• K. S. Rai

      Articles written in Journal of Genetics

    • Cytology ofGnetum Ula brongn - With plate 18 and four text-figures

      P. N. Mehra K. S. Rai

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      Eleven bivalents were observed in the meiosis of microsporocytes ofGnetum ula.

    • Cytogenetic effects of chemosterilants in mosquitoes. III. Development of transplanted ovaries in normal and chemosterilized females ofAedes aegypti

      K. S. Rai V. P. Sharma

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      Two-day old larvae ofAedes aegypti were reared until pupation in 25 ppm of a commonly used mosquito chemosterilant, apholate. This concentration induced complete female infecundity.

      Transplantation experiments involving ovaries from normal adults and adults arising from the above chemical treatment were undertaken. The object was to investigate whether apholate-induced female infecundity results from direct effects on the ovary or from indirect effects on the hormonal and/or yolk protein synthesis or supply.

      The fact that the ovary from an untreated female when implanted in the abdomen of an infecund female develops more or less normally, at least in a qualitative sense, following a blood meal indicates that the yolk proteins and the gonadotrophic hormone are available for ovarian development in chemically treated females. Thus, the humoral factors are not involved in female infecundity and the primary site of action of apholate must be the oocyte. The inhibition of the ovaries in apholate-treated females, must be brought about by degenerative changes in the ovary itself.

      Quantitatively, fewer untreated follicles developed following implantation in the abdomen of a treated female. Furthermore, they did not reach the same stage of development as they did in untreated environment. Possible mechanisms for this retarded development are discussed.

    • Simulation of alternative genetic control systems forAedes aegypti in outdoor cages and with a computer

      C. F. Curtis N. Lorimer K. S. Rai S. G. Suguna D. K. Uppal S. J. Kazmi E. Hallinan K. Dietz

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      Cycling populations ofA. aegypti of wild origin were established in outdoor cages. Releases were then made for 32–43 days of either males carrying chromosome translocations or males of the sex ratio distorter type. The translocation caused a maximum of 50% sterility, but this declined rapidly after termination of releases. The distorter males depressed the proportion of females among the pupae produced in the cage to a minimum of 35% and the distortion of sex ratio persisted for 13 weeks following termination of releases. It was pos sible to simulate the effects of the releases with a computer. Simulations were also made of standard release schedules of three types of genetic material. A strain carrying both sex ratio distortion and a translocation gave the most effective population suppression.

    • Chromosomal localization and genomic organization of cloned repetitive DNA fragments in mosquitoes (Diptera: Culicidae)

      A. Kumar K. S. Rai

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      The chromosomal localization and genomic organization of three cloned repetitive DNA fragments (viz., H-76, H-61, and H-19) isolated from theAedes albopictus genome have been examined inAe. albopictus and six otherAedes species:Ae. aegypti, Ae. seatoi, Ae. flavopictus, Ae. polynesiensis, Ae. alcasidi andAe. katherinensis. The results fromin situ and Southern hybridization analyses show that the sequences homologous to cloned repetitive DNA fragments are dispersed throughout the genome in each species. The sequences homologous to these cloned repetitive DNA fragments are also found inHaemagogus equinus, Tripteroides bambusa andAnopheles quadrimaculatus and are dispersed in their genomes. Data indicate divergence in the amount and the structural organization of sequences homologous to these cloned fragments among mosquito species.

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