linked, or there is a high level of inbreeding in the population created by frequent mating between closely related individuals.
Suppression of ribosomal RNA genes inDrosophila melanogaster
Authors: Kalumuck K. E. , Procunier J. D.
Published: September 2009

The rDNA of fiveYchromosome mutants was examined with respect to their insert free (In−) repeat type multiplicity. The In− repeat number of each mutant was correlated with its hemizygousbobbedphenotype and additivity with anXNObobbed(bb) mutant. Four of these mutants showed a direct relationship between their In− frequency, hemizygousbbphenotype and additivity tests. A fifth mutant,bb1–4, had a sufficient number of In− repeats to ensure viability to the late pupal stage and show additivity; however, the In− repeats genetically behaved as a complete rDNA deletion. Possible mechanisms resulting in the suppression of thebb1–4In− repeats are discussed.
The detection of deleterious selection using ancestors inferred from a phylogenetic history
Authors: Golding G. Brain
Published: September 2009

The widespread use of restriction endonucleases and DNA sequencing provides a wealth of data on the genetic structure of natural populations. From such data, detailed phylogenies can be constructed and qualitatively different kinds of mutational and substitutional processes can be studied. A neutral model can be constructed to describe the frequencies of sequence haplotypes according to the haplotypes from which they arose and the types of substitution that distinguish them. One feature of such a model is that it examines the ancestors of various sequences. Deleterious selection against a character has a distinct effect on descendant sequences. Individuals containing many deleterious characters leave few or no descendants because these individuals are quickly eliminated by selection. Hence, such a model lends itself to the study of deleterious selection. It is possible to determine if selection is required by searching for any set of mutation rates that can explain an observed set of data. Simulations of artificial populations without selection suggest that this method seldom indicates selection when none is present. Furthermore, recent recombination events between the sequences do not induce false indications of deleterious selection. The method may, however, require relatively large simple sizes in order to accurately reflect the true nature of populations. The method is often very conservative and may not indicate selection when it is, in fact, present.
Changes in genetic parameters under restricted index selection
Authors: Mortimer Suzanne I. , James J. W.
Published: September 2009

The ability of restricted selection indices to prevent genetic change in a restricted trait over several generations of selection was studied using deterministic computer models. Four loci, two affecting each trait independently, and two pleiotropic loci, one affecting each trait in the same direction, and one with opposite effects, were modelled. In general, continued effectiveness of the restriction was achieved only when the restricted trait was affected by only one locus. In some conditions (equal gene frequencies), an independent locus and one pleiotropic locus affecting the restricted trait allowed maintenance of the restriction. The results suggest that long-term restriction may be very difficult without re-estimation of parameters.
Inheritance of a meiosis I error expressed in mouse oocytes and modulated by a maternal factor
Authors: Beermann Friedrich , Jenderny Jutta , Hummler Edith , Hansmann Ingo
Published: September 2009

NMRI/Han mice ovulate significant numbers of diploid oocytes after gonadotrophin stimulation, most of them arrested at metaphase I. In contrast, females from other mouse strains ovulate only oocytes having completed meiosis I. We investigated the heritability of the trait Dipl I by analysing F1hybrid females from crosses between the sensitive NMRI/Han stock and two mouse strains (C3H/HeHan and BALB/c) considered as non-sensitive, and females from backcrosses to NMRI/Han males (only crosses with C3H/HeHan). The results show (1) that the trait Dipl I is inheritable; (2) that an X-chromosomal (location proximally from the X–Y pairing region) or autosomal recessive mode of inheritance is excluded; and (3) that the expression of the trait, measured as frequency of diploidy, is modulated by a maternally transmitted factor.