THE SUBSTRUCTURAL ORGANIZATION OF THE CHROMOSOME CORE (SCAFFOLD) IN MEIOTIC CHROMOSOMES OF TRILOPHIDIA-ANNULATA

The substructural organization of chromosome cores or nonhistone prote ins was studied within intact metaphase chromosomes at the second meio tic division in the grasshopper Trilophidia annulata by silver stainin g as well as light microscopy and whole mount electron microscopy of s quash chromosomes. Our results revealed that the metaphase II chromoso me contains a longitudinal, helical coiling core structure. Probably t he two last organizational levels of the core packaging are achieved b y helical coiling. The core structure retains the morphological charac teristics of the original metaphase chromosome, surrounded by a halo o f dispersed materials, which may be composed mainly of nonhistone prot eins. The kinetochore is found to be connected with the chromosome cor e. The present findings combined with our previous observations on the helical structure of metaphase II chromosomes suggest that the foldin g path of the internal core structure in metaphase chromosomes is cons istent with the final helical arrangement of the chromosome itself. Th ese observations also imply that in condensed metaphase chromosomes no nhistone protein may form a compact network structure with helical app earance, which extends throughout the entire chromosome.