bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex ratio distortion and semi-sterility in the progeny of irradiatedGlossina morsitans
Authors: Curtis C. F. , Langley P. A. , Mews A. R. , Offori E. D. , Southern D. I. , Bell P. E.
Published: September 2009

MaleGlossina morsitanswere subjected to various doses of gamma radiation in air or nitrogen and mated to untreated females. The sex ratio of theF1progeny was biased towards males, and this may be explained by the extra vulnerability to dominant lethal induction that the presence of the largeXchromosome gives to female determining sperms. The mean fertility of theF1progeny was subnormal. This was due to the induction of 50 % sterility in a large proportion ofF1individuals. Cytogenetic examination of the progeny of outcrosses ofF1individuals indicated that in most of the semi-steriles there were translocations involving the large autosomes or theYchromosomes. Almost all the normally fertileF1flies gave only cytogenetically normal progeny. TheF1sex-ratio distortion and semi-sterility would provide a ‘bonus’ in the application of the sterile male technique, which would amount to a 15–50% saving in the releases required to achieve a population control target compared with the requirement if theF1was normal.
Reproductive lifespan in irradiated and unirradiated chromosomally XO mice
Authors: Lyon Mary F. , Hawker Susan G.
Published: September 2009

Lifetime reproductive performance was studied in 50 sib-pairs of female mice, one member of each pair chromosomally XX and the other XO. Twenty-five pairs were irradiated with 25 rad X-rays at 10 days of age and 25 were unirradiated. In both the irradiated and control series the XO mice had a significantly shorter reproductive life than the XX ones, but unirradiated XO bred longer than irradiated XX. The median age of unirradiated XO at birth of last litter was 280 days and they had 6·5 ± 0·80 litters, whereas for XX the figures were 420days and 12·6 ± 0·74. The mean litter-size of XO mice was only about 55% and their lifetime productivity 34% of that of their XX sibs. Similarly, the lifetime productivity of irradiated XX females was only 31% of that of unirradiated XX. Histological studies showed that in the unirradiated XO mice reproduction ended through shortage of oocytes, and the resulting secondary ovarian changes were similar to those in irradiated mice. Thus, the differences between human and mouse XO types are to some extent reconciled. Both become sterile through death of oocytes, in humans before puberty and in mice after. This difference may be connected with different times from oogenesis to puberty in the two species.
Multiple gene control of the tRNA aminoacylating system inDrosophila melanogaster
Authors: Rose Raymond W. , Hillman Ralph
Published: September 2009

The stimulation ofin vitrotRNA aminoacylation by post-microsomal supernatant enzymes isolated fromAbnormal Abdomen(A53g) adult flies is a function of the residual genome of these flies rather than of the major mutant gene,A53g. Genes controlling this stimulation are located on theXchromosome as well as on the autosomes. These observations are discussed in terms of the phenotypic effect of the major mutant gene in response to changes in protein synthesis which are under the control of modifier genes responsible for aberrant genetic translation mechanisms.
The lactose system inKlebsiella aerogenesV9A 2. Galactoside permeases which accumulate lactose or melibiose
Authors: Reeve E. C. R. , Braithwaite J. A.
Published: September 2009

Klebsiella aerogenesV9A possesses at least three galactoside permeases, the lactose permease (LacP), the melibiose permease (MelP) and a third permease (GPIII), and also a galactose permease. It is shown that the first three of these permeases all accumulate both lactose and melibiose efficiently, while the galactose permease takes up neither sugar. Lactose only induces LacP and melibiose only induces MelP.d-fucose, isopropyl-β-d-thiogalactoside (IPTG) and methyl-β-d-thiogalactoside (TMG) all induce GPIII, but galactose does not. GPIII takes up both lactose and melibiose but cannot accumulate lactose in the presence of IPTG. Thus substantial differences are found between the galactoside permeases ofKlebsiellaandEscherichia coli.
Isolation of a transducing phage forming plaques onPseudomonas maltophiliaandPseudomonas aeruginosa
Authors: Moillo Agnès M.
Published: September 2009

A temperate phage, M6, has been isolated from a lysogenic strain ofPseudomonas maltophilia. An extended range mutant, M6a, plates onP. aeruginosaand is capable of general transduction in this species. This phage may be of value for comparing the genetic maps of different species ofPseudomonas.
Fixation time of overdominant alleles influenced by random fluctuation of selection intensity
Authors: Ohta Tomoko , Kimura Motoo
Published: September 2009

It was demonstrated that the number of generations until fixation or loss of an overdominant alleles is influenced by random fluctuation of selection coefficients. When 2<Vs, whereis the mean selection coefficient against either homozygote andVsis the between -generation variance of the selection coefficient, overdominance generally accelerates rather than retards fixation of segregating alleles. This finding should have important bearing on our consideration of the behaviour of polymorphic variants which are nearly neutral but have very slight overdominance. When the population size (Ne) is extremely large, not onlyNebut also/Vshave to be considered in discussing the effectiveness of overdominance.
Segregation of co-transduced streptomycin and tetracycline resistance in Staphylococcus aureus
Authors: Grubb W. B. , O'Reilly R. J. , May J. W.
Published: September 2009

