dna的復制ppt課件(編輯修改稿)
2025-05-28 18:05 本頁面
【文章內容簡介】 th 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 recruit 2 prepriming plexes of DnaBDnaC to bind, so that there is one for each of the two (bidirectional) replication forks. ? DnaB protein is delivered to oriC by DnaC protein in the form of a hexameric (DnaB:DnaC)6 plex, but DnaC protein does not enter the protein assemblage at oriC . ? DnaB protein has helicase activity and it further unwinds the DNA in the prepriming plex in both directions, assisted by DNA gyrase. SSB tetramers coat singlestranded regions as they arise . ③ Primer synthesis: each DnaB activates a DnaG primase, in one case to initiate the leading strand, and in the other to initiate the first Okazaki fragment of the lagging strand. （二）復制的延伸： 1. 復制體：酶和相關蛋白在復制叉形成的超分子復合物 2. 先導鏈和后隨鏈的同時復制 ? Lagging template strand通過復制體形成一個環(huán)狀結構， primase已經合成一條引物＃ 2 ? 隨著岡崎片段的合成，環(huán)逐漸變大，直到＃ 2片段末端接近前一岡崎片段的引物 ? 復制體釋放環(huán)， primase合成一個新的引物 3. 環(huán)型 DNA的復制類型： ① θ型（ ） : an origin creates two replication forks that move in opposite directions ② Dloop (mammalian mitochondrial DNA)： ? mtDNA的復制在 H鏈的復制起點 OH開始合成 。 ? 當置換鏈通過 L鏈的復制起點 OL時，開始合成新的 H鏈 。 ? 新的 L鏈合成完成，子代雙鏈被釋放。 Key concepts: Mitochondria use different origin sequences ③ Rolling circles（ φX174 phage ） ? A protein nicks the origin and binds to 5’ end. ? Using the rolling circle, the 3 –OH end of the nick is extended into a new chain. ? The positive strand has grown to double length and repl
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