Showing papers in "Heredity in 1977"
TL;DR: The analysis of covariance structures is adapted to the simultaneous maximum likelihood estimation of genetical and environmental factor loadings and specific variances and the goodness of fit is tested by chi square and standard errors of parameter estimates can be obtained.
Abstract: The analysis of covariance structures (Joreskog, 1973) is adapted to the simultaneous maximum likelihood estimation of genetical and environmental factor loadings and specific variances. The goodness of fit is tested by chi square and standard errors of parameter estimates can be obtained. Any linear model used in univariate genetical analyses can be extended to the multivariate case. Most biological hypotheses about the relationships between variables can be specified by a variety of factor models. Individual parameters can be given fixed values or set to zero and hypotheses concerning the congruence of genetical and environmental correlations can be tested. The method is illustrated with published twin data on cognitive abilities.
411 citations
TL;DR: The results of this study are consistent with the hypothesis that many of the duplicated structural genes of this species have diverged in structure and function subsequent to the origin of the polyploid wheats.
Abstract: The genetic control of the production of multiple forms of lipoxygenase, endopeptidase, acid phosphatase, aminopeptidase, and alcohol dehydrogenase in hexaploid wheat has been studied using the zymogram technique. Aneuploid strains which encompass a range of from zero to four doses of each chromosome in the complement were analysed. The localisation of 22 structural genes to specific chromosome arms is reported. Extensive inter-genomic variation between homoeologous isozyme structural genes has been detected. The results of this study are consistent with the hypothesis that many of the duplicated structural genes of this species have diverged in structure and function subsequent to the origin of the polyploid wheats.
143 citations
TL;DR: This paper attempts to explain how the different heterogametic mechanisms of sex determination, such as male and female heterogamy, can arise from a single ancestor by first building and analysing some models and then comparing the models to relevant data from animals.
Abstract: This paper attempts to explain how the different heterogametic mechanisms of sex determination, such as male and female heterogamety, can arise from a single ancestor. We study this problem by first building and analysing some models and then comparing the models to relevant data from animals. Based on these comparisons, the models appear to be useful for understanding how sex determining mechanisms evolve. Some results of the models include:
129 citations
TL;DR: It is postulated that the S-allele produces several fractions of proteins and S.allele specificity is expressed by a combination of the protein fractions.
Abstract: Analysis of S-specific proteins in stigma of Brassica oleracea L. by isoelectric focusing
101 citations
TL;DR: It is concluded that the reduction or elimination of segments of late replicating DNA from rye chromosomes should be a major object in the breeding of economically useful triticales, and the means of achieving this goal are discussed.
Abstract: Evidence is presented leading to the conclusion that there is, in wheat-rye genotypes, a causal link first, between the presence of late replicating segments of heterochromatin on rye chromosomes and the occurrence of chromosome bridges at anaphase and of other aberrant nuclei in coenocytic endosperm, and second, between the frequency of occurrence of aberrant nuclei in young endosperms and the degree of grain shrivelling at maturity Bridges in coenocytic endosperm of wheat-rye genotypes are caused at anaphase by the failure of rye chromosomes to separate at the telomeres where late replicating DNA is known to be located The frequency of occurrence of aberrant nuclei in endosperms of the seven disomic chromosome addition lines of King II rye to Holdfast wheat fixed at the end of the coenocytic stage is significantly lower in three addition lines lacking a large telomeric block of terminal heterochromatin on one arm (due to its deletion) than in the remaining four addition lines without deletions of terminal heterochromatin Evidence is presented showing a significant positive correlation between the proportion of aberrant nuclei in endosperms of six hexaploid triticales during the first 4 days after pollination, and the degree of grain shrivelling scored at maturity It is concluded that the reduction or elimination of segments of late replicating DNA from rye chromosomes should be a major object in the breeding of economically useful triticales, and the means of achieving this goal are discussed
87 citations
TL;DR: A model for the induction of the DNA changes, involving a type of IS-element has been proposed, and the expression of the induced changes, in terms of altered numbers of copies of particular sequences at specific sites within the genome has been considered.