Extrachromosomal streptomycin and tetracycline resistance in Staphylococcus aureus E169 has been transduced to three different recipients. An analysis of the transductants demonstrates that: (1) in most cases the behaviour of the markers in the transductants is similar to that in the donor; (2) the markers are co-transduced at frequencies of 2–44% and the frequency is highest when the selected marker is streptomycin resistance; (3) in the co-transductants the markers segregate independently, suggesting that they are unlinked.
A genetic map of several mutations affecting the mucopeptide layer ofEscherichia coli
Authors: Wijsman H. J. W.
Published: September 2009

Several temperature-sensitive mutants ofEscherichia coliwere isolated which lyse at the restrictive temperature. Some of these possess a biochemically defined lesion in cell-wall mucopeptide synthesis. Three genes, termedmurC, EandF, have been localized between theaziandleumarkers. From transductional data a fine structure map was constructed of themurmutations, establishing the order of the genes. The genetic relationship between these cell wall genes and neighbouring genes involved in cell division is discussed.
Chromosome translocations inGlossina austeni
Authors: Curtis C. F. , Southern D. I. , Pell P. E. , Craig-Cameron T. A.
Published: September 2009

An autosomal translocation in the tsetse flyGlossina austeniwas studied genetically, cytogenetically and for its effects on viability. Flies homo-zygous for the structural change could be identified by outcrossing to wild-type and demonstrating semi-sterility in all the progeny.

A cytogenetical analysis of male meioses in samples of pupae which were sibs of the semi-sterile progeny showed them to be structurally heterozygous for the translocation. Matings of the translocation heterozygotes and homozygotes gave the expected progeny ratios, with the exception of a deficit of females classified as translocation homozygotes. This was due to their sterility or inviability. Those female homozygotes which did breed showed a subnormal lifetime pupal production. These deleterious recessive effects were probably due to the translocation itself although the influence of linked loci could not be ruled out. These effects would prevent the mass rearing of this particular translocation for a tesetse control project.

Two other stocks which showed semi-sterility were found to carry autosomal translocations and two which currently showed holandric inheritance haveY-autosome translocations. One stock with holandric inheritance of extreme sterility carries a double translocation involving two autosomes and theYchromosome.
Some invariant properties of a geographically structured finite population: distribution of heterozygotes under irreversible mutation
Authors: Maruyama Takeo
Published: September 2009

It is shown that the distribution of the sum of heterozygotes, due to mutant gene(s), that appear in a finite population is invariant under geographical structure, provided that the mutant gene has additive effect on fitness and migration does not change the genetic constitution as a whole population. The expected number of heterozygotes is 2N when Ns = 0 and gradually rises to 4N as Ns increases provided s remains small, where N = the total population size and s = selective advantage of a mutant gene. The distribution of the heterozygosity summed over those generations in which the gene frequency in the entire population is specified, is also shown to be invariant. In the case of a neutral mutant, the density is equal to 4(1 − Y) where Y is the frequency of the mutant in the whole population, and in the selectively advantageous case, it is approximately equal to a constant function 4, provided that the population size times selection coefficient is sufficiently large. These quantities conditional on the fixation of the mutant are shown to be invariant and some special cases are obtained explicitly.
The lactose system inKlebsiella aerogenesV9A: 1. Characteristics of two Lac mutant phenotypes which revert to wild-type
Authors: Reeve E. C. R. , Braithwaite J. A.
Published: September 2009

A wild strain ofKlebsiella aerogenes(V9A), which contains a plasmid Fklaccarrying the genes of thelacoperon, gives two mutant cell types, recognized by the appearance of their colonies on MacConkey lactose agar. These are referred to as ML−and ML−/+, wild-type being ML+. ML−cells can grow rapidly on 1% lactose as carbon source but very slowly on 0·2% unless induced by TMG or D-fucose, or by previous growth on galactose, melibiose or raffinose, which enables them to grow rapidly on 0·2% lactose for 2–4 cell generations. Previous growth on 1% lactose does not induce the ability to grow rapidly on 0·2% lactose. It is concluded that ML−cells have a defect in the lactose permease gene which allows slow uptake of lactose when the external concentration is 0·2% and more rapid uptake when the external concentration is increased. In addition, TMG, D-fucose, galactose, melibiose and raffinose induce one or more other galactoside permeases which can accumulate lactose efficiently but are not induced by lactose. ML−/+cells can grow normally on 0·2% lactose as carbon source, but only after a substantial lag when transferred from glucose, glycerol or sucrose, and after an even longer lag when transferred from melibiose or raffinose. Wild-type cells (ML+) grow normally on 0·2% lactose after a short lag of less than a cell generation time, when transferred from any other carbon source. Cells of each of the three phenotypes (+, −/+ and −) can mutate to give both of the other two phenotypes. Incomplete genetic evidence suggests that the ML−mutation is a result of a reversible change in the Fklacplasmid.
An analysis of temperature-dependent asynapsis inTriticum aestivum
Authors: Bayliss M. W. , Riley Ralph
Published: September 2009

