• H. K. Das

      Articles written in Journal of Genetics

    • Segregation characteristics of multiple chromosomes ofAzotobacter vinelandii

      S. H. Phadnis G. P. Dimri H. K. Das

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      The genome ofAzotobacler vinelandii has been taggedin vivo with transposons. The cells have then been allowed to divide and the pattern of segregation of the genomes has been studied. The results suggest the presence of multiple (possibly identical) copies of the genome inA. vinelandii. Only a fraction of the total number of genomes seem to have been tagged with transposon and an equilibrium between alleles of the same gene with and without the transposon was evident during random segregation.

    • Cloning of a positive regulatory element involved in nitrogen fixation inAzotobacter vinelandii

      M. Amarender Reddy H. K. Das

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      A positive regulatory gene has been cloned fromAzotobacter vinelandii, using its ability to activate the expression ofnifH: lacZ fusion inE. coli. The gene has also been shown to activate the transcription from the P1 promoter ofRhizobium meliloti. It did not, however, hybridize with thenifA gene ofR. meliloti.

    • TheAzotobacter vinelandii chromosome

      Adhar C. Manna H. K. Das

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      The chromosome ofAzotobacter vinelandii was digested with the restriction endonucleasesSpeI (5’-ACTAGT),DraI (5’-TTTAAA) andAsel (5’-ATTAAT) and the products were separated by pulsed-field gel electrophoresis. The sum of the sizes of the restriction fragments comes to around 4.5 megabasepairs. Our earlier studies had revealed the presence of about 80 copies ofnifH, nifD, nifK andleuB genes in a log-phase cell ofA. vinelandii. To determine whether there are multiple identical chromosomes inA. vinelandii or one large chromosome with identical segments joined in tandem, we have subjected gamma-irradiated DNA ofA. vinelandii andEscherichia coli to pulsed-field gel electrophoresis. The results suggest thatA. vinelandii chromosomes contain multiple identical chromosomes of about the same size as that ofE. coli.

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