Antibodies against Z-DNA bind to fixed metaphase chromosomes of man and Cebus albifrons (Platyrrhini, Primate). By indirect immunofluorescence and indirect immunoperoxidase techniques, a heavy staining is detected in some segments of chromosomes of C. albifrons. These segments correspond to Rband-positive heterochromatin, which has a high G+C-base content. Euchromatin of human and Cebus chromosomes show a weak and heterogeneous staining that consistently reproduces an R-and T-banding pattern in both species. Because chromosome homologies previously were demonstrated between these distantly related species by chromosome banding, our results suggest that Z-DNA has been conserved during the course of primate evolution.Repeating sequences of alternating dC and dG deoxynucleotides can form the left-handed duplex DNA conformation, named Z-DNA, as demonstrated by x-ray diffraction studies of crystals of (dC-dG)n (1-3) and fibers of poly (dG-dC)-poly (dG-dC) ( (23, 24), the comparison of the staining patterns produced by antibodies to Z-DNA in euchromatin may be considered a check of the stability of Z-DNA conformation during chromosome evolution.In this work we show (i) that anti-Z-DNA antibodies bind to metaphase chromosomes of man and Cebus in a distinct and specific way and (ii) that an undisputable correspondence exists between the antibody binding and the chromosome banding patterns. In euchromatin, a weak but distinct and consistent staining is observed in the segments corresponding to the Rand T-bands, which are thought to be richer in G-C base pairs both in man and Cebus. Slight differences of intensity are observed from band to band: they are the same for all of the chromosomal segments of man and Cebus, which were found homologous by banding pattern and by gene mapping comparison (23)(24)(25). This fact underlines the stability of Z-DNA conformation during the evolution of mammalian chromosomes. Furthermore, the additional heterochromatic segments existing in Cebus chromosomes exhibit a consistent and very strong binding to anti-Z-DNA antibodies.MATERIAL AND METHODS Obtention of Metaphase Chromosomes. Metaphase cells were obtained from tissue cultures after skin biopsy of a female of C. albifrons held in captivity at the Museum National d'Histoire Naturelle, Paris.Metaphase cells from human lymphocytes were cultured according to usual methods (26). Cell cultures were treated by colchicine for 1 or 2 hr and then for 10 min with a hypotonic solution of diluted human serum (1:6, vol/vol). Cells were fixed in most of the experiments for at least 40 min with two different solutions (solution I, ethanol/chloroform/acetic acid, 6:3:1, vol/ vol; solution II, ethanol/acetic acid, 3:1, vol/vol). A prolonged fixation (45 min to 48 hr), with only the last fixative solution was used for some human cultures.The following banding methods were used to characterize the chromosomes of the specimen of C. albifrons: R-banding 5890 The publication costs of this article were defrayed in part by page charge payment. T...