bluuebunny/crossref_metadata_2025 huggingface dataset:
A mathematical model of extranuclear genes and the genetic variability maintained in a finite population
Authors: Takahata Naoyuki , Maruyama Takeo
Published: September 2009

A mathematical theory of population genetics accounting for the genes transmitted through mitochondria or chloroplasts has been studied. In the model it is assumed that a population consists ofNmmales andNffemales, the genetic contribution from a male is β and that from a female 1 – β, and each cell line containsneffective copies of a gene in its cytoplasm. Assuming selective neutrality and an infinite alleles model, it is shown that the sum (H) of squares of allelic frequencies within an individual and the corresponding sum (Q) for the entire population are, at equilibrium, given by

and

where ρ = 2β(1−β),Ne= {β2/Nm+(1−β)2/Nf}−1, λ is the number of somatic cell divisions in one generation, andvis the mutation rate per cell division. If the genes are transmitted entirely through the female the formulae reduce to Ĥ ≃ 1/(1 + 2nv) andQ^≃ 1/{1 + (2Neλ+ 2n)υ}. Non-equilibrium behaviours ofHandQ^are also studied in the case of a panmictic population. These results are extended to geographically structured models, and applied to existing experimental data.
Exchange between the ribosomal RNA genes ofXandYchromosomes inDrosophila melanogastermales
Authors: Maddern R. H.
Published: September 2009

The genes coding for the 18s and 28s ribosomal RNA (rRNA) are present on both theXandYchromosomes ofD. melanogasterat a site known as thebobbedlocus. Exchange was observed in males between a normally orientatedXandYchromosome (Dp(1; 1)scv1andBSY y31d) with a frequency of 0·079%. One-quarter (7 in 27) of these exchange products between two + chromosomes which both carried sufficient rRNA genes for abb+phenotype exhibited abbphenotype. Evidence is presented that one-half, and possibly all, of the exchanges involved the repetitivebbgenes. These results together with those reported by Palumbo, Caizzi & Ritossa (1973) imply that the repeatedbbgenes of either (or both) theXorYchromosome are not arranged with uniform polarity and, further, that spermatogonial exchange between theXandYchromosomes may be restricted to thebbloci.
A mathematical study on the distribution of the number of repeated genes per chromosome
Authors: Takahata Naoyuki
Published: September 2009

I develop a mathematical model which can account for a distribution of the number of repeated genes per chromosome under the joint effects of sister chromatid exchange (SCE), inter-chromosomal crossing-over (ICC), and selection. The model can be applied not only to the cases of small gene clusters but also to multigene families. Based on this model, an appropriate mathematical formula is derived and used to obtain the equilibrium distribution. Assuming stabilizing selection and two simple schemes concerning SCE and ICC, I numerically calculate the equilibrium distribution and compare the result with observations on frequencies of single and triple α-haemoglobin genes in primates. It is also shown that if SCE and ICC occur according to the same probabilistic law, the distinction between them does not make much sense in the equilibrium distribution.
Direct and correlated responses to selection for plasma thyroxine levels in mice
Authors: Tilakaratne N. , Hill W. G. , Land R. B.
Published: September 2009

Selection was carried out in mice for concentration of thyroxine hormone (T4) in plasma of males at 11 weeks of age over seven generations. Selection was practised for high level in two replicate lines and for low level in two replicate lines, and there was an unselected control. There was a response in both directions, and the divergence of 12·4 ng/ml observed in generation seven was equivalent to about 20% of the base population mean or nearly one phenotypic standard deviation. The realised heritability was 9%.

Plasma thyroxine level had a repeatability of 0·54 when two measurements were made 24 h apart. The responses made at 11 weeks in males were also evident in both males and females at 5 weeks. Plasma tri-iodo thyronine (T3) concentrations showed a correlated response almost as large, relative to the mean level, as that in T4.

Positive correlated responses were observed in total weights of the litter at 12 days, and in individual weights at 3, 6 and 9 weeks, the responses in the early weights being greater relative to their mean. The results suggest that the correlated weight changes were due to genetic responses in maternal characteristics, probably milk production, rather than individual growth.
A Method for the Selection of Deletion Mutations in the L-Proline Catabolism Gene Cluster ofAspergillus nidulans
Authors: Arst Herbert N. , Jones Susan A. , Bailey Christopher R.
Published: September 2009

Interest in the selection of mutations affecting L-proline catabolism inAspergillus nidulansis heightened by the involvement of one of the very few examples of a cluster of functionally related genes in an eukaryote and by an increasing awareness of the biological phenomena in which proline and proline catabolism participate. ThesasA-60 (semialdehyde sensitive) mutation inA. nidulansresults in toxicity of catabolic precursors of L-glutamic γ-semialdehyde (or its internal Schiff base L-Δ1-pyrroline-5-carboxylate) and succinic semialdehyde, apparently without affecting the catabolic pathways concerned. AssasA-60 is unlinked to theprngene cluster, specifying the gene products necessary for L-proline catabolism and as L-proline, a precursor of L-glutamic γ-semialdehyde, is highly toxic tosasA-60 strains, this forms the basis of a powerful positive selection technique for obtaining a number of types ofprnmutations. Many of theseprnmutations can be directly classified according to the gene product(s) affected on the basis of growth phenotype with respect to L-arginine and L-ornithine utilization, proline-dependent resistance to certain toxic amino acid analogues and effect on supplementation of proline auxotrophies. The availability of both a positive selection technique and an extensive nutritional screening system has enabled the identification of fourteen spontaneous deletion mutations, recognized as extending into theprnB gene, specifying the principal L-proline permease, and into at least one otherprngene. These deletion mutations have been partially characterized both genetically and biochemically. In particular their use has greatly facilitated fine-structure mapping of theprncluster and aided studies of the regulation ofprngene expression.
Unstable drug resistance inStaphylococcus aureusM4
Authors: Grubb W. B. , Annear D. I.
Published: September 2009

