Showing papers in "Journal of Genetics in 1964"

Equilibria under natural selection at a sex-linked locus

Abstract: An equilibrium of a pair of allelomorphs at a sex-linked locus can be stable under natural selection if the fitnesses of the mutant hemizygote and homozygote differ from that of the normal in opposite directions, even if the female heterozygote is less fit than the mean of the homozygotes. But if the fitnesses of the mutant homozygote and liemizygote differ in the same direction from those of the normals, stability demands that the heterozygous female should be fitter than either homozygote. The facts as to human glucose-6-phosphate dehydrogenase are discussed in the light of these findings. In this case it seems likely that there is real heterosis, but this may not be true for most such equilibria found in nature.

Glucose-6-phosphate dehydrogenase deficiency in an Indian rural area

Abstract: Glucose-6-phosphate dehydrogenase deficiency exists in the Godavari valley in the Eastern Ghats of India. Both the partial Negro and the complete Caucasian type are found. The frequency differs greatly in adjacent communities. In the area of Thallavaram it reaches 12.2±2.9%, being less elsewhere.

Heterostyly in Biophytum sensitivum DC

Abstract: Heterostylism inBiophytum sensitivum DC is described with measurements of style and anther lengths and pollen grain diameters The fertility of different crosses is compared One type of illegtimate union is moderately fertile

Local somatic colour changes inSalvia splendens

Abstract: An attempt has been made to give an explanation of the origin of single and particularly of combined differently coloured spots, found in the inflorescence of heterozygous plants ofSalvia splendens. The method of comparing the type of colouring of the spots to the phenotypes of the genotypically Known Salvia colour forms was used. The paired, or more complex combined (and seccndarily also the single) spots are considered to be a phenotypical expression of reciprocal somatic gene (block, chromosome) exchanges under the cytological disturbances proposed.

Reversed bean vines

Abstract: Artificial reversal of the direction of coiling in two species of bean vine caused an increase in the weight ratio of beans to shucks. The reversed vines produced twice the percentage of inverted colour beans.

Interaction between genotype and temperature for wing length, bristle number and EGG count inDrosophila ananassae

Abstract: Data on wing length, bristle number and egg count were collected on two groups of full-sibs ofDrosophila ananassae, separated and raised at temperatures of 20° and 25°C from larval to adult stage. The flies raised at 20°C had longer wings and fewer bristles than those raised at 25°C. The number of eggs laid was also reduced at 20°C.

Phenotypic, genetic and environmental correlations between chaeta number and wing length inDrosophila melanogaster

Abstract: Biometric data on bristle numbers for two segments and wing length of 936 femaleDrosophila melanogaster derived from a wild stock are presented. Heritabilities were about 0.4. The genetic correlation between the two bristle numbers was +.91, the environmental correlation insignificant. The genetic correlations between wing length and the bristle numbers were +39 and +.17, the environmental correlations again insignificant.

Analysis of 6 × 6 diallel cross for EGG production in Drosophila melanogaster

Abstract: 1. There is a considerable amount of interaction between the environment and the genetic factors controlling egg production InDrosophila melanogaster. 2. The genes affecting egg production exhibit both additive genetic effects and dominant deviations. They also show non-allelic interactions. The non-allelic interaction between G and D results in low egg production. 3. An asymmetry in the distribution of positive and negative allels exists in the parents, which was understandable as three of the six lines included in the trial were selected for low egg production and the other three for high egg production. 4. There are probably present more dominant than recessive genes affecting egg Production in the parental stock used in these studies; the ratio of recessives to dominants being of the order of 1:4. Low egg production is due to recessive genes, high egg production to their dominant allels. 5. Dominance deviations present were largely unidirectional. 6. The order of dominance of the six lines used was D, B, E, C, A, F.

Some anatomical characteristics of eight inbred strains of Mesocricetus auratus auratus (Syrian hamster)

Abstract: Anatomical characteristics of eight inbred lines (17 to 22 generations of brothersister mating) were compared. Several differences in body and organ weights were observed which vary in statistical significance at different age levels. Sex differences in all lines are smaller body weight, but larger kidney and spleen weights in females. Salient strain characteristics are: dental caries susceptibility in one line; hereditary, dystrophy-like myopathy in another; large body size in another line and significantly smaller body size from birth to 2f days in still another line. There were also significant line-characteristic differences in heart and lung weight and in the weight of interscapular brown fat. Gonads were smallest in the dystrophic line and in males of another line the thyroid size was abnormally small at 21 days of age.

Selection after grossing two homozygous stocks in a partially self-fertilized population

Abstract: The distribution of the genotypes in the successive generations on crossing two homozygous lines has been considered for populations where both selfing and natural crossing exist simultaneously. Different cases of selections that breeders use in the breeding programme have been discussed. The formulae are given by which the genotype frequencies in a given generation can be expressed in terms of those in the preceding generation.