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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 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] Several other changes in the PRNP gene (called polymorphisms) do not cause prion diseases but may affect a person's risk of developing these diseases or alter the course of the ...
Chronic wasting disease (CWD), sometimes called zombie deer disease, is a transmissible spongiform encephalopathy (TSE) affecting deer.TSEs are a family of diseases thought to be caused by misfolded proteins called prions and include similar diseases such as BSE (mad cow disease) in cattle, Creutzfeldt–Jakob disease (CJD) in humans, and scrapie in sheep. [2]
The infectious agent is a misfolded form of a host-encoded protein called prion (PrP). Prion proteins are encoded by the Prion Protein Gene . [22] The two forms of prion are designated as PrP c, which is a normally folded protein, and PrP sc, a misfolded form which gives rise to the disease.
Facultative intracellular parasites are capable of living and reproducing in or outside of host cells. Obligate intracellular parasites, on the other hand, need a host cell to live and reproduce. Many of these types of cells require specialized host types, and invasion of host cells occurs in different ways. [2]
Non-cellular life, also known as acellular life, is life that exists without a cellular structure for at least part of its life cycle. [1] Historically, most definitions of life postulated that an organism must be composed of one or more cells, [2] but, for some, this is no longer considered necessary, and modern criteria allow for forms of life based on other structural arrangements.
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]
For the virus to reproduce and thereby establish infection, it must enter cells of the host organism and use those cells' materials. To enter the cells, proteins on the surface of the virus interact with proteins of the cell. Attachment, or adsorption, occurs between the viral particle and the host cell membrane.