Staphylococcus aureusM4 has chromosomal resistance to streptomycin, plasmid-borne resistance to penicillin and tetracycline and probably chromosomal inducible erythromycin resistance. It also has constitutive erythromycin resistance which is unstable and linked to kanamycin and lincomycin resistance and the ability to produce a diffusible pigment. Variants have been isolated which have stable kanamycin, lincomycin and constitutive erythromycin resistance and these do not produce the diffusible pigment. In transduction experiments kanamycin, lincomycin and constitutive erythromycin resistance were always co-transduced together with streptomycin resistance. The transduction frequencies were approximately 100 times higher with the stable variants compared with the parent. The transductants, irrespective of the donor used, all had stable resistance and did not produce the diffusible pigment. Although transduction with UV-irradiated transducing lysates was characteristic of a plasmid, no corresponding plasmid DNA has been detected.
The satellite DNAs of Drosophila simulans
Authors: Lohe A. R.
Published: September 2009

The resolution of antibiotic-CsCl gradients enabled an examination of the satellite DNAs in the nuclear DNA of Drosophila simulans. Of the eight distinct satellite DNAs which were detected, four band at almost the same buoyant density in CsCl but can be resolved in netropsin sulphate-CsCl gradients. Each consists of a repeated sequence which, in five of the satellites, is shown to be arranged in tandem for long regions of the chromosomal DNA. One satellite (1·697 g/ml in CsCl) contains repeated sequences interspersed with other sequences. The satellite DNAs were compared with the satellite DNAs known to be present in the sibling species, D. melanogaster. The two species have different overall complements of satellite DNAs, but one satellite (1·672 g/ml) may be identical.
Chromosomal locations ofcatA, pobA, pcaA, dcuandchugenes inPseudomonas aeruginosa
Authors: Matsumoto Hideki , Nakazawa Teruko , Ohta Shin , Terawaki Yoshiro
Published: September 2009

Eleven catabolic markers have been located on the chromosome ofPseudomonas aeruginosaPAO using FPS-mediated conjugation and G101 transduction. Most of these markers are located in the region 20–35 min, and the remainder in the region later than 60 min. Fourchugenes concerned in the sequential degradation of choline to glycine are closely linked.
Further observations on intragenic recombination inDrosophila melanogaster
Authors: Hilliker Arthur J. , Chovnick Arthur
Published: September 2009

This report examines several issues bearing upon intragenic recombination in higher eukaryotes. The fine structure data accumulated in our analysis of the genetic organization of the rosy locus inDrosophila melanogaster. Firstly, we confirm that a conversion event has a markedly less than 50% probability of resulting in flanking marker exchange, a finding consistent with more recent analyses of the availableSaccharomycesdata (e.g. Fogelet al.1978). As reported earlier, co-conversion of recombinationally separable sites within therosylocus occurs (McCarron, Gelbart & Chovnick, 1974). In this report, we demonstrate that the frequency of co-conversion is inversely proportional to the distance between co-converting sites. As in fungi, real conversion frequency differences are observed amongrosymutant alleles, and the data suggest that there may be a relationship between allele conversion frequency and map position. UnlikeNeurosporaandSaccharomyces, only one flanking marker exchange class is recovered from any given mutant heteroallele recombination experiment. In this respect, theDrosophilasystem resemblesAspergillus. As inNeurosporaandSaccharomyces, rosylocus intragenic recombinants associated with flanking marker exchange exhibit interference with crossing over in adjacent regions, while no interference is seen among recombinants exhibiting parental flanking markers. Finally, experimental results are discussed which demonstrate the occurrence of postmeiotic segregation inDrosophila. These analogies betweenDrosophilaand fungi provide further evidence in support of the notion that eukaryotes share common molecular mechanism(s) of meiotic recombination.
The recovery and preliminary examination of a temperature sensitive suppressor of thecryptocephalmutant ofDrosophila melanogaster
Authors: Sparrow John C.
Published: September 2009

The recovery of two EMS induced mutations which are dominant suppressors of the lethality ofcryptocephalinDrosophila melanogasterare described. One of these mutationsSu(crc)1is described in detail. It maps very close tocryptocephalat 54·7 on the second chromosome and its suppression of cryptocephal is temperature-sensitive. Temperature shift experiments show that the temperature-sensitive period is from before the pupariation until 12 h post pupariation. The temperature-sensitive period ofSu(crc)1is discussed in relation to the expression ofl(2)crc, head eversion and the timing of pupal chitin synthesis.
Evidence for Two Regions in the MousetComplex Controlling Transmission Ratios
Authors: Styrna Józefa , Klein Jan
Published: September 2009

