118-474: Nudiviruses are a genus of anthropod viruses that constitute the family Nudiviridae . Insects and marine crustaceans serve as natural hosts to this family of viruses. Nudiviruses are double-stranded DNA viruses, with their genome notably ranging from 130-140 kilobases in length. There are 20 species in this family, assigned to 4 genera. Diseases associated with this family include: death in larvae, and chronic disease in adults. The family Nudiviridae contains
236-425: A virion , consists of nucleic acid surrounded by a protective coat of protein called a capsid . These are formed from protein subunits called capsomeres . Viruses can have a lipid "envelope" derived from the host cell membrane . The capsid is made from proteins encoded by the viral genome and its shape serves as the basis for morphological distinction. Virally-coded protein subunits will self-assemble to form
354-464: A "Universal Palindrome Day". Other universal palindrome days include, almost a millennium previously, 11/11/1111 , the future 12/12/2121 , and in a millennium 03/03/3030 . A phonetic palindrome is a portion of speech that is identical or roughly identical when reversed. It can arise in context where language is played with, for example in slang dialects like verlan . In the French language , there
472-448: A "fudge" ). This is generally considered the first English-language palindrome sentence and was long reputed, notably by the grammarian James "Hermes" Harris , to be the only one, despite many efforts to find others. (Taylor had also composed two other, "rather indifferent", palindromic lines of poetry: "Deer Madam, Reed", "Deem if I meed". ) Then in 1848, a certain "J.T.R." coined "Able was I ere I saw Elba", which became famous after it
590-486: A German libretto by Marcellus Schiffer. It is essentially a dramatic palindrome. Through the first half, a tragedy unfolds between two lovers, involving jealousy, murder and suicide. Then, in the reversing second half, this is replayed with the lines sung in reverse order to produce a happy ending. The music of Anton Webern is often palindromic. Webern, who had studied the music of the Renaissance composer Heinrich Isaac ,
708-606: A basic optical microscope. In 2013, the Pandoravirus genus was discovered in Chile and Australia, and has genomes about twice as large as Megavirus and Mimivirus. All giant viruses have dsDNA genomes and they are classified into several families: Mimiviridae , Pithoviridae, Pandoraviridae , Phycodnaviridae , and the Mollivirus genus. Some viruses that infect Archaea have complex structures unrelated to any other form of virus, with
826-572: A canal – Panama ". The 19-letter Finnish word saippuakivikauppias (a soapstone vendor), is the longest single-word palindrome in everyday use, while the 12-letter term tattarrattat (from James Joyce in Ulysses ) is the longest in English. The word palindrome was introduced by English poet and writer Henry Peacham in 1638. The concept of a palindrome can be dated to the 3rd-century BCE, although no examples survive. The earliest known examples are
944-418: A capsid diameter of 400 nm. Protein filaments measuring 100 nm project from the surface. The capsid appears hexagonal under an electron microscope, therefore the capsid is probably icosahedral. In 2011, researchers discovered the largest then known virus in samples of water collected from the ocean floor off the coast of Las Cruces, Chile. Provisionally named Megavirus chilensis , it can be seen with
1062-581: A capsid, in general requiring the presence of the virus genome. Complex viruses code for proteins that assist in the construction of their capsid. Proteins associated with nucleic acid are known as nucleoproteins , and the association of viral capsid proteins with viral nucleic acid is called a nucleocapsid. The capsid and entire virus structure can be mechanically (physically) probed through atomic force microscopy . In general, there are five main morphological virus types: The poxviruses are large, complex viruses that have an unusual morphology. The viral genome
1180-596: A cell, viruses exist in the form of independent viral particles, or virions , consisting of (i) genetic material , i.e., long molecules of DNA or RNA that encode the structure of the proteins by which the virus acts; (ii) a protein coat, the capsid , which surrounds and protects the genetic material; and in some cases (iii) an outside envelope of lipids . The shapes of these virus particles range from simple helical and icosahedral forms to more complex structures. Most virus species have virions too small to be seen with an optical microscope and are one-hundredth
1298-639: A cellular structure, which is often seen as the basic unit of life. Viruses do not have their own metabolism and require a host cell to make new products. They therefore cannot naturally reproduce outside a host cell —although some bacteria such as rickettsia and chlamydia are considered living organisms despite the same limitation. Accepted forms of life use cell division to reproduce, whereas viruses spontaneously assemble within cells. They differ from autonomous growth of crystals as they inherit genetic mutations while being subject to natural selection. Virus self-assembly within host cells has implications for
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#17330861773601416-493: A different DNA (or RNA) molecule. This can occur when viruses infect cells simultaneously and studies of viral evolution have shown that recombination has been rampant in the species studied. Recombination is common to both RNA and DNA viruses. Coronaviruses have a single-strand positive-sense RNA genome. Replication of the genome is catalyzed by an RNA-dependent RNA polymerase . The mechanism of recombination used by coronaviruses likely involves template switching by
1534-559: A few species, or broad for viruses capable of infecting many. Viral infections in animals provoke an immune response that usually eliminates the infecting virus. Immune responses can also be produced by vaccines , which confer an artificially acquired immunity to the specific viral infection. Some viruses, including those that cause HIV/AIDS , HPV infection , and viral hepatitis , evade these immune responses and result in chronic infections. Several classes of antiviral drugs have been developed. The English word "virus" comes from
1652-549: A fluid, by Wendell Meredith Stanley , and the invention of the electron microscope in 1931 allowed their complex structures to be visualised. Scientific opinions differ on whether viruses are a form of life or organic structures that interact with living organisms. They have been described as "organisms at the edge of life", since they resemble organisms in that they possess genes , evolve by natural selection , and reproduce by creating multiple copies of themselves through self-assembly. Although they have genes, they do not have
