Qhov sib txawv tseem ceeb ntawm kev lag luam thiab kev ua lag luam yog qhov kev sib txuas ntawm lagging strand tsis txuas ntxiv thiab nws tshwm sim nyob rau hauv kev coj rov qab mus rau kev loj hlob replication diav rawg thaum lub synthesis ntawm coj strand yog tas mus li thiab nws tshwm sim nyob rau hauv tib txoj kev raws li kev loj hlob replication fork.
DNA replication yog ib qho tseem ceeb ntawm cov txheej txheem lom neeg uas tshwm sim hauv txhua yam kab mob. Thaum pib ntawm cov txheej txheem replication, ob lub strands ntawm ob lub helix unwind ntawm ib leeg thiab qhib rau cov txheej txheem. Ces txhua strand ua ib tug qauv rau tus ntxhais strand. DNA replication tshwm sim ntawm "replication diav rawg" tsim los ntawm helicase enzyme, uas yog lub luag hauj lwm rau kev tawg ntawm hydrogen bonds, txuas ob DNA strands ua ke. Qhov tshwm sim ib leeg DNA strands ua cov qauv rau cov khoom tsim tshiab DNA strands hu ua "lagging thiab ua cov strands". Lagging strand synthesis yog tsis tu ncua thaum coj strand synthesis yog tas mus li. Ntxiv mus, muaj ob peb lwm qhov sib txawv ntawm kev lag luam thiab cov thawj coj raws li tau tham hauv kab lus no.
Laging Strand yog dab tsi?
Lagging strand yog ib qho ntawm ob qhov kev sib txuas tshiab DNA hauv DNA rov ua dua tshiab. Nws tshwm sim nyob rau hauv 3'-5' kev taw qhia, uas yog cov kev taw qhia rov qab mus rau loj hlob replication diav rawg. Lub synthesis ntawm ib tug tshiab strand ntawm replication DNA nyob rau hauv lagging strand yog los ntawm cov creation "Okazaki fragments", uas yog luv luv ntu ntawm ntau yam ntev.
Daim duab 01: Lagging Strand thiab Leading Strand hauv DNA Replication
Ntxiv mus, ib qho enzyme hu ua DNA-ligase yog lub luag haujlwm rau kev koom nrog cov fragments no ua ke. Yog li, kev ua haujlwm ntawm DNA-ligase enzyme yog qhov tseem ceeb rau kev sib txuas ntawm cov hlua khi.
Dab tsi yog Leading Strand?
Txoj hlua yog lwm qhov tsim tshiab DNA strand uas tau rov ua dua tsis tu ncua, tsis zoo li cov hlua khi. Yog li ntawd, cov synthesis ntawm no coj strand tsis xav tau DNA-ligase kev ua ub no. Tsis tas li ntawd, txoj hlua khi yog nyob rau hauv 5 'mus rau 3' kev taw qhia. Nws yog qhov kev taw qhia no uas qhov kev hloov pauv hloov pauv.
Dab tsi yog qhov zoo sib xws ntawm Kev Lag Luam thiab Kev Ua Lag Luam?
- Lagging thiab ua strand yog ob txoj hlua uas tshwm sim los ntawm DNA replication txheej txheem.
- Nyob rau ib leeg.
- Txawm li cas los xij, lub tsev thaiv ntawm txhua txoj hlua yog deoxyribonucleotides.
- Tsis tas li, DNA polymerase enzyme catalyzes cov synthesis ntawm ob leeg.
- Ntxiv mus, kev sib txuas ntawm ob txoj hlua tshwm sim tib lub sijhawm.
Dab tsi yog qhov txawv ntawm Kev Lag Luam thiab Kev Ua Lag Luam?
Lagging thiab ua strands yog ob txoj hlua uas tshwm sim los ntawm DNA replication txheej txheem. Hauv kev txhais, lagging strand yog ib qho ntawm ob txoj hlua uas tsim los ntawm cov khoom tawg thaum lub sij hawm DNA replication. Nyob rau hauv sib piv, coj strand yog cov strand tsim tsis tu ncua thaum lub sij hawm DNA replication. Yog li, qhov no yog qhov sib txawv tseem ceeb ntawm kev lag luam thiab kev ua lag luam. Tsis tas li ntawd, lagging strand template yog tig mus rau 3 'mus rau 5' kev taw qhia thaum coj strand template yog tig mus rau 5' mus rau 3' kev taw qhia. Yog li, qhov no yog qhov sib txawv tseem ceeb ntawm kev lag luam thiab kev ua lag luam. Ntxiv mus, qhov sib txawv ntxiv ntawm kev lag luam thiab kev ua lag luam yog cov txheej txheem synthesis. Lub synthesis ntawm lagging strand tshwm sim tsis tu ncua nyob rau hauv fragments thaum lub synthesis ntawm coj strand tshwm sim tsis tu ncua thaum lub sij hawm replication txheej txheem.
Ntxiv mus, qhov lagging strand synthesis tshwm sim nyob rau hauv fragments hu ua Okazaki fragments, tab sis tsis yog thawj strand synthesis. Tsis tas li ntawd, ib qho kev sib txawv ntawm kev lag luam thiab kev coj strand yog cov kev taw qhia ntawm synthesis. Cov kev taw qhia ntawm synthesis ntawm lagging strand yog 3'→ 5'. Txawm li cas los xij, cov kev taw qhia ntawm kev sib txuas ntawm txoj hlua khi yog 5'→ 3'. Tsis tas li ntawd, lagging strand synthesis xav tau cov primers tshiab, feem ntau kom haum rau cov xwm txheej rov ua dua. Txawm li cas los xij, DNA rov ua dua ntawm txoj kab ua ntej yuav tsum tau ua thawj zaug xwb.
Hauv qab infographic qhia txog qhov sib txawv ntawm kev lag luam thiab kev ua lag luam hauv daim ntawv tabular.
Summary – Lagging vs Leading Strand
DNA replication yog ib qho txheej txheem tseem ceeb tshwm sim hauv cov kab mob nyob. Nws duplicates DNA molecules. Ob txoj hlua tshiab uas tsim tawm thaum lub sij hawm DNA replication yog lagging strand thiab ua strand. Hauv kev hais txog qhov sib txawv ntawm kev lag luam thiab kev ua lag luam, lub lag luam strand yog cov strand uas tsim tawm tsis tu ncua hauv Okazaki fragments nyob rau hauv 3' - 5' kev taw qhia thaum coj strand yog cov strand tsim tsis tu ncua nyob rau hauv 5'- 3' kev taw qhia. Dhau li ntawd, lagging strand synthesis yuav tsum tau primase, DNA ligase uas tsis yog DNA polymerase thaum ua strand synthesis xwb yuav tsum tau DNA polymerase.