Four newthaplotypes,tTu1throughtTu4, are described, three of them derived from thetw12tfhaplotype and one (tTu4) from thetw2haplotype. ThetTu1andtTu4haplotypes cause taillessness inT/tTu1orT/tTu4heterozygotes, lack the lethality factor, weakly suppress recombination in theT−H−2interval, and are transmitted to offspring fromtTu/+ males at nearly Mendelian ratios. ThetTu3haplotype resemblestTu1andtTu4except for the fact that theT/tTu3heterozygotes have normal-length tails. ThetTu2haplotype probably carries the lethal factor oftTu12tf, suppresses crossing-over in theT-H-2andtf-H-2intervals, and displays a slightly subnormal transmission ratio. In the compound heterozygotetTu1/tTu2, the male transmission ratio of thetTu1chromosome is close to that of the originaltTu12tfhaplotype. A similar effect is observed in thetTu3/tTu2heterozygote. This observation is interpreted as evidence for two regions within thetcomplex controlling the male transmission ratios. One of the regions is close to the tail-modifying region, the other is close to the lethality factor. Our findings parallel closely those made in the segregation distorter system inDrosophila.
Lens opacity: a new gene for congenital cataract on chromosome 10 of the mouse
Authors: Lyon Mary F. , Jarvis Susan E. , Sayers Irene , Holmes Roger S.
Published: September 2009

Mouse mutant genes which result in defects similar to those of medical importance in man may be of value as models for the study of the defect concerned. We report here a new gene causing congenital cataract in the mouse, which may be useful in the understanding of cataract in man.

A further point of interest is that Kratochvilova & Ehling (1979) have recently developed a new method of measuring increased mutation rates in the mouse, by examining offspring of animals treated with mutagens for the presence of cataracts due to mutant genes. For the purposes of this test it is valuable to have information on the number and map position of loci which can mutate to give cataracts.
Allelic variation at several different genetic loci determines the major urinary protein phenotype of inbred mouse strains
Authors: Hainey Sheila , Bishop J. O.
Published: September 2009

We have examined the major urinary protein (MUP) phenotype of three inbred mouse strains by one-dimensional isoelectric focusing in acrylamide gels. Each strain gave a distinct pattern of major and minor bands. In the three strains together, seven major and about seven minor bands were observed. F1 phenotypes were intermediate. F2 phenotypes can be explained by recombination between allelic variants at four or more different genetic loci. We propose that variation in MUP phenotype is due in fact, to allelic variation at approximately seven structural gene loci, some of which are linked on chromosome 4. The remainder may or may not be linked to these.
Linkage disequilibrium, genetic distance and evolutionary distance under a general model of linked genes or a part of the genome
Authors: Takahata Naoyuki
Published: September 2009

A general model of linked genes or a part of a genome is proposed which enables us to study various problems in molecular population genetics in a unified way. Several formulae with special reference to the linkage disequilibrium and genetic distance are derived for neutral mutations in finite populations, based on the method of diffusion equations. It is argued that the model and formulae are useful particularly when observations are made in terms of DNA sequence.
Genetic analysis of thetw73haplotype of the mouse using deletion mutations: evidence for a parasitic lethal mutation
Authors: Babiarz Bruce , Garrisi G. John , Bennett Dorothea
Published: September 2009

Matings between mice bearing the dominant deletionThpand mice segregating for thetw73haplotype failed to produce the expected viable tailless (Thp/tw73) progeny. Histological analysis of litters fromThp/ + × + /tw73matings revealed an abnormal class of embryos which failed to implant normally between days 6·5 and 7·5 of gestation, and were indistinguishable fromtw73/tw73homozygotes.Thphomozygotes displayed a different lethal phenotype, failing to successfully make the transition from morula to blastocyst at day 3·5. These studies indicate that the mutation responsible for thetw73implantation defect maps within theThpdeletion. Sincetw73is viable with another deletion,Torl, thetw73defect must occur in the region of non-overlap betweenThpandTOrl. The possibility that thetw73-associated implantation defect is a parasitic lethal mutation (p), mapping to the proximal part of thetw73chromosome, is discussed.
The relationship between heterochromatic homology and meiotic segregation of compound second autosomes during spermatogenesis inDrosophila melanogaster
Authors: Hilliker Arthur J. , Holm David G. , Appels R.
Published: September 2009

In this report we examine the meiotic segregation of compound second autosomes sharing varying extents of heterochromatic and euchromatic homology. The second chromosome heterochromatin does not appear to influence the random meiotic segregation of compound second autosomes during spermatogenesis; however, the proximal euchromatin is implicated in male meiotic pairing. We conclude that male autosomal meiotic pairing sites are specific euchromatic chromosomal regions.
Mutants affecting amino acid cross-pathway control inNeurospora crassa
Authors: Barthelmess Ilse B.
Published: September 2009

Arginine-requiring mutants ofNeurospora crassawere isolated using a strain partially impaired in an enzyme of the arginine pathway (bradytroph). Among these, five strains were found which carry mutations at a new locus,cpc-1+. The recessivecpc-1alleles interfere with the cross-pathway control of amino acid biosynthetic enzymes. The enzymes studied, three of arginine and one each of histidine and lysine biosynthesis, fail to derepress under conditions which normally result in elevation of enzyme concentration, namely arginine, histidine or tryptophan limitation. Enzymes not involved in amino acid biosynthesis are still able to derepress in the presence ofcpc-1. In wild-type backgound, i.e. with the bradytroph replaced,cpc-1strains lose the original arginine-requirement.cpc-1mutations confer sensitivity of growth to 3-amino-1,2,4-triazole.
The extent to which gene conversion can change allele frequencies in populations
Authors: Lamb B. C. , Helmi S.
Published: September 2009