Measurements of chiasma frequency over a range of temperatures from 9 to 35 °C in euploid wheat and lines nullisomic for chromosome 5D showed the absence of chromosome 5D greatly to increase the sensitivity of chiasma frequency to temperature, resulting in complete univalence at the lowest temperatures. Careful examination of meiotic prophase showed the lowering of chiasma frequency to be correlated with failure of zygotene chromosome pairing, justifying the use of the term asynaptic. Observation of the pairing behaviour of an isochromosome in the nullisomic 5D background suggested that the asynapsis was due to a failure in the mechanism of chromosome pairing rather than of the pre-alignment of homologues. The observed effects in the absence of chromosome 5D could be due to the presence of a recessive allele at the locus of chromosome 5A, also known to control stability of chiasma frequency to temperature. In conclusion it is pointed out that in euploid wheat the sensitivity of chiasma frequency to temperatures within the normal meteorological range could influence the cytological stability of the wheat crop.
A possible source of primary nucleotide chain breaks in recombinant structures in eukaryotes
Authors: Hastings P. J.
Published: September 2009

It is argued that the primary break-points for meiotic recombination arise from the replication of regions in which DNA synthesis is delayed until meiotic prophase. The gaps would be in nucleotide chains of opposite polarity in sister chromatids. This would place a restriction on the recombination models of Holliday and of Whitehouse, so that neither is able to explain observed chromatid interference. It follows that if the primary breaks originate in the manner proposed here, the Whitehouse and Holliday models are either both wrong or both right.
Unusual recombination values and the mapping of the lethal miniature in the house mouse
Authors: Wallace Margaret E. , Mallyon S. A.
Published: September 2009

Data are presented from a balanced backcross experiment involving three linkage group VI markers in the house mouse. These establish the order N–Ca–bt (naked–caracul–belted), and confirm the unusual recombination values reported earlier; the values for male heterozygotes are about 4 times those for the female ones. The linkage group is extended by the linkage of miniature, mn, with N and Ca, here reported. Data are given which establish the order mn–N–Ca–bt; they indicate that the recombination values for males may be greater than those for females for some way to the left of the N–Ca–bt segment.
The characterization of an alanine racemase mutant ofEscherichia coli
Authors: Wijsman H. J. W.
Published: September 2009

Among temperature-sensitive mutants ofEscherichia colia strain was discovered requiring D-alanine for growth. It was proved to possess an altered alanine racemase. The structural gene for this enzyme, designatedalr, is located betweenmetBandpur A. The properties of the enzyme and its locus suggest that it is not under control of the mechanisms which regulate mucopeptide formation. A suppressor of thealrmutation was discovered neartrp, and termedmsuA.
The relationship between the transfer systems of some bacterial plasmids
Authors: Alfaro Guillermo , Willetts Neil
Published: September 2009

The relationship between the transfer systems of several plasmids was investigated, using as criteria complementation of a series of transfer-deficientFlacmutants, the efficiency of plating of F-specific phages, and identification of surface exclusion systems. The transfer systems of ColV2 and ColVBtrpwere similar to that of F except for surface exclusion: ColVBtrpspecified a surface exclusion system different from that of F, and ColV2 did not specify any detectable system. The transfer system of R1–19 was also similar to that of Flac, but the products oftraA,traIandtraJwere plasmid-specific. R1–19 determined the same surface exclusion system as ColVBtrp, and this was under the control of the transfer inhibitor. The transfer systems of ColIbdrdandFlacwere unrelated. ColEl was transferred byFlac traI−mutants, but not by mutants in other cistrons.
Sex-linked variegation modified by selection in brindled mice
Authors: Falconer D. S. , Isaacson J. H.
Published: September 2009

The sex-linked gene,brindled, in the mouse produces a coat-colour variegation in heterozygous females. There is much individual variation in the relative areas of mutant and wild-type colour, but it was not known if any of this variation was genetic. The main object, when the experiments were started, was to test the simple expectation of the Lyon hypothesis, that ifX-inactivation is random the variegation should not be modifiable by selection. On the assumption that the variegation is due toX-chromosome inactivation, modification by selection would show that the inactivation process, or some property of the derived cell populations, is under genetic control. Heterozygous females were accordingly selected for the area of coat showing the mutant colour. Selection based on individual phenotypes was ineffective, but four cycles of reciprocal recurrent selection based on progeny-means produced a ‘High’ line with 64% mutant area and a ‘Low’ line with 30% mutant area, from a base population with 53% mutant area. Autosomal modifiers were not responsible for the response; the difference between the selected lines was entirely due to properties of theXchromosomes carrying thebrindledgene. The changed properties of theXchromosomes were not restricted to the locus ofbrindled, but extended at least as far as the locus oftabby. The chromosomes carrying the wild-type allele ofbrindledwere not altered by the selection, but normalXchromosomes from other strains affected the degree of variegation. It was concluded that the difference between the selected lines was due either to non-random inactivation or to somatic cell selection. It was not possible to distinguish between these two mechanisms. The results obtained in these experiments with a structurally normalXchromosome were in all essentials similar to those obtained by Cattanach with hisX-autosome translocation.
A model relating the replication and expression of colicin factor E2-P9
Authors: Hardy K. G. , Meynell G. G.
Published: September 2009