1770-530: A form of Ionic meter called Sotadic or Sotadean verse, which is sometimes said to have been palindromic, since it is sometimes possible to make a sotadean line by reversing a dactylic hexameter. A 1st-century Latin palindrome was found as a graffito at Pompeii . This palindrome, known as the Sator Square , consists of a sentence written in Latin: sator arepo tenet opera rotas 'The sower Arepo holds with effort
1888-445: A genome size of only two kilobases; the largest—the pandoraviruses —have genome sizes of around two megabases which code for about 2500 proteins. Virus genes rarely have introns and often are arranged in the genome so that they overlap . In general, RNA viruses have smaller genome sizes than DNA viruses because of a higher error-rate when replicating, and have a maximum upper size limit. Beyond this, errors when replicating render
2006-454: A given alphabet is a typical example of a language that is context-free , but not regular . This means that it is impossible for a finite automaton to reliably test for palindromes. In addition, the set of palindromes may not be reliably tested by a deterministic pushdown automaton which also means that they are not LR(k)-parsable or LL(k)-parsable . When reading a palindrome from left to right, it is, in essence, impossible to locate
2124-506: A ladder. The virus particles of some virus families, such as those belonging to the Hepadnaviridae , contain a genome that is partially double-stranded and partially single-stranded. For most viruses with RNA genomes and some with single-stranded DNA (ssDNA) genomes, the single strands are said to be either positive-sense (called the 'plus-strand') or negative-sense (called the 'minus-strand'), depending on if they are complementary to
2242-436: A life form, because they carry genetic material, reproduce, and evolve through natural selection , although they lack some key characteristics, such as cell structure, that are generally considered necessary criteria for defining life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life" and as replicators . Viruses spread in many ways. One transmission pathway
2360-472: A limited range of hosts and many are species-specific. Some, such as smallpox virus for example, can infect only one species—in this case humans, and are said to have a narrow host range . Other viruses, such as rabies virus, can infect different species of mammals and are said to have a broad range. The viruses that infect plants are harmless to animals, and most viruses that infect other animals are harmless to humans. The host range of some bacteriophages
2478-408: A prime target for natural selection. Segmented genomes confer evolutionary advantages; different strains of a virus with a segmented genome can shuffle and combine genes and produce progeny viruses (or offspring) that have unique characteristics. This is called reassortment or 'viral sex'. Genetic recombination is a process by which a strand of DNA (or RNA) is broken and then joined to the end of
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#17330861773602596-511: A research genome sequencing project discovered that many of the bases on the Y-chromosome are arranged as palindromes. A palindrome structure allows the Y-chromosome to repair itself by bending over at the middle if one side is damaged. It is believed that palindromes are also found in proteins, but their role in the protein function is not clearly known. It has been suggested in 2008 that
2714-527: A role in replication and can act as enhancers . The drs identified in various nudivirus genomes have no homology to each other and are present in both coding and noncoding regions . OrNV: 14 repeat regions 30-84 bp in length with varying AT% GbNV: 14 repeat regions 11 to 42 bp in length up to 96% AT rich. ToNv : 5 repeat regions 160-262 bp in length. HzNV-1: 6 repeat regions 24- 81 bp in length. HgNV: 7 repeat regions 58.8 to188 bp in length. PmNV : 10 repeat regions. Some nudiviruses have
2832-401: A single nucleocapsid surrounded by an envelope and range from 30nm to 120nm in length. They replicate in the nucleus of infected host cells and in some parasitoid wasp species, a nudivirus genome , in proviral form, is integrated into the wasp genome and produces virus like particles called polydnaviruses that are injected into lepidopteran larvae and are thought to facilitate parasitization of
2950-445: A single program. When the composer revised the work in 2003, he prescribed such a palindromic performance, with the twenty moments first played in a "forwards" version, and then "backwards". Each moment is a complex musical unit and is played in the same direction in each half of the program. By contrast, Karel Goeyvaerts 's 1953 electronic composition, Nummer 5 (met zuivere tonen) is an exact palindrome: not only does each event in
3068-412: A single viral particle that is released from the cell and is capable of infecting other cells of the same type. Viruses are found wherever there is life and have probably existed since living cells first evolved . The origin of viruses is unclear because they do not form fossils, so molecular techniques are used to infer how they arose. In addition, viral genetic material occasionally integrates into
3186-456: A small part of the total diversity of viruses has been studied. As of 2022, 6 realms, 10 kingdoms, 17 phyla, 2 subphyla, 40 classes, 72 orders, 8 suborders, 264 families, 182 subfamilies , 2,818 genera, 84 subgenera , and 11,273 species of viruses have been defined by the ICTV. The general taxonomic structure of taxon ranges and the suffixes used in taxonomic names are shown hereafter. As of 2022,
3304-605: A wide diversity of sizes and shapes, called ' morphologies '. In general, viruses are much smaller than bacteria and more than a thousand bacteriophage viruses would fit inside an Escherichia coli bacterium's cell. Many viruses that have been studied are spherical and have a diameter between 20 and 300 nanometres . Some filoviruses , which are filaments, have a total length of up to 1400 nm; their diameters are only about 80 nm. Most viruses cannot be seen with an optical microscope , so scanning and transmission electron microscopes are used to visualise them. To increase
3422-553: A wide variety of unusual shapes, ranging from spindle-shaped structures to viruses that resemble hooked rods, teardrops or even bottles. Other archaeal viruses resemble the tailed bacteriophages, and can have multiple tail structures. An enormous variety of genomic structures can be seen among viral species ; as a group, they contain more structural genomic diversity than plants, animals, archaea, or bacteria. There are millions of different types of viruses, although fewer than 7,000 types have been described in detail. As of January 2021,
