ULTRASTRUCTURE OF THE NUCLEOLUS AND REPLICATION SITES OF RIBOSOMAL DNA IN Allium cepa

作     者：郝水 焦明大 邢苗 

作者机构：Department of Biology Northeast Normal University 

出 版 物：《Science China Chemistry》 (中国科学（化学英文版）)

年 卷 期：1991年第34卷第3期

页      面：281-289页

核心收录：

学科分类：0810[工学-信息与通信工程] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 07[理学] 0708[理学-地球物理学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0703[理学-化学] 0704[理学-天文学] 0812[工学-计算机科学与技术（可授工学、理学学位）] 

主　　题：nucleolus replication sites rDNA Allium cepa 

摘      要：Our conventional EM observations indicate that the nucleolus of Allium cepa is composed of the fibrillar centre (FC), fibrillar component (F) and granular region (G). FC is an elec- tron-lucid zone which contains condensed or loosened chromatin. F is a circular, highly elec- tron-dense component which surrounds FC and consists of compact fibrils. EM autoradiographic (EM ARG) studies with ~3H- UdR reveal that the synthesis of ribosomal RNA (rRNA) takes place in F. G is situated around F and composed of granules about 25 to 30 nm in diameter. EM ARG studies with ~3H- TdR demonstrate that silver grains are predominantly located in G of the nucleolar periphery and the region of the nucleolus-associated chromatin. In addition, ~3H- TdR labels are also present, but with a much lower frequency, in FC. F and G of the nu- cleolar interior. According to the distribution and sphere of silver grains in different compo- nents of the nucleolus, we suggest that the replication sites of ribosomal DNA (rDNA) are mainly located in G of the nucleolar periphery and the region of the nucleolus-associated chro- matin. Our observations also suggest that some segments of rDNA initiate their replication in FC and then move to the nucleolar periphery.