.5 The contrast between interphase chromatin
and mitotic chromosomes
Figure 18.10 A thin section through a nucleus stained with Feulgen shows heterochromatin as compact regions clustered near the nucleolus and nuclear membrane. Photograph kindly provided by Edmund Puvion.
? 核仁（nucleolus）见于间期的细胞核内， 呈圆球形，一般1-2个，也有多达3-5个的 。，呈中圆形或椭圆形的颗粒状结构，没 ??
有外膜。核仁在分裂前期消失，分裂末期 又重新出现。核仁的主要功能是转录rRNA 和组装核糖体单位。 ?
.5 The contrast between interphase chromatin and
mitotic chromosomes
Figure 18.9 The sister
chromatids of a mitotic pair each consist of a fiber (~30 nm in diameter) compactly folded into the chromosome. Photograph kindly provided by E. J. DuPraw.