The observed dependence of lacuna counts on the growth phase of colicinogenic cultures suggests a relationship between the probability of colicin synthesis, and the number of colicin factors, per cell.
Long-term selection for a quantitative character in large replicate populations ofDrosophila melanogaster: 1. Response to selection
Authors: Yoo B. H.
Published: September 2009

The response to long-term selection for increased abdominal bristle number was studied in six replicate lines ofDrosophila melanogasterderived from thescCanberra outbred strain. Each line was continued for 86–89 generations with 50 pairs of parents selected at an intensity of 20%, and subsequently for 32–35 generations without selection. Response continued for at least 75 generations and average total response was in excess of 36 additive genetic standard deviations of the base population (σA) or 51 times the response in the first generation. The pattern of longterm response was diverse and unpredictable typically with one or more accelerated responses in later generations. At termination of the selection, most of the replicate lines were extremely unstable with high phenotypic variability, and lost much of their genetic gains rapidly upon relaxation of selection.

The variation in response among replicates rose in the early phase of selection to level off at approximately 7·6around generation 25. As some lines plateaued, it increased further to a level higher than would be accommodated by most genetic models. The replicate variation was even higher after many generations of relaxed selection. The genetic diversity among replicates, as revealed in total response, the individuality of response patterns and variation of the sex-dimorphism ratio, suggests that abdominal bristle number is influenced potentially by a large number of genes, but a smaller subset of them was responsible for selection response in any one line.
Long-term selection for a quantitative character in large replicate populations ofDrosophila melanogaster: II. Lethals and visible mutants with large effects
Authors: Yoo B. H.
Published: September 2009

Lethal frequencies on the second and third chromosomes were estimated three times in six replicate lines ofDrosophila melanogasterselected for increased abdominal bristle number, at G 14–16, G 37–44 and G 79. Ten lethals were detected at a frequency of about 5% or higher at G 14–16, of which only one recurred in subsequent tests. Another ten lethals which had not been detected previously were found at G 37–44, and the 5 most frequent ones recurred at G 79. In the last test, 15 presumably new lethals were detected, of which at least 4 appeared well established. In addition, six reversions (fromsctosc+), a new mutant at the scute locus andscawere discovered. The effects on the selected character of some lethals and visible mutants were large and variable, but not always sufficient to explain the observed frequencies. The major lethals detected at G 37–44 and G 79 for the first time were most probably ‘mutations’ (in the broad sense) which occurred during selection. The likely origins of such ‘mutations’ were discussed, with a suggestion that the known mutation rate for recessive lethals would not be incompatible with the observed frequency of occurrence of the ‘mutations’.
Size of population required for artificial selection
Authors: Nicholas F. W.
Published: September 2009

It is widely acknowledged that genetic drift is an important source of variation in response to artificial directional selection. How large should a selection line be in order to reduce the effect of genetic drift to an acceptably low level?

This paper investigates two criteria that can be used to answer this question in relation to short-term response to selection. The first criterion is coefficient of variation of response, and the second criterion is chance of success, where a successful selection programme is one in which the observed response is greater than a certain proportion, β, of expected response.

For a simple mass selection programme with intensityiand heritabilityh2, the size of population required in order for the coefficient of variation of response to be γ aftertgenerations, is approximately 2/(γih)2t, and the size required for the chance of success to be α aftertgenerations is approximately 2{zα/(β−l)ih}2/t, wherezαis the standard normal deviate corresponding to the probability α.

As an example, suppose it is required that aftertgenerations the coefficient of variation of response be 10% or that there be a 90% chance of achieving at least 9/10 of expected response. Sinceih≤ 2 in most selection programmes, the size of population required is at least 50/tor 82/trespectively. Ifih≤ 1, the corresponding sizes are 200/tand 328/t.

Results are extended to enable the calculation of size of population required for any type of artificial directional selection programme, including those in which generations overlap.
Genic determination of the autogamy trait in the hypotrich ciliate,Euplotes crassus
Authors: Dini Fernando , Luporini Pierangelo
Published: September 2009

Cross-fertilizing stocks ofEuplotes crassus, differing as to the ability to undergo autogamy, were subjected to breeding analysis. The resulting data are consistent with the interpretation that a single locus (a) with a pair of alleles (a+;a−) controls the ability to undergo autogamy. The two alleles express a simple dominance relationship in which the dominant allele (a+) permits expression of the autogamy trait. Cross-breeding experiments also suggest that thealocus is not linked to themtlocus which determines the mating-type trait.
Chromosomal change and rectangular evolution in North American cyprinid fishes
Authors: Gold J. R.
Published: September 2009