Abstract: The conditions for the induction and stabilisation of environmentally induced changes in flax, and the characterisation of these changes for six characters have been reviewed. A model for the induction and expression of these changes has been proposed. The environmental conditions for the successful induction of heritable changes comprise at least two components; a specific inducing component, for example a particular fertiliser treatment, which is required to induce the change, and a general inducing component, providing for vigorous healthy growth, which is necessary for the induced changes to be inherited. Stable induced changes require appropriate environments for their maintenance, for example heated greenhouses for the first 5 weeks of seedling growth and adequate pot size. Under certain growth conditions the induced changes can themselves be modified. DNA differences induced in the different genotrophs can occur at a number of sites within the genome, including the ribosomal RNA cistrons. Environmental induction causes changes in the isozyme band patterns of peroxidase, acid phosphatase and esterase isozymes. The genotrophs behave as distinct genetic types in crosses, with a complex pattern of inheritance of the hairy septa character. The association between the different induced characters is examined. All the genotrophs can be distinguished from each other on at least one of the six characters. A model for the induction of the DNA changes, involving a type of IS-element has been proposed. The expression of the induced changes, in terms of altered numbers of copies of particular sequences at specific sites within the genome, has been considered.
83 citations
TL;DR: The western North American shrub Atriplex canescens is predominantly dioecious, but most populations contain some monoecious individuals, and a sex-determining mechanism is proposed of XXXX for pistillate plants, XXYY for staminate plants, and XXXY for monoeciously plants and those that vacillate among floral phenotypes from year to year.
Abstract: The western North American shrub Atriplex canescens is predominantly dioecious, but most populations contain some monoecious individuals. A tetraploid half-sib family consisting of 665 individuals was evaluated annually for floral phenotype (sex expression) from 1972-75. The autumn/winter of 1972-73 started out mild and wet and then turned unusually cold. The half-sib family expressed a very different sex ratio in the 1973 growing season than in the three other years. A sex-determining mechanism is proposed of XXXX for pistillate plants, XXYY for staminate plants, and XXXY for monoecious plants and those that vacillate among floral phenotypes from year to year.
78 citations
TL;DR: Samples of mature plants of Lotus corniculatus show that the polymorphism for cyanogenesis in this species is not directly comparable with that in Trifolium repens, and there is a decline in the frequency of the cyanogenic form from the Netherlands to Scandinavia.
Abstract: The environmental factors influencing a steep morph-ratio cline in a maritime population of Lotus corniculatus have been studied in detail. The frequency distribution of cyanogenic plants in the cline has remained stable for 16 years, plants very near the sea being predominantly acyanogenic, whereas 200 m inland 70 per cent of the plants are cyanogenic. Analyses of the biotic, edaphic and microclimatic environment of this population showed that an exposure gradient (wind and windborne salt) and the distribution of known selective herbivores were the only factors which were consistently associated with the cline. On the basis of these results and the hypothesis that cyanogenesis is a protection against herbivores it was predicted that other sites along the coast, which showed similar environmental variation, should also show a similar distribution of selective herbivores and of cyanogenic plants. It was confirmed that at sites exposed to wind and windborne salt the selective herbivores were rare and the frequency of cyanogenic plants was low. At sites which were less exposed, the numbers of selective herbivores and the frequency of cyanogenic plants were both higher.
69 citations
TL;DR: The genetic basis and mechanism of male recombination are discussed, along with its possible influence on adaptability in natural populations.
Abstract: Spontaneous second chromosome recombination has been observed in males of Drosophila melanogaster newly derived from natural populations. From a Cambridge, England, natural population, two lines out of 20 showed male recombination, and in an Oklahoma, U.S.A., natural population all of 25 lines showed male recombination. One line, OK1, was characterised in more detail, and it was observed that male recombination was probably caused by dominant second and dominant third chromosome elements. The majority of recombination events in the second chromosome occurred in the centromeric region and in the right arm, and male recombinants were recovered in clusters, suggesting that some male recombination occurs in premeiotic cells. Since both single and multiple recombinants were recovered, it was possible to measure chromosome interference for male recombination. This interference was observed to be negative. Finally, there is a reciprocal-cross effect associated with male recombination and F1 female sterility in the OK1 line. This effect on male recombination is apparently not caused by a cytoplasmic suppressor of recombination. The genetic basis and mechanism of male recombination are discussed, along with its possible influence on adaptability in natural populations.
60 citations
TL;DR: The contribution of two of the major causes of non-normality in the distribution of pure-breeding lines derivable by single seed descent from an F2, namely, linear epistasis and genotype × micro-environment interaction are examined theoretically by algebraic models and computer simulations.
Abstract: The causes and consequences of non-normality in predicting the properties of recombinant inbred lines
58 citations
TL;DR: Field and laboratory data indicate that interpopulation differences in minimum size at first reproduction are inherited and probably represent local adaptations.
Abstract: Inherited interpopulation differences in size at first reproduction in threespine stickleback, Gasterosteus aculeatus L.
