bluuebunny/crossref_metadata_2025 huggingface dataset:
A test for the rare male mating advantage in coisogenic strains of Drosophila melanogaster
Authors: Markow Therese A.
Published: September 2009

Experiments were carried out to see if rare male mating advantage could be detected when males differ at only one locus. The eye colour mutant sepia was inserted into a strain of Drosophila melanogaster homozygous for a first, second, and third chromosome from the Canton-S strain. Tests for the rare male advantage were conducted using ratios of 4:1, 1:1, and 1:4 of the coisogenic wild-type and sepia males. No deviations from expected types of matings were observed. The results are discussed with respect to possible conditions necessary for the rare male effect to occur.
Diapause in the gypsy moth: environment-specific mode of inheritance
Authors: Lynch Carol Becker , Hoy Marjorie A.
Published: September 2009

Preliminary investigation of the genetic basis of diapause in the gypsy moth, Lymantria dispar, involved a comparison of reciprocal crosses between wild-type moths and a selectively bred ‘non-diapause’ strain with the parental stocks, where half of the eggs resulting from each of the four mating types were exposed to one month of chill at 5 °C. The presence of chill dramatically altered the phenotypic expression of diapause-dependent characteristics. Early hatching was completely recessive in unchilled eggs, while hatching time was intermediate in chilled eggs, and there was no difference between reciprocal hybrids. Proportion of eggs hatching and, therefore, number of larvae produced was also influenced by chill. Unchilled hybrids did not differ substantially from wild-type eggs, while chilled hybrids were closer to the performance of the selected line. In this case, a significant reciprocal difference indicated some involvement of sex-linkage in the inheritance of diapause.
Inheritance and morphology of exencephaly, a neonatal lethal recessive with partial penetrance, in the house mouse
Authors: Wallace Margaret E. , Knights P. J. , Anderson Janice R.
Published: September 2009

An inherited exencephaly in the mouse is described, using embryos at 11–17 days gestation. The cephalic portion of the neural tube remains open on the dorsal surface, the bony vault of the brain fails to develop, and the tissues of the brain are exposed; the development of these tissues, which is somewhat variable, is described. There is strong evidence that the condition is due to a single recessive gene, xn, with full viability until birth. Penetrance is twice as high in females as in males, and it varies overall according to the genetic milieu studied, from 33% to 84%. These features, and the absence of pleiotropic effects and of genetic evidence of associated chromosomal anomalies, make its inheritance different from that of exencephalies so far described.
Mitochondrial instability in a strain ofSaccharomyces cerevisiae
Authors: Evans I. H. , Wilkie D.
Published: September 2009

A haploid strain ofSaccharomyces cerevisiaehas been described which, on glucose medium, segregates vegetatively a high frequency of mutants with different degrees of respiratory impairment. The range of mutants seemingly encompasses both non-revertible ρ- petites and revertible point mutations resembling leakymit- mutations. The segregants have aberrant cytochrome contents and reduced growth capabilities on fermentable sugars other than glucose; these defects apparently correlate with the degree of respiratory impairment. Genetic analysis of this mutator phenomenon has implicated a nuclear gene which appears to show specificity of interaction with the mitochondrial genome as well as a requirement for glucose repression. The mutator effect seems to extend also to the loci in mitochondrial DNA for resistance to the antibiotics erythromycin and oligomycin.
Strain variation in spermatozoal glycosidases in inbred mice
Authors: Self Steven J. , Winchester Bryan G. , Archer James R.
Published: September 2009

Ten glycosidases were measured in suspensions of spermatozoa from the vasa deferentia of two inbred mouse strains and their intercrosses. Eight of these glycosidases were associated with the sperm cells and all of these showed genetical variation between the strains except α-l-fucosidase with optimal activity at pH 5·4. In contrast liver enzyme activities showed no significant variation except α-l-fucosidase. Genetic studies indicated that the variation of spermatozoal β-d-hexosaminidase, α-d-mannosidase, α-l-fucosidase and β-d-galactosidase are inherited at autosomal loci and α-d-galactosidase variation showsX-linked inheritance. We propose a new provisional gene symbol (Afuc-2) for a spermatozoal variant of α-l-fucosidase.
Compatibility and sex specific phage plating characteristics of the TOL and NAH catabolic plasmids
Authors: White G. P. , Dunn N. W.
Published: September 2009

