Prematurely condensed chromosomes of the Indian muntjac: A model system for the analysis of chromosome condensation and banding

摘要

Premature chromosome condensation, PCC, was induced in interphase cells of the Indian muntjac (Muntiacus muntjak), by fusion with mitotic Lu106 (human) or muntjac cells, using inactivated Sendai virus. The G1 and G2 chromosomes appeared as single-respectively double-structured threads of variable length. Calculations of relative chromosome lengths at variable degrees of condensation indicated that the chromosome arm is the basic unit for chromosome condensation. Application of a G-banding procedure on PCC chromosomes demonstrated a clear differentiation of dark and light bands. Comparative analysis of banding patterns in metaphase, prophase and PCC chromosomes demonstrated a positive relationship between the number of G-bands and chromosome length. Based on the banding pattern at metaphase, a model system for the interpretation of differential chromosome condensation and band expression in prophase and PCC chromosomes is suggested. Condensation and banding indices were defined and exemplified for chromosome 1. By comparing PCC and metaphase chromosomes, it was found that proximal regions were proportionally less extended than intercalary regions and that terminal regions were about equally extended. There were proportionally fewer dark G-bands in more extended compared to less extended regions. Exceptions from both these trends and their significance are pointed out.