3540-466: Is a context-free language, but it is not regular . The word palindrome was introduced by English poet and writer Henry Peacham in 1638. It is derived from the Greek roots πάλιν 'again' and δρóμος 'way, direction'; a different word is used in Greek, καρκινικός 'carcinic' (lit. crab-like ) to refer to letter-by-letter reversible writing. The ancient Greek poet Sotades (3rd-century BC) invented
3658-469: Is a 224-word long poem, "Dammit I'm Mad", written by Demetri Martin . "Weird Al" Yankovic 's song " Bob " is composed entirely of palindromes. Joseph Haydn 's Symphony No. 47 in G is nicknamed "the Palindrome". In the third movement, a minuet and trio , the second half of the minuet is the same as the first but backwards, the second half of the ensuing trio similarly reflects the first half, and then
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3776-416: Is a feature of many bacterial and some animal viruses. Some viruses undergo a lysogenic cycle where the viral genome is incorporated by genetic recombination into a specific place in the host's chromosome. The viral genome is then known as a " provirus " or, in the case of bacteriophages a " prophage ". Whenever the host divides, the viral genome is also replicated. The viral genome is mostly silent within
3894-405: Is a major change in the genome of the virus. This can be a result of recombination or reassortment . The Influenza A virus is highly prone to reassortment; occasionally this has resulted in novel strains which have caused pandemics . RNA viruses often exist as quasispecies or swarms of viruses of the same species but with slightly different genome nucleoside sequences. Such quasispecies are
4012-529: Is a palindrome when its digits are the same when reversed. Only the digits are considered in this determination and the component separators (hyphens, slashes, and dots) are ignored. Short digits may be used as in 11/11/11 11:11 or long digits as in 2 February 2020 . A notable palindrome day is this century's 2 February 2020 because this date is a palindrome regardless of the date format by country (yyyy-mm-dd, dd-mm-yyyy, or mm-dd-yyyy) used in various countries. For this reason, this date has also been termed as
4130-410: Is a palindrome, as is the slow movement of his String Quartet No. 1 . His hour-long String Quartet No. 9 consists of thirty-two variations and a fugue on a palindromic theme of Haydn (from the minuet of his Symphony No. 47). All of Simpson's thirty-two variations are themselves palindromic. Hin und Zurück ("There and Back": 1927) is an operatic 'sketch' (Op. 45a) in one scene by Paul Hindemith, with
4248-437: Is a submicroscopic infectious agent that replicates only inside the living cells of an organism . Viruses infect all life forms , from animals and plants to microorganisms , including bacteria and archaea . Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky 's 1892 article describing a non-bacterial pathogen infecting tobacco plants and
4366-518: Is also written as an acrostic square. Indeed, composing palindromes was "a pastime of Roman landed gentry". Byzantine baptismal fonts were often inscribed with the 4th-century Greek palindrome, ΝΙΨΟΝ ΑΝΟΜΗΜΑΤΑ (or ΑΝΟΜΗΜΑ ) ΜΗ ΜΟΝΑΝ ΟΨΙΝ (" Nipson anomēmata mē monan opsin ") 'Wash [your] sin(s), not only [your] face', attributed to Gregory of Nazianzus ; most notably in the basilica of Hagia Sophia in Constantinople . The inscription
4484-400: Is associated with proteins within a central disc structure known as a nucleoid . The nucleoid is surrounded by a membrane and two lateral bodies of unknown function. The virus has an outer envelope with a thick layer of protein studded over its surface. The whole virion is slightly pleomorphic , ranging from ovoid to brick-shaped. Mimivirus is one of the largest characterised viruses, with
4602-525: Is called a "delayed palindrome" (56 has a delay of 1 and 59 has a delay of 3). In January 2017 the number 1,999,291,987,030,606,810 was published in OEIS as A281509 , and described as "The Largest Known Most Delayed Palindrome", with a delay of 261. Several smaller 261-delay palindromes were published separately as A281508 . Every positive integer can be written as the sum of three palindromic numbers in every number system with base 5 or greater. A day or timestamp
4720-439: Is caused by cessation of its normal activities because of suppression by virus-specific proteins, not all of which are components of the virus particle. The distinction between cytopathic and harmless is gradual. Some viruses, such as Epstein–Barr virus , can cause cells to proliferate without causing malignancy, while others, such as papillomaviruses , are established causes of cancer. Some viruses cause no apparent changes to
4838-399: Is controversy over whether the bornavirus , previously thought to cause neurological diseases in horses, could be responsible for psychiatric illnesses in humans. Palindrome A palindrome is a word, number , phrase, or other sequence of symbols that reads the same backwards as forwards, such as madam or racecar , the date " 22/02/2022 " and the sentence: "A man, a plan,
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4956-512: Is correct. It seems unlikely that all currently known viruses have a common ancestor, and viruses have probably arisen numerous times in the past by one or more mechanisms. The first evidence of the existence of viruses came from experiments with filters that had pores small enough to retain bacteria. In 1892, Dmitri Ivanovsky used one of these filters to show that sap from a diseased tobacco plant remained infectious to healthy tobacco plants despite having been filtered. Martinus Beijerinck called
5074-457: Is equal to the original sequence in reverse complement. A palindromic DNA sequence may form a hairpin . Palindromic motifs are made by the order of the nucleotides that specify the complex chemicals ( proteins ) that, as a result of those genetic instructions, the cell is to produce. They have been specially researched in bacterial chromosomes and in the so-called Bacterial Interspersed Mosaic Elements (BIMEs) scattered over them. In 2003,
5192-498: Is first recorded in 1728, long before the discovery of viruses by Dmitri Ivanovsky in 1892. The English plural is viruses (sometimes also vira ), whereas the Latin word is a mass noun , which has no classically attested plural ( vīra is used in Neo-Latin ). The adjective viral dates to 1948. The term virion (plural virions ), which dates from 1959, is also used to refer to
5310-548: Is found on fonts in many churches in Western Europe: Orléans (St. Menin's Abbey); Dulwich College ; Nottingham ( St. Mary's ); Worlingworth ; Harlow ; Knapton ; London ( St Martin, Ludgate ); and Hadleigh (Suffolk) . A 12th-century palindrome with the same square property is the Hebrew palindrome, פרשנו רעבתן שבדבש נתבער ונשרף perashnu: ra`avtan shebad'vash nitba`er venisraf 'We explained
