SINTESIS DNA
description
Transcript of SINTESIS DNA
SINTESIS DNASINTESIS DNA
ALUR INFORMASI GENETIK
Flow of information replication DNA DNAtranscription RNAtranslation protein
dsDNA
5’5’3’3’
antiparallel
dsDNA is always antiparallel
complementary
GGATGCGT
3’-CCTACGCA-5’
Two ssDNA molecules joined bystandard base-pairing rulesIn dsDNA, the strands are alwayscomplementary.
TB
5’- -3’
Bacterial DNA replicationDNA synthesis using a DNA template
Complementary base pairing (A=T, GC) determines the sequence of the newly synthesized strand.
DNA replication always proceeds from 5’ to 3’ end.
REAKSI PERPANJANGAN
Overview of bacterial DNA replication
single origin (in bacteria)bidirectionaltheta structuresreplication forksemi-conservative
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bacterial DNA replication
bacterialchromosome
origin (start point) bidirectional
two replication forks
thetastructure
semi-conservative
+
**
*
*
Enzim yang terlibat dalam Replikasi
SSB (ssDNA binding protein) Binds to and stabilizes ssDNA
helicaseUnwinds duplex DNA
ssDNA binding protein
binds to and stabilizes ssDNA
prevents base pairing
ssDNA binding protein
All DNA polymerases require a primer
DNA is synthesized 5' to 3'
Important facts
TB
TemplateTemplate
• A sequence of DNA or RNA that directs A sequence of DNA or RNA that directs the synthesis of a complementary the synthesis of a complementary sequencesequence
• The initial segment of a polymer that is to be The initial segment of a polymer that is to be extended on which elongation dependsextended on which elongation depends
PrimerPrimer
primasesynthesizes a short RNA primerusing a DNA template
RNA primer(a short starting sequence made of RNA)
primase
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PolimerasePolimerase
• Memerlukan primer dan cetakan DNAMemerlukan primer dan cetakan DNA• Polimerisasi diperpanjang pada 3’Polimerisasi diperpanjang pada 3’• Aktivitas eksonuklease Aktivitas eksonuklease 3’-5’3’-5’, berfungsi , berfungsi
sebagai proofreadingsebagai proofreading• Aktivitas eksonuklease Aktivitas eksonuklease 5’-35’-3’ untuk ’ untuk
menghilangkan primermenghilangkan primer
DNA polymerase III
Synthesizes DNA from a DNAtemplate and proofreads
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DNA polymerase I
Synthesizes DNA from a DNAtemplate and removes RNA primers.
DNA ligaseJoins DNA strands together by forming phosphodiester bonds
DNA ligase
replication fork
5'
5'
3'
3'
template strands
lagging strand
leading strand
helicasessDNA binding proteins
RNA primer
3'
5'Leading strand synthesis
helicase
ssDNA binding proteins
DNA polymerase
3'
5'
helicase
ssDNA binding proteins
DNA pol III
3'
5'Leading strand synthesis
DNA
helicasessDNA binding proteins
(primase)pol III
3'
Lagging strand synthesis (discontinuous) Okazaki
fragment(~1000 bases)3'
5'
Primer removalpol III
pol I
pol I
3'
5'
5’ to 3’exonucleaseactivity
Proofreading
Pol III removes misincorporated basesusing 3' to 5' exonuclease activity
This decreases the error rate to about10-10 per base pair inserted
Ligase DNALigase DNA
• Menyambung dua fragmen Okasaki Menyambung dua fragmen Okasaki dengan membentuk ikatan fosfodiester dengan membentuk ikatan fosfodiester antara 3’-OH fragmen 1 dengan 5’-P antara 3’-OH fragmen 1 dengan 5’-P fragmen 2fragmen 2
DNA ligase
Ligation
KEPERLUAN REPLIKASI DNAKEPERLUAN REPLIKASI DNA
• TEMPLATE (CETAKAN)TEMPLATE (CETAKAN)• PRIMER : 3’-OH - PERPANJANGANPRIMER : 3’-OH - PERPANJANGAN• PREKURSOR : dNTPPREKURSOR : dNTP• Enzim : polimerase DNA, helikase, Enzim : polimerase DNA, helikase,
primase, SSBP, ligaseprimase, SSBP, ligase
5
3
5
Lokus awal replikasi (Ori)Lokus awal replikasi (Ori)
INISIASI
Prokaryotic vs. EukaryoticProkaryotic vs. Eukaryotic
• Bacterial cells have one giant looped Bacterial cells have one giant looped chromosomechromosome
• Replication can occur in one or two directionsReplication can occur in one or two directions– OneOne origin of replicationorigin of replication
• In Eukaryotes In Eukaryotes manymany origins of replicationorigins of replication exist exist– These form replication bubblesThese form replication bubbles– Eventually bubbles meet and replication is Eventually bubbles meet and replication is
donedone– Replication forks - where DNA is opened upReplication forks - where DNA is opened up
REPLIKON E.coliREPLIKON E.coli
REPLIKON MAMALIAREPLIKON MAMALIA
Since all known DNA polymerasesneed a primer, how are the ends oflinear DNA replicated in eukaryotes?
