CAS BI 203 Lecture 17: Lecture #17
7 Dec 2017
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Document Summary
5s component comes from outside of the nucleolus but you need it along with the ribosomal rna components 28s, 5. 8s, and 18s to make the ribosome. The nucleolus is where ribosomal rna is transcribed and the ribosome is assembled including the proteins: the ribosome does not come together until translation. Therefore, in the nucleolus, the large subunit and the small subunit are separated: both subunits become the full ribosome in the cytosol. Ribosomal proteins are produced in the cytoplasm and imported to the nucleolus, where they assemble with the pre-rrna prior to cleavage. Immunocytochemistry is used to locate where the cajal bodies are located within the nucleus. This was done using antibodies against specific proteins. Nuclear speckles: following assembly and maturation in cajal bodies, snrnps are transferred to speckles, which also contain splicing factors. Speckles are recruited to actively transcribed genes where pre-mrna processing occurs. Cajal bodies assembly of the spliceosomes. Nuclear speckles where splicing is actually taking place.
