MICR 2420 Study Guide - Meiosis, Penicillin, Acidophile

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9/16/2013 6:50:00 AM
Viruses
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)
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
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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
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
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Bacteria
Prokaryotes
Free living organisms that may live in ecosystems
Stressful environments that includes predation, osmotic stress
(membranes), nutrient limitation, temperature/pH fluctuations
Prokaryotes (Including bacteria and archaea) share traits such as a thick,
complex outer envelope; a compact genome; and tightly coordinated cell
functions
Mollicutes
Contain DNA, Ribosomes, Cytoplasm and Plasma membrane and
are the most basic of all bacteria
Don‟t require lots of energy to survive and are very small and
compact and can fit through small spaces
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