CSB351Y1 Study Guide - Midterm Guide: Restriction Fragment Length Polymorphism, Ionic Strength, Iodine

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CSB351
Lecture 1 Discovery and Nature of Viruses
“o hat’s a ius?
o Lwoff
Strictly intracellular
Potentially pathogenic
Infectious
Only one type of nucleic acid
Multiply only in that one type of nucleic acid
Cannot grow or perform binary fission
No Lipmann system
Cannot produce ATP/ribosomes
No energy, pretty much
o Someone else
Tiny submicroscopic particle
Can multiply in living cells, inducing illness
Can attack everything
o Goodheart
Genetic material in a protective coating
No metabolism, no mobility, no response, no growth
Ca e osideed alie solel due to ailit to tasit geeti ode
With possibility of mutation
o Regadless…
Duig epodutio, ius isets itself ito host ell’s ahie
Genes of virus cause cell to either produce more virus or to adapt to
further serve the virus
When ready, virus leaves either through budding or through splitting
cell open
Viral properties
o Smaller than life
o Simpler than life
Only a few genes worth of nucleic acid plus a shell of protein, in general
o Cannot multiply in vitro
Requires life in order to reproduce
Hijaks host’s uleus, itohodia, iosoe, et.
Life cycle
o Virus enters cell
Receptor recognizes virus and lets it in
Virus attaches to cell membrane and gets involuted
Vesicle opens up, then viral capsid
o Viral replication
Viral nucleic acids converted, somehow, to mRNA
mRNA translated, viral proteins made
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Capsid made after viral nucleic acids, since capsid is marker to stop
replication
o Exit
Lysis
Enough viral nucleic acids packaged into capsids provides signal to get
show on the road
Cell bursts open and new virus particles pop out
Budding
“ae sigal, eept it’s to go to the plasa eae ad ud off
Glycoproteins added as necessary to lipid membrane
New virus particles bud off
Lecture 2 Composition of Viruses
Nucleic acids
o RNA or DNA, but not both
Ribose vs deoxyribose
Phosphate backbone is very charged (negative)
Glycosidic (covalent) bonds between NH group of acid (pos. 9 of purine/1 of
piidie to ’ of suga
Phosphates link to sugas at ’ ad ’
’ ad ’ eds of DNA
o Covered with protein
o Some viruses contain lipids and carbohydrates
Enveloped, for example
o Nucleic acids and proteins are not covalently linked, but rather maintained by non-
covalent interactions
Hydrogen bonds, charge, hydrophobicity, etc.
Allows for easy uncoating
o Modified nucleic acids
Some viruses have modified nucleic acids
m7G
Guanine, but with methylated cap
o ’-’ lik, hih is uusual
Methylated cap marks RNA to be translated
o Cap-binding enzyme finds it and brings it over to ribosome
Most tRNA hae aps, soe do’t
o Poliovirus, for one
Prevents degradation by exonucleases, promotes translation of mRNA
and +ssRNA
o Nucleic acid synthesis
RNA polymerase binds to double stranded DNA
Helicase splits open double strands
RNA polymerase continues along one strand, adding complementary
nucleotides
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o Synthesis enzymes
Polymerases
Add uleotides to ’ ed of a stad of DNA/RNA
Sequence determined by following template strand
o Add complementary to template strand
Some RNA polymerases do not require primer
o Primers are small segments of DNA/RNA that are hybridized to
the template strand
o Polease lathes oto pie to fid out hee it’s goig
DNA polymerases require primers
Most viruses code for their own polymerases
Classes of polymerase
DNA-dependent RNA polymerase (DdRp)
o Take DNA template, write mRNA
Nuclear, mostly
o Only pox viruses and other huge viruses code for this
Most cells use cellular DNA-dependent RNA polymerase
Those go to nucleus
Po does’t eed to go to uleus, it has its own DNA
and its own DdRp
RNA-dependent RNA polymerase (RdRp)
o Take RNA template, make RNA
Cytoplasmic
o Encoded by RNA viruses so they can replicate
+ssRNA make their own in cytoplasm
-ssRNA, dsRNA bring their own in capsid
RNA-dependent DNA polymerase (RdDp/RT)
o Take RNA template, make DNA
o Retroviruses
This is reverse transcriptase
o Modification enzymes
Methylase
Adds methyl groups to bases
Most RNA, a +ssRNA iuses hae ethlated ’ aps
Nuclease
Cleave the individual nucleotides in a stretch of acids
Endonuclease
o From the middle
Exonuclease
o From the end
Ribonuclease
o RNA
Deoxynuclease
o DNA
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Document Summary

Lecture 1 discovery and nature of viruses: o (cid:449)hat"s a (cid:448)i(cid:396)us, lwoff. Lecture 2 composition of viruses: nucleic acids, rna or dna, but not both, ribose vs deoxyribose, phosphate backbone is very charged (negative, glycosidic (covalent) bonds between nh group of acid (pos. Join two stretches of nucleic acids together through covalent bonding: hydrolysis, rna and dna ligases, shapes, helical, rod-shaped capsid with nucleic acid embedded inside wall of rod, hollow. Icosahedral: 20-sided ball of repeated subunits (cid:862) phe(cid:396)i(cid:272)al(cid:863, enveloped. Lipid envelope surrounding viral nucleic acids: bacteriophage, rou(cid:374)d (cid:271)all o(cid:374) top of heli(cid:272)al (cid:396)od, plus (cid:862)legs(cid:863) Lipid bilayer derived from host cell: ha and na synthesized in cell, characterization, split off of virus with glycosidase, glycoproteins tend to stick out of envelopes, electrophorese to get size/charge, mass spectrometry to gt. Larger s = further down: equilibrium/isopycnic, separate based on density, gradient. Infectivity assays: depends on ability of virus to multiply in host.

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