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Genetic element that can multiply only in a living house
Latin word for poison
Virus
What is the most abundant biological entity on earth?
Virus
What does a virus need for energy, metabolic, intermediates, and protein synthesis
Host cell
Viruses have their own ____ genome
Nucleic acid
A genetic element that contains either RNA or DNA surrounded by a protein capsid in that replicate only Inside host cells
Virus
The viral genome, surrounded by a protein coat, and sometimes other layers, which is the infectious virus particle
Virion
When was the first vaccine for rabies developed?
Late 1800s
What did Louis Pasteur hypothesize was the cause of rabies
A living thing, smaller than bacteria
What do people show that a disease tobacco was caused by a virus?
Dimitri ivanovski and martinus beijerinck
Who discovered an animal virus that causes foot and mouth disease in cattle
Loeffler and frosch
What did the early researchers find out about viruses through filtration?
When an infected liquid was filtered, it was still contaminated, which meant that it was contaminated with something smaller than bacteria
What is the first classical scenario of the origin of viruses?
Progressive hypothesis, a.k.a. escaped genes
What did the progressive hypothesis scenario predict?
Genetic fragments escaped from cells, and then entered into another cell to reproduce
What is the second scenario of the origin of viruses?
Regressive hypothesis
What does the regressive hypothesis predict?
Viruses evolved from complex organisms that lost genetic information over time in adopted a parasitic approach to replication
What is the third classical scenario of the origin of viruses?
Virus first
What does the virus first origin of viruses predict
Viruses existed before other organisms
What is the strong and weak evidence of the virus first hypothesis
Strong - The first replicating molecules consisted of RNA
Weak - The nucleus is a result of an Endo symbiotic like event of an envelope DNA virus
What is one of the main reasons viruses are not considered living
They are not cellular
When do viruses show traits of life, such as hereditary, development, and evolution
After they have attached to a living host
What do cells do to the genetic make up of the infected host cell?
Influence it
True or false, viruses have shaped away cells, tissues, bacteria, plants, and animals have evolved
True
What percentage of the human genome consist of sequences that come from viruses?
8%
What percentage of bacterial DNA contains viral sequences
10 to 20%
These parasites cannot multiply, unless they invade a specific wholesale, and instruct its genetic and metabolic machinery to make and release new viruses
Obligate, intracellular, parasites
How did the old system Classify animal, viruses
Based on their hosts and the diseases they caused
How does the new system classify animal viruses?
Based on the host and the disease they cause, structure, chemical composition, and similarities in genetic make up
How many families are not yet assigned to an order?
84
How much more viruses are there than bacteria and archaea combined?
10x
Viruses are ultra microscopic in size which ranges fromā¦
20nm up to 1,000 nm in diameter
What is the basic structure of a virus?
A protein shell (Capsid) Which surrounds nucleic acid core
What two things can Nucleic acid be but not both
DNA or RNA
What on the viruses surface gives them high specificity for attachment to host cells
Molecules a.k.a. spikes
What do things does a virus lack?
Enzymes for metabolism and machinery for synthesizing proteins
How are viruses best observed
With special stains and electron Microscopy
What do viruses bear no resemblance to and lack any of the protein synthesizing machinery found in them
Cells
What are the three parts to the structure of a virus?
External Coating, Core containing nucleic acids, Matrix proteins and enzymes (Sometimes)
This is the protein shell that surrounds the genome of a virus
Capsid
This type of virus has no other layers
Naked virus
This virus has an outer layer consisting of a phospholipid bilayer and viral proteins
Enveloped virus
This is the nucleic acid and protein in envelope viruses
Nucleocapsid
Spikes can be found on what two types of viruses
Naked or envelope
What do spikes allow viruses to do?
Dock onto a host cell
This is the most prominent feature of a viral capsid, which Can be expressed as two primary types _____ And _____
Capsid
Helical
Icosahedral
What is a viral capsid made from
Capsomeres which spontaneously self assemble
This type of structure can only be found in the viruses that infect bacteria, and they are never envelope
Complex capsid structure
These types of Viruses take a bit of the cell membrane when they are released from a host cell
Enveloped viruses
What three locations can an envelope virus bud from?
Cell membrane, nuclear envelope, endoplasmic reticulum
An envelope virus is more flexible than the capsid, which means they areā¦
Pleomorphic
The sum total of the genetic information carried by an organism
Genome
In comparison to a cell, Viral genes are quite _____
Small
Why do cells have a larger genome than viruses?
It allows them to carry Out complex metabolic activity thatās necessary for independent life
What type of genes do viruses typically possess?
The ones needed to invade host cells
This type of virus is single-stranded or double stranded, which makes it linear or circular
DNA virus
This virus can be double stranded, but more often times it single stranded
RNA virus
Name the four types of RNA viruses based on the descriptions below
Ready for immediate translation
Must be converted before translation
Individual genes exist on separate pieces of RNA
Carry their own enzymes to convert RNA to DNA
positive sense RNA
Negative sense, RNA
Segmented
Retrovirus
What are the phases of the animal viral replication cycle?
Adsorption
Penetration
Uncoating
Synthesis
Assembly
Release
How long is the replication cycle?
Varies from 8 hours to 36 hours
What is the only way of virus can invade a host cell?
By making an exact fit with a specific host molecule
The limited range of cells that a virus can infect
Host range
What type of viruses affect the below systems?
Liver cells of human
Intestinal and nerve cells of primates
Various cells of all mammals
hepatitis B
Poliovirus
Rabies
What occurs during penetration and uncoating on the viral envelope with the host cell membrane?
Direct fusion - Envelope merges directly with the cell membrane
This process is when an entire virus is engulfed by the cell and enclosed in a vacuole or vesicle
Endocytosis
During the synthesis phase what type of Virus enters the host cells nucleus and is replicated and assembled there
DNA virus
During the synthesis phase what type of Virus is replicated and assembled in the cytoplasm
RNA virus
This phase is when the virus has put together using parts manufactured during the synthesis process
Assembly
this phase is the number of viruses released by infected cells, is viable controlled by the size of the virus and the health of the host cell
Release
what allows viruses to be shed gradually without the sudden destruction of the cell
Budding
This is when the cell harbors the virus, and is not immediately lysed and can last for a few weeks to the remainder of the hostels life
Carrier relationship
Viral DNA incorporated into the DNA of the host
Provirus
Periodically becomes activated under the influence of various stimuli like herpes
Chronic latent state
Because animal viruses can permanently alter genetic material what can it cause
Cancer
What is the name for cancer causing viruses
Oncogenic
What percentage of cancers are caused by viruses?
13%
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