TL;DR: Inter-stock breeding results indicate that the obesity in the Zucker-Koletsky hybrid stock is also inherited in a recessive manner, and it is proposed that f be renamed fak until it can be proven that fa and fak are identical.
Abstract: The breeding data on Zucker rats and on Koletsky rats confirm that the obesity in these two strains of rats is inherited recessively and results from single gene mutations. Mating a Zucker heterozygote to a Koletsky heterozygote produced obese F1 progeny. Inter-stock breeding results indicate that the obesity in the Zucker-Koletsky hybrid stock is also inherited in a recessive manner. The gene that controls obesity in the Zucker rats, fatty (fa), and the gene that controls obesity in the Koletsky rats, f, are thus alleles at the same locus. We propose that f be renamed fak until it can be proven that fa and fak are identical.
TL;DR: An appreciable rate of self-fertilisation has been found in the four populations but the individual test plants give highly variable results, and an important part of the variation may be ascribed to differences in the densities of local male- fertile plants in the first few metres around the test plants.
Abstract: To determine the rate of self-fertilisation in male-fertile plants of thyme, four populations, homozygous for dominant chemical marker alleles, were chosen. Male-sterile plants and male-fertile plants with the corresponding recessive marker alleles were transplanted into these populations and the seedlings obtained by growing the seeds gathered in 1974 and 1975 from these test plants were analysed. An appreciable rate of self-fertilisation has been found in the four populations (0·36, 0·49, 0·35 and 0·10) but the individual test plants give highly variable results (from 0 to 0·79). The figures were rather consistent from one year to the next. An important part of the variation in self-fertilisation may be ascribed to differences in the densities of local male-fertile plants in the first few metres around the test plants.
TL;DR: There was a constant relationship between cell mass and DNA amount per cell for all species, irrespective of the basic genome size, extent of DNA replication or of the information content of the genome.
Abstract: The extent of variation in cell mass, and in the size of the cell population of cotyledons has been examined to determine their relative roles in the evolution of variation in seed weight within the genus Vicia. In the 12 species examined there were highly significant correlations between seed weight and cotyledon cell number, and between seed weight and mean cell mass. The extremes differed by a factor of 625 fold in dry seed weight; of this variation, most (140 fold) was attributable to variation in the size of the cell population and only a 4.47-fold change was due to differences in cell mass. The cotyledon cells of all the species, irrespective of their seed weight showed very high levels of replication of their DNA. The implications of these data in terms of the evolution of seed mass in Vicia is considered. There was a constant relationship between cell mass and DNA amount per cell for all species, irrespective of the basic genome size, extent of DNA replication or of the information content of the genome. The basis of this relationship, and its evolutionary implication, is considered.
TL;DR: The experiment demonstrated a correlation between survival in alcohol-supplemented media and enzyme activity, which supports the hypothesis that enzyme activity per se, rather than some other attribute of allelic differences, may be responsible for the previously observed selective advantage of high activity alleles on alcohol media.
Abstract: Relative egg to adult viability was compared in three stocks of Drosophila melanogaster differing in alcohol dehydrogenase (ADH) activity. Two of these, Grell's standard ADHS and a mutant ADHS strain producing half the normal number of ADH molecules, had the same electrophoretic mobility. The experiment demonstrated a correlation between survival in alcohol-supplemented media and enzyme activity. This supports the hypothesis that enzyme activity per se, rather than some other attribute of allelic differences, may be responsible for the previously observed selective advantage of high activity alleles on alcohol media.
TL;DR: A model involving a specific pairing of homologous double-stranded nucleic acid molecules is applied to some parts of genetic recombination, a part of which can be described by a highly compact and symmetrical structure.
Abstract: A model involving a specific pairing of homologous double-stranded nucleic acid molecules is applied to some parts of genetic recombination. The most original features of this application of the model relate to the initiation process, a part of which can be described by a highly compact and symmetrical structure. The model also provides a simple view of the formation of hybrid nucleic acid. The possibilities of detecting four-strand structures are briefly discussed.
TL;DR: The whole chromosome analysis shows that the heterosis exhibited in the F1 between the parents is explained by the dispersion of increasing chromosomes between theParents with directional dominance for increasing loci, combined with between chromosome interactions.
