Recognition of two types of positive staining chromosomal material by manipulation of critical steps in the N-banding technique.

The nucleolar regions on chromosomes 1B and 6B of Triticum aestivum L. cv Chinese Spring wheat can reliably be observed after careful control of the Giemsa N-banding technique. Identification of rye (Secale cereale) chromosomes using N-banding is demonstrated and compared to a simple C-banding method. The N-banding in rye chromosomes and the nucleolar sites on 1B and 6B of wheat differ from the normal N-banding sites of wheat chromosomes. Further, the banding of these nucleolar regions and of the rye chromosomes does not reappear in preparations that have been retreated with hot acid buffer. These differences provide evidence for at least two types of chromatin that stain darkly (positively) using N-banding. The critical procedures in the N-banding technique and the use of alternatives to 1 M NaH2PO4 buffer are discussed along with the possible basis of N-band formation.