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A prion / ˈ p r iː ɒ n / ⓘ is a misfolded protein that induces misfolding in normal variants of the same protein, leading to cellular death.Prions are responsible for prion diseases, known as transmissible spongiform encephalopathy (TSEs), which are fatal and transmissible neurodegenerative diseases affecting both humans and animals.
The subsequent demonstration that human prion diseases were transmissible reinforced the importance of spongiform change as a diagnostic feature, reflected in the use of the term "spongiform encephalopathy" for this group of disorders. Prions appear to be most infectious when in direct contact with affected tissues.
Self-replication is a fundamental feature of life. It was proposed that self-replication emerged in the evolution of life when a molecule similar to a double-stranded polynucleotide (possibly like RNA) dissociated into single-stranded polynucleotides and each of these acted as a template for synthesis of a complementary strand producing two double stranded copies. [4]
Prions are proteins of particular amino acid sequences in particular conformations. They propagate themselves in host cells by making conformational changes in other molecules of protein with the same amino acid sequence, but with a different conformation that is functionally important or detrimental to the organism.
On the Writing of Speculative Fiction" is an essay by American science fiction writer Robert A. Heinlein. It was first published in 1947, also appearing in Writing Science Fiction & Fantasy: 20 Dynamic Essays By the Field's Top Professionals in 1993, and The Nonfiction of Robert Heinlein: Volume I in 2011.
Speculative fiction in technology of reproduction may involve cloning and ectogenesis, i.e., artificial reproduction). [2] [3] The latter part of the 2000s decade has also seen an upswing of films and other fiction depicting emotional struggles of assisted reproductive technology in contemporary reality rather than being speculation. [11]
The geneticist Dan Koboldt observes that while science and technology play major roles in fiction, from fantasy and science fiction to thrillers, the representation of science in both literature and film is often unrealistic. [28] In Koboldt's view, genetics in fiction is frequently oversimplified, and some myths are common and need to be debunked.
Others insert additional amino acids into the protein or cause an abnormally short protein to be made. These mutations cause the cell to make prion proteins with an abnormal structure. The abnormal protein PrP Sc accumulates in the brain and destroys nerve cells, which leads to the mental and behavioral features of prion diseases. [citation needed]