DR GOPAL MURTI / SCIENCE PHOTO LIBRARY DR GOPAL MURTI / SCIENCE PHOTO LIBRARY
Transmission electron micrograph of a section through a nucleolus (central body), a region of the nucleus where genes which specify the structure of ribosomal RNA are active. The dark- staining material at the edge of the body is RNA, which forms into ribosomal particles once exported to the cytoplasm. The fine, dense, granular regions within the body are sites at which RNA synthesis is occurring on the ribosomal RNA genes. The coarser granular material is ribosomal RNA awaiting export to the cytoplasm. Ribosomes are the sites of protein synthesis. The edge of the nucleus, broken by nuclear pores, is visible at bottom. Mag: x51,300 at 8x10",x1,600 at 35mm size.
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