CHAPTER 6 GUIDE Flashcards
What are the 3 components of animal virus?
1.Capsid 2.Spikes 3.DNA
What are the 8 components of bacterial virus?
1.DNA 2.Head 3.Internal Proteins 4.Neck 5.Tail Sheath 6.Tail Fibers 7.Pins 8.End Plate
What is Lysogenic Cycle?
one of two cycles of viral reproduction, characterized by integration of the bacteriophage nucleic acid into the host’s genome or formations of a circular replicon in the bacterial cytoplasm.
What do you call the part of the process where the genetic material of the bacteriophage merges into/alters the genetic material of the bacteria?
Prophage
Explain how the Prophage functions?
it can be transmitted to daughter cells at each subsequent cell division at later events (such as UV radiation or the presence of certain chemicals) can release it causing proliferation of new phages via the lytic cycle.
What is the net effect of the Lytic cycle to the infected cell?
results in the destruction of the infected cell and its membrane
What is the difference between the lytic and lysogenic phage cycles?
in the lytic phage, the viral DNA exists as a separate molecule within the bacterial cell, and replicates separately from the host bacterial DNA . The location of viral DNA in the lysogenic phage cycle is within the host DNA, therefore in both cases the virus/phage replicates using the host DNA machinery, but in the lytic phage cycle, the phage is a free floating separate molecule to the host DNA.
Where does the lytic cycle occurs?
in Virulent viruses
When do the symptoms of a viral infection occur?
when the virus is in a lytic state
When does the lysogenic cycle occur?
it occurs after the viral infection is over
What is the thing that remains permanent in the cell?
viral DNA or RNA
What happenes if the prophage undergoes any stress or mutation or is exposed to UV radiation?
the viral lysogenic cycle can change into the viral lytic cycle. In which case, there will be symptoms of a new viral infection.
What is the Acellular?
pertains to a tissue that is not made of cells or not divided into cells (such as hyphae of some fungi)
Capsid is made from what?
made of several protein subunits
What are Capsomers?
a subunit of capsid,an outer covering of protein that protects the genetic material of a virus
What did Capsomers do to form the Capsid?
Self-assemble
What is Nucleocapsid?
refers to the association of capsid proteins with nucleic acid in viruses
What are the compositions of the nucleocapsid?
nucleic acid surrounded by a coat of protein
What is an Envelope?
a lipid bilayer that contains viral proteins, usually including the proteins that enable the virus to bind to the host cells
What are Spikes?
protein structures that are studded to the envelope
What is the function of the Spikes?
help the virus to invade host cells
What is the naked virus?
https://www.youtube.com/watch?v=y3NKRbVA4Lka virus without an enclosing envelope, consisting only of a nucleocapsid
What is the Helical Capsid?
usually formed from one protein that interlocks to form a helix-like structure around the viral genome
What is the ICohedral?
consists of identical subunits that make up equilateral triangles that are in turn arranged in a symmetrical fashion
What is the Complex virus?
possess a capsid that is neither purely helical nor purely icosahedral,may possess extra structures such as protein tails or a complex outer wall
What is the bacteriophage?
virus that infects and replicates within bacteria
What is the retrovirus?
a virus that uses RNA as its genetic material; after infecting a cell
What is Reverse Transcriptase?
it is an enzyme to convert its RNA into DNA
What is the hoset range?
refers to the spectrum of cells that a phage can infect and lyse
What is the Lytic Phage?
takes over the machinery of the cells to make phage components
What is the function of the Lytic phage?
it then destroys or lyses the cell, releasing new phage particle
What is the Lysogenic/temperate phage?
incorporate their nucleic acid into the chromosome of the host cell and replicate with it as a unit without destroying the cell; under certain conditions lysogenic phages can be induced to follow a lytic cycle
What is the phage?
virus that infects bacteria
What is the Prophage?
lysogenic DNA that is embedded in the host’s DNA
What is transduction?
the process by which foreign DNA is introduced into a cell by a virus or viral vector
What is Cytophathic effects?
refers to structural changes in host cells that are caused by viral invasion
What is the Latent State?
state in which a pathogenic virus lie dormant within a cell
What is the oncovirus?
a virus that can cause cancer
Can you see a virion with a light microscope?
No.
Explain why is it impossible to see a virion using light microscope?
Virions are too small to see with a light microscope. It can be seen using electron microscopy.
What are the criteria’s to determine if viruses are alive?
living things have cells, viruses do not; living things reproduce, most viruses do not have tools to reproduce; living things use energy, the viruses do not use any energy outside of a host cell; lastly, living things respond to their environment, viruses interact with the cells they infect but most of this is simply based on virus anatomy
Is there any debate whether a virus is alive or not?
Yes
What are the 2 things that make up viruses?
- core of genetic material (either RNA or DNA)
- protective coat called a capsid.
