Mohamed Alkarni
Virology is that the science concerned with the study of the biology of viruses and viral diseases, including the distribution, biochemistry, physiology, biology, ecology, evolution and clinical aspects of viruses. Virology is that the investigation of infections – submicroscopic, parasitic particles of hereditary material contained during a protein coat–and infection like operators. It centers around the resulting parts of infections: their structure, grouping and advancement, their approaches to taint and adventure have cells for duplicate , their cooperation with have life form physiology and insusceptibility, the maladies they cause, the methods to confine and culture them, and their utilization in exploration and treatment. Virology is a subfield of microbiology.
Martinus Beijerinck is usually called the daddy of Virology. Sadly, he didn't live long enough to truly see his virus particles under the electro. In 1905n microscope or find out how widespread and important they're. The most useful and most generally used arrangement distinguishes viruses consistent with the sort of macromolecule they use as genetic material and therefore the viral replication method they employ to coax host cells into producing more viruses: DNA viruses (divided into double-stranded DNA viruses and single-stranded DNA viruses), RNA viruses (divided into positive-sense single-stranded RNA viruses, negative-sense single-stranded RNA viruses and therefore the much less common double-stranded RNA viruses), reverse transcribing viruses (double-stranded reverse-transcribing DNA viruses and single-stranded reverse-transcribing RNA viruses including retroviruses). The most recent report by the International Committee on Taxonomy of Viruses (2005) records 5,450 infections, composed in more than 2,000 species, 287 genera, 73 families and three requests. Virologists likewise study subviral particles, irresistible substances outstandingly littler and less complex than infections: viroids (stripped round RNA atoms tainting plants), satellites (nucleic corrosive atoms with or without a capsid that require an aide infection for disease and propagation), and prions (proteins which will exist during a neurotic adaptation that incites other prion atoms to expect that exact same compliance). Taxa in virology aren't really monophyletic, in light of the fact that the developmental connections of the shifted infection bunches stay hazy. Three theories in regards to their cause exist: Viruses emerged from non-living issue, independently from yet in corresponding to cells, maybe inside such a self-duplicating RNA ribozymes practically like viroids. Infections emerged by genome decrease from prior, increasingly equipped cell life shapes that became parasites to have cells and in this manner lost the greater part of their usefulness; tests of such minuscule parasitic prokaryotes are Mycoplasma and Nanoarchaea.
Viruses arose from mobile genetic elements of cells (such as transposons, retrotransposons or plasmids) that became encapsulated in protein capsids, acquired the power to "break free" from the host cell and infect other cells.
Of particular interest here is mimivirus, an enormous virus that infects amoebae and encodes much of the molecular machinery traditionally related to bacteria. Two possibilities are that it's a simplified version of a parasitic prokaryote or it originated as an easier virus that acquired genes from its host. The evolution of viruses, which frequently occurs together with the evolution of their hosts, is studied within the field of viral evolution. While viruses reproduce and evolve, they are doing not engage in metabolism, don't move, and depend upon a number cell for copy . The often-debated question of whether or not they are alive or not may be a matter of definition that doesn't affect the biological reality of viruses.
A retrovirus may be a sort of RNA virus[a] that inserts a replica of its genome into the DNA of a number cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own polymerase enzyme to supply DNA from its RNA genome, the reverse of the standard pattern, thus retro (backwards). The new DNA is then incorporated into the host cell genome by an integrase enzyme, at which point the retroviral DNA is mentioned as a provirus. The host cell then treats the viral DNA as a part of its own genome, transcribing and translating the viral genes along side the cell's own genes, producing the proteins required to assemble new copies of the virus. Although retroviruses have different subfamilies, they have three basic groups. The oncoretroviruses (oncogenic retroviruses), the lentiviruses (slow retroviruses) and therefore the spumaviruses (foamy viruses). The oncoretroviruses are ready to cause cancer in some species, the lentiviruses ready to cause severe immunodeficiency and death in humans and other animals, and therefore the spumaviruses being benign and not linked to any disease in humans or animals. Many retroviruses cause serious diseases in humans, other mammals, and birds. Human retroviruses include HIV-1 and HIV-2, the explanation for the disease AIDS. Also the Human T-lymphotropic virus (HTLV) causes disease in humans. The murine leukemia viruses (MLVs) cause cancer in mouse hosts. Retroviruses are valuable research tools in biology , and that they are used successfully in gene delivery systems.
Virions of retroviruses contains enveloped particles about 100 nm in diameter. The outer lipid envelope consists of glycoprotein. The virions also contain two identical single-stranded RNA molecules 7–10 kilobases in length.The two molecules are present as a dimer, formed by base pairing between complementary sequences. Interaction sites between the two RNA molecules have been identified as a "kissing -loop complex". Although virions of various retroviruses don't have an equivalent morphology or biology, all the virion components are very similar. The retroviral genome is packaged as viral particles. These viral particles are dimers of single-stranded, positive-sense, linear RNA molecules. Retroviruses (and rotaviruses in general) follow a layout of 5–gag–pro–pol–env–3 in the RNA genome. gag and pol encode polyproteins, each managing the capsid and replication. The pol region encodes enzymes necessary for viral replication, like polymerase , protease, and integrase. Depending on the virus, the genes may overlap or fuse into larger polyprotein chains. Some viruses contain additional genes. The lentivirus genus, the spumavirus genus, the HTLV / bovine leukemia virus (BLV) genus, and a newly introduced fish virus genus are retroviruses classified as complex. These viruses have genes called accessory genes, additionally to gag, pro, pol, and env genes. Accessory genes are located between pol and env, downstream from the env, including the U3 region of LTR, or within the env and overlapping portions. While accessory genes have auxiliary roles, they also coordinate and regulate viral organic phenomenon . In addition, some retroviruses may carry genes called oncogenes or on genes from another class. Retroviruses with these genes (also called transforming viruses) are known for their ability to quickly cause tumors in animals and transform cells in culture into an oncogenic state.