• G. H. Beale

      Articles written in Journal of Genetics

    • Genetics and chemistry of flower colour variation inLathyrus odoratus

      G. H. Beale G. M. Robinson Robert Robinson R. Scott-Moncrieff

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      1. The inheritance of two new flower colour factors—bright and salmon—is described. Bright is an incomplete recessive, and salmon a recessive factor hypostatic to red (e).

      2. Two factors, red (e) and salmon (sm), are associated with a difference in the degree of oxidation of the anthocyanins in the flowers, and with a similar difference in the leucoanthocyanins in the seed coats.

      3. One factor, dull (d), is associated with a difference ofpH in the cell sap of the flowers.

      4. At least seven factors—dark wing (dw), copper (k), maroon (m), mauve (co); bright (br), picotee (p) and hooded (h)—are associated with differences in the relative amounts of anthocyanin and anthoxanthin co-pigment.

      5. Variation in methylation of the anthocyanin is correlated with the quantity of anthoxanthin.

      6. Variation in glycosidal residues has not so far been associated with any genetic factor.

      7.Lathyrus odoratus agrees very closely with plants of other genera in regard to the inheritance of comparable chemical differences.

    • The genetics ofverbena. I

      G. H. Beale

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      The garden forms of “Verbena hybricla” show variations of two kinds, the first apparently derived from differences between its four reputed parental species, the second -from mutations which have taken place since the original hybridization about a hundred years ago.

      The second group depends on ten gene differences, which show complete dominance of a common wild type. The first group on the other hand depends on eight gene differences which show various degrees of dominance.

      There are two sets of triple allelomorphs controlling colour, which are remarkable in that the extreme members of each series determine the same phenotype and differ only in that one is dominant, the other recessive. to the intermediate allelomorph. Possibly the dominant member is derived from a species difference, the recessive from mutation.

      Aberrant ratios, modifying factors and extremely close linkages occur with exceptional frequency and are probably due to the hybrid origin of the group.

      The pigment chemistry will be described later. I would be most grateful if collectors or others in South America would supply seeds from the wild of any species mentioned in this paper, or any other closely related species.

    • The genetics ofVerbena - II. Chemistry of the flower colour variations

      G. H. Beale J. R. Price R. Scott-Moncrieff

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    • Gene relations and synthetic processes

      G. H. Beale

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      The genetic phenomena of mutation, dominance and epistasy are analysed to discover if they may be used as indicators of the direction of synthetic processes. From general considerations the following conclusions are drawn:

      Mutation away from a standard wild type usually results in the formation of simpler substances, i.e. those requiring a smaller number of stages for their synthesis. Hence, where there is a qualitative difference brought about by a gene substitution, the substance associated with the mutant gene is likely to be an intermediate product in the synthesis of the substance associated with the wild-type gene.

      Dominance cannot be used as an indicator of synthetic processes in those organisms which have a proportion of non-recessive mutants, since there is no sign that dominant mutants differ from recessive mutants in any developmental way. But dominance of the wild type in most organisms is fairly complete and therefore direction of mutation, when not already known, can be inferred.

      Epistasy of the type which gives a 9:3:4F2 ratio is concluded to be an indication that a reaction brought about by an epistatic gene is an essential precursor of a reaction brought about by the corresponding hypostatic gene.

      These conclusions are applied to variations affecting anthocyanins. It is deduced that cyanidin derivatives are synthetically simpler than delphinidin, but the relation of pelargonidin derivatives to the other anthocyanins is not clear. Monosides are apparently simpler than diglycosides, though more data are required on this type of substitution. All the known mutations affectingpH of the petal cell sap are in the direction acid → alkaline. Natural selection has apparently favoured the production of a more acid sap in the petals than in the plant in general.

      The anthocyanin data confirm that: (1) Changes in the wild-type phenotype do not occur at random, but preponderantly in one direction, from the complex to the simple, and (2) That dominance is associated with wild-type allelomorphsirrespective of the nature of the chemical changes produced by a gene substitution.

    • The calculation and precision of linkage values from tetrad analysis

      K. Mather G. H. Beale

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      The usual type of genetic experiment utilizes only one of the four spores resulting from meiosis in a mother cell. In some organisms it is possible to make a genetical analysis of all four spores, and such analyses will yield considerably more information about linkage of two genes, or of gene and centromere, than does the common type of genetical experiment. The observations made on different spores of the same tetrad are, however, not independent but the problems of estimation which arise may be overcome by the method of maximum likelihood.

      Estimation of the recombination fraction and its variance from completely and incompletely analysed tetrads with and without viability disturbances is considered. The relative values of the various types of data are given, and the appropriate method of combining them in a single estimation is also given. Special attention is paid to the cases of close linkage of two genes, and linkage of a gene to the centromere.

      The calculation of coincidence values and their variances is discussed.

      Many of the calculations are illustrated arithmetically, using data from segregation inNeurospora crassa.

    • An unstable gene inPortulaca: Mutation rate at different temperatures

      A. C. Fabergé G. H. Beale

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      A variety ofPortulaca grandiflora with coloured mutation spots on its stems and petals was subjected to temperatures of 25, 30, 35 and 40° C. for 6 weeks. Four clones were used, and four plants of each clone. The number of mutations was estimated by counting the spots on a sample of the stems.

      It was found that there is a significant reduction in mutation rate with rising temperature, whether one takes as a standard a unit of stem length, a cell, or a unit of time.

      This fractionalQ10 is incompatible with a direct application of Delbrück’s theory, according to which mutations are changes in the position of atoms in a molecule produced by thermal agitation. In its simple form, this theory requires aQ10 of about 5.

      It is suggested that mutations can be classified into (a) aschistic, due to breakdown of an existing allele, and (b) schistic, due to inexact copying in gene reproduction. There are indications that our mutations in the unstable gene ofPortulaca belong to the second class, but this is by no means certain. If it belongs to the first type, the effect of temperature must be quite indirect; if to the second, temperaturemight act fairly directly.

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