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Midterm

BIOC 4403 Study Guide - Midterm Guide: Polyadenylation, Glaucophyte, Prokaryote


Department
Biochem & Molecular Biology
Course Code
BIOC 4403
Professor
Archibald John
Study Guide
Midterm

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Plastids Origin endosymbiosis membranes Evolution
Primary Directlyfrom
cyanobacteria
Prokaryote‐>
eukaryote two
Result:redalgae,greenalgae(inc.plants),
glaucophyte.
Exception:dinoflagellate,minicircles,0.4‐10kbpin
size;0‐5genes/circle.
Secondary Primaryplastid‐
bearingalgae
Eukaryote‐>
eukaryote
Threeor
four
Atleast3times,bothredandgreenalgaeinvolved.
Someofthemostabundantphotosyntheticmicrobes
acquiredplastidsinthismanners.
‐ultrastructure,proteinimport;
‐bipartiteN‐terminalleadersequences(SPs&TPs)
Hypothesisexplainingtheretentionoforganellargenomes
Hypothesis Explanation Success Failure
Hydrophobicity Proteinsencodedinorganellar
genomesareextremely
hydrophobic,difficult/impossible
toimportacrossthemembranes
oftheorganelle
holds(moreorless)for
mitochondria
Plastidsimportnumerous
nucleus‐encodedproteinsthat
are‘veryhydrophobic’,and
organelle‐encodedproteinsare
oftenhydrophilic.
Redox
regulation
keyproteinsencodedinorganellar
genomesmustbequicklyand
directlyregulatedbytheredox
stateofthemitochondrion
wherethe
mitochondrialgenome
hasdisappeared,an
electrontransport
chainisnolongerused
ThegenecontentofmtDNAs
neverthelessvariesgreatlyacross
eukaryoticdiversity
Geneticcode
disparity
Organellargeneticcodesdiffer
slightlyfromtheeukaryotic
nuclearcode,somegenesmay
losefunctionwhentheyare
transferred.
Allanimalsandmost
fungihaveatleastone
geneticcodedisparity
betweentheirnuclear
andmitochondrial
genomes.
Astandardgeneticcodeisused
inthemitochondriaofmany
othereukaryoticlineages.Nota
problemforchloroplastsatall.
Exonrecognitionby
splicingmachinery Splicesites Splicingcodes Exonexpression
StrongExon high Good,strong5’SS
andstrong3’SS
Highconc.ofsplicing
enhancers(+) Constitutiveexons
Intermediateexon Intermediate Exonscanbeincludedorskipped
WeakExon Low/poor Poor,weak5’SS
andweak3’SS
Highconc.ofsplicing
silencers(‐)
Exonspredominantly
skipped

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