• S. S. Prabhu

      Articles written in Journal of Genetics

    • Sterility mutations inDrosophila melanogaster

      S. S. Prabhu

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      In an attempt further to test Berg’s inference that there are “much more numerous sterility mutations in theX-chromosome than in the second chromosome and possibly more than in all the autosomes taken together”, experiments were devised to find the frequency of the “male-specific”. (producing sterility in the males only, leaving the females fertile) and “female-specific” (producing sterility in the females only, leaving the males fertile) dominant sterility mutations produced by X-rays in the autosomes, as these had not been studied by Berg.

      The results obtained show that such sex-specific dominant sterility mutations must be very rare, as compared with recessive sterility mutations of all kinds. Berg’s original conclusion, therefore, is confirmed.

      Consideration of the data on sterility of the different classes ofF1 andF2 males and females shows that the rather high percentage of sterility among the male offspring of irradiated males is due, in very large measure, to absence or incompleteness of theY-chromosome in the affectedF1 males.

      By far the greater part of the sterility of the grandsons of irradiated males is due to sterility genes located in theX-chromosome. Localization of eight of theseX-steriles shows at least five, and possibly as many as seven of them, to be located in the relatively short region between garnet and forked. This lends support to a suggestion made by Berg that not merely theX-chromosome as a whole, but its active region, contains per unit of length a greater number of genes affecting sex than do the other chromosomes, and it is in agreement with data by Berg & Kovalev dealing with the location of seventeenX-steriles.

      The present data, however, limit considerably more than those heretofore obtained the extent of the active region chiefly concerned in theX-chromosome sterility mutations, and suggest that most of them must be confined to a region not over ten linkage units long, and perhaps even to a single locus. This transfers a large part of the problem involved in the high frequency ofX-chromosome sterility mutations (and perhaps much of the problem of sex determination also) from theX-chromosome as a whole to this small region, or locus.

    • Analysis of 6 × 6 diallel cross for EGG production inDrosophila melanogaster

      H. P. Singh S. S. Prabhu Prem Narain Swastika Negi

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      There is a considerable amount of interaction between the environment and the genetic factors controlling egg production InDrosophila melanogaster.

      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.

      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.

      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.

      Dominance deviations present were largely unidirectional.

      The order of dominance of the six lines used was D, B, E, C, A, F.

    • Variation in conception rates due to sires in six breeds of zebu cattle

      R. K. Sharma S. S. Prabhu

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    • Analysis of a 6 × 6 diallel cross for hatchability inDrosophila melanogaster

      S. S. Prabhu Prem Narain H. P. Singh Swastika Rawat

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    • Fecundity, egg-size and hatchability inDrosophila melanogaster with an X-chromosome held unchanged

      N. K. Mazumdar S. S. Prabhu

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      An investigation was carried out inDrosophila melanogaster to find out the effect of one unchanged and one changing X-chromosome and changing autosomes belonging to distinct stocks on the fecundity, egg-length, egg-volume and hatchability of the flies. The stocks selected were such that they differed from each other significantly in respect of all the traits studied.

      For keeping the X-chromosome intact, throughout the generations of testing, the balanced technique employingscute inversion No. 1 of Sinitskaya that balanced practically the entire X-chromosome as reported by. Müller and Prokofyeva (1934) was employed. TheBar gene on this chromosome acted as the marker. The stocks utilised were N-8 (normal) and b-297 (marked).

      Reciprocal crosses were made between N-8 and b-297. Repeated backcrosses were made of the resulting progeny to either of the two stock flies, selecting in each case, the female containing the marked chromosome till on an average 15/16 of the autosomes of one parental stock was replaced by those of the other parental stock, while the marked X-chromosome and an unmarked X-chromosome remained intact.

      At each stage of backcrossing, observations were made on fecundity, egg-length, egg-volume (calculated) and hatchability.

      Results showed that in case of fecundity, the genes affecting fecundity were not necessarily more numerous on the X-chromosome than in all the autosomes taken together as suggested by Berg (1937). In fact the data showed that the contribution of the autosomes is more than that of the X-chromosome. In case of egg-length and egg-volume there was evidence to suggest the presence of a few dominant genes radically affecting egg-length in the X-chromosome. This appeared to be so in a more pointed manner in case of hatchability which was a character with practically zero heritability.

    • Variation in gestation period due to sires in eight breeds of zebu cattle

      R. K. Sharma S. S. Prabhu

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      The influence of sires on gestation periods ofAmrit Mahal, Gir, Hallikar, Kangayam,Kankrej, Ongole, Sindhi (2 herds) andTharparker breeds of Indian cattle was studied from the records of 45 sires maintained at different farms in India. Only gestation periods terminating in normal births were considered and only bulls with a minimum of 2 calves of the same sex for a given cow included.

