6dsDNAantiparallel5’3’3’5’dsDNA is always antiparallel
7Two ssDNA molecules joined by standard base-pairing rules complementary5’-GGATGCGT-3’3’-CCTACGCA-5’Two ssDNA molecules joined bystandard base-pairing rulesIn dsDNA, the strands are alwayscomplementary.TB
8Bacterial DNA replication DNA synthesis using a DNA templateComplementary base pairing(A=T, GC) determines the sequenceof the newly synthesized strand.DNA replication always proceeds from5’ to 3’ end.
39Prokaryotic vs. Eukaryotic Bacterial cells have one giant looped chromosomeReplication can occur in one or two directionsOne origin of replicationIn Eukaryotes many origins of replication existThese form replication bubblesEventually bubbles meet and replication is doneReplication forks - where DNA is opened up
43Replication of the ends of linear DNA Since all known DNA polymerasesneed a primer, how are the ends oflinear DNA replicated in eukaryotes?5'3'RNA primertemplatenewly synthesized DNA
44repetitive DNA at the end of linear eukaryotic chromosomes Telomeresrepetitive DNA at the end of lineareukaryotic chromosomes(GGGGTT)nExamplen =GGGGTTGGGGTTGGGGTT5'
45Telomerases 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.AACCCCAACtelomerase
46Human telomerase Telomerase = ribonucleoprotein complex Ribo = ribosomal/RNA associationNucleo = nuclear localizationProtein = contains a proteinResponsible for maintaining telomere length in eukaryotic chromosomesMain components:Telomerase reverse transcriptaseHuman telomerase RNA (hTR)
47Human telomerase (2) Reverse transcriptase Transcribes RNA to DNA (rather than the usual DNA to RNA)Telomeres – repeated regions at the end of eukaryotic chromosomeshTR is the template for the repeated region
48Human telomerase (3) hTR 11-nt templating region consists of: Repeat template: CUAACCCAlignment domain: UAACPositions telomerase on the DNA strandProvides template for repeat region
52For most cells, telomeres are added during development 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.
53INHIBITOR TOPOISOMERASE ANTIBIOTIK QUINOLON : MENGHAMBATTOPOISOMERASE BAKTERI GRAM NEGATIF,MODIFIKASI BAKTERI GRAM POSITIFDAN AEROBIKCamptothecin : INHIBITOR TOPOISOMERASE I SEBAGAI ANTI KANKER DENGAN MENSTABILKAN BENTUK ENZIM TERIKAT PADA DNA SECARA KOVALEN
54TOPOISOMERASE SBG TARGET Novobiocin – subunit ATPase GyrBAsam naladiksat – Gyr ACiprofloxacin (oral) – stop replikasiMENGGANGU PROSES PEMOTONGAN DAN PENYAMBUNGANUNTAI DNA