Inna Sergeychik

Genetics

Professor Sartori

November 8, 2010

Mad Cow Disease and Prions

        Mad Cow disease is formally known as Transmissible Spongiform Encephalopathy, and it has been linked to be the cause of other diseases. This disease is believed to be involved in a transmembrane protein called PRP (.sup.c). PRP is a prion that has a normal and infectious scrapie form. The biggest disease believed to be caused by mad cow disease is New-Variant Creutzfeldt-Jacob disease (vCJD).

        A prion is defined as a proteinaceous infectious particle that lacks nucleic acids. There are four levels of to a protein structure, which need to be understood before prions could be learned about. The primary structure consists of a repeating sequence of N-C-C. The secondary structure has an alpha helix, and a beta sheet. The tertiary structure is the final three-dimensional structure of a protein. The quaternary structure consists of multiple polypeptides bound together by covalent bonds into a single larger protein.

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 The level of a protein that actually affects prions is the secondary structure. There are two forms of prions, a normal cellular prion, and an infectious form. The prion is encoded by a single gene on the 20th human chromosome. The normal prion is converted by an unknown sequence of events in which the coiled structure is refolded into a beta-sheet. In the infectious form, the prion is insoluble and the plaques are surrounded by spongy holes causing spongiform encephalopathy. The prions induce death in the host without any signs of immune response to the infectious agent.

Prions cause mad ...

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