5428-433: Is from medieval rather than ancient times. The second word, borrowed from Greek, should properly be spelled gyrum . In English, there are many palindrome words such as eye , madam , and deified , but English writers generally cited Latin and Greek palindromic sentences in the early 19th century; though John Taylor had coined one in 1614: "Lewd did I live, & evil I did dwel" (with the ampersand being something of
5546-607: Is identical in sequence to the viral mRNA and is thus a coding strand, while negative-sense viral ssDNA is complementary to the viral mRNA and is thus a template strand. Several types of ssDNA and ssRNA viruses have genomes that are ambisense in that transcription can occur off both strands in a double-stranded replicative intermediate. Examples include geminiviruses , which are ssDNA plant viruses and arenaviruses , which are ssRNA viruses of animals. Genome size varies greatly between species. The smallest—the ssDNA circoviruses, family Circoviridae —code for only two proteins and have
5664-431: Is limited to a single strain of bacteria and they can be used to trace the source of outbreaks of infections by a method called phage typing . The complete set of viruses in an organism or habitat is called the virome ; for example, all human viruses constitute the human virome . A novel virus is one that has not previously been recorded. It can be a virus that is isolated from its natural reservoir or isolated as
5782-583: Is listed in dictionaries as being the longest single-word palindrome. The 9-letter term redivider is used by some writers, but appears to be an invented or derived term; only redivide and redivision appear in the Shorter Oxford English Dictionary; the 9-letter word Malayalam , a language of southern India, is also of equal length. According to Guinness World Records , the Finnish 19-letter word saippuakivikauppias (a soapstone vendor),
5900-409: Is not a Lychrel number as 56 + 65 = 121, and 121 is a palindrome. The number 59 becomes a palindrome after three iterations: 59 + 95 = 154; 154 + 451 = 605; 605 + 506 = 1111, so 59 is not a Lychrel number either. Numbers such as 196 are thought to never become palindromes when this reversal process is carried out and are therefore suspected of being Lychrel numbers. If a number is not a Lychrel number, it
6018-621: Is often written as NisiOisiN to emphasize this. Some people have changed their name in order to make it palindromic (including as the actor Robert Trebor and rock-vocalist Ola Salo ), while others were given a palindromic name at birth (such as the philologist Revilo P. Oliver , the flamenco dancer Sara Baras , the runner Anuța Cătună , the creator of the Eden Project Tim Smit , and the Mexican racing driver Noel León ). There are also palindromic names in fictional media. "Stanley Yelnats"
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#17330861773606136-555: Is repeated in reverse order, without alteration to word order within each line, and in a way that the second half continues the "story" related in the first half in a way that makes sense, this last being key. Palindromes often consist of a sentence or phrase, e.g., "A man, a plan, a canal, Panama", "Mr. Owl ate my metal worm", "Do geese see God?", or "Was it a car or a cat I saw?". Punctuation, capitalization, and spaces are usually ignored. Some, such as "Rats live on no evil star", "Live on time, emit no evil", and "Step on no pets", include
6254-675: Is replicated exactly in the opposite direction. For example, a G ♯ 3—13 half-steps down from A4 is replicated as a B ♭ 5—13 half-steps above. Just as the letters of a verbal palindrome are not reversed, so are the elements of a musical palindrome usually presented in the same form in both halves. Although these elements are usually single notes, palindromes may be made using more complex elements. For example, Karlheinz Stockhausen 's composition Mixtur , originally written in 1964, consists of twenty sections, called "moments", which may be permuted in several different ways, including retrograde presentation, and two versions may be made in
6372-614: Is still uncertain. Micro RNAs ( miRNAs ) are small non-coding RNA molecules that play important roles in the regulation of genes in eukaryotic organisms. Virus encoded miRNAs are commonly reported in DNA viruses and several nudiviruses have been reported to encode miRNAs. The first reported nudivirus encoded miRNA was from Heliothis zea nudivirus-1 which was shown to regulate virus latency. Two other viruses Drosophila innubila nudivirus and Oryctes rhinoceros nudivirus have also been reported to encode miRNA molecules from transcriptomic studies, however
6490-445: Is the name of the main character in Holes , a 1998 novel and 2003 film . Five of the fictional Pokémon species have palindromic names in English ( Eevee , Girafarig, Farigiraf, Ho-Oh, and Alomomola), as does the region Alola. The 1970s pop band ABBA is a palindrome using the starting letter of the first name of each of the four band members. The digits of a palindromic number are
6608-699: Is the phrase une Slave valse nue ("a Slavic woman waltzes naked"), phonemically / yn slav vals ny / . John Oswald discussed his experience of phonetic palindromes while working on audio tape versions of the cut-up technique using recorded readings by William S. Burroughs . A list of phonetic palindromes discussed by word puzzle columnist O.V. Michaelsen (Ove Ofteness) include "crew work"/"work crew", "dry yard", "easy", "Funny enough", "Let Bob tell", "new moon", "selfless", "Sorry, Ross", "Talk, Scott", "to boot", "top spot" (also an orthographic palindrome), "Y'all lie", "You're caught. Talk, Roy", and "You're damn mad, Roy". The longest single-word palindrome in
6726-649: Is the world's longest palindromic word in everyday use. English palindrome sentences of notable length include mathematician Peter Hilton 's "Doc, note: I dissent. A fast never prevents a fatness. I diet on cod", and Scottish poet Alastair Reid 's "T. Eliot, top bard, notes putrid tang emanating, is sad; I'd assign it a name: gnat dirt upset on drab pot toilet." In English, two palindromic novels have been published: Satire: Veritas by David Stephens (1980, 58,795 letters), and Dr Awkward & Olson in Oslo by Lawrence Levine (1986, 31,954 words). Another palindromic English work
6844-475: Is through disease-bearing organisms known as vectors : for example, viruses are often transmitted from plant to plant by insects that feed on plant sap , such as aphids ; and viruses in animals can be carried by blood-sucking insects. Many viruses spread in the air by coughing and sneezing, including influenza viruses , SARS-CoV-2 , chickenpox , smallpox , and measles . Norovirus and rotavirus , common causes of viral gastroenteritis , are transmitted by
