Abstract
A maize genetic marker strain (designated as the 2NOR strain) was found to carry a cytologically-visible “duplication” of the nucleolar organizer region (NOR). The 2 NOR condition is a simply inherited cytological marker which is transmitted normally through mega- and microsporogenesis and is associated when homozygous with a nucleolus approximately 64% greater in volume than that of two representative normal inbred lines of maize.—Utilizing DNA · rRNA hybridization techniques and the 2 NOR strain plus two unrelated inbred lines with normal NOR's, the chromosomal site of DNA complementary to rRNA was shown to be localized in the NOR. To our knowledge, this is the first report on the localization of rDNA cistrons in the NOR of plants. An estimate was made of 17,000 rDNA cistrons per diploid nucleus for normal maize.—The 2 NOR strain was shown to possess approximately twice as many rDNA cistrons (34,000) as normal maize. The usefulness of this 2 NOR condition for plant protein improvement programs is being investigated.
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Phillips, R.L., Kleese, R.A. & Wang, S.S. The nucleolus organizer region of maize (Zea mays L.): Chromosomal site of DNA complementary to ribosomal RNA. Chromosoma 36, 79–88 (1971). https://doi.org/10.1007/BF00326423
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DOI: https://doi.org/10.1007/BF00326423