The sex specific bacteriophage PR4 has been found to plate onP. aeruginosastrains harbouring the TOL catabolic plasmid or the plasmid pND2 derived from TOL. Based on this, attempts were made to place TOL into aPseudomonasplasmid incompatibility group and by showing that pND2 is incompatible with the R plasmid R2, TOL has been placed into the P-9 group. The NAH catabolic plasmid has been reported to be incompatible with TOL, pND2 and a variety of other plasmids derived from TOL. Thus, these plasmids also would appear to belong to the P-9 incompatibility group.
Analysis of linkage disequilibria between allozyme loci in natural populations ofDrosophila melanogaster
Authors: Langley Charles H. , Smith Diana B. , Johnson F. M.
Published: September 2009

Linkage disequilibria between pairs of 8 polymorphic enzyme loci (αGpdh, Mdh, Adh, Est-6, Pgm, Odh, Est-CandAcph) in some 100 natural population samples ofDrosophila melanogasterwere examined. The estimates of linkage disequilibrium were made from zygotic frequencies. The magnitude of linkage disequilibria are small and similar to those in previous reports. Variation in linkage disequilibrium among related subpopulations was analysed by analysis of variance of the correlation coefficients. Despite the small absolute value of linkage disequilibrium there is a suggestion of a correlation among related subpopulations. The magnitude of linkage disequilibrium was observed to be positively correlated with linkage. Two cage populations were observed to demonstrate large amounts of linkage disequilibrium between closely linked loci in contrast to the situation in natural populations. This is attributable to the finite sizes of these cage populations.
Does Muller's ratchet work with selfing?
Authors: Heller R. , Smith J. Maynard
Published: September 2009

The accumulation of deleterious mutations in a finite diploid selfing population is investigated. It is shown that the conditions for accumulation are very similar to those for the accumulation of mutations in an asexual population by ‘Muller's ratchet’. The ratchet is likely to operate in both types of population if there is a large class of slightly deleterious mutations.
Maternal effects on body weight in mice selected for large and small size
Authors: Al-Murrani W. K. , Roberts R. C.
Published: September 2009

Fertilized eggs were transferred reciprocally between large and small mothers, to study maternal effects on body weight in mice selected for large and small size, respectively. Prenatal maternal effects were not important in our material, but postnatal maternal effects were detectable. The postnatal effects accrued mostly from the inadequacy of small mothers for large offspring; small offspring were largely unaffected by the type of mother. Genetic maternal effects were only of limited importance; maternal influences of environmental origin arose from variation in litter size.
Characterization of a new choline locus inAspergillus nidulansand its significance for choline metabolism
Authors: Markham Paul , Bainbridge Brian W.
Published: September 2009

A new locus for choline-requirement has been identified inAspergillus nidulansand designatedchoC3. It has been located to linkage group VIII at a position 31·9 ± 2·2 map units to the left of thesDlocus.

It is proposed that this locus codes either for the enzyme that catalyses the transmethylation of phosphatidyl monomethylaminoethanol to phosphatidyl dimethylaminoethanol or for a molecule essential for the synthesis or function of this enzyme.
Effective method for the isolation of non-nodulating mutants ofRhizobium trifolii
Authors: Żurkowski Witold , Lorkiewicz Zbigniew
Published: September 2009

Non-nodulating mutants ofRhizobium trifoliiwere found in cultures incubated at 35 °C for 7 days. From among ten strains incubated at the elevated temperature six became non-nodulating. The frequency of Nod−mutants inR. trifoliicultures varied from 1 to 75% depending on the strain tested. It is suggested that gene(s) controlling nodulation are located on a large plasmid.
Multiple allelism at the locus controlling warfarin resistance in the Norway rat
Authors: Greaves J. H. , Ayres P. B.
Published: September 2009