5' 3'
RNA primer
template
newly synthesized DNA
Replication of the ends of linear DNA
repetitive DNA at the end of lineareukaryotic chromosomes
Telomeres
(GGGGTT)n
Example
n = 20 - 200
GGGGTT GGGGTT GGGGTT
5'
Telomerases are enzymes that add DNA repeats to the 3' end of DNA.
Telomerases are composed of protein and an RNA molecule that functions as the template for telomere synthesis.
AACCCCAAC
telomerase
Human telomeraseHuman telomerase
• Telomerase = ribonucleoprotein complexTelomerase = ribonucleoprotein complex– Ribo = ribosomal/RNA associationRibo = ribosomal/RNA association– Nucleo = nuclear localizationNucleo = nuclear localization– Protein = contains a proteinProtein = contains a protein
• Responsible for maintaining telomere Responsible for maintaining telomere length in eukaryotic chromosomeslength in eukaryotic chromosomes
• Main components:Main components:– Telomerase reverse transcriptaseTelomerase reverse transcriptase– Human telomerase RNA (hTR)Human telomerase RNA (hTR)
Human telomerase (2)Human telomerase (2)
• Reverse transcriptaseReverse transcriptase– Transcribes RNA to DNA (rather than the Transcribes RNA to DNA (rather than the
usual DNA to RNA)usual DNA to RNA)• Telomeres – repeated regions at the end Telomeres – repeated regions at the end
of eukaryotic chromosomesof eukaryotic chromosomes• hTR is the template for the repeated hTR is the template for the repeated
regionregion
Human telomerase (3)Human telomerase (3)
• hTR 11-nt templating region consists of:hTR 11-nt templating region consists of:– Repeat template: CUAACCCRepeat template: CUAACCC– Alignment domain: UAACAlignment domain: UAAC
• Positions telomerase on the DNA strandPositions telomerase on the DNA strand• Provides template for repeat regionProvides template for repeat region
AACCCCAAC
5'GGGGTTGGGGTT
5'
telomerase
AACCCCAAC
5'
5'GGGGTTGGGGTT GGGGTT
primase
GGGGTT GGGGTT GGGGTT
pol III
pol I5'
ligase
telomeric repeats
For most cells, telomeres are added during development. Later telomerase becomes inactive.
Hence, as cells divide the DNA becomes shorter.
Note that telomerase is reactivated in many types of cancer cells.
INHIBITOR TOPOISOMERASE
ANTIBIOTIK QUINOLON : MENGHAMBAT TOPOISOMERASE BAKTERI GRAM NEGATIF,MODIFIKASI BAKTERI GRAM POSITIF DAN AEROBIK
Camptothecin : INHIBITOR TOPOISOMERASE I SEBAGAI ANTI KANKER DENGAN MENSTABILKAN BENTUK ENZIM TERIKAT PADA DNA SECARA KOVALEN
TOPOISOMERASE SBG TARGETTOPOISOMERASE SBG TARGET
• Novobiocin – subunit ATPase GyrBNovobiocin – subunit ATPase GyrB• Asam naladiksat – Gyr AAsam naladiksat – Gyr A• Ciprofloxacin (oral) – stop replikasiCiprofloxacin (oral) – stop replikasi
MENGGANGU PROSES PEMOTONGAN DAN PENYAMBUNGAN UNTAI DNA