An important question in evolutionary biology concerns the manner and tempo in which organismal and/or genetic changes that promote evolutionary divergence occur. One recent hypothesis, termedrectangular evolution, holds that most significant evolutionary change occurs during occasional or periodic speciation episodes, with long periods of evolutionary stability in the interim. An alternative view, termedphyletic gradualism, holds that evolutionary divergences proceed by the slow and even accumulation of genetic differences within populations of established species. Two brief tests of rectangular evolution are presented using chromosomal data from North American cyprinid fishes (minnows), a group known to have experienced heterogeneous rates of splitting. Within the rapidly speciated genusNotropis, rates of chromosomal evolution appear slower relative to other, less rapidly speciated confamilial genera. Species ofNotropisalso are less divergent chromosomally, on the average, than are species from other cyprinid genera. These results are in compatible with a rectangular mode of chromosomal divergence these fishes. The results also reveal inconsistencies with a gradual mode chromosomal divergence, but at present this hypothesis cannot be falsified. Consideration of these and other data suggests that different levels of the cyprinid genome may follow independent evolutionary paths.
T(16: 17)43H translocation as a tool in analysis of the proximal part of chromosome 17 (including T-t gene complex) of the mouse
Authors: Forejt Jiří , Čapková Jana , Gregorová Soňa
Published: September 2009

Linkage relationships of three gene markers of chromosome 17, namely Brachyury (T), tufted (tf), and Histocompatibility-2 (H-2), to the break-point of T(16; 17)43H male sterile translocation were established. The following order was found: T−tf−T43H−H-2. In all cases the translocation break was found in cis to H-2k, haplotype, no recombinant being found among 218 backcross individuals examined. More than 60 viable and fertile animals trisomic for the proximal part of chromosome 17 (including T-t genetic complex) have been recovered among progeny of T43H/+ female translocation heterozygotes as a result of adjacent −2 disjunction at first meiotic division. Mutation tf has been assigned to band 17B in chromosome 17 by comparing the location of T190Ca and T43H genetic and cytological breakpoints. Recombination between centromere 17 and T43H break was reduced almost to zero in the presence of Rb(16.17)7Bnr translocation. The unexpected restoration of male fertility was observed in T43H/Rb7Bnr hybrids (T43H/+ males being completely sterile) which made it possible to prepare the first homozygotes for T43H male–sterile translocation. Direct estimation of chiasma frequencies in centromere 17−T43H region indicated an 11 cM distance between the centromere 17 and the proximal end of t12 haplotype. The significance of centromere −t (or H-2) distance on the predictable restrictions of the possible haploid manifestation of T-t or H-2 gene products on sperm membrane is discussed.
Sex differences in fitness and selection for centric fusions between sex-chromosomes and autosomes
Authors: Charlesworth D. , Charlesworth B.
Published: September 2009

A model of centric fusions between theXorYchromosome and an autosome carrying a selected locus is studied. It is assumed that fusions are not associated with any fitness effects, and that all chromosomes disjoin regularly from their homologues. It is shown that a necessary condition for the fusion to be favoured is that there is a selectively maintained sex difference in allele frequencies at the selected locus. If this condition is satisfied, the initial rate of increase of a rareY-autosome fusion is about three times that of anX-autosome fusion, with the same parameter values. Computer calculations of the final equilibrium states reached by populations containing such fusions were done.
Selection for recombination in a polygenic model
Authors: Smith J. Maynard
Published: September 2009

Normalizing selection with a moving optimum can result in strong selection for increased recombination. This conclusion is based on computer simulation of an infinite, random-mating diploid population with additive, polygenic determination of the selected phenotype. There can also be selection for increased recombination with a fluctuating optimum, and with directional selection. These effects which arise in an infinite population appear to be large compared to the additional effects arising in a finite population because of the random generation of linkage disequilibrium.
Transformation inEscherichia coli: studies on the nature of donor DNA after uptake and integration
Authors: Hoekstra W. P. M. , Bergmans H. E. N. , Zuidweg E. M.
Published: September 2009

ChromosomalE. coliDNA appears to be sensitive towardsin vivoDNA restriction when transformed to a restrictiveE. colirecipient. It is therefore concluded that transforming chromosomal donor DNA is present in a double-stranded form immediately after uptake.

Genetic analysis ofE. colitransformants, obtained with UV-irradiated donor DNA under conditions that exclude photorepair, show, especially in auvrBrecipient, loss of donor DNA information compared with the situation where DNA was not subjected to UV-irradiation. Similar conclusions were arrived at after genetic analysis of transductants obtained with UV-irradiated particles of the generalized transducing phage P1. The processing inE. coliof DNA after P1 transduction is thus similar to that of transforming DNA. The observations are discussed and a possible explanation based on single-stranded DNA integration is presented in detail.
Repair of double-strand breaks and lethal damage in DNA ofUstilago maydis
Authors: Leaper S. , Resnick M. A. , Holliday R.
Published: September 2009

The size of nuclear DNA from wild-typeUstilago maydiswas determined to be approximately 6·09 ± 0·3 × 108daltons from neutral sucrose gradient sedimentation analysis. Following exposure to ionizing radiation the nuclear DNA size was reduced due to the production of double-strand breaks in the DNA. These breaks were repaired when the irradiated cells were incubated in medium for at least one hour after irradiation. The repair was seen as a shift in the DNA profile from a low molecular weight region where the control DNA sedimented. Inhibition of protein synthesis by cycloheximide prevented this type of repair. Blocking protein synthesis also decreased the survival of irradiated wild-type cells but not radiation-sensitive mutants. Protein synthesis was necessary within the first one and a half hours after irradiation for the survival of wild-type cells to be unaffected. The results provide additional evidence for an inducible repair process inU. maydis.
Evidence for duplicate genes coding for 6-phosphogluconate dehydrogenase in rye
Authors: Rao I. Narayana , Rao M. V. Prabhakara
Published: September 2009