What is the function of Capsomers?
protects the genetic material of a virus
What are the 3 functions of Capsids?
- protect the nucleic acid from digestion by enzymes 2.contains special sites on its surface that allow the virion to attach to a host cell 3.provide proteins that enable virion to penetrate the host cell membrane
What are 3 the functions of Envelopes?
- enables the virus to attach to cells 2.aids in entry into cells and release of the capsid contents into the cells 3.packaging of newly formed viral particles
What is the function of Spikes?
essential for host specificity and viral infectivity, and also for attachment
What kind of nucleic acids do viruses have?Are they single, or double stranded?Can viruses have both?
All viruses contain nucleic acid and can either be double-stranded or single-stranded RNA or DNA, and they cannot have both.
How are viral envelopes formed?
Enveloped viruses are formed by budding through cellular membranes, usually the plasma membrane but sometimes an internal membrane such as the ER, Golgi, or nucleus.
The envelope is composed of what?
Two lipid layers layers interspersed with protein molecules (lipoprotein bilayer) and may contain material from the membrane of a host cell.
Are viral spikes found on naked viruses?
Yes
What are the 3 categories of the viral shapes?
1.helical 2.icosahedral 3.complex
What are the 6 steps of Viral Replication?
1.Attachment 2.Penetration 3.Uncoating 4.Replication 5.Assembly 6.Release
Explain Attachment being one of the steps in Viral Replication.
A virus attaches to a specific receptor site on the host cell membrane through attachment proteins in the capsid or via glycoproteins embedded in the viral envelope. The specificity of this interaction determines the host (and the cells within the host) that can be infected by a particular virus
Explain Penetration being one of the steps in Viral Replication.
The nucleic acid of bacteriophages enters the host cell naked, leaving the capsid outside the cell. Plant and animal viruses can enter through endocytosis, in which the cell membrane surrounds and engulfs the entire virus. Some enveloped viruses enter the cell when the viral envelope fuses directly with the cell membrane
Explain Uncoating being one of the steps in Viral Replication.
Once inside the cell, the viral capsid is degraded and the viral nucleic acid is released, which then becomes available for replication and transcription
Explain Replication being one of the steps in Viral Replication.
The replication mechanism depends on the viral genome. DNA viruses usually use host cell proteins and enzymes to make additional DNA that is transcribed to messenger RNA (mRNA), which is then used to direct protein synthesis. RNA viruses usually use the RNA core as a template for synthesis of viral genomic RNA and mRNA. The viral mRNA directs the host cell to synthesize viral enzymes and capsid proteins, and to assemble new virions. Of course, there are exceptions to this pattern. If a host cell does not provide the enzymes necessary for viral replication, viral genes supply the information to direct synthesis of the missing proteins. Retroviruses, such as HIV, have an RNA genome that must be reverse transcribed into DNA, which then is incorporated into the host cell genome
Explain Assembly being one of the steps in Viral Replication.
newly formed viral nucleic acid and structural proteins are brought together to form the nucleocapsid of the virus
Explain Release being one of the steps in Viral Replication.
new virions are released in the host organism, which are then able to infect adjacent cells and repeat the replication cycle
What is the virus that can cause cancer?
Oncovirus
Explain how viruses can cause cancer?
When viruses cause an infection, they spread their DNA, affecting healthy cells’ genetic makeup and potentially causing them to turn into cancer
What are two viruses that may increase a person’s risk of developing cancer?
human immunodeficiency virus (HIV) and hepatitis C virus (HCV).
Compare the “life cycles” of the lytic and the lysogenic bacteriophages. Can the same phage be both?
The lytic cycle involves the reproduction of viruses using a host cell to manufacture more viruses,the viruses then burst out of the cell, the lysogenic cycle involves the incorporation of the viral genome into the host cell genome, infecting it from within. Only a few virus can be both lytic and lysogenic.
What is Transduction?
it is a process after the virus has multiplied, many copies of the virus erupt from the infected cell
What is the Plaque?
plaque refers to a clear zone produced by a phage which is formed by lysis of bacterial cells in the medium.
Are viruses simpler and smaller than bacteria and fungi?
Yes
Why is the medical treatment of viruses so difficult?
When viruses infect cells, they take over the cell’s “machinery” hence the cell will not be able to carry out its normal processes, the host cell becomes a virus-manufacturing plant which makes viral parts that reassemble into whole viruses and infect other cells.
What is the term “Prions” refers to?
to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins.
What make prions so medically dangerous?
abnormal folding of the prion proteins leads to brain damage and the characteristic signs and symptoms of the disease.
How are viruses and prions different?
Viruses are made up of nucleic acids and proteins while prions lack in genetic code (nucleic acids) viruses cause lots of diseases while prions have been known to cause brain diseases only.