6962-484: The Oxford English Dictionary is the 12-letter onomatopoeic word tattarrattat , coined by James Joyce in Ulysses (1922) for a knock on the door. The Guinness Book of Records gives the title to the 11-letter detartrated , the preterite and past participle of detartrate , a chemical term meaning to remove tartrates . The 9-letter word Rotavator , a trademarked name for an agricultural machine,
7080-474: The CD4 molecule—a chemokine receptor —which is most commonly found on the surface of CD4+ T-Cells . This mechanism has evolved to favour those viruses that infect only cells in which they are capable of replication. Attachment to the receptor can induce the viral envelope protein to undergo changes that result in the fusion of viral and cellular membranes, or changes of non-enveloped virus surface proteins that allow
7198-445: The DNA is formed by two paired strands of nucleotides , and the nucleotides always pair in the same way ( Adenine (A) with Thymine (T), Cytosine (C) with Guanine (G)), a (single-stranded) sequence of DNA is said to be a palindrome if it is equal to its complementary sequence read backward. For example, the sequence ACCTAGGT is palindromic because its complement is TGGATCCA , which
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#17330861773607316-540: The International Committee on Taxonomy of Viruses (ICTV) was formed. The system proposed by Lwoff, Horne and Tournier was initially not accepted by the ICTV because the small genome size of viruses and their high rate of mutation made it difficult to determine their ancestry beyond order. As such, the Baltimore classification system has come to be used to supplement the more traditional hierarchy. Starting in 2018,
7434-625: The Latin vīrus , which refers to poison and other noxious liquids. Vīrus comes from the same Indo-European root as Sanskrit viṣa , Avestan vīša , and Ancient Greek ἰός ( iós ), which all mean "poison". The first attested use of "virus" in English appeared in 1398 in John Trevisa 's translation of Bartholomeus Anglicus 's De Proprietatibus Rerum . Virulent , from Latin virulentus ('poisonous'), dates to c. 1400 . A meaning of 'agent that causes infectious disease'
7552-484: The NCBI Virus genome database has more than 193,000 complete genome sequences, but there are doubtlessly many more to be discovered. A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus , respectively. Most viruses have RNA genomes. Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes. Viral genomes are circular, as in
7670-539: The common cold , influenza , chickenpox , and cold sores . Many serious diseases such as rabies , Ebola virus disease , AIDS (HIV) , avian influenza , and SARS are caused by viruses. The relative ability of viruses to cause disease is described in terms of virulence . Other diseases are under investigation to discover if they have a virus as the causative agent, such as the possible connection between human herpesvirus 6 (HHV6) and neurological diseases such as multiple sclerosis and chronic fatigue syndrome . There
7788-422: The faecal–oral route , passed by hand-to-mouth contact or in food or water. The infectious dose of norovirus required to produce infection in humans is fewer than 100 particles. HIV is one of several viruses transmitted through sexual contact and by exposure to infected blood. The variety of host cells that a virus can infect is called its host range : this is narrow for viruses specialized to infect only
7906-430: The germline of the host organisms, by which they can be passed on vertically to the offspring of the host for many generations. This provides an invaluable source of information for paleovirologists to trace back ancient viruses that existed as far back as millions of years ago. There are three main hypotheses that aim to explain the origins of viruses: In the past, there were problems with all of these hypotheses:
8024-408: The polyomaviruses , or linear, as in the adenoviruses . The type of nucleic acid is irrelevant to the shape of the genome. Among RNA viruses and certain DNA viruses, the genome is often divided into separate parts, in which case it is called segmented. For RNA viruses, each segment often codes for only one protein and they are usually found together in one capsid. All segments are not required to be in
8142-447: The three domains . This discovery has led modern virologists to reconsider and re-evaluate these three classical hypotheses. The evidence for an ancestral world of RNA cells and computer analysis of viral and host DNA sequences give a better understanding of the evolutionary relationships between different viruses and may help identify the ancestors of modern viruses. To date, such analyses have not proved which of these hypotheses
8260-403: The "middle" until the entire word has been read completely. It is possible to find the longest palindromic substring of a given input string in linear time . The palindromic density of an infinite word w over an alphabet A is defined to be zero if only finitely many prefixes are palindromes; otherwise, letting the palindromic prefixes be of lengths n k for k =1,2,... we define
8378-440: The 1st-century CE Latin acrostic word square , the Sator Square (which contains both word and sentence palindromes), and the 4th-century Greek Byzantine sentence palindrome nipson anomemata me monan opsin . Palindromes are also found in music (the table canon and crab canon ) and biological structures (most genomes include palindromic gene sequences ). In automata theory , the set of all palindromes over an alphabet
8496-527: The ICTV began to acknowledge deeper evolutionary relationships between viruses that have been discovered over time and adopted a 15-rank classification system ranging from realm to species. Additionally, some species within the same genus are grouped into a genogroup . The ICTV developed the current classification system and wrote guidelines that put a greater weight on certain virus properties to maintain family uniformity. A unified taxonomy (a universal system for classifying viruses) has been established. Only
8614-457: The Pussy Cat , is a palindrome. The first movement from Constant Lambert 's ballet Horoscope (1938) is entitled "Palindromic Prelude". Lambert claimed that the theme was dictated to him by the ghost of Bernard van Dieren , who had died in 1936. British composer Robert Simpson also composed music in the palindrome or based on palindromic themes; the slow movement of his Symphony No. 2
8732-510: The ability to integrate into their host genome, like FaENV, NiENV, VcENV that are permently integrated into their host and HzNV-1 that integrates as part of an latent infection. A latent HzNV-1 infection can be reactivated generate a lytic viral infection The ability of these viruses to maintain their replication after integration distinguishes them their baculovirus ancestor. In many organisms, apoptosis can be regarded as an early defense mechanism against viral infection. Some viral genes allow
