[魯國共筆目錄](/f422AdmtSGeEnkS-LwYuqA)
# DNA

## DNA replication
|步驟| 原核生物|真核生物|
|---|---|---|
|認出起點<br>(<font color="red">A、T rich</font>)|Dna A|ORC|
|解開雙股|DNA B helicase<br>(binds to Dna A)|<font color="red">MCM complex</font>|
|維持雙股| Single-strand DNA-binding proteins(<font color="red">SSB</font>)<br>(一旦結合上DNA，就會吸引其他SSB<br>(**cooperative binding**))|同右|
|做出primer|primase|<font color="red">DNA polymerase α</font>|
|解開超螺旋|Type I Topoisomerase<br>=>斷**單股**、去除negtive supercoiled<br>Type II Topoisomerase<br>=>斷**雙股**、變成negtive supercoiled<br>(ex: <font color="red">Gyrase</font>)|Eukaryotic topoisomerase II|
|圈住單股DNA| DNA Polymerase III <font color="red">β subunit</font><br>(由**clamp loader**花3ATP接上β clamp)|<font color="red">PCNA</font>|
|複製DNA| <font color="red">DNA polymerase III</font><br>=>**複製引導、落後股**<br><font color="red">DNA polymerase I</font><br>=>**去除RNA引子**(5’ to 3’exonuclease)、<br>=>補起落後股的Gap(polymerase)<br><br><font color="red">**Klenow fragment**</font><br>DNA Polymerase I **去除**5’ to 3’exonuclease<br>(剩==DNA polymerase+3’ to 5’exonuclease==) | DNA polymerase 𝛿<br>=>複製**lagging strain**<br>DNA polymerase ε<br>=>複製**leading strain**<br>DNA polymerase α<br>=>lagging strand引子合成<br>DNA polymerase γ<br>=>複製**粒線體DNA** |
|修復錯誤|DNA polymerase I <br>=><font color="red">3’ to 5’exonuclease</font>|DNA polymerase β|
|連接斷片|Ligase|同右|

## DNA repair
|Repair system|修復傷害|參與酵素|
|---|---|---|
|Direct repair|Thymine dimers|**Photolyase**<br>(需要==光==、僅發生於原核)<br><font color="red">FADH^-^</font>(提供電子)|
|Nucleotide Excision Repair (NER)|Thymine dimers|<font color="red">ABC exinuclease</font><br>>**Uvr**A, **Uvr**B=>辨識<br>>**Uvr**C=>切除|
|Base-Excision Repair<br> (BER)|鹼基出錯<br>(ex: uracil, xanthine)|<font color="red">DNA glycosylases<br>AP endonuclease</font>|
|Mismatch DNA Repair|DNA複製出錯|**Mut**L-**Mut**S=>辨識錯誤序列<br>**Mut**H=>辨識<font color="red">G**A**TC</font><br>(A沒被甲基化表示為舊股)<br>(人類趁複製叉通過後偵測)|
|Recombinational Repair<br>(Homologous recombination)|雙股DNA斷裂<br>有同源染色體|<font color="red">**BRCA1/2**</font><br>MRN complex<br>**Rad51**(細菌為**RecA**)<br> =>協助單股DNA找到互補DNA|
|Recombinational Repair<br>(Nonhomologous end joining)<br> (**NHEJ**)|雙股DNA斷裂|**Ku**70/80(bind斷裂DNA end)<br>**DNA-PK**(移除鹼基直到可配對)<br>**Artemis**<br>(參考V(D)J recombination)|
|*SOS response|原核DNA損傷|RecA與單股DNA結合<br>將<font color="red">LexA</font>(轉錄抑制子)分解<br>啟動SOS反應<br>(UvrA/B/C, **UmuC/D**等)|
|*Alkyltransferase |O^6^-methylguanine|甲基轉移至甲基轉移酶的Cys上|