Summary
Ten telocentric B chromosomes, identical in size and banding pattern have been observed at mitosis in root tips of a plant of Fritillaria tenella (2n = 18), prepared and stained by Giemsa to show C-banding. It is proposed that, following formation of an initial B by misdivision at one side of the centromere in a sub-terminal univalent chromosome at meiosis in an ancestral plant, the Bs have multiplied with successive generations of breeding. It is assumed that this occurred by post-meiotic non-disjunction either in pollen or embryosac, so as to produce gametes with double the number of Bs. The centromeric structure of the Bs was complex and sometimes appeared to consist of a single innermost dot contiguous with a tiny terminal bipartite C-band. The supposition is made that the single dot is one of the two dots representing the centromere, the other sometimes being orientated out of view. Further heterochromatin was present in the Bs as shown by the presence of a prominent C-band at the telomeric end. All the A chromosomes showed C-bands, with as many as 12 in one M. Heteromorphy in respect of bands was evident in an M chromosome.
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La Cour, L. Differential Giemsa staining of B chromosomes of Fritillaria tenella. Heredity 41, 101–103 (1978). https://doi.org/10.1038/hdy.1978.68
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DOI: https://doi.org/10.1038/hdy.1978.68