Two warfarin-resistant strains of the Norway rat, Rattus norvegicus, derived independently from wild populations in Wales and Scotland and both homozygous for a major gene at the warfarin-resistance locus, Rw, were found to differ in their hypoprothrombinaemic response to simultaneous dosage with warfarin and vitamin K. The Welsh strain gave a small response and the Scottish strain a large response. These two response levels segregated in Mendelian fashion in various crosses involving the two resistant strains and a third, non-resistant strain. This indicates that the Rw locus has a series of three multiple alleles, denoted Rww, Rws and Rw+. The results are discussed briefly in relation to biochemical, ecological and evolutionary aspects of warfarin resistance.
The relationship between t and H-2 complexes in wild mice: I. The H-2 haplotypes of 20 t-bearing strains
Authors: Sturm Sabine , Figueroa Felipe , Klein Jan
Published: September 2009

Twenty t haplotypes were extracted from wild mice captured at several locations in Europe, Israel, North Africa, and South America. The haplotypes were designated tTuw1 through tTuw20. The H-2 haplotypes of the lines were defined using antisera and monoclonal antibodies specific for private antigenic determinants controlled by known H-2 alleles and by antisera produced using the new t lines as donors. The tTuw haplotypes fall into four groups according to the H-2 haplotype associated with them. Haplotypes tTuw10 through tTuw18 are associated with H-2W30, previously found to be linked with haplotypes of the tw1 group. Haplotypes tTuw1 through tTuw6 are associated with a new H-2 haplotype, H-2w36, characterized by the determinant H-2.107. Haplotypes tTuw7 through tTuw9 are associated with another new H-2 haplotype, H-2w37, characterized by determinants H-2.108 and H-2.111. And finally, haplotypes tTuw19 and tTuw20 are associated with yet another new H-2 haplotype, H-2w38, characterized by determinants H-2.33 and H-2.109. These findings suggest that the t polymorphism might be more extensive and more intricate than it was previously thought to be and that at least some of the t-associated H-2 haplotypes, and probably also the t haplotypes themselves, are related to one another in their origin.
Close linkage between albumin and vitamin D binding protein (Gc) loci in chicken: a 300 million year old linkage group
Authors: Juneja R. K. , Sandberg K. , Andersson L. , Gahne B.
Published: September 2009

Evidence for close genetic linkage between the structural loci for serum albumin (Alb) and serum vitamin D binding protein (Gc) in chicken is presented. The results are based on a study of a single sire family comprising 36 informative offspring. No recombinants have been observed. It is concluded that this linkage in the chicken is homologous to the close linkage of the albumin and Gc loci reported in man and the horse. Thus, this linkage group has most probably been conserved for at least 300 million years.
Analysis of chromosome pairing and breakage in pearl millet
Authors: Koduru Prasad R. K. , Murthy T. G. K. , Lakshmi K. V. , Rao M. Krishna
Published: September 2009

The relationship between chromosome pairing and chromosome fragmentation has been studied in a gene controlled mutant of pearl millet (2n= 14). Premeiotic mitosis, premeiotic cell development and early prophase I are normal without any fragments, which first appear at pachytene. The extent of fragmentation varies from zero to very extreme with two discrete classes of plants, namely those with partial fragmentation and those with multiple fragmentation. A quantitative analysis of bivalent distribution and the distribution of AI bridges in desynaptic and fragmented cells show all of them to be nonrandom events. We suggest that in cells showing partial fragmentation the bridges and fragments result from U-type exchanges at pachytene. The reduced frequency of AII bridges indicates relatively low sister chromatid reunion at pachytene. In multiple fragmented plants numerous minute fragments were seen from pachytene. Despite these anomalies most PMCs complete meiosis but subsequently abort at the pollen grain stage. The mutant gene also causes disturbances in the sequence of meiotic development in the ear and in the synchronous development of PMCs within an anther. It has no effect on the tapetum or on the physiological development of the anther.
Increased sensitivity to cell killing and mutagenesis by chemical mutagens in thymidine-kinase-deficient subclones of a Friend murine leukaemia cell line
Authors: McKenna P. G. , Yasseen A. A.
Published: September 2009