8850-484: The basis of similarities. In 1962, André Lwoff , Robert Horne , and Paul Tournier were the first to develop a means of virus classification, based on the Linnaean hierarchical system. This system based classification on phylum , class , order , family , genus , and species . Viruses were grouped according to their shared properties (not those of their hosts) and the type of nucleic acid forming their genomes. In 1966,
8968-426: The cell to survive for longer while producing more virions; Heliothis zea Nudivirus 1 (HzNV-1 or Hz-1 virus), a nudivirus with a broad host range, has been shown to block an induced-apoptosis gene ( hhi1 ). A functional anti-apoptosis gene, (Hz-iap2), has been found to suppress the hhi1 gene which can cause the cell to die. A second inhibitor gene (Ac-iap2) to the hhi1 gene has been also discovered, but its function
9086-572: The class Naldaviricetes that is composed of three other large dsDNA virus families: Baculoviridae , Hytrosaviridae and Nimaviridae. Nudiviruses infect only insects and marine crustaceans . Transmission of nudiviruses occurs horizontally by feeding, mating and vertically from mother to offspring. Infections can be lethal for the larvae and can possibly reduce the fitness of the host by reducing offspring production and survival among adults. Nudiviruses are double stranded DNA viruses, characterized by their rod shape. Their virions are made of
9204-410: The contrast between viruses and the background, electron-dense "stains" are used. These are solutions of salts of heavy metals, such as tungsten , that scatter the electrons from regions covered with the stain. When virions are coated with stain (positive staining), fine detail is obscured. Negative staining overcomes this problem by staining the background only. A complete virus particle, known as
9322-418: The discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 11,000 of the millions of virus species have been described in detail. The study of viruses is known as virology , a subspeciality of microbiology . When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting
9440-431: The extreme of the ssRNA virus case. Viruses undergo genetic change by several mechanisms. These include a process called antigenic drift where individual bases in the DNA or RNA mutate to other bases. Most of these point mutations are "silent"—they do not change the protein that the gene encodes—but others can confer evolutionary advantages such as resistance to antiviral drugs . Antigenic shift occurs when there
9558-446: The filtered, infectious substance a "virus" and this discovery is considered to be the beginning of virology. The subsequent discovery and partial characterization of bacteriophages by Frederick Twort and Félix d'Herelle further catalyzed the field, and by the early 20th century many viruses had been discovered. In 1926, Thomas Milton Rivers defined viruses as obligate parasites. Viruses were demonstrated to be particles, rather than
9676-513: The following genera: During their first discovery, nudiviruses were classified as a subgroup in the Baculoviridae family . Originally it was assumed that nudiviruses were nooccluded baculoviruses. In 2007, the genus Nudivirus was proposed to include viruses similar to the Oryctes rhinoceros virus. In 2013, Nudiviruses were classified as the family Nudiviridae . Today, nudiviruses are assigned to
9794-399: The form of single-stranded nucleoprotein complexes, through pores called plasmodesmata . Bacteria, like plants, have strong cell walls that a virus must breach to infect the cell. Given that bacterial cell walls are much thinner than plant cell walls due to their much smaller size, some viruses have evolved mechanisms that inject their genome into the bacterial cell across the cell wall, while
9912-851: The formation of nudiviral OBs. Currently, there is not a general life cycle established for nudiviruses. Gene content comparison and phylogenetic analyses show that nudiviruses share 20 core genes with baculoviruses and form a monophyletic sister group with them. Fossil calibration estimate this association arose 100 million years ago(Mya), while the last common ancestor of nudiviruses and baculoviruses existed approximately 312 Mya. Baculoviruses and nudiviruses differ in gene content, genome organization, cytopathology, infection of adults and most likely in host range. The 20 core genes common in both baculoviruses and nudiviruses are involved in RNA transcription, DNA replication, virion structural components and many other functions. Gene content and sequence similarity suggest that
10030-415: The glutton who is in the honey was burned and incinerated', credited to Abraham ibn Ezra in 1924, and referring to the halachic question as to whether a fly landing in honey makes the honey treif (non-kosher). The palindromic Latin riddle " In girum imus nocte et consumimur igni " 'we go in a circle at night and are consumed by fire' describes the behavior of moths. It is likely that this palindrome
10148-406: The host. At some point, the provirus or prophage may give rise to the active virus, which may lyse the host cells. Enveloped viruses (e.g., HIV) typically are released from the host cell by budding . During this process, the virus acquires its envelope, which is a modified piece of the host's plasma or other, internal membrane. The genetic material within virus particles, and the method by which
10266-517: The infected cell. Cells in which the virus is latent and inactive show few signs of infection and often function normally. This causes persistent infections and the virus is often dormant for many months or years. This is often the case with herpes viruses . Viruses are by far the most abundant biological entities on Earth and they outnumber all the others put together. They infect all types of cellular life including animals, plants, bacteria and fungi . Different types of viruses can infect only
10384-469: The larvae. Nudiviruses have localized infection and are associated with specific cell pathogenesis and varies among species. Vesicles containing virions have been observed for HzNV-2 and OrNV and aid in infecting subsequent cells. Virions sexually transmitted during mating, like Hznv-2, target reproductive tissues, cause the malformation of reproductive tissues in infected adult Helicoverpa Zea . In cells, enveloped and non enveloped particles were observed in
10502-520: The listener on the central movement, much as one would focus on the centre of the cross in the crucifixion. Other examples are found in Bach's cantata BWV 4, Christ lag in Todes Banden , Handel's Messiah and Fauré's Requiem . A table canon is a rectangular piece of sheet music intended to be played by two musicians facing each other across a table with the music between them, with one musician viewing