The 6-phosphogluconate dehydrogenase (6-PGD) E.C. no. 1.1.1.44, zymogram phenotypes of wheat–rye addition lines and triticale were determined. Genes involved in the production of 6-PGD were located on the long arms of C and F chromosomes of Imperial Rye and the long arms of II and IV chromosomes of King II rye. The results indicate that this enzyme is a dimer.
A study of pili onPseudomonas aeruginosa
Authors: Bradley David E.
Published: September 2009

Pseudomonas aeruginosacarries polar pili which act as receptors for RNA-containing bacteriophages. In order to confirm, that these pili were not involved in the transfer of the sex factor FP 2, eleven bacterial strains, both FP 2+and FP 2−, were examined in the electron microscope for the presence of pili and tested for sensitivity to the RNA phage PP7. Pili were found on all strains save one which was resistant to phage PP7. It was also found by electron microscopy that about 25 times more pili per cell were present after PP7 adsorption than before it. This result is discussed with reference to the pilus retraction theory, providing further evidence that some kinds of pili retract instead of acting as simple tubes for the transfer of genetic material. The strong supporting evidence provided by the infective processes of male-specific coliphages is discussed and compared to current knowledge ofP. aeruginosaRNA phages.

It was also found that pili were present on the host strain for theP. aeruginosafilamentous phage Pf. Although similar in appearance to RNA phage pili, these differed in that they did not adsorb phage PP7. However, it seemed likely that they were receptors for Pf. A structural comparison is made betweenP. aeruginosapili andEscherichia coliF-pili. It is possible thatP. aeruginosapili could be coded for by a plasmid other than FP 2.
Population size and protein variation in man
Authors: Haigh John , Maynard Smith John
Published: September 2009

The ‘neutral mutation theory’ holds that most amino acid substitutions in evolution are selectively neutral. The known pattern of variation in human haemoglobins can only be made consistent with this theory if the human species has passed through a bottleneck of numbers in the recent past. If this theory is true, estimates of the necessary size and duration of this bottleneck can be made. A theory is developed which leads to an estimate ofYg, n, the number of alleles present in a population which arise betweengandngenerations ago, and hence to the estimate

whereuis the neutral mutation rate andNethe effective population size, for the probability that a population contains no such alleles. Using data on haemoglobins, this gives an approximate upper limit to the time elapsed since the bottleneck in human numbers. Either such a bottleneck occurred, or the neutral mutation theory is false; data on other proteins will enable a choice between these possibilities to be made.
Interspecific crosses and crossing-over inNeurospora
Authors: Newcombe K. D. , Threlkeld S. F. H.
Published: September 2009

Through a series of backcrosses the centromere region of linkage group I ofNeurospora crassawas transferred to theN. sitophilagenome, and through another series of backcrosses the centromere region of linkage group I ofN. sitophilawas transferred toN. crassa. Strains thus synthesized showed, in further crosses, that theN. sitophilacentromere region acts as a dominant enhancer of cross-over frequencies across linkage group I of the two species.
The effects of inversions and theC(3)Gmutation on intragenic recombination inDrosophila
Authors: Carlson Peter S.
Published: September 2009

The effects of heterozygous inversions and of theC(3)Gmutation on recombination between alleles of the rudimentary locus ofDrosophila melanogasterwere analysed. It is shown that the presence of either of these genetic alterations significantly changes the frequency and type of intragenic recombinants which are produced.
Histocompatibility mutations in mice: chemical induction and linkage with the H-2 locus
Authors: Egorov I. K. , Blandova Zinaida K.
Published: September 2009

Young mice of the strains A/Y and B10.D2 were repeatedly treated with diethylsulphate (DES) in different doses (36 to 1100 mg/kg). At the age of 9 weeks they were mated to females of the strains A. CA (‘A’ group) and C57BL/10Eg (‘D’ group) respectively. 2101 progeny of these matings were tested for histocompatibility by skin grafting. The spontaneous H-mutation rates were 6·96 × 10−4per gamete in the A group and 9·6 × 10−4per gamete in D group. In progeny of treated males the H-mutation rates were 0 in A group and 5·79 × 10−3per gamete in D group, showing apparent effect of paternal DES treatment on mutation frequency in the last group. Two mutations of theH-2locus were found, which together with the other threeH-2mutations published so far yielded a mutation rate of 5·18 × 10−4per gamete. The mutation rate of theH-2locus is higher than the expected rate per H-locus, indicating a great genetic complexity ofH-2.
Position of the translocation break T(2;9)138Ca in linkage group IX of the mouse
Authors: Klein Jan , Klein Dagmar
Published: September 2009

The translocation break T(2;9)138Ca is located about three map units from the H-2 region on the non-centromeric side of the IXth linkage group. The recombination frequency in the T-H-2 interval is increased in the presence of the T138 translocation to about twice its value in the absence of the translocation.
Sexuality in Neurospora crassa I. Mutations to male sterility
Authors: Weijer J. , Vigfusson N. V.
Published: September 2009

