dna的復(fù)制ppt課件(參考版)
2025-05-04 18:05本頁(yè)面
【正文】 ?RNA1的編碼區(qū)在引物 RNA編碼區(qū)的 5‘末端，轉(zhuǎn)錄方向與引物 RNA相反，因此與引物 RNA的 5’末端互補(bǔ) ?RNA1通過(guò)氫鍵配對(duì)與引物 RNA前體相互作用，阻止了RNase H加工引物前體，使其不能轉(zhuǎn)化為有活性的引物而對(duì)復(fù)制起負(fù)調(diào)控作用。而在基因組其它區(qū)域的 GATC位點(diǎn)，在復(fù)制后 min內(nèi)即被甲基化。子代鏈復(fù)制過(guò)程中，產(chǎn)生半甲基化 DNA。 ? DAM甲基化酶使腺嘌呤上的 N6位點(diǎn)甲基化。端粒酶實(shí)際上是一種逆轉(zhuǎn)錄酶。主要由一串十分簡(jiǎn)單和串聯(lián)重復(fù)的序列組成 如四膜蟲(chóng)： GGGGTT ? 端粒功能：操持染色體的穩(wěn)定性 ? 端粒酶 (Telomerase) ：一種含RNA的蛋白復(fù)合物，能使端粒延伸。H42 四聚體和 H2AH42 四聚體和 H2A→ 339?！?539。 ? 再由特異性限制內(nèi)切酶在連接處交錯(cuò)切割，產(chǎn)生 3’ 凹端 ? 由 DNA多聚酶 Ⅰ 在 3’OH上延伸填滿新的空缺，產(chǎn)生兩條完整的雙鏈。 ? 兩個(gè) 5’端有空缺的分子通過(guò) 3’端凸出的重復(fù)序列互補(bǔ)配對(duì)。 ? 新的 L鏈合成完成，子代雙鏈被釋放。Trich DNA is melted. ② Helicase is bound to the plex and creates the replication fork. ③ The first nucleotides of the new chain are synthesized into the primer ① DnaA protein is the initiation factor : ? The four 9 bp consensus sequences on the right side of oriC provide the initial binding sites for DnaA. It binds cooperatively to form a central core around which oriC DNA is wrapped. ? Then DnaA acts at three ATrich 13 bp tandem repeats located in the left side of oriC. In the presence of ATP, DnaA melts the DNA strands at each of these sites to form an open plex ? HU protein has the capacity to bend DNA, and is involved in building the structure that leads to formation of the open plex. ? Transcriptional activation: RNA polymerase could be required to read into the origin from adjacent transcription units. The act of transcription could be associated with a structural change that assists melting of DNA. Hu ② The replication fork is generated ? 24 monomers of DnaA bind at the origin, and they
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