Forensic biology - virus

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  • Created by: aarafa11
  • Created on: 02-06-20 00:49
how are viruses no cells
no nucleus, organelles, cytoplasm, no metabolism; no internal cellular structure; cannot replicate without a living host cell
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basic structure of a virus
Spike/ glycoprotein– attach to receptor site on host cell; Envelope- phospholipid by-layer, not always present; Caspid– protein coat; Nucleic acid– DNA OR RNA
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what is it's nucleic acid
Have DNA or RNA, not both like cells; Contains genetic information to synthesise new viral particles; Can be single (**) or double stranded (ds):
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whats the abbreviation for each strand
Double stranded DNA – dsDNA; Double stranded RNA – dsRNA; Single stranded DNA or RNA – ssDNA, ssRNA
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how does the genetic information look like
linear, circular or segmented in form
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what is a capsid made of
a polymer of Capsomers; May form from a few different proteins or just one; Capsomers spontaneously form the capsid; Arrangement is symmetrical and gives two basic shapes
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what are the 2 structure the capsid can form
helical; icosahedral
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how is capsid very important in protecting virus particle from
Desiccation; Acid conditions of the stomach; Degradative enzymes
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what is the purpose of capsid
protects the virus & attachment of viruses lacking an envelope to the surface of the host cell
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what is the envelope madeof
lipid bilayer
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what is the envelope derived from
the membrane of the host cell; Plasma or organelle membrane can be used; Often formed from plasma membrane of the host cell when they move through it to leave the cell
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what is the purpose of the envelope
Helps virus to evade host immune system; But, it is modified by the products from the viral genome
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What is the term given to a virus without a envelope
naked
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what are the Enveloped viruses are more susceptible to environmental pressure
Freezing-thaw; pH less than 6 or greater than 8; Chemical disinfectants
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what must envelope require to remain viable
body fluids; Transmission is therefore mainly by bodily fluids or respiratory droplets
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how are spikes formed
Projection from the viral envelope that may be present
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what are spikes made of
proteins/ glycoproteins
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what is the importance of spieks
attachment to receptor sites on the surface of host cell; Receptor sites often specific to a cell type and\or species; Thus, virus can be very specific about species and cell type infected; Can also cause Haemagglutination
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how are viruses classified
Based on shape, presence\absence of envelope, size & genetics also used to classify viruses
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how is the the writing of species different to other cells
often not Latinised, but still given in italics
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what is the species name of HIV
Family: Retoriviridae; Genus: Lentivirus; Species: Human immunodeficiency virus
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what are the types viruses that are part of the group 1 classification
dsDNA
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what are the types viruses that are part of the group 2 classification
ssDNA
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what are the types viruses that are part of the group III classification
dsRNA
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what are the types viruses that are part of the group IV classification
ssRNA (+) sense
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what are the types viruses that are part of the group V classification
ssRNA (-) sense
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what are the types viruses that are part of the group VI classification
ssRNA (+) sense with DNA intermediate
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what are the types viruses that are part of the group VII classification
ssRNA (+) sense with RNA intermediate
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theories of where virus come from
Escaped gene theory; Regressive theory; Co-evolution theory
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Escaped gene theory
Originate from normal cellular nucleic acids; DNA viruses could have evolved from plasmids, which can self replicate; RNA viruses may have evolved from mRNA
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Regressive theory
Cells regressed to form simpler virus particles; Some live parasitically in eukaryotic cells; Parasitism frequently associated with simplification; Possible parasitic cell lost all but essential gene (virus that have envelope)
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Co-evolution theory
Viruses evolved with life; i.e. as cells developed through the process of chemical evolution, so did viruses; Viruses took advantage of the opportunity offered by the developing cells
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hwo to synthesis DNA virus
envelope, capsid, DNA enters; uncoats; DNA enters nucleus; replication & transcription of vDNA; translation of viral mRNA; viral proteins enter nucleus; assemble proteins; exit
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where does the synthesis RNA virus occur
outspide nucleus
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what kind of senses will the RNA virus make after the synthesis of RNA
Most RNA viruses will make both (+) sense and (-) sense copies of their genome
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what kind of host cells does (+) senses use
biomolecular machinery to synthesis viral proteins; i.e. RNA (+) acts as mRNA and the host’s ribosomes translate this into proteins
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what is the purpose of (-) sense in RNA synthesis
used to synthesise new (+) sense RNA for genome of new viruses
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why is it a problem that cell don't synthesis RNA
RNA viruses cannot hijack the hosts biochemistry to replicate their RNA; High rate of error during the copying (1 in 104) process; Due to the lack of a proofreading exonuclease activity
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how does RNA Dependant RNA polymerase (RdRp) cause Genetic change also facilitated by template/strand switching
Strand switching by RdRps during replication allows for recombination
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what does RNA Dependant RNA polymerase (RdRp) facilitate
rearrangement of genes or; acquisition of new ones from other viruses or hosts; repair viral genomes (Above + mutation rate - aids virus is evading host immune system)
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what classification of virus does retroviruses copy
dsDNA
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what happens after reverse transcription in RNA virus synthesis
RNA part then degraded to form ssDNA; Single stand of DNA replicated to form dsDNA; Integrase enzyme inserts dsDNA it into the host’s chromosome
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why do virus shred when matured virus pass through the cell membrane
regular release of mature virus particles; either through exocytosis or virus budding through plasma membrane
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what is the problem with shredding of matured virus
This does not kill the cell directly, but may damage or eventually exhaust it
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what class is the flu/influenza virus in
A, B & C
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which class of influenza flu virus is a major cause of human disease
A & B
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what is This does not kill the cell directly, but may damage or eventually exhaust it
Antigens present on the Haemagglutinin (H) and Neuraminidase (N)
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how does influenza affect cells
Epithelium cells lining respiratory tract are ciliated to move mucus out; Cilia become damaged and disappear due to virus infection; Dead cells and accumulated mucus exploited by opportunistic bacteria, leading to infection and death
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how did the Pandemic flu arise
Influenza virus A
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what does the pandemic flu do
build up of pressure in lungs; Result of over reaction by the immune system – Cytokine storm; Uncontrolled cytokines release resulting in hyperinflammation
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how was covid-19 caused
virus Severe acute respiratory syndrome coronavirus 2 - SARS-CoV-2; This is an enveloped RNA(+) virus
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similarities between SARS-CoV & SARS-CoV-2
cellular receptor - the protein angiotensin-converting enzyme 2 (ACE2)
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Other cards in this set

Card 2

Front

basic structure of a virus

Back

Spike/ glycoprotein– attach to receptor site on host cell; Envelope- phospholipid by-layer, not always present; Caspid– protein coat; Nucleic acid– DNA OR RNA

Card 3

Front

what is it's nucleic acid

Back

Preview of the front of card 3

Card 4

Front

whats the abbreviation for each strand

Back

Preview of the front of card 4

Card 5

Front

how does the genetic information look like

Back

Preview of the front of card 5
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