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Subviral agents are pathogenic entities that can cause disease, but lack various fundamental properties of viruses. Subviral agents consist of satellites , viroids , prions , defective interfering particles , viriforms , and, most recently, obelisks .
Viroids were shown to consist of short stretches (a few hundred nucleotides) of single-stranded RNA and, unlike viruses, did not have a protein coat. Viroids are extremely small, from 246 to 467 nucleotides, smaller than other infectious plant pathogens; they thus consist of fewer than 10,000 atoms.
Virusoids are essentially viroids that have been encapsulated by a helper virus coat protein. They are thus similar to viroids in their means of replication (rolling circle replication) and in their lack of genes, but they differ in that viroids do not possess a protein coat. Both virusoids and viroids encode a hammerhead ribozyme.
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 origins of viruses are unclear: some may have evolved from plasmids, others from bacteria. Viruses are sometimes considered to be a life form, because they carry genetic material, reproduce and evolve through natural selection. However they lack key characteristics (such as cell structure) that are generally considered necessary to count as ...
Transmissible spongiform encephalopathies (TSEs), also known as prion diseases, [1] are a group of progressive, incurable, and fatal conditions that are associated with the prion hypothesis and affect the brain and nervous system of many animals, including humans, cattle, and sheep.
The potato spindle tuber viroid (PSTVd, Pospiviroid fusituberis) was the first viroid to be identified. [1] [2] [3] [4] PSTVd is a small, single stranded circular RNA ...
Humans can be infected with many types of pathogens, including prions, viruses, bacteria, and fungi, causing symptoms like sneezing, coughing, fever, vomiting, and potentially lethal organ failure. While some symptoms are caused by the pathogenic infection, others are caused by the immune system's efforts to kill the pathogen, such as ...