Wild-type Friend murine leukaemia (clone 707) cells and two thymidinekinase-deficient subclones, 707BUE and 707BUF, were compared for sensitivity to killing and mutagenesis by the chemical mutagens, ethyl methane sulphonate (EMS),N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), mitomycin C (MMC), and methyl methane sulphonate (MMS). The two thymidine-kinase-deficient subclones were significantly more sensitive to killing by each of the four chemical mutagens than were wild-type cells. The increased sensitivity to killing by the four mutagens was also reflected in increased mutagenesis (per unit dose of mutagen) to 6-thioguanine resistance. In the light of these results, the significance of thymidine kinase in DNA repair and mutagenesis is discussed.
The phasmid as a tool for plasmid genetics: II. Isolation of point mutations that affect replication of a ColE1-related plasmid
Authors: Cesareni Gianni , Castagnoli Luisa , Brenner Sydney
Published: September 2009

The insertion of a high-copy-number plasmid into a lambdoid phage chromosome which lacks a functional repressor gene confers on the hybrid ‘phasmid’ the capacity to grow on an immune lysogen. This was found to be due to titration of repressor because of plasmid replication. We have exploited this property in order to isolate mutants that affect plasmid replication. These mutants have been mapped in a region that was previously characterized as necessary for plasmid replication and incompatibility properties. Some of the mutations could revert at frequencies characteristic of single-base-pair change mutations.
Genetic background affects expression of t haplotype in mouse sperm
Authors: Olds-Clarke Patricia , McCabe Susan
Published: September 2009

Two aspects of sperm phenotype were examined for tw32/+ males of the inbred strains C3H and C57BL/6 (B6). Sperm from fertile C3H-tw32/+ males very rarely achieved fertilization in vitro, while sperm from congenie C3H-+/+ males had no such difficulties. The presence of tw32 had no effect on ability of B6 sperm to undergo fertilization in vitro. In fertile hybrid males produced from crosses of B6 and C3H strains, tw32 significantly reduced, but did not inhibit completely, the sperms' ability to fertilize in vitro. The presence of tw32 decreased by a factor of two the frequency of abnormal sperm heads in males of the B6 strain, but doubled the frequency in the C3H strain. Hybrid males resembled the C3H strain in this respect. The presence of T or T2J had no effect on the level of sperm abnormalities in any strain. These results emphasize the importance of genetic background in expression of t haplotypes in sperm, and suggest that tw32 can influence a range of sperm characteristics, by interacting with products of other loci.
Genetic basis and natural variation of α-amylase isozymes in barley
Authors: Brown A. H. D. , Jacobsen J. V.
Published: September 2009

Two physiologically and biochemically distinct groups of α-amylase (E.C.3.2.1.1) isozymes are synthesized when isolated aleurone layers of barley are incubated with gibberellic acid (GA3). Isoelectric focusing of the α-amylases showed that the isoelectric points of the isozymes of one group were near pH 5, whereas those of the second group were close to pH 6. Using wheat–barley addition lines, the genes for these groups were located in barley chromosomes 1 and 6 respectively. Joint segregation in the F2 generation of appropriate crosses indicated that the isozymes within each group were inherited collectively, and were attributed to codominant alleles segregating at two presumably complex loci, α-Amy 2 and α-Amy 1.

