CNRI / SCIENCE PHOTO LIBRARY CNRI / SCIENCE PHOTO LIBRARY
False-colour transmission electron micrograph (TEM) of a typical nucleus of an active, protein secreting cell (nucleus at left). The nuclear envelope (separating nucleus from cytoplasm) consists of 2 layers of membrane, broken at intervals by nuclear pores (3 are visible here). The pores permit the exchange of metabolites between the nucleus & cytoplasm, & probably allow RNA molecules to enter the cytoplasm. The material coloured orange is a type of chromatin (the genetic material of the cell - DNA) which is active in protein synthesis: the colouring technique shows material converging on nuclear pores. Magnification: X 10,000 at 35mm size.
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