Abstract: The genetical architecture of height in the cross between the wheat varieties Chinese Spring and Cappelle-Desprez is examined using crosses involving the complete set of single chromosome substitution lines of Cappelle-Desprez into Chinese Spring. Seventeen of the 21 chromosome pairs exhibit genetical variation with respect to this character and in addition to additive and dominance effects, epistatic effects of an additive × additive type are shown to be an important component of the variation. The details of the genetical architecture revealed by whole chromosome analysis on the one hand and conventional generation means analysis on the other are very similar. However, the whole chromosome analysis reveals a much greater complexity and in particular shows that the heterosis exhibited in the F1 between the parents is explained by the dispersion of increasing chromosomes between the parents with directional dominance for increasing loci, combined with between chromosome interactions. Estimation of the effects of individual chromosomes is attempted but a satisfactory model is not found. Nevertheless, tentative predictions as to the consequences of new chromosomal combinations are made on the basis of the best fitting model.
TL;DR: It is demonstrated that classical sexual recombination occurs in this group of rotifers, using acrylamide gel electrophoresis to identify clones of Asplanchna girodi homozygous for two different alleles at a single malic enzyme locus.
Abstract: Data exist suggesting both the presence and absence of recombination in monogonont rotifers. It was therefore previously unknown whether members of this group have true sexual reproduction. We have used acrylamide gel electrophoresis to identify clones of Asplanchna girodi homozygous for two different alleles at a single malic enzyme locus. Crosses made among these clones produced heterozygotes, thus demonstrating that classical sexual recombination occurs in this group of rotifers.
TL;DR: Joint selection for both extremes of mean performance and of sensitivity to a macroenvironmental variable is proposed in this paper for both mean and sensitivity to macro-environmental variables, and the results show that both extremes are equal.
Abstract: Joint selection for both extremes of mean performance and of sensitivity to a macroenvironmental variable
TL;DR: It was concluded that the genetic basis of pupal colour dimorphism in the swallowtail Papilio polyxenes is a threshold trait with quantitative genetic variation underlying the two phenotypes, thus explaining the occurrence of mismatches between pupal and background colour.
Abstract: The genetic basis of pupal colour dimorphism in the swallowtail Papilio polyxenes was studied by surveying the frequencies of brown and green pupae in broods from 23 wild caught females, and by selecting for production of brown and green pupae. It was concluded that the genetic basis of the dimoprhism is a threshold trait with quantitative genetic variation underlying the two phenotypes. It was further concluded that the dimorphism is maintained in nature by weak stabilising selection, thus explaining the occurrence of mismatches between pupal and background colour.
TL;DR: The use of precise precursors in the biosynthetic pathway to anthocyanidin formation provided confirmatory evidence for the identification of the genes involved in the somatic aberrations.
Abstract: Many aberrant somatic sectors on the corollas of heterozygous Antirrhinum majus can be related to a number of genetic causes while twin-spots are attributed to somatic crossing-over, hitherto, considered a relatively rare occurrence in higher plants. The administration of caffeine increases the frequency of single aberrant sites and also of twin-spots. The inclusion of the unstable genes nivea-recurrens and pallida-recurrens has no effect on the frequency of twin-spots. Homozygosity following somatic crossing-over is presumed for several loci and some evidence is presented for deficiency aberrations. The use of precise precursors in the biosynthetic pathway to anthocyanidin formation provided confirmatory evidence for the identification of the genes involved in the somatic aberrations.
TL;DR: It was able to show, however, that cold temperature does not act directly as a selective agent on the polymorphism of cyanogenesis in L. corniculatus.
Abstract: Genotype × environment interactions associated with temperature were shown to occur in populations of L. corniculatus. The effects were related to the genetic structure of the populations. We were able to show, however, that cold temperature does not act directly as a selective agent on the polymorphism of cyanogenesis in L. corniculatus.
TL;DR: There was a deficiency of resistant males in the F2 litters whereas phenotypic ratios were close to expectation in F2 females and backcrosses, and it appears that the heterozygote may also be at a selective disadvantage in the absence of warfarin.
Abstract: Dominant warfarin resistance and a recessive haemorrhagic trait are apparently controlled by the same allele Rw2. Twenty-eight F2 litters and 18 backcross litters of wild rats were scored for resistance when 8 weeks of age. There was a deficiency of resistant males in the F2 litters whereas phenotypic ratios were close to expectation in F2 females and backcrosses. Any deficiency of resistant males in F2 litters could be due to the selective death of the Rw2Rw2 genotype. The size of F2 and backcross litters at birth is similar whereas by 8 weeks the former are significantly smaller than the latter. Samples of rats from populations in mid Wales were scored for resistance. There was a significant decline in the frequency of phenotypic resistance in one large population (N≈500) starting when the frequency of the Rw2 allele was relatively low (c. 0·10–0·23). Since few alleles can be lost by selective death of Rw2Rw2 males in these circumstances it appears that, in the absence of warfarin, the heterozygote may also be at a selective disadvantage. Where rats are intensively poisoned with warfarin both Rw2 and its alternative Rw1 are maintained in populations by heterozygous advantage. The ecological unreality of the concept of segregational load is discussed. Strong selection influences the frequency of the alleles of Rw. Chance must also have an important role. Populations of rats in rural areas are widely scattered and sometimes small in size. There is an unpredictable amount of movement between these populations which occur in very heterogeneous environments.