The extent of genetic variation at these two loci was examined in 40 lines of Hordeum spontaneum (the wild progenitor of barley), and in a complex gene pool representative of H. vulgare (composite cross XXI). Variation at the α-Amy 1 locus was much more extensive than that at the α-Amy 2 locus. The genetic variation at both α-amylase loci exceeded that at the majority of other allozyme loci. However the α-amylase loci were less variable than the two loci coding for the seed storage protein, hordein. The wild species was found to contain much genetic diversity, which might be useful in modifying α-amylase activity by breeding. Parallels between the genetics and variation of α-amylase in barley and wheat were noted.
Selection against harmful mutations in large sexual and asexual populations
Authors: Kondrashov Alexey S.
Published: September 2009

Selection against harmful mutations in large populations is studied assuming that the rate of fitness decrease grows with every new mutation added to a genome. Under this reasonable assumption (Mayr, 1970) the average fitness of a sexual population, without linkage between the loci, is higher, and the average equilibrium number of harmful mutations per individual lower, than in an asexual population. If a gamete contains on the average one or more new mutations, the resulting advantage of sexual reproduction and recombination seems to be sufficient to counterbalance the double advantage of parthenogenesis. Moreover, selection against harmful mutations is probably the most powerful factor preventing linkage disequilibrium even with epistatic interaction between the loci.
Deletion mapping of theniiAniaD gene region ofAspergillus nidulans
Authors: Tomsett A. Brian , Cove David J.
Published: September 2009

The genetic fine-structure of theniiAniaD gene region ofAspergillus nidulanshas been studied using deletion mapping. Deletions were identified asniiAniaD double mutants and comprised 1% of spontaneous chlorate-resistant mutants. All such double mutants were shown to involve deletions and their frequency was not increased by mutagenic treatment with eitherN-methyl-N′-nitro-N-nitrosoguanidine or with ultraviolet light. Deletion maps of theniaD andniiA genes have been constructed. A further class of mutation was also mapped using the deletions. Thesecrnmutations, which affect a gene whose function is as yet unknown, map on the centromere proximal side ofniiA. This analysis of a eukaryote gene cluster will provide a framework upon which to base studies of the regulation of the nitrate assimilation pathway.
Temperature-sensitive mutants ofPhysarum polycephalum– expression of mutations in amoebae and plasmodia
Authors: Burland Tim , Dee Jennifer
Published: September 2009

Over 100 temperature-sensitive mutants ofmt-h (apogamic) strains ofPhysarum polycephalumwere isolated either by testing clones of mutagenized amoebae (ATS mutants) or by the more laborious method of testing plasmodia derived from such clones (PTS mutants). When amoebae and plasmodia of each mutant were tested for growth temperature sensitivity on different media (to give optimum growth of each phase), only 21% of 73 ATS mutants and 32% of 31 PTS mutants appeared to be temperature-sensitive in both phases, suggesting that the majority of mutants are phase-specific, as concluded from several similar studies by previous authors. When the mutants were tested on a third medium which allows growth of both amoebae and plasmodia, many of the mutants no longer had a temperature-sensitive phenotype in either phase. Among the remainder, 51% of ATS mutants and 67% of PTS mutants were temperature-sensitive in both phases. It was suggested that certain media have a remedial effect on some temperature-sensitive mutants so that the phenotype is apparently normal. Thus, the proportion of phase-specific mutants may be over-estimated if tests of temperature-sensitivity are done on the different media commonly used for culture of amoebae and plasmodia respectively. It was concluded that the most efficient procedure for isolation of temperature-sensitive mutants expressed in plasmodia is to screen clones of amoebae on a medium resembling as closely as possible that which is to be used for testing plasmodia.
The functional units of macronuclear assortment inTetrahymena thermophila
Authors: McCoy J. Wynne
Published: September 2009

Macronuclei assorting simultaneously forH, Chx, Mpr, andco, and containing only one or two copies of theHDallele produced several combinations of phenotypes at the other loci, instead of only one or two such combinations. It follows that macronuclear subnuclei, if they exist at all, must frequently exchange parts. Models involving somatic recombination, transient subnuclei, or progressive chromosome fragmentation are discussed as possible explanations.
Variability in the timing and outcome of macronuclear assortment inTetrahymena thermophila
Authors: McCoy J. Wynne
Published: September 2009

New experimental designs have detected unexpectedly large variations in the time at which macronuclear assortment begins, and in the ratios of the stabilized products. Variation is detected between strains, and, within strains, between conjugating pairs. TheChxlocus gave results ranging from late assortment (40–60 fissions) to early assortment with skewed input, indicating the existence of some relation between the parameters of input ratio and time of determination.
Embryonic bone growth in lines of mice selected for large and small body size
Authors: Blakley Ann
Published: September 2009

