• N. K. Notani

      Articles written in Journal of Genetics

    • Monohybrid and dihybrid segregations in the progenies of tobacco transformed for kanamycin resistance with a Ti-vector system

      Patricia Viegas Helena Mathews C. R. Bhatia N. K. Notani

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      A chimeric DNA construction having nopaline synthase promoter, coding sequences of neomycin phosphotransferase gene conferring resistance to antibiotic kanamycin and OCS (octopine synthase) polyadenylation sequences bracketed by T-DNA ends was transferred to tobacco. Leaf discs were infected withA. tumefaciens containing disarmed, cointegrate plasmid pGV3850:: 1103 and allowed to form a callus in the presence of kanamycin. Shoots regenerated from infected leaf discs either through the callus or arising directly were further selected for their ability to root in kanamycin-containing media. Among the nine transgenic plants that were progeny tested, the transferred bacterial gene segregated as monohybrid ratio (3 KanR: 1 Kans) in seven. Segregation data of two plant progenies indicated the presence of two independent loci of KanR DNA insertion (15 KanR: 1 Kans). Back-cross segregation data were consistent with the monohybrid or independent assortment of duplicate factors. Thus in the two cases, a minimum independent integration of two copies of T-DNA each with a KanR marker is inferred.

    • Decreased extrachromosomal fixation of chimeric plasmid in strain N19 ofHaemophilus influenzae Rd.

      Vasudha P. Joshi N. K. Notani

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      Chromosomal DNAcarrying closely-linked genetic marker allelesstrrnovr produces roughly equivalent number of StrR (streptomycin-resistant) and NovR (novobiocin-resistant) transformants from wild type strain but widely differnt ratios (StrR50: NovR1) from a mutant strain N19. Reduction in AmpR (vector marker) extra chromosomal transformants is observed in N19 with chimeric plasmids carrying chromosomal DNA inserts fromnov region. Thus, AmpR transformants with chimeric plasmid DNA pJl-8N2 and pJl-8N19 are two to three orders of magnitude lower in N19 than in wild type. However, pJl-8NaIR33, pKuvrl, p3 and p10 DNA transform N19 and Rd with near-equal efficiency. Reduction in AmpR transformants is intermediate (30 to 100-fold lower) in strain N19 with pJ18StrR38 and pD7. These data are interpreted to suggest the presence of a small “aberration” in thenov region.

    • Analysis of a case of somatic instability in a strain of maize from India

      S. B. Allagikar S. E. Pawar R. K. Mitra N. K. Notani

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      A case of somatic instability affecting aleurone colour in a strain of maize from India with flint background was analysed. The somatic instability is localized to theC1 (Inhibitor) allele ofC locus on the short arm of chromosome 9. Molecular tests indicated thatAc is not present in the Indian stock and the evidence is consistent with the involvement of theEn (Spm) transposable element in the instability. The presence of theEn (Spm)-like element in the stock would suggest that these elements have been present in the maize genome for a long time. A new allele ofshrunken (sh1) gene with a somewhat unorthodox breeding behaviour is also described.

    • Heritable transformation of tobacco byAgrobacterium-mediated transfer of theStreptomyces-derived herbicide resistance genebar

      Patricia M. Viegas N. K. Notani

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      Thebar gene ofStreptomyces hygroscopicus encodes an enzyme that detoxifies the herbicide Basta. We have transferred theStreptotnyces-derived bar gene to tobacco through theAgrobacterium tumefaciens gene delivery system. Expression ofbar was driven by two different promoters, TR2’ or CaMV 35S, in two DNA constructs. TR2’ is a weak promoter in tobacco. CaMV 35S is, on the other hand, a strong promoter in tobacco, and transformation using the CaMV 35S promoter construct yielded Basta-resistant transgenic plants. Out of the over one hundred transformants obtained, most could be grown to maturity. Four of these were characterized by genetic and molecular methods. Subsequently, one of the four plants was not resistant and did not show presence ofbar DNA. The remaining three plants contained one or more copies ofbar DNA at one or two loci. Segregation data were consistent with this observation: we obtained ratios of either 3:1 (single locus) or 15:1 (two loci) Basta-resistant:Basta-sensitive in the F2 generation. Field-grown plants showed resistance to Basta up to a level of 4000 g of active ingredient per hectare.

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