Size: 5-10µm(high animal); 5-20µm(High plant) Volume ratio of nucleus to cytoplasm: 1:10 (9) Shape: Spherical or oval Contain: 4 subunits • Nuclear Envelope • Chromatin • Nucleolus • Nuclear Matrix (nuclear skeleton) Preface Chapter 7 Nucleus pl. nuclei
Section1. Nuclear envelope I. Nuclear membrane II. Nuclear pore complex (NPC) III. Nuclear lamina Section2. Chromatin Section3. Chromosome Section4. Nucleolus & Nuclear Matrix/skeleton
I. Structure Section 3. Chromosome 1. Four types: see the right 2. Main subunits: 2.1 Centromere: Primary constriction (主缢痕) (1) Definition: The highly constricted region of a chromosome that is the position at which the pair of chromatids are held together. Centrosome
(2) Function: Serve both as linker sites of sister chromatids, and as attachment sites for microtubules of the mitotic spindle. (3) Composition: Centromere DNA; Centromere associated proteins. ① ② （有丝分裂纺锤体微管）
(4) Subunits: 3主要+1次要 inner outer ① Pairing domain: The interaction site for Metaphase chromatids (sister chromatids). Include two types of proteins: INCENP (inner centromere proteins); CLIP (chromatid linking proteins). These two types of proteins are responsible for the paring of chromatids
③ kinetochore domain: Composed of highly repeated satellite DNA. ② Central domain： (Centromere DNA) (动粒/着丝点) Inner plate（内板） Middle space/interzone (中间间隙) Outer plate（外板） (microtubule) ④ Fibrouscorona: corona fiber（微管蛋白） （纤维冠）
着丝粒DNA 配对结构域 中央结构域 动粒结构域 Centromere formation
2.2 Secondary constriction: 次缢痕 着丝粒蛋白特异标记 浅染缢缩？ 由于染色体DNA上基 因转录，折叠晚了。 导致折叠压缩程度不 高，吸附染料较少。 (没有跟上大部队) 主缢痕 什么基因？ P280,282
For the reason that the rRNA (excluding 5srRNA) genes are located here and they are involved in ribosomes biogenesis. These secondary constrictions are also called as NOR. 某些次缢痕是rRNA(5srRNA除外)基因的所在部位。 则次缢痕与间期细胞核内核仁形成有关（组织者）。 故，这些次缢痕又称核仁组织区(nucleolar organizing region，NOR) 。 次缢痕可作为染色体的“鉴定标记”。 rRNA基因？ (5srRNA外) 28S、18S和5.8S
2.3 Satellite: 随体 A spherical segment at the end of a chromosome. secondary constriction (次缢痕) (nucleolar organizing region, NOR) (centromere) Primary constriction (主缢痕) satellite