Virus replication 21-1 lab answers

Multiple, full-length RNA strands of negative polarity complementary to the positive-stranded genomic RNA are formed from these intermediates, which may then serve as templates for the production of RNA with positive polarity, including both full-length genomic RNA and shorter viral mRNAs. In this case, the negative-stranded genome can be converted directly to mRNA.

Additionally, full-length positive RNA strands are made to serve as templates for the production of the negative-stranded genome. Group VI viruses have diploid two copies ssRNA genomes that must be converted, using the enzyme reverse transcriptase , to dsDNA; the dsDNA is then transported to the nucleus of the host cell and inserted into the host genome. The characteristics of each group in the Baltimore classification are summarized in Table As an Amazon Associate we earn from qualifying purchases.

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The Chemistry of Life. The Cell. Evolutionary Processes. Biological Diversity. Plant Structure and Function. Animal Structure and Function. Learning Objectives In this section, you will explore the following questions: How were viruses first discovered and how are they detected?

What three hypotheses describe the evolution of viruses? What is the basic structure of a virus? How are viruses classified? Big Idea 3 Living systems store, retrieve, transmit and respond to information essential to life processes. Enduring Understanding 3. A Heritable information provides for continuity of life. Essential Knowledge 3. Science Practice 6. Learning Objective 3. Figure Nataro and S. Sears, unpub. Stressed cells express more xCT receptors than non-stressed cells. The KSHV virion causes cells to become stressed, thereby increasing expression of the receptor to which it binds.

This figure shows three relatively complex virions: the bacteriophage T4, with its DNA-containing head group and tail fibers that attach to host cells; adenovirus, which uses spikes from its capsid to bind to host cells; and HIV, which uses glycoproteins embedded in its envelope to bind to host cells. Notice that HIV has proteins called matrix proteins, internal to the envelope, which help stabilize virion shape. Virus Classification by Genome Structure and Core.

Table Rabies transmission occurs when saliva from an infected mammal enters a wound. The virus travels through neurons in the peripheral nervous system to the central nervous system where it impairs brain function, and then travels to other tissues. The virus can infect any mammal, and most die within weeks of infection. Smallpox is a human virus transmitted by inhalation of the variola virus, localized in the skin, mouth, and throat, which causes a characteristic rash. Before its eradication in , infection resulted in a 30—35 percent mortality rate.

The virus, shown clustered in the micrograph right , is transmitted orally and causes a variety of illnesses in vertebrates, including human eye and respiratory infections. William Gary, Jr. Virus Classification by Capsid Structure. The capsid of the a polio virus is naked icosahedral; b the Epstein-Barr virus capsid is enveloped icosahedral; c the mumps virus capsid is an enveloped helix; d the tobacco mosaic virus capsid is naked helical; and e the herpesvirus capsid is complex.

Previous Next. IFNs in combination with ribavirin may have increased activity in vitro when compared to IFNs alone against some coronaviruses; however, the effectiveness of this combination in vivo requires further evaluation [ ]. The SARS and MERS outbreaks have stimulated research on these viruses and this research has identified a large number of suitable antiviral targets, such as viral proteases, polymerases, and entry proteins.

Significant work remains, however, to develop drugs that target these processes and are able to inhibit viral replication. Only limited options are available to prevent coronavirus infections. Vaccines have only been approved for IBV, TGEV, and Canine CoV, but these vaccines are not always used because they are either not very effective, or in some cases have been reported to be involved in the selection of novel pathogenic CoVs via recombination of circulating strains.

Vaccines for veterinary pathogens, such as PEDV, may be useful in such cases where spread of the virus to a new location could lead to severe losses of veterinary animals.

These vaccines include recombinant attenuated viruses, live virus vectors, or individual viral proteins expressed from DNA plasmids. Such antibodies would be most useful for protecting healthcare workers. In general, it is thought that live attenuated vaccines would be the most efficacious in targeting coronaviruses. This variant only caused mild disease and completely protected swine from TGEV.

Despite this success, vaccine development for coronaviruses faces many challenges [ ]. First, for mucosal infections, natural infection does not prevent subsequent infection, and so vaccines must either induce better immunity than the original virus or must at least lessen the disease incurred during a secondary infection. Second, the propensity of the viruses to recombine may pose a problem by rendering the vaccine useless and potentially increasing the evolution and diversity of the virus in the wild [ ].