Mutations giving rise to sexual sterility were induced in Neurospora crassa macroconidia by ultraviolet-light irradiation. Thirty mutants were isolated on the basis of their male sterility in crosses with a wild-type strain. When used as the male parent these mutants exhibited a wide spectrum of sexual behaviour patterns ranging from the production of only small brown protoperithecia (complete male sterility) to the production of large and normally pigmented perithecia but with an undeveloped ostiole and very few if any spores. For many of the mutants the behaviour pattern is different when the strain is used as the female parent. Segregation data reveal that none of these mutants represent mutations of the mating-type locus. These findings suggest that the sexual development cycle is blocked at various stages in the different mutant strains. All attempts to restore fertility by supplying various additives to the medium or by varying the incubation time and temperature were unsuccessful. Conidial viability tests carried out on many of the strains revealed no abnormality in this respect. The aberrant segregation patterns exhibited by many of the mutants are discussed.
Evidence of non-random X chromosome activity in the mouse
Authors: Cattanach B. M. , Williams C. E.
Published: September 2009

X-linked modification of the heterozygous phenotypes of X-linked genes has been detected in the X chromosomes of several inbred strains of mice. The effect is similar to that of the alternative ‘states’ or alleles, of theX chromosome controlling element, Xce, identified in T(1; X)Ct X chromosomes. Tests on two such differing X chromosomes have indicated that the phenotypic modification results either from non-random inactivation of the two X chromosomes or from selection operating on the two cell populations differentiated by X-inactivation. The data provide evidence of non-random X chromosome activity in the somatic cells of the female mouse.
Cortical morphogenesis inParamecium aurelia:mutants affecting cell shape
Authors: Whittle J. R. S. , Chen-Shan L.
Published: September 2009

In order to investigate the importance of the nuclear genotype during morphogenesis of the cortex inParamecium aurelia, a search was made for conditional and unconditional mutants affecting cell shape. Ten different mutants were readily recovered following mutagenesis withN-methyl-N-nitro-N-nitrosoguanidine on stock 51s of syngen 4. The detailed pattern of surface units remained unchanged in these mutants but each one can be described as resembling a normal cell twisted about its long axis. Nine of the mutants complement each other and show no linkage. The remaining mutant, a ‘chain former’, has conditional expression, and is only recognizable at 35 °C. The penetrance of this mutant is affected by the food organism used. The conditional mutant also interacts with seven of the other mutants in pairwise homozygous combinations so that in these genotypes it can be classified after growth at 25 °C. The mutants are discussed in relation to the search for genie effects on the cortical pattern.
Genetic locus determining resistance to phage BF23 and colicins E1, E2and E3inEscherichia coli
Authors: Jasper Paula , Whitney Eleanor , Silver Simon
Published: September 2009

The gene for resistance to phage BF23 and colicins E1, E2and E3,bfe, was mapped by a combination of conjugation and transduction crosses. Co-transduction ofbfewas found with markers in the region between 76 and 79 min on theEscherichia coligenetic map. The highest frequency of co-transduction was found withargH(47%). Three-factor transductional crosses showed unambiguously thatbfelies betweenargHandsupM, at about 77·5 min on the map.
Consequences of double cross-over detections on the functional interpretation of segment ‘29’ in Podospora anserina
Authors: Touré B. , Picard M.
Published: September 2009

Double cross-overs were detected in a few crosses involving segment ‘29’ mutants of locus ‘14’ in Podospora anserina. The occurrence of such recombination events made it necessary to reconsider the localization of three mutants. Use of an outside marker and the analysis of many other crosses allowed these mutants to be mapped unambiguously. The change in the localization of one of these mutants together with complementation tests on a new mutant leads to the conclusion that the polycistronic unit of transcription contains only four cistrons instead of the five previously thought to exist.
The genetics of some second chromosome melanotic tumour mutants ofDrosophila melanogaster
Authors: Sparrow John C.
Published: September 2009

The genetic relationships of the available second chromosome melanotic tumour mutants inDrosophila melanogasterhave been investigated. Complementation tests demonstrate the existence of new alleles of thetu bwlocus and show thattu-Wandtu-gare alleles. The data suggest that there is a minimum of three major gene loci on the second chromosome involved in tumorigenesis. A number of modifier genes were found which affect the penetrance of the major tumour genes analysed. These and the problems they cause in mapping the low penetrant tumour genes are discussed. It has not been possible to maptu-48a, tu- Wandtu-gaccurately, due largely to the presence of modifier genes. It appears that the genetic basis for melanotic tumour formation is complex.
The mutagenicity of amino acid analogues inCoprinus lagopus
Authors: Talmud Philippa J. , Lewis D.
Published: September 2009

The amino acid analoguesp-fluorophenylalanine (PFP) and ethionine (ETH) are strongly mutagenic inCoprinus lagopus. The most pronounced effect was found with suppressor mutations of themet-1locus. PFP, at a concentration of 2·4 × 10−4M, increased the mutation frequency 500 fold and ETH, at a concentration of 2·4 × 10−3M, 30 fold over the spontaneous mutation frequency. From the spectrum of suppressors of themet-1locus and the dominant revertants of thead-82locus, induced by analogue treatments, it was concluded that both analogues induce single base-change mutations. The dose response curves follow a sigmoid plot, revealing that within a certain range of analogue concentrations, muta-genesis is strongly dose dependent.

