Drouin R, Lemieux N, Richer C L
Département d'Anatomie, Faculté de Médecine, Université de Montréal, Québec, Canada.
Cytogenet Cell Genet. 1991;57(2-3):91-9. doi: 10.1159/000133121.
As chromosomes condense during early mitosis, their subbands fuse in a highly coordinated fashion. Subband fusion occurs when two large subbands flanking one minor subband come together to form one band, which takes on the cytological characteristics of the original flanking subbands. Using four different banding techniques--GTG (G-bands obtained with trypsin and Giemsa), GBG (G-bands obtained with BrdU and Giemsa), RHG (R-bands obtained by heating and Giemsa), and RBG (R-bands obtained with BrdU and Giemsa)--we studied subband fusion from prophase (1,250 bands per haploid set) to late metaphase (300 bands). To quantify the condensation process, a fusion index was established. We found that chromosomes contain preferential zones of condensation. From prophase to late metaphase, the early replicating subbands (R-subbands) fuse more readily with each other than do the late-replicating subbands (G-subbands). R-bands usually replicate early and condense late independently of the adjacent G-bands, which replicate late but condense early. Therefore, chromosome bands can undergo DNA replication and chromatin condensation relatively autonomously. Our data suggest that (1) chromosome replication and condensation are closely connected in time, (2) the metaphase bands represent independent units of chromatin condensation, and (3) the condensation process is an important feature of chromosome organization.
在有丝分裂早期染色体浓缩时，它们的亚带以高度协调的方式融合。当位于一个较小亚带两侧的两个大亚带聚集在一起形成一条带时，就会发生亚带融合，该条带呈现出原始侧翼亚带的细胞学特征。我们使用四种不同的显带技术——GTG（用胰蛋白酶和吉姆萨获得的G带）、GBG（用BrdU和吉姆萨获得的G带）、RHG（通过加热和吉姆萨获得的R带）和RBG（用BrdU和吉姆萨获得的R带）——研究了从前期（单倍体组有1250条带）到中期后期（300条带）的亚带融合。为了量化浓缩过程，建立了一个融合指数。我们发现染色体含有优先浓缩区。从前期到中期后期，早期复制的亚带（R亚带）彼此之间比晚期复制的亚带（G亚带）更容易融合。R带通常早期复制且后期浓缩，独立于相邻的G带，而G带晚期复制但早期浓缩。因此，染色体带可以相对自主地进行DNA复制和染色质浓缩。我们的数据表明：（1）染色体复制和浓缩在时间上紧密相连；（2）中期带代表染色质浓缩的独立单位；（3）浓缩过程是染色体组织的一个重要特征。