      Male and female calf bearing gestations were considered separately since significant differences existed between the two in the majority of cases. h2 (heritability estimate) was estimated by sib-analysis and the components of variance due to sire, dam and environment calculated, and the percentage contribution of each to the total variance estimated.

      Significant variation in gestation period due to sire was found inGir andKangayam breeds only forfemale births. In case of all other breeds and herds of a breed no significant effect due to sire was found for births of either sex which suggested that the sire influence on gestation period in Indian breeds was generally small and negligible.

      The contribution of the sire to the total variation in gestation period was also found to be small in general. The exceptions are theSindhi herd at Bangalore (21.6%) for male births andAmrit Mahal (23.8%) andGir (19%) animals for female births.

      Estimates of h2 for female births were found to be either zero, or small and negligible or large with large sampling errors that made the estimates undependable with the exception ofKankrej where the estimate was 0.55±0.09. In general, it was concluded that h2 for gestation period in Indian cattle breeds was small and negligible. Where significant variation was obtained as inKankrej in our study and inHariana of Haringhata in a different study reported in the literature, it was explained as due to use of sires obtained from widely varying sources, or due to the animals being still in the process off development as dual purpose animals through selective breeding.

    • Variation in the frequency of occurrence of blood group factors inHariana andJersey-Sindhi crossbred cattle

      Harpreet Singh N. D. Khanna S. S. Prabhu

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      Isoimmunisations were done between pairs ofHariana cattle which resulted in production of 14 isoimmune sera. By selective absorption, 14 specific reagents were isolated from iso-immune sera prepared fromHariana cattle. The antibodies for the J factor are naturally present in serum of certain animals, therefore, the J-reagent was prepared fromKumaum-Hill cattle serum. While 11 reagents were comparable with internationally recognised reagents, four specific reagents could not be compared to any standard reagent; probably, they contained antibodies against some new factor present inHariana.

      Blood typing of about 157 heads ofHariana and 97 heads ofJersey-Sindhi crossbreds was done with the 15 reagents.

      The frequency of occurrence for theHariana andJersey-Sindhi crossbreds with respect to 15 antigens revealed highly significant differences with respect to six (C, R, W, J, M, Iz33) antigens and significant difference for the Zt’ factor.

      The comparisons of incidences of occurrence of blood-group factors for two herds each ofHariana, andJersey-Sindhi crossbred animals showed significant variations in their incidence amongst different herds within the same breed also.

    • Fecundity and hatchability inDrosophila melanogaster with a second chromosome held unchanged

      Win Moi Tait S. S. Prabhu

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      An investigation was carried out inDrosophila melanogasler to find out the effect of an unchanged chromosome II and changing the remaining chromosomes on the fecundity and hatchability. The stocks selected differed distinctly from each other in respect of both the traits. They were N-2 which was a normal wild type strain maintained in the laboratory and C-l containing a marked and completely balanced chromosome II obtained from outside.

      Reciprocal crosses were made between N-2 and G-l Hies. Selecting F-l females with the marked chromosome in one case, repeated backcrosses were made with N-2 males from stock and in another case with C-l males. In each generation, the fecundity and the hatchability were noted.

      Results showed that the chromosome II contained genes for fecundity and hatchability which were more than in all the other chromosomes put together.

    • Studies on biochemical polymorphism in bovines. I. Haemoglobin variations inHariana breed of cattle

      N. D. Khanna Chet Ram K. N. Tandon S. S. Prabhu

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      The haemoglobin variants in 371Hariana and 39Hariana cross with local breed (Desi) were studied using the starch gel electrophoresis technique. Five different haemoglobin types were observed viz. HbBB, HbBG, HbBA, HbCA and HbAA. Out of these, HbBG has not been reported previously in Indian cattle. The age and sex were found to have no significant effect on the occurrence of haemoglobin types. The population was found to be in Hardy-Weinberg equilibrium.

    • Supernumerary teats (SNT) in Indian buffaloes

      J. N. Dwivedi S. S. Prabhu

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    • Quantitative genetic studies in the mouse (Mus musculus L.) I. Litter size

      H. V. Dadlani S. S. Prabhu

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    • Quantitative genetic studies in the mouse (Mus Musculus L.) - II Litter weight

      H. V. Dadlani S. S. Prabhu

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    • Quantitative genetic studies in the mouse (Mus Musculus L.) - III. Body weight

      H. V. Dadlani S. S. Prabhu

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