The gene conversion parameters which affect allele frequencies in populations are defined, and their ranges and typical values are given for several genera of fungi, where meiotic octads and tetrads provide the best information on conversion. Both gene conversion and disparity in direction of conversion are common. Data fromAscobolus immersusshow that conversion properties are largely stable with time, but can be changed environmentally and by genetic conversion control factors. Equations are given for the interactions of selection, mutation and gene conversion in determining equilibrium frequencies. Numerical examples, using typical values of conversion parameters from the fungal data, show that for alleles which are selectively neutral or have very low selection coefficients, conversion will often have very large effects on their equilibrium frequencies and may lead to fixation. Where selection coefficients are higher, conversion has major effects on the frequencies of deleterious recessive alleles, but lesser effects on deleterious dominant alleles: a critical comparison is that ofswith 2y. The available estimates for conversion parameters (at least in fungi) are of a magnitude to make gene conversion an important factor in evolution.
A computer model of speciation by founder effects
Authors: Charlesworth B. , Smith D. B.
Published: September 2009

A computer model of a two-locus genetic system with epistatic selection was used to investigate factors influencing the probability of the origin of reproductive isolation, due to a genetic revolution following a founder event (Mayr, 1954; Carson, 1975). Restricted population size can sometimes cause such a system to drift from one equilibrium to another, which can result in loss of fitness to hybrids with the ancestral population. The chance of such an event was found to be low unless the bottleneck in population size associated with the founder event was preceded by many generations of relaxed selection. It is highest when the bottleneck is not prolonged and when the population size during the bottleneck is not too small. It seems to be difficult to achieve a high degree of reproductive isolation in one step by this method, and it is concluded that it is unlikely to be a major cause of rapid speciation, although it could be a contributory factor.
Non-random X-chromosome inactivation in the mouse: difference of reaction to imprinting
Authors: Falconer D. S. , Isaacson J. H. , Gauld I. K.
Published: September 2009

Selection for increased and for decreased expression of the sex-linked gene brindled (Mobr) in heterozygous females produced two lines with non-randomXchromosome inactivation. In the High line theXchromosome marked by brindled was active in about 60% of cells, while in the Low line it was active in about 25% of cells. The whole of the difference was caused by the chromosomes carrying brindled: neither the unmarkedXchromosome nor the autosomes were differentiated. There was a positive correlation between the expression of brindled in daughters and mothers. This was probably not caused by residual genetic variation, but was more probably a maternal effect similar to that described by Cattanach & Papworth (1981). On this assumption the daughters' scores were adjusted to a standard maternal score. Enzyme assays on females doubly heterozygous for brindled and for the sex-linkedPgk-1locus proved that the percentage of brindled in the coat provided an accurate measure of theX-inactivation proportions in the blood, liver and kidney. The accuracy was improved by adjustment for maternal score. In the selection lines, brindled was always inherited from the mother. When brindled was transmitted by male parents the probability of activation of its chromosome was increased by 8 percentage points in the High line and 18 in the Low line. This effect of the parental source is much greater than has previously been reported. The responses to selection can be interpreted in terms of theXcelocus controlling the activation probability, different alleles on the chromosomes carrying brindled being selected in the two lines. If this interpretation is correct, the alleles on one or both of the chromosomes carrying brindled were different from any of the three known alleles. The different effects of male transmission in the two lines can be described as a difference between the two chromosomes in their reactions to imprinting. This difference might possibly also be due to theXcelocus.
Genetic basis of susceptibility to splenic lipofuscinosis in mice
Authors: Crichton D. N. , Shire J. G. M.
Published: September 2009

Spleens with black pigment in them were found in 4–57% of mice from 17 stocks, all sublines of C57BL or with significant C57BL ancestry. Splenic lipofuscinosis was absent from 16 stocks, including three C57BL/6By × BALB/cBy recombinant - inbred lines. Progeny testing showed all C57BL/6J mice to be equally likely to develop black spleens. The penetrance of lipofuscinosis differed between sublines but not between the sexes or between laboratories. Susceptibility to lipofuscinosis showed dominant, autosomal, inheritance in F1 hybrids. Observations on backcrosses and on recombinant inbred lines and their intercrosses indicated the existence of two genetic factors. Splenic lipofuscinosis was prevented either by a deficiency of melanin or by homozygosity for a non-C57BL allele close to thec-pregion of chromosome 7. The presence of a C57BL allele at a locus on another chromosome is necessary for lipofuscinosis to occur.
Theoretical study on the accumulation of selfish DNA
Authors: Ohta Tomoko
Published: September 2009

The accumulation of selfish DNA in eukaryotic genomes was studied from the standpoint of population genetics. Selfish DNA is assumed to replicate itself within a haploid set. For the selectively neutral case, the fate of a single self-replicating DNA segment (unit) within a population was investigated by the method of the probability generating function, and by Monte Carlo simulation, with special reference to the probability of survival and average number of units per haploid set. For the selectively deleterious case at the organismal level, the equilibrium between new occurrence and selective elimination was studied, and the average and variance of the number of units per haploid set in the population was examined by Monte Carlo simulation. It is shown that the process of self-replication (duplication–deletion) plays an essential role for the maintenance and elimination of selfish DNA.
The effect of an unusual chromosome architecture on disjunction and non-disjunction in Drosophila
Authors: Falk Raphael
Published: September 2009

