In the last two-decade, numbers of giant dsDNA, icosahedral viruses have been discovered and assigned to the NCLDV clade. The major capsid proteins of these viruses consist of two consecutive jelly-roll domains, assembled into trimers, with six fold symmetry. The capsomers are assembled into arrays that have either p6 as in Paramecium bursaria Chlorella virus 1 or p3 symmetry as in Mimivirus (Xiao & Rossmann 2011).
Mimivirus has a capsid (icosahedral) diameter of 400 nm with protein filaments of 100 nm from the surface of the capsid, comprising the total length of the virus up to 600 nm. While most of the other discovered large viruses size varies between 400 nm and 800 nm (Xiao et al., 2009). Mimivirus shares similar morphological characteristics with all members of the NCLDV group of viruses. The central core of the virion appears as a dark region under the electron microscope. An internal lipid layer surrounding the central core seen in all other NCLDV viruses this features present in Mimivirus (Xiao et al., 2009).
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However, the virions of P. sibericum like pandoraviruses morphologically but are still being the largest (1.5 μm in length), with a 60 nm thickness of the enveloped hexagonal structure that missing in pandoraviruses. Pandoravirus and P. sibericum both have the apical pore. Wile, the virion of M. sibericum is a spheric shape covered with 2 to 4 layers of fibers. Faustovirus virions have an icosahedral capsid without fibers. As for virions of all previous giant viruses, the internal lipid membrane surrounding the core and fuses with the vacuole membrane is to release the dsDNA
The biological significance of this article is due in part to the fact that viruses are being considered as partway-living things. Even though they are only halfway living, per se, they are still an important part of the study of living things because of the unique way in which they “live” and continue to reproduce by taking advantage of host cells. The information in this article relates to biologists in that viruses provide an entirely different element of potential life, as they are a cause for reconsideration when it comes to defining and determining life and non-life forms. This
* Flaviviruses: share a common size (40-60nm), symmetry (enveloped, icosahedral nucleocapsid), nucleic acid (positive-sense, single stranded RNA approximately 10,000-11,000 bases), and appearance in the electron microscope. Therefore, images of West Nile virus are representative for this group of viruses.
The argument on whether viruses are considered living or dead has been debated in science for years. While this topic has been extensively researched, a conclusion has yet to be reached. However, from my own research, I concluded that viruses are non-living. To better understand this topic, I will discuss cell theory, the differences between a prokaryote and a eukaryote cell, and the structures and functions of a nucleus and cell wall organelles.
Viruses are microscopic particles that invade and take over both eukaryotic and prokaryotic cells. They consist of two structures, which are the nucleic acid and capsid. The nucleic acid contains all genetic material in the form of DNA or RNA, and is enclosed in the capsid, which is the protein coating that helps the virus attach to and penetrate the host cell. In some cases, certain viruses have a membrane surrounding the capsid, called an envelope. This structure allows viruses to become more stealthy and protected. There are two cycles in which a virus can go into: lytic and lysogenic. The lytic cycle consists of the virus attaching to a cell, injecting its DNA, and creating more viruses, which proceed to destroy the host. On the other hand, the lysogenic cycle includes the virus attaching to the cell, injecting its DNA, which combines with the cell’s DNA in order for it to become provirus. Then, the provirus DNA may eventually switch to the lytic cycle and destroy the host.
A virus is a small capsule that contains DNA or RNA, viruses, unlike bacteria are not self sufficient and need a host in
RSV belongs to the paramyxovirus family of viruses. The virion encompasses a helical nucleocapsid packaged in a lipoprotein envelope attained from the host cell plasma membrane during budding. The external surface of the envelope contains a periphery of surface spikes.
The virus fuses with the cell’s plasma membrane. The capsid proteins are removed, releasing the viral proteins and RNA. Reverse transcriptase catalyzes the synthesis of a DNA strand complementary to the viral RNA. Reverse transcriptase catalyzes the synthesis of a second DNA strand complementary to the first. The double-stranded DNA is incorporated as a provirus into the cell’s DNA. Proviral genes are transcribed into RNA molecules, which serve as genomes for the next viral generation and as mRNAs for translation into viral proteins. The viral proteins include capsid proteins and reverse transcriptase (made in the cytosol) and envelope glycoproteins (made in the ER). Vesicles transport the glycoproteins from the ER to the cell’s plasma membrane. Capsids are assembled around viral genomes and reverse transcriptase molecules. New viruses bud off from the host cell.
Nipah virus, Arena Virus and Francisella tularensis are bioterrorism agents. They work in various ways to harm the host. Francisella tularenis is considered a Tier 1 bioterrorism agent and Nipah virus is an overlap select agent that affects humans and agriculture both. They have been harmful in the past. Though, Nipah virus is a newer virus than the other two. This review will focus on their emergence, pathogenicity and symptoms of the diseases they cause.
Where it is still unclear the origins of viruses, one thing is clear, they are a very important part of the horizontal gene transfer, which drastically increases genetic diversity.
The SH (small hydrophobic) protein, matrix protein (M), and the M2 protein are envelope-associated proteins that are not involved in viral attachment or syncytium formation (3). Other proteins such as the nucleoprotein (N), phosphoprotein (P), and the large nucleoprotein (L) are in the nucleocapsid. NS-1 and NS-2 are non-structure protein that is only found in the infected cells but not present in virions (3).
For example, viruses do not use energy and raw materials to grow and reproduce, and they are not made of one or more of the basic fundamental units of life – a cell. Compared to a cell, which includes organelles that enable the structure to grow and reproduce, a virus can only reproduce if another cell is present and that cell has organelles that the virus can inject its own DNA or RNA into and use it for its own replicating or mutating purposes. Viruses are made of a protein coat or capsid with its DNA or RNA genetic material enclosed inside of the capsid. In comparison, in addition to having organelles that use energy to help the cell develop, grow, and reproduce with the help of DNA, the cell by definition is enclosed in a membranous boundary,
A virus is a capsule containing genetic material, even smaller than bacteria. The main task of virus is to reproduce. However, viruses need a suitable host to
There is still a great deal of information to learn from the study of viruses and the continued exploration of the viral genome is crucial in understanding how viruses communicate, transmit from host to host and evade immune responses. The ever-change nature of the viral genome has shown us that the most dangerous viral infections of today may be undermined by newer and more effective viruses, resulting in catastrophic outcomes. Through the study of viruses, it is the hope of the scientific community to be ahead of the viral curve, preventing infections before they even
The norovirus is small and round. It is only 27-35 nm in diameter. The virus contains a single- stranded RNA genome. Noroviruses are divided into five genogroups, G1- G5. Of these five genogroups, only G1, G2, and G4 are known to infect humans. G2 is the most common in adult cases of gastroenteritis. 1 “Noroviruses are not enveloped and contain an outer protein capsid encapsulating an RNA genome.”2
Dengue virus(50nm) belongs to family Flaviviridae. The mature dengue virion consists of a positive (+)single-stranded RNA genome surrounded by an icosahedral or isometric nucleocapsid about 30 nm in diameter. This nucleocapsid is covered by a lipid envelope. The complete