Lecture #12

Lecture #12 - 3/9/2009 Chapter 12 The Cell Nucleus and the...

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3/9/2009 1 Chapter 12 The Cell Nucleus and the Control of Gene Expression The cell nucleus a) electron micrograph of an interphase HeLa cell nucleus with a pair of nucleoli b) a schematic showing the major components of the nucleus
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3/9/2009 2 Nuclear pore complex Nuclear membrane heterochromatin The nuclear envelope a) schematic diagram showing the double membrane, nuclear pore complex, nuclear lamina, and the continuity of the outer membrane with the rough endoplasmic reticulum. The inner surface of the nuclear envelope is line by a dense filamentous meshwork called the nuclear lamina which is thought to support the nuclear envelope and to serve as a site of attachment for chromatin fibers at the nuclear periphery. b) electron micrograph of a section through a portion of the nuclear envelope of an onion root tip cell The nuclear lamina Top: Nucleus of a cultured human cell that has been stained with fluorescently labeled antibodies to reveal the nuclear lamina (red) , and the nuclear matrix stained green Bottom: The nuclear lamina- electron micrograph of a freeze-dried, metal-shadowed nuclear envelope of a xeonpus oocyte that has been extracted with a nonionic detergent Triton X100. The lamina appears as a rather continuous meshwork comprising filaments oriented roughly perpendicular to one another. The nuclear lamina is made up of lamin (intermediate filament) whose assembly- disassembly is regulated by phosphorylation
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3/9/2009 3 The structure and function of the nuclear pore complex Nuclear pores contain a complex, basket like apparatus called the nuclear pore complex (NPC) that appears to fill the pore like a stopper, projecting into both the cytoplasm and nucleoplasm. The movement of materials through the nuclear pore Electron micrograph of the nuclear-cytoplasmic border of an amoeba taken a few minutes after injection with colloidal gold particles coated with nuclear signal protein (peptide). These particles are seen to pass through the center of the nuclear pores on their way from the cytoplasm to the nucleus. The inset shows a portion of the nuclear envelope at higher magnification. Electron micrograph of a section through the nuclear envelope of an insect cell showing the movement of granular material (presumably ribosome) through a nuclear pore.
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3/9/2009 4 Model of the nuclear pore complex (NPC). The NPC contains about 100 different polypeptides called nucleoporins and consists of several parts, including a 1) spoke ring assembly (two yellow rings and a rose colored spokes), 2) a nuclear basket that resembles a fish trap, 3) a central plug or transporter and eight cytoplasmic filaments. A three-dimensional model based on high resolution electron microscopy showing the nuclear pore complex as it would appear from the cytoplasm. Importing proteins from the cytoplasm into the nucleus
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Lecture #12 - 3/9/2009 Chapter 12 The Cell Nucleus and the...

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