Two homologous autosomes of Drosophila that were attached to form a single entire compound autosome II were found to affect the segregation of the sex chromosomes in both males and females. The compound segregated nearly always from an attachedX.Ychromosome in males with no other sex chromosome. When two sex chromosomes were present together with the compound they differed in their tendency to segregate from the compound. In males theX.Ychromosome segregated more often from the compound than did theYchromosome, and theYchromosome segregated more often from the compound than did the regularXchromosome. In females theX.Ysegregated more often from the compound than did the regularXchromosome. This preferential segregation in females was observed for exchangeXchromosomes as well as for the non-exchange chromosomes.

In the presence of the compound the frequency of primary non-disjunction of the sex chromosomes was elevated in both females and males; usually both sex chromosomes segregatedfromthe compound and only rarelywithit.

Flies devoid of most of the proximal heterochromatin of the sex chromosomes die. However, when the compound autosome was present some such flies survived. This indicates that a segment of the proximal heterochromatin of the sex chromosomes was intercalated into the compound when it was constructed. It was concluded that the segment intercalated into the compound carries specific sites for sex chromosome disjunction. Specific sites determine sex chromosome disjunction in males. In females they determine the disjunction of the sex chromosomes in cooperation with exchange pairing.
Genetic analysis of transmission ratio distortion byt-haplotypes in the mouse
Authors: Bennett Dorothea , Alton Althea K. , Artzt Karen
Published: September 2009

Lethal and semilethalt-haplotypes in the mouse are polymorphic in wild populations, where they are presumably maintained by transmission distortion from males, which transmit the aberrant chromosome to over 95% of progeny. We report here measurements of transmission ratio that show an unexpectedly strong effect of background genotype, specifically genes on the homologous chromosome, on the degree of transmission distortion oft-haplotypes. We also provide additional evidence that withint-haplotypes two separable elements co-operate to control transmission distortion, and that the system is thus closely analogous to segregation distortion in Drosophila, as has been previously proposed by Gluecksohn-Waelsch & Erickson (1970), Demin, Safronova & Lapkina (1978), and Styrna & Klein (1982).
Further studies on the alcohol dehydrogenases in barley: evidence for a third alcohol dehydrogenase locus and data on the effect of an alcohol dehydrogenase – 1 null mutation in homozygous and in heterozygous condition
Authors: Harberd N. P. , Edwards K. J. R.
Published: September 2009

This paper presents evidence that the alcohol dehydrogenases (ADHs) in barley are specified by three loci. Six distinct ADH isozymes are observed following native slab polyacrylamide gel electrophoresis of crude extracts from flooded wild-type roots. Three of these isozymes are missing in flooded roots of plants homozygous for the Adhl-M9 mutation. The results also indicate that a simple binomial model (incorporating random dimerization and no inhibitive interaction of the two subunit species within heterodimers) is unable to account for the distribution of the total ADH activity between the ADH isozymes observed. Finally, the level and distribution of ADH activity in heterozygous (Adhl+ / Adhl-M9) flooded roots is not what would be expected if these contain only one-half of the available ADH1 protomers and the same frequency of available ADH2 and ADH3 protomers as is contained in the flooded roots of wild-type homozygotes (Adhl + / Adhl + ).
Genetic variation of wild mouse populations in southern Germany: I. Cytogenetic study
Authors: Adolph Sabine , Klein Jan
Published: September 2009

Some 400 wild mice (Mus domesticus) from southern Germany (the triangle formed by the cities Tübingen, Heidenheim and Friedrichshafen) were karyotyped and, in 243 of them, the chromosome compositions were determined by banding techniques. Virtually all mice tested carried at least one pair of metacentric chromosomes; some mice had up to ten metacentric chromosomes. Based on their chromosome composition, five mouse populations could be distinguished. Population I was characterized by the diploid chromosome number of 2n = 38 and the presence of two copies of metacentric chromosome Rb(4.12)1Tu. This translocation was also found in virtually all mice captured in southern Germany, almost always in a homozygous state. Mice of other populations had extra metacentric chromosomes Rb(5.15)15Tu (population II), Rb(13.14)17Tu (population III), Rb(5.14)18Tu (population IV) and Rb(11.13)6Tu (population V). In addition, rare variants (1 or 2 mice) were found in the different populations, which were heterozygous for additional metacentric chromosomes. Population V was quite heterogeneous in that it contained up to five metacentric chromosomes in addition to those mentioned. The number and the composition of these metacentric chromosomes varied from place to place. With the exception of population I, the individual populations occupied geographically distinct areas: Representatives of population I were found concentrated in one area, but, in addition, some were scattered over the entire studied region.
Production and modification of Mu (G–) phage particles inE. coli K12andErwinia
Authors: Toussaint Ariane , Schoonejans Eric
Published: September 2009