Using analogue resistant mutants, it has been shown that PFP mutagenesis is a function of its incorporation into protein. However, ETH mutagenesis is independent of protein incorporation but can be correlated with the degree of ethylation of nucleic acids. The synergistic effect PFP and ETH supports the evidence of the different mutagenic actions of the two analogues.
The age of an allele in a finite population
Authors: Maruyama Takeo
Published: September 2009

The age of an allele segregating in a finite population may be defined in two ways. They are (1) the age of a mutant gene that has never reached fixation in the population, and (2) the age including any fixation period in the past. Theoretical expressions for these are derived on the assumption that every mutant is unique.
An extensive behavioural and genetic analysis of the Pawn mutants inParamecium aurelia
Authors: Chang Sheng-Yung , Houten Judith Van , Robles Laura J. , Lui Simmy S. , Kung Ching
Published: September 2009

Pawns are behavioural mutants which show impairment in membrane excitability and are, therefore, devoid of normal avoiding reactions. We obtained 103 lines of Pawns through mutagenesis and screening. Among those that yielded to breeding studies, 59 lines belonged to thepwAcomplementation group and 38 lines belonged to thepwBgroup. No other genic loci were found in this extensive analysis. Mutants of thepwAlocus showed various degrees of phenotypic leakiness. Based on the pheno- and genotypic differences, we estimated that at least 45 independent mutational events were represented in these 103 Pawn lines.
Chiasma variation and control in pollen mother cells and embryo-sac mother cells of rye
Authors: Davies E. D. G. , Jones G. H.
Published: September 2009

Mean chiasma frequencies and the amounts of between-bivalent chiasma variation were computed for pollen mother cells (p.m.c.) and embryo-sac mother cells (e.m.c.) of five distinct inbred rye lines. Despite the considerable differences for both these metrics shown by the different lines, very little variation was seen between p.m.c. and e.m.c. belonging to the same lines. It is concluded that chiasma formation in p.m.c. and e.m.c. of rye is governed and regulated by a single controlling system of genes and that variation in this genetic system is expressed identically in the two sexes.
Differences between tabby and downless mouse epidermis and dermis in culture
Authors: Sofaer J. A.
Published: September 2009

The semi-dominant X-linked gene tabby (Ta) in the mouse, and one of its recessive autosomal mimics, downless (dl) each produces a mutant syndrome that includes absence of hairs on the tail due to failure of tail hair follicle initiation. However, whereas downless tails failed to produce hair follicles in culture on the chick chorioallantoic membrane, which is in keeping with the adult phenotype of both downless and tabby mice, tabby tails produced follicles at about 40% of the control level. Furthermore, in contrast to previous findings for downless, the culture of mixed genotype epidermis-dermis combinations provided no evidence of a primary epidermal effect in tabby.
Genetic analysis of amidase mutants ofPseudomonas aeruginosa
Authors: Betz Joan L. , Brown Jane E. , Clarke Patricia H. , Day Martin
Published: September 2009

Mutants ofPseudomonas aeruginosa, which differed in amide growth phenotype from the wild-type strain, were subjected to genetic analysis using the generalized transducing phage F116. The map order of some mutational sites was determined by 3-factor crosses in which a mutation in the linked regulator geneamiRwas used as the outside marker to determine the relative order of mutations in the amidase structural geneamiE. Acetamide-positive transductants were recovered in crosses between amidase-negative strains and strains PhB3(PAC377), V2(PAC353) and V5(PAC356) producing mutant amidases which hydrolyse phenylacetamide and valeramide but not acetamide. Some recombinants carried the mutationamiE16 determining the properties of the mutant B amidase produced by strain B6(PAC351) from which both PhB and V class mutants were derived, while other recombinants produced A amidase determined by the wild-typeamiEgene.
The role of latent viruses in subline differentiation in inbred strains of mice
Authors: Wickramaratne G. A. De S.
Published: September 2009

The possibility that changes in latent viruses would contribute to the differentiation of sublines in inbred strains of mice was investigated using the Bittner virus and the BALB/c strain of mice. The results show that, at least for this combination, there is no reason for implicating latent viruses in subline differentiation.
Genetic regulation and pattern formation: A study of theyellowlocus inDrosophila melanogaster
Authors: Nash William G. , Yarkin Rhoda J.
Published: September 2009

Many of theyellowalleles found inDrosophila melanogasterresult in a unique pattern of phenotypic expression. These patterns follow the morphologically distinct cell types of the cuticle, so that for one allele all the bristles of the head and thorax might be mutant, while most of the fly appears wild type. A comparison of many differentymutants demonstrates that theyellowphenotype is expressed independently in most if not all the different cell types which form the cuticle. Control of this expression appears to reside at theyellowlocus itself.