Chromomeric pattern of maize pachytene chromosomes after trypsin treatment.

The bivalent chromomeres of maize were analyzed by means of enzymatic treatment with trypsin. The aim was to verify if the effect of swelling observed in human meiotic chromosomes also occurs in these bivalents, and if this morphological change allows a greater visual resolution of the chromomeric pattern. Bivalents treated with trypsin showed a structure with sequential and linear distribution of small rings. Comparisons between bivalent morphology, treated and non-treated, indicated a collinearity among the sequences of rings and the chromomeres. The results obtained were considered useful to analyze and to make a chromomere map. This treatment can also provide cytological evidence that may help to understand the pairing process. It was concluded that the ring-shape was caused by trypsin-induced "disjoining" just in the chromomeric but not in the interchromomeric regions.