Embryonic tibia growth was measured in large, small and control mouse embryos in situ and in organ culture. In situ tibias of the large line were longer than controls which were longer than tibias of the small line. Relative growth was approximately equal among lines. In culture tibias of the small line grew more than controls and as much as or more than tibias of the large line. Embryonic genotype appears to be more important in regulating tibia growth than uterine environment. Humoral differences among lines may influence tibia growth.
Genetic regulation of differentiation inPhysarum polycephalum
Authors: Honey N. K. , Poulter R. T. M. , Teale D. M.
Published: September 2009

Plasmodial formation in the MyxomycetePhysarum polycephalumis controlled by a mating type (mt) locus. There are a number of different heterothallicmtalleles; and also a variant,mth, that allows plasmodial formation in pure clones. This paper reports an analysis of this differentiation system. The strainCL(mth) forms plasmodia in pure clones (i.e. it selfs).CLwas mutagenized with NMG and 21 mutants unable to differentiate into amoebae were isolated. The mutants, together withCLd, fell into two complementation groups, twelve indifAand ten indifB. Both complementation groups are closely linked or allelic to themtlocus.difArepresents a gene essential for plasmoclial formation, but it is suggested thatdifBrepresents a class of revertants to themt2heterothallic state. A model of the control of plasmodial formation is proposed in which themtlocus is suggested to code for the repressor of thedifAgene. Genetic control is explained in terms of the dilution of allele-specific repressors.
A mechanism for RNA–RNA splicing and a model for the control of gene expression
Authors: Murray Vincent , Holliday Robin
Published: September 2009

A mechanism for RNA–RNA splicing is proposed. A species of RNA (‘splicer’ RNA) hybridizes to precursor mRNA across the splice point. This hybridization can be with intron or exon sequences or both. The double-stranded RNA structure precisely indicates to the splicing enzymes the exact location for exon ligation.

A model for the control of gene expression is presented. The regulation of synthesis of different splicer RNAs will also control which precursor mRNA molecules are spliced. The removal of intervening sequences from a precursor mRNA molecule could be both a signal for that molecule to be transported to the cytoplasm and a means of allowing gene expression.
Heritability of cranium bifidum and spina bifida in the golden hamster
Authors: Moffa A. M. , White J. A.
Published: September 2009

The heritability (h2) and frequency of the neural tube closure defects, cranium bifidum (CB) and spina bifida (SB), have been estimated for a population of 9-day-old hamster embryos through half-sibling analysis. The average frequency of the total affected embryos per litter is approximately 17% while the pooled estimate forh2based on between sires and between dams within sires components was 4%. This value points to the importance of environmental factors in contributing to the variance in defect frequencies observed within this population.
R.SmaI cleavage map of the transfer region of theE. coliK12 sex factor F
Authors: Willetts Neil , Johnson Gillian
Published: September 2009

A map of the seventeen R.SmaI sites within the 33·4 kb transfer region of plasmid F has been obtained. The number of R.SmaI sites contrasts sharply with the few sites for other restriction endonucleases with hexanucleotide specificity. Location of the R.SmaI sites in γtratransducing phages allowed physical location of lambda insertions into thetraB,traFandtraHgenes.
Isolation and characterization of bleomycin-resistant clones of CHO cells
Authors: Brabbs Sylvia , Warr J. R.
Published: September 2009

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

Population cages were set up containing anX-chromosome balancer, and either a single wild-type chromosome(homozygous cages) or a mixture of wild-type chromosomes(heterozygous cages). The balancer chromosome was eliminated more rapidly from the heterozygous cages, indicating that chromosome heterozygotes are at an advantage over chromosome homozygotes. The disadvantage ofX-chromosome homozygosity in the female is estimated to be about 40%. From earlier studies it is known that the average disadvantage of homozygosity for either of the two major autosomes ofD. melanogasteris approximately 80%. Since these autosomes are both about twice as long as theXchromosome, the disadvantage per unit length is similar for both chromosomal types.

