Viruses Flashcards
What is the purpose of the envelope?
The envelope is a structure found In many viruses which surrounds the capsid it is made up of a lipid bilayer and often times helps the virus bond to a cell
What is a capsid and what is it’s function?
The capsid is a protective protein shell which houses the viruses genetic material. The main functions of the capsid are to protect the viral genetic material from cellular digestion, it has proteins on its surface that allow bonding to host cells. The capsid also contains proteins to allow the virus to break through the host cell membrane
What does nucleic acid do?
Nucleic acid functions basically the same way in viruses as it does in multi-celled organisms. But the molecules housing genetic material can range from DNA to RNA with many different stranding patterns
What is a tegument?
Also known as the viral matrix the tegument lines the space between the viral envelope and capsid generally teguments are responsible for housing proteins helping viruses evade the immune response as helping with viral cell invasion
What are prions
Prions are mis folded proteins which misfold more proteins and degrade cells brain matter etc.
Explain the difference between sense and anti sense DNA
The sense strand acts as a coding strand which actually codes for genetic material antisense strand is non coding and acts as a strand running anti to the sense strand
Baltimore classification 1
This viral group is comprised of viruses with double stranded DNA and simply hijacks host cells for replication purposes
how are viruses important in the evolution of cellular genomes?
viruses are important in the evolution of cellular genomes because when viruses integrate their DNA into a host cell many times the viral DNA gets passed on in humans viral DNA accounts for 1/10 of the genome.
why are we unable to develop as many antivirals as we are antibiotics?
since viruses use the host cell for growth and replication it is hard to create drugs which target a virus but not the host cell.
what are cloning vectors?
cloning vectors refers to when a virus has its genetic material removed and artificial genes are inserted so when the virus infects a cell the cell starts producing the product of the new gene
what are bacteriophages?
viruses that infect bacteria
what is host range?
host range refers to the groups of species that can be infected by one strain of virus
what are plaques and how are they important in counting viral cells in a culture?
plaques are clear spots in a lawn of cells where the presence of a virus has caused the lysing of the nearby cells
what are reading frames
the reading frame refers to what portion of genetic materials read and translated into subsequent proteins because viruses have very small genomes multiple reading frames are used on a very small amount of DNA making up a genome of less than ten genes
are large viral genomes possible?
large viral genomes are possible and usually can code for a couple of hundred genes
what are viroids?
viroids are like viruses in that they contain small amounts of genetic material which infects and replicates in plants but they lack things like a capsid and other protective layers seen in viruses
what are ribozymes?
ribozymes are pieces of RNA that are capable of catalyzing reactions. in medicine they may be useful because they can cleave specific RNA sequences involved in cancer
virus capids take two main shapes what are they
icosahedral or filamentous
what does an icosahedral capsid look like
an icosahedral capsid has 20 sides and has twenty identical triangular faces with three unique types of axis a five fold a three fold and a two fold
how can we observe viruses?
viral particles can be observed by transmission electron microscopy but to see the capsid you need to use digital reconstruction via cryo-em
what are spike protiens
spike proteins are proteins which attach the envelope to the capsid.
we have the ability to culture bacteriophages why dont we use them as a class of antibiotic especially against antibiotic resistant bacteria
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what is the basic structure of a filamentous virus?
a filamentous virus is composed of capsid monomers which are stacked in a coiled cylinder, a short tail of proteins extend from one side of the capsid which aid in attachment to host cells
many bacteriophages are actually very complex true or false?
true: many bacteriophages used the same basic packaging as other viruses but have excess structures that allow them to more easily attach and infect bacterial cells.
viruses are not classified by genetic relation due to the high amount of mutation they experience and the fact that many viruses may have arisen from different sources instead we classify them by…
genome composition- which refers to how genetic information is packaged capsid symmetry envelope- presence or absence size of virus particle host range
Baltimore group 2
this class is composed of viruses with a single strand of coding DNA which must first transcribe a complimentary strand using host DNA polymerase the virus can then replicate
Baltimore group 3
this group is composed of double stranded RNA viruses these viruses require an RNA dependent RNA polymerase which is a viral protein which allows for the generation of RNA by transcribing from RNA
Baltimore group 4
this group consists of sense strand RNA which can code directly for all of the protiens needed for the virus to replicate but must first synthesis an anti-sense strand of RNA in order to replicate
Baltimore group 5
this group is composed of viruses which contain anti-sense RNA. these viruses must carry with them transcription factors to help synthesis a sense strand of RNA and then the proteins contained in the virus
Baltimore group 6
group 6 is composed of retroviruses these viruses use a protein called reverse transcriptase to turn their RNA genome into DNA which is then integrated into a host’s genome
Baltimore group 7
pararetroviruses these viruses start out with a DNA genome which is then transcribed into RNA then reverse transcribed (using either a packaged or host cell reverse transcriptase) back into DNA which is integrated into the host genome.
how are viruses compared via genetic analysis?
viruses are compared at orthologs or orthologous genes which are genes of common ancestry within two different genomes
what is proteomics
proteomics is the comparison of viruses using their proteins rather than their DNA
there are four major steps in all viral life cycles what are they?
host recognition- the connection of viruses to an appropriate host cell
genome entry- virus must enter the cell and gain access to host cell genome
assembly of virons- viral components are expresses and assembled
exit and transmission- new viruses must exit the cell and infect new hosts
how do viruses recognize their host cells?
viruses recognize their host cells by surface receptors that are already in place on host cells, usually these receptors are actually proteins with important functions that are used as recognized binding sites
ebola
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parvovirus
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influenza
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adenovirus
most commonly used gene therapy virus
what is the lytic cycle?
the lytic cycle is when the virus immediately produces as many virus particles as possible and causes cell lysis
what is the lysogeny cycle
lysogeny is when the virus integrates into a hosts genome and then replicates along with the cells generally stress on the host cells can cause the virus to enter the lytic cycle
what is transduction?
transduction is when a virus as it is leaving a cell grabs little pieces of host genomes and ends up transferring those genes to the next host it comes into contact with
how does transduction affect host genomes?
transduction is responsible for a large part of host genome evolution this is one way many different animals incorporate and pass on new genes
what is the slow release cycle
the slow release cycle is different from both the lytic and lysogony cycle in this cycle viruses are incorporated into the host genome then viruses are slowly released from the cell and the genetic material is maintained and replicated during cellular division
do bacteria have an adaptive defense mechanism?
yes bacteria have developed an adaptive defense mechanism where upon destruction a small piece of viral genetic material found in all viruses called a CRISPR is incorporated into RNA Cas proteins which allow bacterial cells to remember the particular virus
what is a major difference between DNA and RNA viruses and how they replicate
RNA viruses can replicate in the cytoplasm without ever interacting with DNA, versus DNA viruses must enter the nucleus of the host cell fro replication to occur
how does replication occur for RNA viruses with a sense strand of RNA
viruses with a sense strand of RNA first use a ribosome to translate RNA dependent RNA polymerase which then copies the RNA genome then capsid protiens are translated using host ribosomes and finally virons are assembled in the cytoplasm
what are the tree ways plant viruses can infect plants
transmission of viruses through damaged tissues
transmission of viruses through animal hosts
transmission of viruses though prodgeny
once inside a plant how do viruses infect new cells
in order for viral particles to move between cells in a plant they must use the plasmodesmata