10620-416: The material is replicated, varies considerably between different types of viruses. The range of structural and biochemical effects that viruses have on the host cell is extensive. These are called ' cytopathic effects '. Most virus infections eventually result in the death of the host cell. The causes of death include cell lysis, alterations to the cell's surface membrane and apoptosis . Often cell death
10738-447: The melody is reversed in time and pitch from the other. A large-scale musical palindrome covering more than one movement is called "chiastic", referring to the cross-shaped Greek letter " χ " (pronounced /ˈkaɪ/.) This is usually a form of reference to the crucifixion; for example, the Crucifixus movement of Bach's Mass in B minor . The purpose of such palindromic balancing is to focus
10856-507: The minuet is repeated. The interlude from Alban Berg 's opera Lulu is a palindrome, as are sections and pieces, in arch form , by many other composers, including James Tenney , and most famously Béla Bartók . George Crumb also used musical palindrome to text paint the Federico García Lorca poem "¿Por qué nací?", the first movement of three in his fourth book of Madrigals . Igor Stravinsky 's final composition, The Owl and
10974-438: The music upside down compared to the other. The result is somewhat like two speakers simultaneously reading the Sator Square from opposite sides, except that it is typically in two-part polyphony rather than in unison. Palindromic motifs are found in most genomes or sets of genetic instructions. The meaning of palindrome in the context of genetics is slightly different, from the definition used for words and sentences. Since
11092-563: The nucleus and have been found to successfully replicate in infect ovarian moth cell lines, but did not replicate in fat body cells. In OrNV, replication occurs in the nucleus in midgut and fat body cells. In TpNV, replication occurs in the nucleus of the salvalary glands. The specific cell localization is a distinctive characteristic that differentiates nudivruses from baculoviruses. Three species form Occlusion bodies (OBs), ToNV, PmNV and OrNV. In PmNV OBs are transmitted orally and are sensitive to acid conditions. Host proteins may be involved in
11210-399: The nudiviruses GbNV, HzNV-1, and OrNV form a monophyletic group of nonoccluded double-stranded DNA viruses, which separated from the baculovirus lineage before this radiated into dipteran-, hymenopteran-, and lepidopteran-specific clades of occluded nucleopolyhedroviruses and granuloviruses. The coding sequences vary among the nudivirus species and encode between 87 to 154 proteins depending on
11328-461: The original virus. Their life cycle differs greatly between species, but there are six basic stages in their life cycle: Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface. This specificity determines the host range and type of host cell of a virus. For example, HIV infects a limited range of human leucocytes . This is because its surface protein, gp120 , specifically interacts with
11446-416: The polymerase during genome replication. This process appears to be an adaptation for coping with genome damage. Viral populations do not grow through cell division, because they are acellular. Instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they assemble in the cell. When infected, the host cell is forced to rapidly produce thousands of copies of
11564-400: The prevalent existence of palindromes in peptides might be related to the prevalence of low-complexity regions in proteins, as palindromes frequently are associated with low-complexity sequences. Their prevalence might also be related to an alpha helical formation propensity of these sequences, or in formation of protein/protein complexes. In automata theory , a set of all palindromes in
11682-960: The ranks of subrealm, subkingdom, and subclass are unused, whereas all other ranks are in use. The Nobel Prize-winning biologist David Baltimore devised the Baltimore classification system. The ICTV classification system is used in conjunction with the Baltimore classification system in modern virus classification. The Baltimore classification of viruses is based on the mechanism of mRNA production. Viruses must generate mRNAs from their genomes to produce proteins and replicate themselves, but different mechanisms are used to achieve this in each virus family. Viral genomes may be single-stranded (ss) or double-stranded (ds), RNA or DNA, and may or may not use reverse transcriptase (RT). In addition, ssRNA viruses may be either sense (+) or antisense (−). This classification places viruses into seven groups: Examples of common human diseases caused by viruses include
11800-422: The regressive hypothesis did not explain why even the smallest of cellular parasites do not resemble viruses in any way. The escape hypothesis did not explain the complex capsids and other structures on virus particles. The virus-first hypothesis contravened the definition of viruses in that they require host cells. Viruses are now recognised as ancient and as having origins that pre-date the divergence of life into
11918-479: The result of spread to an animal or human host where the virus had not been identified before. It can be an emergent virus , one that represents a new virus, but it can also be an extant virus that has not been previously identified . The SARS-CoV-2 coronavirus that caused the COVID-19 pandemic is an example of a novel virus. Classification seeks to describe the diversity of viruses by naming and grouping them on
12036-622: The role of these miRNAs and their role in virus-host interactions is yet to be experimentally determined. In the southwest Pacific islands, OrNV has been shown to be an effective biocontrol agent against the palm pest, the coconut rhinoceros beetle. The word "nudivirus" comes from the Latin nudus , which means naked and virus , poison. Naked refers to the fact that most do not have the dense protein bodies which surround baculoviruses . However occluded nudiviruses, with such protein bodies, such as those of Tipula oleracea and Penaeus monodon have been characterized. Virus A virus
12154-419: The same read backwards as forwards, for example, 91019; decimal representation is usually assumed. In recreational mathematics , palindromic numbers with special properties are sought. For example, 191 and 313 are palindromic primes . Whether Lychrel numbers exist is an unsolved problem in mathematics about whether all numbers become palindromes when they are continuously reversed and added. For example, 56
12272-451: The same virion for the virus to be infectious, as demonstrated by brome mosaic virus and several other plant viruses. A viral genome, irrespective of nucleic acid type, is almost always either single-stranded (ss) or double-stranded (ds). Single-stranded genomes consist of an unpaired nucleic acid, analogous to one-half of a ladder split down the middle. Double-stranded genomes consist of two complementary paired nucleic acids, analogous to