TL;DR: The strength of the selection was very much modified by an interaction between temperature and density, and evidence for a chemical mechanism which mediates frequency dependent selection, by conditioning, in the larval environment is discussed.
Abstract: Selection in egg-to-adult viability was investigated at the Esterase-6 locus of Drosophila melanogaster. A factorial experiment was carried out with three variables, temperature, density and genetical composition; there were four temperatures (15°, 20°, 25° and 30°), three densities (115 ml, 10 ml and 2.5 ml of food). Strong frequency dependent selection was observed in many environments. The strength of the selection was very much modified by an interaction between temperature and density. The results are discussed in relation to evidence for a chemical mechanism which mediates frequency dependent selection, by conditioning, in the larval environment.
TL;DR: A non-parametric approach is proposed, that does not require the definition of a mapping function, computation of coefficients of coincidence, nor knowledge of map length or sex differences in recombination.
Abstract: The problem of obtaining a genetic map of a linkage group from pair-wise recombination data is considered. A non-parametric approach is proposed, that does not require the definition of a mapping function, computation of coefficients of coincidence, nor knowledge of map length or sex differences in recombination. An application to Bridges and Morgan's (1923) data on chromosome 3 of Drosophila melanogaster is presented.
TL;DR: The effective size of a natural Drosophila subobscura population has been computed by drawing together various pieces of ecological information and the value, for both variance and inbreeding effective numbers, is approximately 400.
Abstract: The effective size of a natural Drosophila subobscura population has been computed by drawing together various pieces of ecological information. The value, for both variance and inbreeding effective numbers, is approximately 400. This is largely due to reductions caused by a winter bottleneck and non-random distributions of family sizes. Areas where such estimates might be refined further are pointed out, and the implications of the results are discussed.
TL;DR: If the L1 and L2 testers prove to be inadequate due to the presence of common loci, modifications of the analyses are proposed which correct the resulting biases in the genetical components of variation.
Abstract: When the population under investigation consists of highly inbred lines the full triple test-cross of Kearsey and Jinks (1968) supplemented by the selfed progenies of the population allows unambiguous and independent tests for epistasis and the adequacy of the pure-breeding testers, L1 and L2. This can also be achieved by supplementing the simplified triple test-cross of Jinks, Perkins and Breese (1969) with the selfed progenies of the L1i and L2i families. If the L1 and L2 testers prove to be inadequate due to the presence of common loci, modifications of the analyses are proposed which correct the resulting biases in the genetical components of variation.
TL;DR: The genetical consequences of common alleles in the L1 and L2 testers of a simplified version of the triple test-cross which is applicable to populations of inbred lines are examined and the test for epistasis under these circumstances becomes ambiguous and can spuriously detect non-allelic interactions when they may not exist.
Abstract: The genetical consequences of common alleles in the L1 and L2 testers of a simplified version of the triple test-cross which is applicable to populations of inbred lines are examined. The test for epistasis under these circumstances becomes ambiguous and can spuriously detect non-allelic interactions when they may not exist although it still provides a test for epistasis and the adequacy of the testers simultaneously. The tests of significance and the estimates of additive variation are biased to an extent related to the dominance and dominance x additive effects of the common loci while the significance and estimates of dominance variation are deflated because they reflect the dominance effects at the non-common loci only. The covariance of sums and differences is also underestimated for the same reasons. These expectations are illustrated by analysing the 190 simplified triple test-crosses that could be extracted from a 20 x 20 diallel set of crosses between pure-breeding lines of Nicotiana rustica.
TL;DR: It is concluded that the latter alternative seems at least equally plausible judging from the available data, and that there appears to be no reason to believe that the spread of radiate groundsel is a measure of continuing hybridisation.
Abstract: Over the past 20 years there has been a rapid spread in the British Isles of the radiate variant of Senecio vulgaris L. The evidence that this variant has arisen (a) from introgression into S. vulgaris by S. squalidus, or (b) as a mutant of S. vulgaris, is summarised. It is concluded that the latter alternative seems at least equally plausible judging from the available data, and that there appears to be no reason to believe that the spread of radiate groundsel is a measure of continuing hybridisation.