PROFESSORS P. MOTTA & T. NAGURO / SCIENCE PHOTO LIBRARY PROFESSORS P. MOTTA & T. NAGURO / SCIENCE PHOTO LIBRARY
Nucleolus and chromatin fibres. Coloured high resolution scanning electron micrograph (SEM) of the nucleolus and chromatin fibres of a primordial testis germ cell nucleus (8-week-old human embryo). The nucleolus (centre) is a specialized region of the nucleus. It is the site for synthesis of ribosomal RNA and proteins. Surrounding the nucleolus are chromatin fibres. The chromatin fibres form a diffuse network which contains the chromosomes. The chromosomes contain the genetic instructions for an organism but only become visible when the cell divides. Magnification unknown.
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