MICR2420 FULL COURSE NOTES

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9/16/2013 5:50:00 AM
POCHViruses
Baltimore Virus Classification
Group 1 (Double Stranded DNA): Make their own DNA
polymerase or use Hosts. RNA polymerase is that of hosts or
viruses
Group 2 (Single Stranded DNA): Require host DNA Polymerase
to make complimentary strand. The DNA is then transcribed by host
RNA polymerase.
Group 3 (Double stranded RNA): Viruses contain Viral
dependent RNA Polymerase that they have packaged for instant
transcription
Group 4 (+ single stranded): + strand can serve directly as
mRNA however requires synthesis of strand to form double
stranded RNA intermediate
Group 5 (- single stranded): Need Viral RNA dependent RNA
polymerase to transcribe (-) into mRNA (+). Often segmented RNA.
Group 6 (+ single strand): retroviruses that use reverse
transcriptase which transcribes RNA into double stranded DNA
which is then integrated into host genome (HIV)
Group 7(Double stranded DNA): Use reverse transcriptase. First
copy DNA into RNA then reverse transcribe the RNA into progeny
DNA using R. transcriptase found in virion. (Hepatitis B Virus)
Some viruses envelop themselves in host membrane as a form of camo.
Tegument is a package of proteins and enzymes a virus may use for
quicker infection time and less lag
Filamentous Virus (helical capsid)
Genomes are too large and cannot be packed into an icosahedral
Some of the material is packed outside and these viruses are fairly
flexible (such as ebola)
Multiple Helical Packages
Collection of helical genome segments
Constantly transforming and evolving (influenza)
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Complex Viruses
Bacteriophages
Land and eject genetic material into bacteria
Asymmetrical Viruses
Vaccinia poxvirus (chicken pox)
No symmetrical capsid and it stabilized by covalent connection of two
strands (in a circle)
No capsid, DNA is enclosed by a core envelope surrounded by a
membrane that comes from the host
Contain a large number of accessory proteins (enzymes and regulatory
proteins).
Viral Genomes
Efficiently packed into an mRNA like structure
Use different starts to produce different proteins
Long Terminal Repeats (LTR) signatures of viruses that represent
scars on the host genome
Viruses are made of at least a capsid and nucleic acid
HERVs
Human endogenous Retroviruses
Make up 8% of the human genome (Recognized by LTR)
HERVs are the remains of ancient viruses that once infected the
germline and incorporated themselves into our genome
Over the millennia they have become degraded and non-functional
(Or have they?)
Not entirely junk DNA
Recent onset psychosis and multiple sclerosis patience show
evidence of transcription of HERV genes
MS Patients in particular respond well to interferon beta therapy
which suppresses retroviral replication
Viroid
Extremely simple and no protective capsid
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Usually RNA molecules that infect plants
Some have catalytic activity (Cleave very specific RNA sequences to
interfere with transcription and translation; may be useful in
medicine)
Prions
Consist of proteins only
Not Viruses or cells
They contact and force normal proteins to change their confirmation
Bacteria
Prokaryotes
Free living organisms that may live in ecosystems
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