We studied the amount of Mu(G+) and Mu(G−) phages in different Mu lysates prepared either upon induction or upon infection ofE. coliandErwiniastrains. We also looked at the level of expression of the modification function (mom) by Mu(G−) phages, both after induction and after infection ofE. coliandErwinia. The expression ofmomseems to be regulated in the same manner inE. coliand in the strain ofErwinia carotovoratested. The proportion of both types of Mu(G+) and Mu(G−) phages in induced lysates is very variable and we found growth conditions favouring the production of Mu(G−) particles. This should extend the use of Mu as a genetic tool and as a generalized transducing phage to many enterobacteria.
Abuffspore colour mutant inSordaria brevicollisshowing high-frequency conversion: 2. Loss of the high-frequency conversion
Authors: Macdonald Mary V. , Whitehouse Harold L. K.
Published: September 2009

A mutant, YS17, at thebuffspore colour locus inSordaria brevicollishas previously been described. It shows conversion with high frequency, predominantly to wild type, and is believed to act as a recognition site for an endonuclease that initiates recombination at the YS17 site. The discovery is now reported of a gene that causes loss of the high-frequency conversion shown by the YS17 mutant. The gene was present in existing stocks of the fungus. It reduces the conversion frequency of YS17 to a level similar to that of otherbuffmutants, from which it is inferred that the YS17 mutant no longer acts as an initiation site for recombination. When the conversion frequency of YS17 is low the bias in conversion to wild type rather than to mutant is lost, suggesting that this bias may relate to the initiation of recombination at the site. The loss of high frequency conversion of YS17 appears to be determined by a single recessive gene linked to mating type and unlinked tobuff. It is suggested that the dominant allele induces recombination at the site of YS17 by controlling either the synthesis or the activity of an endonuclease that is capable of recognising the nucleotide sequence at the YS17 site. Some anomalous results point to the existence of modifiers of the action of the gene.
Nitrite toxicity inAspergillus nidulans: a new locus in aproA1 pabaA6 yA2strain
Authors: Pombeiro Sandra R. C. , Martinez-Rossi Nilce M. , Rossi Antonio
Published: September 2009

This report describes the existence of a mutation in aproA1 pabaA6 yA2strain ofAspergillus nidulans, which prevents it growing on elevated concentrations of nitrite. The nitrite toxicity marker (nihA) resulted from a mutation in a single gene representing a new locus in linkage group I, and behaved as a recessive character. The observed recombination frequencies betweennihAandproA1and betweennihAandpabaA6were about 1 and 11%, respectively. Nitrite toxicity was not due to a defect in nitrite reductase, because the mutant grew well on nitrate. Furthermore, ammonium protected bothnis-5andniiA−strains against nitrite toxicity, which was not observed for thenihAstrain. Since growth of the mutant was inhibited more by a mixture of ammonium and nitrite, compared to nitrite alone, it is proposed that theproA1 pabaA6 yA2strain has a mutation leading to increased efficiency in nitrite uptake, which is not repressed by ammonium.
Shikimate dehydrogenase – a biochemical marker for group 5 chromosomes in the Triticinae
Authors: Koebner R. M. D. , Shepherd K. W.
Published: September 2009

Structural genes for the isozymes of shikimate dehydrogenase (E.C.1.1.1.25) have been located on chromosome arms 5AS, 5BS and 5DS of wheat, 5RS of cereal rye and on chromosome 5CuofAegilops umbellulataby electrophoretic techniques. This character provides a useful genetic marker for these previously unmarked chromosome arms, and the results support the notion of the conservation of gene synteny groups within the Triticinae.
The intrachromosomal mapping of a glucose phosphate isomerase structural gene, using allelic variation among stocks of Chinese Spring wheat
Authors: Chojecki A. J. S. , Gale M. D. , Holt Linda M. , Payne P. I.
Published: September 2009

Detectable allelic variation at theGpi-1loci on the short arms of the homoeologous group 1 chromsomes in wheat is not common. However, a variant null allele at theGpi-D1locus is present in some stocks of Chinese Spring. This has allowed the locus to be mapped between the ω-gliadin locus carried distally on the short arm of chromosome 1D,Gli-D1(34·5%) and the high-molecular-weight glutenin subunit locus carried near the centromere on the long arm,Glu-D1(36·2%). The origin of this isoenzyme polymorphism in Chinese Spring stocks is described and its potential significance is discussed in relation to quantitative analysis of aneuploids, alien chromosome addition and substitution lines and intervarietal chromosome substitution lines involving Chinese Spring.
Chromosomal control of early embryonic development in mice: II. Experiments on embryos with structural aberrations of autosomes 7, 9, 14 and 17
Authors: Baranov V. S.
Published: September 2009

Perculiarities of preimplantation and early postimplantation development were studied in embryos with partial deletions and duplications of chromosomes 7, 9, 14 and 17, in the progeny of mice heterozygous for the unequal reciprocal translocations T(7; 14)2Iem, T(16; 17)43H and T(9; 17)138Ca. Deficiencies for any part of autosomes 9 or 14 combined with duplications of the corresponding segments of autosomes 7 or 17 do not affect preimplantation development, though they are lethal soon after implantation. Deficiency for the distal part of chromosome 7 (Df7F4) induces embryonic death by the early blastocyst stage. Deficiencies for the distal part of chromosome 17 (Df17El–E5), as well as for its proximal region (Df17AB) carrying all genes of theT-tcomplex, have no detrimental effects on cleavage, blastulation and implantation, but are lethal after implantation, mostly during early neurulation. Deficiency for the middle part of chromosome 17 (Df17CD) is expressed just after a few cleavage divisions, and these embryos all die by the morula stage. It is suggested that the genes of the CD region of chromosome 17 and of the F4 region of chromosome 7 are of major significance for genetic control of early development in the laboratory mouse.
Haematopoietic role for Patch (Ph) revealed by newWmutant (Wct) in mice
Authors: Loutit J. F. , Cattanach B. M.
Published: September 2009