12390-403: The second half of the piece occur according to an axis of symmetry at the centre of the work, but each event itself is reversed, so that the note attacks in the first half become note decays in the second, and vice versa. It is a perfect example of Goeyvaerts's aesthetics, the perfect example of the imperfection of perfection. In classical music , a crab canon is a canon in which one line of
12508-462: The size of most bacteria. The origins of viruses in the evolutionary history of life are still unclear. Some viruses may have evolved from plasmids , which are pieces of DNA that can move between cells. Other viruses may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer , which increases genetic diversity in a way analogous to sexual reproduction . Viruses are considered by some biologists to be
12626-514: The spaces. Some names are palindromes, such as the given names Hannah, Ava, Aviva, Anna, Eve, Bob, and Otto, or the surnames Harrah, Renner, Salas, and Nenonen. Lon Nol (1913–1985) was Prime Minister of Cambodia. Nisio Isin is a Japanese novelist and manga writer, whose pseudonym (西尾 維新, Nishio Ishin ) is a palindrome when romanized using the Kunrei-shiki or the Nihon-shiki systems, and
12744-608: The species. The order of the genes in the genomes of the viruses found in nudiviridae are poorly conserved. There are 32 core genes conserved among nudiviruses that are involved in various viral functions. The conservation of the 8 pif proteins, suggest the mode of infection for nudiviruses is conserved. Tandem direct repeats (Drs) are a common feature found in nudiviruses. These regions are characterized by their imperfect palindromic core. The number direct repeat regions vary among nudivirus species and hypothesized to function like baculovirus Homologous regions. These regions can play
12862-399: The structure-mediated self-assembly of the virus particles, some modification of the proteins often occurs. In viruses such as HIV, this modification (sometimes called maturation) occurs after the virus has been released from the host cell. Release – Viruses can be released from the host cell by lysis , a process that kills the cell by bursting its membrane and cell wall if present: this
12980-457: The study of the origin of life , as it lends further credence to the hypothesis that life could have started as self-assembling organic molecules . The virocell model first proposed by Patrick Forterre considers the infected cell to be the "living form" of viruses and that virus particles (virions) are analogous to spores . Although the living versus non-living debate continues, the virocell model has gained some acceptance. Viruses display
13098-603: The unit of reversal is the word ("Is it crazy how saying sentences backwards creates backwards sentences saying how crazy it is?"). Word-unit palindromes were made popular in the recreational linguistics community by J. A. Lindon in the 1960s. Occasional examples in English were created in the 19th century. Several in French and Latin date to the Middle Ages . There are also line-unit palindromes, most often poems . These possess an initial set of lines which, precisely halfway through,
13216-446: The viral messenger RNA (mRNA). Positive-sense viral RNA is in the same sense as viral mRNA and thus at least a part of it can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA-dependent RNA polymerase before translation. DNA nomenclature for viruses with genomic ssDNA is similar to RNA nomenclature, in that positive-strand viral ssDNA
13334-824: The viral capsid remains outside. Uncoating is a process in which the viral capsid is removed: This may be by degradation by viral enzymes or host enzymes or by simple dissociation; the end-result is the releasing of the viral genomic nucleic acid. Replication of viruses involves primarily multiplication of the genome. Replication involves the synthesis of viral messenger RNA (mRNA) from "early" genes (with exceptions for positive-sense RNA viruses), viral protein synthesis , possible assembly of viral proteins, then viral genome replication mediated by early or regulatory protein expression. This may be followed, for complex viruses with larger genomes, by one or more further rounds of mRNA synthesis: "late" gene expression is, in general, of structural or virion proteins. Assembly – Following
13452-503: The virus to enter. Penetration or viral entry follows attachment: Virions enter the host cell through receptor-mediated endocytosis or membrane fusion . The infection of plant and fungal cells is different from that of animal cells. Plants have a rigid cell wall made of cellulose , and fungi one of chitin, so most viruses can get inside these cells only after trauma to the cell wall. Nearly all plant viruses (such as tobacco mosaic virus) can also move directly from cell to cell, in
13570-460: The virus useless or uncompetitive. To compensate, RNA viruses often have segmented genomes—the genome is split into smaller molecules—thus reducing the chance that an error in a single-component genome will incapacitate the entire genome. In contrast, DNA viruses generally have larger genomes because of the high fidelity of their replication enzymes. Single-strand DNA viruses are an exception to this rule, as mutation rates for these genomes can approach
13688-399: The wheels'. It is also an acrostic where the first letters of each word form the first word, the second letters form the second word, and so forth. Hence, it can be arranged into a word square that reads in four different ways: horizontally or vertically from either top left to bottom right or bottom right to top left. Other palindromes found at Pompeii include "Roma-Olina-Milo-Amor", which
13806-659: Was (implausibly) attributed to Napoleon (alluding to his exile on Elba). Other well-known English palindromes are: "A man, a plan, a canal – Panama" (1948), "Madam, I'm Adam" (1861), and "Never odd or even" (1930). The most familiar palindromes in English are character-unit palindromes, where the characters read the same backward as forward. Examples are civic , radar , level , rotor , kayak , madam , and refer . The longest common ones are rotator, deified, racecar , and reviver ; longer examples such as redivider , kinnikinnik , and tattarrattat are orders of magnitude rarer. There are also word-unit palindromes in which
13924-562: Was extremely interested in symmetries in music, be they horizontal or vertical. An example of horizontal or linear symmetry in Webern's music is the first phrase in the second movement of the symphony , Op. 21. A striking example of vertical symmetry is the second movement of the Piano Variations , Op. 27, in which Webern arranges every pitch of this dodecaphonic work around the central pitch axis of A4. From this, each downward reaching interval
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