Finally, it has been shown in FIPV that vaccination with S protein leads to enhanced disease [ ]. Owing to the lack of effective therapeutics or vaccines, the best measures to control human coronaviruses remain a strong public health surveillance system coupled with rapid diagnostic testing and quarantine when necessary.

For international outbreaks, cooperation of governmental entities, public health authorities, and health care providers is critical. During veterinary outbreaks that are readily transmitted, such as PEDV, more drastic measures such as destruction of entire herds of pigs may be necessary to prevent transmission of these deadly viruses.

Over the past 50 years the emergence of many different coronaviruses that cause a wide variety of human and veterinary diseases has occurred. It is likely that these viruses will continue to emerge and to evolve and cause both human and veterinary outbreaks owing to their ability to recombine, mutate, and infect multiple species and cell types.

Future research on coronaviruses will continue to investigate many aspects of viral replication and pathogenesis. First, understanding the propensity of these viruses to jump between species, to establish infection in a new host, and to identify significant reservoirs of coronaviruses will dramatically aid in our ability to predict when and where potential epidemics may occur.

As bats seem to be a significant reservoir for these viruses, it will be interesting to determine how they seem to avoid clinically evident disease and become persistently infected.

Second, many of the non-structural and accessory proteins encoded by these viruses remain uncharacterized with no known function, and it will be important to identify mechanisms of action for these proteins as well as defining their role in viral replication and pathogenesis. These studies should lead to a large increase in the number of suitable therapeutic targets to combat infections.

Third, gaining a complete picture of the intricacies of the RTC will provide a framework for understanding the unique RNA replication process used by these viruses. Finally, defining the mechanism of how coronaviruses cause disease and understanding the host immunopathological response will significantly improve our ability to design vaccines and reduce disease burden.

Helena Jane Maier, Email: ku. Erica Bickerton, Email: ku. Paul Britton, Email: ku. National Center for Biotechnology Information , U. Published online Feb Anthony R. Fehr and Stanley Perlman , M. Author information Copyright and License information Disclaimer. Stanley Perlman, Email: ude.

Corresponding author. This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source.

This article has been cited by other articles in PMC. Abstract Coronaviruses CoVs , enveloped positive-sense RNA viruses, are characterized by club-like spikes that project from their surface, an unusually large RNA genome, and a unique replication strategy.

Classification Coronaviruses CoVs are the largest group of viruses belonging to the Nidovirales order, which includes Coronaviridae , Arteriviridae , Mesoniviridae , and Roniviridae families. Open in a separate window. Virion Structure Coronavirus virions are spherical with diameters of approximately nm as depicted in recent studies by cryo-electron tomography and cryo-electron microscopy [ 2 , 3 ].

Coronavirus Life Cycle Attachment and Entry The initial attachment of the virion to the host cell is initiated by interactions between the S protein and its receptor. Table 1 Coronavirus receptors. Replicase Protein Expression The next step in the coronavirus lifecycle is the translation of the replicase gene from the virion genomic RNA. Table 2 Functions of coronavirus non-structural proteins nsps. Replication and Transcription Viral RNA synthesis follows the translation and assembly of the viral replicase complexes.

Pathogenesis Animal Coronaviruses Coronaviruses cause a large variety of diseases in animals, and their ability to cause severe disease in livestock and companion animals such as pigs, cows, chickens, dogs, and cats led to significant research on these viruses in the last half of the twentieth century.

Diagnosis, Treatment, and Prevention In most cases of self-limited infection, diagnosis of coronaviruses is unnecessary, as the disease will naturally run its course. Conclusion Over the past 50 years the emergence of many different coronaviruses that cause a wide variety of human and veterinary diseases has occurred.

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A major determinant for membrane protein interaction localizes to the carboxy-terminal domain of the mouse coronavirus nucleocapsid protein. Perlman S, Netland J. Coronaviruses post-SARS: update on replication and pathogenesis. Nat Rev Microbiol. Identification of a novel coronavirus from a beluga whale by using a panviral microarray. Identification of diverse alphacoronaviruses and genomic characterization of a novel severe acute respiratory syndrome-like coronavirus from bats in china.

Discovery of the first insect nidovirus, a missing evolutionary link in the emergence of the largest RNA virus genomes.

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