A new mutant (Wct) has been identified at theWlocus of the mouse. The homozygote is poorly viable. Whereas the heterozygote (Wct/ +) is only mildly anaemic likeWυ/ +, the double heterozygoteWct+ / +Phis considerably more anaemic thanWυ+ / +Phand it andWsh+ / +Phhave significantly raised leucocyte counts.Wct+ / +Phis also unduly radiosensitive to whole body X-irradiation, 50% dying from haematopoietic failure at a dose of 4·59 ± 0·14 Gy, whereas the median forWct/ + was 6·49 ± 0·28 Gy. Serial blood counts of mice after low- or sub-lethal doses of X-rays revealed significantly more profound depression of counts of both red cells and leucocytes inWct+, and more notably inWct+ / +Ph, than in + / + orWsh/ + (haematologically normal) iso-dosed mice. We conclude that control of haematopoiesis by chromosome 5 is not confined to theWlocus but is shared by the linked genePh(and perhapsRw) and that expression of the change is not limited to the erythron but involves the pluripotent haematopoietic stem cell.
Map and function ofgadmutations inPhysarum polycephalum
Authors: Shinnick T. M. , Anderson R. W. , Holt C. E.
Published: September 2009

Amoebae and plasmodia are alternate vegetative forms in the life cycle of the acellular slime mouldPhysarum polycephalum. Haploid amoebae carrying heterothallic alleles of thematA(ormt) locus ordinarily form plasmodia only by crossing, but occasionally give rise to mutants that form plasmodia by selfing as well as by crossing. Twelve independently isolated mutants of this type have been studied. Eight carry mutations (termedgador greater asexual differentiation mutations) within approximately 0·2 map units ofmatA. Another mutation (gad-12) is linked neither tomatAnor to any of 9 other markers tested. The remaining three mutations are linked tomatAand map as follows:matA–0·5 units –gad-4–4 units –gad-6– 8 units –gad-11. One mutation,gad-11, has been tested in strains carrying each of the fivematAalleles (matAl, 2, 3, 4, andh) available in a common genetic background; the mutation is expressed with all five alleles. The mutationnpfF1(formerlyaptA1), which was isolated as a suppressor of selfing in Colonia (matAh) amoebae, suppresses the action of each of the 12gadmutations. The similarly isolated mutationnpfA1is also epistatic to eight of the mutations, but permits selfing withgad-5, 6, 12and13. For double mutant strains containinggad-12andgad-1, 2, 4, 6or11, the selfing behaviour of each double mutant differs from that of either single mutant. Mixtures ofgad−npfF1withgad+npf+amoebae readily form plasmodia, a result suggesting thatgadmutations are dominant or semi-dominant. We conclude that the commitment of a cell to differentiate into a plasmodium is under the control of a complex group of genes linked tomatA.
Quantitative genetics and the evolution of ontogeny: I. Ontogenetic changes in quantitative genetic variance components in randombred mice
Authors: Cheverud James M. , Leamy Larry J. , Atchley William R. , Rutledge J. J.
Published: September 2009

We report the results of an ontogenetic analysis of quantitative genetic variance components with two replicates drawn from the randombred ICR strain of mice. A total of 432 mice from 108 full-sib families raised in a cross-fostering design were used to estimate direct effects heritability, maternal effects, and environmental effects for weight, head length, trunk length, trunk circumference, and tail length at 17, 24, 31, 38, 45, 52, 59, and 66 days of age. There was no significant difference in heritability between the replicates. Heritabilities either stayed more or less constant with age at about 0·30 (weight, trunk length, trunk circumference) or increased slightly with age (head length, tail length). Maternal effects decreased with age from a maximum of about 0·50 at weaning to about 0·15 at age 66 when growth was nearly complete. Environmental effects increased in relative importance during ontogeny.
Oocyte specific regulation of PGK-1 isozyme activity in female germ cells of the mouse
Authors: McMahon Andy
Published: September 2009

The expression of electrophoretic variant forms of the X-linked enzyme phosphoglycerate kinase (PGK-1) was examined during the ontogeny of the female germ-line followingX-chromosome reactivation. Non-growing oocytes from foetal and neonatal ovaries of heterozygous females show a higher PGK-1A isozyme activity, a reflection of prior non-randomX-inactivation favouring activity of theX-chromosome carrying thePgk-1aallele andXceclocus. On oocyte growth, the total PGK-1 enzyme activity increases 40–50 fold and the pattern of PGK-1 isozyme expression changes giving an electrophoretic pattern now skewed in favour of the PGK-1B isozymic form. Activity of the PGK-1B isozyme exceeds that of PGK-1A in all growing oocytes with a total activity greater than 0·075 nmol h−1oocyte−1. Mice homozygous for eitherPgk-1allele show similar PGK-1 specific activities in somatic tissues where oneX-chromosome is active, but oocytes ofPgk-lbhomozygotes show a higher specific activity compared to those ofPgk-1ahomozygotes. Thus increased activity of the PGK-1B isozyme relative to the PGK-1A isozyme is specific to growing oocytes.
Nonprogressive sperm motility is characteristic of most completethaplotypes in the mouse
Authors: Olds-Clarke Patricia
Published: September 2009

