ANALYSIS OF CEREAL CHROMOSOMES BY ATOMIC-FORCE MICROSCOPY

Atomic force microscopy has been applied to the study of plant chromos omes from cereal grasses Triticum aestivum (bread wheat), Triticum tau schii, and Hordeum vulgare (barley). Using standard mitotic metaphase squashes, high resolution images have been obtained of untreated chrom osomes and also of chromosomes after C-banding, N-banding, and in situ hybridization. The true 3-dimensional nature of the images permits de tailed analysis of the surface structure and, on untreated uncoated ch romosomes, surface features on a length scale consistent with nucleoso me structures have been observed. C+ and N+ regions are manifest as ar eas of high relief on a slightly collapsed chromosome structure. In si tu hybridization leads to a more severe degradation of the native stru cture, although it is still possible to correlate the optical signal w ith the topography of the hybridized chromosome.