BothX-chromosomal and autosomal heterosis can be explained by either dominance or overdominance at individual loci. However, a dominance model can only explain the similarity if many of theX-linked loci (about 50%) are limited in expression to the female.
Seasonal variation in the frequencies of the alcohol dehydrogenase isoalleles of Drosophila: correlation with environmental factors
Authors: Gionfriddo Maria A. , Vigue Charles L. , Weisgram Pierre A.
Published: September 2009

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

Estimation of meiosis and sporuiation efficiencies in the fission yeast by ascus analysis

Genet. Res. (1979), 33, 109–119

Page 113, line 9: formula should read

Page 113, 4 lines from foot of page:

‘pi’ should read ‘Pi’
Effective population size: the effects of sex, genotype, and density on the mean and variance of offspring numbers in the flour beetle,Tribolium castaneum
Authors: Wade Michael J.
Published: September 2009

In this paper I present the results of an experimental study of the effects of genotype and density on the mean and variance of offspring numbers in both sexes of the flour beetle,Tribolium castaneum. From the observed variance in offspring numbers the effective population size at several different densities is estimated using the methods of Crow & Morton (1955).

I found that both the mean and variance of offspring numbers varied with genotype and density. In general, males were more variable in offspring numbers than females and this variability increased with density. Individuals homozygous for the black body colour mutant,b/b, were less variable in offspring numbers than + / + individuals, but the latter produced more offspring at most densities. As density increased, + / + individuals became more variable in offspring numbers whereasb/bindividuals were less sensitive in this regard. These findings are discussed in relation to the ecology of selection at the black and closely linked loci.
A transposing forked-duplication with position effect variegation in Drosophila
Authors: Shukla P. T. , Auerbach C.
Published: September 2009

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

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

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

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

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

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

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

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

Cockerels singly or doubly heterozygous (t1/ +, t2/ + and tl/t2, respectively; collectively heterokaryotypic, HTK) for two different Z-autosome translocations (t1, t2) produce an array of chromosomally balanced and unbalanced spermatozoa owing to adjacent segregation and nondisjunction at the first meiotic division. This study addresses the developmental capacity of embryos derived from matings of control ( + / + ) and HTK (tl/ +, t2/ +, tl/t2) cockerels with hens bearing normal chromosome complements (+ /W).

Estimates of the hatchability of fertile eggs sired by + / +, tl/ +, t2/ + and tl/t2 cockerels were 82·8%, 43·0%, 41·3% and 10·9%, respectively. Approximately 75% of the mortality observed in embryos sired by HTK cockerels occurred by four days of incubation. Developmental arrest generally occurred earlier in embryos sired by t2/+ and tl/t2 cockerels than in those by tl/ + cockerels. These differences reflect variation in the degree of embryonic chromosome unbalance expected among embryos of the different sire groups. The pattern of mortality after three days was similar in embryos sired by HTK cockerels. In control embryos, mortality was highest on days 20–21 of incubation.

Chromosome analysis of 16/18 h embryos, day 1/5 embryos and hatched chicks sired by HTK cockerels revealed that most, if not all, chromosomally unbalanced embryos died during development; the majority before three days of incubation. Partial monosomy for chromosome one was found to be more deleterious to embryonic development than partial trisomy.
Isolation and characterization of deficiencies exposing therudimentarylocus ofDrosophila melanogaster
Authors: Naguib Fardos N. M. , Jarry Bruno
Published: September 2009

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

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

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

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

pMO1111, a derivative of FP110 carrying a Tn1insert, has been used to generate two plasmid primes carryingPseudomonas aeruginosachromosome. pMO1112 has been shown to carry thepro-82+gene and pMO1113 carriesargH+andlys-12+. pMO1112 is considerably more stable than pMO1113 in arecA+background.
Gametic selection and the selection component analysis
Authors: Nadeau Joseph H. , Dietz Klaus , Tamarin Robert H.
Published: September 2009

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