Epididymal sperm from male mice carryingtw32(t12complementation group) exhibit a peculiar nonprogressive type of motility called ‘dancing’; sperm from congenie wild-type mice do not. To determine whether this effect was unique totw32or common to all t haplotypes, sperm from mice carrying otherthaplotypes were examined. A male was considered to have nonprogressive sperm if more than 20% of the motile sperm had nonprogressive trajectories. The mean percentage of nonprogressive but motile sperm for 33 wild-type and Brachyury males of various genetic backgrounds was 4. All males carryingtw12(tw1complementation group),tw5ortw73, and 56% of males carryingt0ortLub1had nonprogressive motile sperm. Five per cent of males carryingtchromatin or a deletion in the proximal (to the centromere) half of thetcomplex had nonprogressive motile sperm, but all males carryingtchromatin in the distal half of thetcomplex had nonprogressive motile sperm. These observations suggest that the factor or factors causing nonprogressive sperm motility may be common to all completethaplotypes, and located in the distal region of thetcomplex.
Effects of linkage on response to directional selection from new mutations
Authors: Keightley P. D. , Hill W. G.
Published: September 2009

The influence of linkage on the rates of response to continued directional selection of quantitative traits deriving from variation contributed by new mutations in finite populations is investigated. Mutant genes are assumed to have additive effects which are randomly sampled from a symmetric distribution, and to be randomly located on the chromosome. Results were obtained by Monte Carlo simulation.

The expected steady rate of response, when variability from new mutations is balanced by that lost by drift and selection, is reduced the tighter the linkage, but the reduction is small unless there are few, short chromosomes. For a given rate of new mutational variance per haploid chromosome set per generation, greater effects of linkage are obtained in large than in small populations, because more mutants segregate. The response and influence of linkage are essentially the same whether the new variance is due to many genes of small effect or few of large effect.

The variability of response between replicates and generations was investigated, and the contribution to this of new mutants or recombination of existing mutants compared. Usually most genetic variability was due to the occurrence of a new favourable mutant of large effect.
A new type of plasmodium formation inPhysarum polycephalum
Authors: Anderson Roger W. , Truitt Christine L.
Published: September 2009

Haploid amoebae ofPhysarum polycephalummay form plasmodia sexually by ‘crossing’, which involves cellular and nuclear fusion, or asexually by ‘selfing’, which occurs without nuclear fusion. In most amoebal strains, selfing is seen in clonal cultures only at very low frequency. In the present study, we have shown that selfing occurs at a similarly low frequency in mixtures of crossing-incompatible amoebae, but is stimulated in crossing-compatible mixtures. In certain compatible mixtures involving mutant strains, where crossing is temperature-sensitive, selfing may be stimulated even at a temperature that largely or wholly abolishes crossing. The extent to which selfing is stimulated appears to be influenced bymatB, a locus which is known to affect the frequency of amoebal fusion. We have failed to detect any filter-transmissible factor that might be responsible for the effects we have observed. We suggest a sequence of events that might bring about ‘stimulated selfing’ as a consequence of abortive crossing.
Identification of a male determinant on the X chromosome of housefly (Musca domestica L.) populations in South-East England
Authors: Denholm I. , Franco M. G. , Rubini P. G. , Vecchi M.
Published: September 2009

Houseflies collected from eight pig-breeding farms were used to investigate the nature of sex determinants in fly populations of South-East England. Earlier observations had shown that their sex determination mechanism was not of the standard (XX females, XY males) type.

Most flies of both sexes were XX; the male determining Y chromosome of standard populations was rare. Test-crosses to females of standard multimarked strains and crosses using aneuploid (OX) flies identified two dominant male determinants, one on autosome 3 (M III) and another on the X chromosome (Xm), and provided the first demonstration in this species of an active involvement of the X chromosome in sex determination. A small secondary constriction on X appeared to indicate reliably the presence of Xm. Most individuals in field populations were Xm homozygotes, implying the presence of an unlocated female determinant F,† epistatic to Xm and M III.

M III was less common and differed in frequency between samples. Its increased frequency in a strain selected in the laboratory with the pyrethroid insecticide permethrin might be due either to genetic drift, or to linkage between M III and a gene on autosome 3 that confers resistance to pyrethroids in houseflies.
Absence of detectable gametic disequilibrium between thet-complex and linked allozyme-encoding loci in house mice
Authors: Nadeau Joseph H.
Published: September 2009

To determine the extent of gametic disequilibrium between loci linked to thet-complex in house mice, alleles of four allozyme-encoding loci associated with elevent-complexes recently found in wild mice and sixteent-complexes maintained in laboratory colonies were identified. The allozyme-encoding loci included in the survey were complement component-3, kidney catalase, glyoxalase-1 and phosphoglycerate kinase-B. In contrast to published surveys showing strong disequilibrium between theH-2complex,t-complex protein-1 and thet-complex, disequilibrium between thet-complex and linked allozyme-encoding loci was not detected. This result is discussed in terms of several hypotheses concerning the structure of mouse populations and the mechanisms maintaining gametic disequilibrium between theH-2complex,t-complex protein-1 and thet-complex.