CSB351Y1 Study Guide - Midterm Guide: Restriction Fragment Length Polymorphism, Ionic Strength, Iodine
CSB351
Lecture 1 – Discovery and Nature of Viruses
• “o hat’s a ius?
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 osideed alie solel due to ailit to tasit geeti ode
• With possibility of mutation
o Regadless…
▪ Duig epodutio, ius isets itself ito host ell’s ahie
• 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
• Hijaks host’s uleus, itohodia, iosoe, 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
• “ae sigal, eept it’s to go to the plasa eae ad 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
piidie to ’ of suga
▪ Phosphates link to sugas at ’ ad ’
• ’ ad ’ eds 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 ’-’ lik, hih is uusual
• Methylated cap marks RNA to be translated
o Cap-binding enzyme finds it and brings it over to ribosome
• Most tRNA hae aps, soe 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 uleotides to ’ ed of a stad 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 Polease lathes oto pie to fid out hee it’s goig
• 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 uleus, 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 iuses hae ethlated ’ 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.