Flashcards in MicroBio Q's TF CH 5 Deck (64):
The genetic material found in a virion is usually what?
Either DNA or RNA
Viral particles are composed of what?
DNA or RNA, a coat of protein, and layers of carbohydrates, lipids and additional proteins
What is the best microscopic methods for studying viruses?
What is the function of the viral capsid?
To the protect the viral genome
The Tobacco mosaic virus exhibits which type of capsid symmetry?
An example of a virus that exhibits binal symmetry is known as what?
Viral spikes or peplomers are involved in what?
Which structures are associated with the influenza virus?
Neuraminidase enzyme, hemagglutinin protein, and glycoproteins
The most common viral nucleic acid types are what?
dsDNA and ssRNA
What is the first step in the generalized viral life cycle?
Attachment of virus to host cell
What is viral host specificity most likely attributed to?
Interaction between receptors on the surface of the host cell and ligands on the surface of virions
Which mechanisms do eukaryotic viruses enter host cells through?
Through fusion of the viral envelope with the host cell membrane, entry by endocytosis, and injection of nucleic acid
Which types of viruses must carry their own replication enzymes in their nucleocapsid?
RNA viruses only
Where does the energy that is required for bacteriophage assembly come from?
Host metabolic activity
What is a common virion release method observed in enveloped viruses?
What is the name of the relationship with the host cell in which the virus remains within the host without destroying it called?
What does an advantage of lysogeny to the host include?
Resistance to superinfection
When more phage are present in the environment than there are host cells, which type of host relationship is most desirable?
What are microscopic and/or macroscopic damages to host cells caused by eukaryotic viruses called?
What is the name for a type of viral infection in which there is a low release of virions without cell death?
What cellular genes required for normal growth, but when mutated or overexposed, cause carcinogenesis?
Which of the following viruses is NOT definitely linked to causing cancer in humans?
Which methods can be used to cultivate plant viruses?
Grow in cultures of plant cells lacking cell walls, mechanically break leaves to expose cells to infection, or graft diseased part onto a healthy plant
What can be used to determine direct counts of viral particles?
What is an indirect method of counting animal viruses?
The number of plaque-forming units (PFUs) is calculated from a viral plaque assay by.....?
Multiplying the number of plaques per volume by the dilution
What is teh dilution taht contains the number of viral cells large enough to destroy 50% of the host cells or organisms called?
The lethal dose
What are infectious RNAs that primarily infect plants called?
What are infectious proteins responsible for bovine spongiform encephalopathy called?
Viruses are considered to be living organisms
Scientists classify viruses based on genome structure, life cycles, morphology, and genetic relatedness
Most viruses are approximately the same size as bacteria (0.2 to 2 micrometers)
Hos-independent growth has never been observed in either the bacterial or archaeal viruses
The size of a helical capsid is influenced by both its protomores and the nucleic acids enclosed within the capsid
The icosohedral capsid maximizes efficiency and requires few genes for its coding
An envelope is present in all viruses
Spikes can be used to identify many types of viruses
All virions lack enzymes
Most DNA viruses use dsDNA as their genetic material
Many RNA viruses have segmented genomes with each segment coding for a protein
Viral attachment to the host cell is a random process
Variation in receptors used by a virus for attachment is partly responsible for host specificity
All viruses inject their nucleic acid into the cytoplasm of their host, leaving the capsid outside and attached to the cell wall
Human immunodeficiency virus (HIV) enters the host cell by fusing directly with the host cell plasma membrane
DNA and RNA viruses replicate using the same processes
Bacteriophages are assembled in the host cytoplasm
All animal viruses are assembled in the cytoplasm
Many nonenveloped viruses lyse their host cells at the end of the intracellular phase
When viral cells are released via budding, the host cell may survive and continue releasing virions for some time
Actin filaments in the cytoskeleton can aid in the release of eukaryotic viruses
Temperate phages must release from the host cell via lysis
Temperate phages can integrate their genome with the host genome
Host cells that are infected with a temperate virus cannot be infected by other virions of the same type
temperate phages can alternate between lysogenic and lytic stages
Lysogeny enables survival of host cells in an environment with low multiplicity of infection (MOI)
A chronic infection is a situation in which a virus slowly releases virions without killing the cell
Most human viruses associated with cancer have dsDNA genomes
Some strains of human papillomavirus (HPV) can cause cervical caner
Tumor activator proteins promote formation of tumors in human dsDNA viruses
Viruses are easily cultivate in agars and broths, much like bacteria
Plaque assays determine viral numbers based on infectivity of the virus
The number of plaque-forming units (PFUs) is equal to the number of viruses because all virions are infective
The infectious dose (ID60) of a virus is the dose that, when given to a number of hosts, causes and infection of 50% of the hosts under particular conditions