The Effects of Low Temperature and Colchicine on Chromosome Structure in Urodele Developmental Stages

I. A comparison of euchromatic and heterochromatic condensation patterns

Abstract

An investigation has been made of the differential reactivity of chromosomes in urodele developmental stages after exposure to colchicine and low temperature. Embryonic stages of Ambystoma maculatum and Triturus viridescens, and larvae of A. maculatum were maintained at low temperature for specific periods of time. Colchicine was added to the experimental stages one to two days prior to fixation. All stages studied demonstrated a differential reactivity or differential staining of the heterochromatin after maintenance at the low temperature. Prolonged treatment of the chromosomes in colchicine at low temperature produced a supercoiling phenomenon which reduced or obscured the heterochromatic areas, but did not completely eliminate the segmentation. These observations are discussed in relationship to asynchronous replication of heterochromatin in mammalian cells.