Qhov sib txawv tseem ceeb ntawm qhov zoo thiab qhov tsis zoo ntawm DNA supercoiling yog tias thaum lub sij hawm zoo supercoiling ntawm DNA, DNA strand yog overwound piv rau lub xeev so, thaum lub sij hawm tsis zoo supercoiling ntawm DNA, DNA strand yog nyob rau hauv qhov txhab piv rau lub lub xeev so.
DNA supercoiling yog qhov sib tw ntawm DNA strand (dhau-winding lossis nyob rau hauv winding), thiab nws txiav txim siab npaum li cas ntawm cov strand. Topoisomerases yog cov enzymes uas pab txhawb thiab tswj DNA supercoiling los txhim kho DNA replication thiab transcription. Lawv muaj nyob rau hauv tag nrho cov hlwb, nrog rau cov kab mob thiab tib neeg. DNA supercoiling yog ib qho tseem ceeb rau ntau cov txheej txheem ntawm tes xws li DNA compacting thiab gene qhia, los ntawm kev tswj kev nkag mus rau cov noob caj noob ces. Muaj ob hom DNA supercoiling ua zoo supercoiling thiab tsis zoo supercoiling.
Dab tsi yog qhov zoo ntawm supercoiling ntawm DNA?
Zoo supercoiling ntawm DNA yog txheej txheem uas DNA strand yog overwound piv rau lub xeev so. Qhov no tshwm sim thaum ob-helical conformation ntawm DNA (sab tes xis) yog twisted tighter (tshaj qhov txhab nyob rau hauv txoj cai-tes) kom txog rau thaum lub helical qauv yuav distorted thiab loj hlob mus rau ib theem ntawm 'knot.'
Daim duab 01: Supercoiling ntawm DNA
lej equations elaborate ntawm qhov zoo supercoiling ntawm DNA. DNA tsis zoo supercoiled thaum lub sij hawm ib txwm muaj tab sis tshwm sim tsuas yog thaum lub sij hawm cellular txheej txheem, piv txwv li, los pab mitosis qhov twg duplicated viv ncaus DNAs raug cais mus rau hauv cov ntxhais hlwb thaum lub sij hawm interphase nyob rau hauv kev loj hlob thiab tu ntawm topologically associating domains. Cov chaw no yog TADs. Ntxiv mus, thaum lub sij hawm mitotic chromosome los ua ke, nws tau pom tias condensin induces zoo supercoiling ntawm DNA. Condensing yog ib qho loj protein complex uas ua lub luag haujlwm tseem ceeb hauv mitotic chromosome los ua ke thiab ua rau cov supercoiling zoo nyob rau hauv ATP hydrolysis-dependent yam.
Dab tsi yog qhov tsis zoo supercoiling ntawm DNA?
Negative supercoiling ntawm DNA yog txheej txheem uas DNA strand nyob rau hauv qhov txhab piv rau lub xeev so. Qhov no tshwm sim thaum ob chav helical conformation ntawm DNA (sab laug-tes) yog twisted sib dua (nyob rau hauv lub qhov txhab nyob rau hauv ib tug sab laug hom) kom txog rau thaum lub helical qauv yuav so ntau tshaj li ib txwm so B daim ntawv ntawm DNA. Nws pab txhawb DNA replication thiab transcription los ntawm topoisomerase enzymes.
Daim duab 02: Tsis zoo Supercoiling ntawm DNA
Supercoiling ntawm DNA tsim ob hom qauv hu ua plectoneme lossis toroid. Qee zaum, nws tuaj yeem yog qhov sib xyaw ntawm ob qho tib si. Thaum lub sij hawm tsis zoo supercoiling ntawm DNA, lub DNA molecule yuav tsim ib tug ob-pib txoj cai-tes helix nrog davhlau ya nyob twg loops (plectoneme) los yog ib tug pib sab laug-tes helix (lub toroid). Plectonemes muaj ntau dua nyob rau hauv qhov, tshwj xeeb tshaj yog nyob rau hauv cov kab mob.
Dab tsi yog qhov zoo sib xws ntawm qhov zoo thiab qhov tsis zoo ntawm DNA supercoiling?
- zoo thiab tsis zoo supercoiling ntawm DNA muaj nyob rau hauv tag nrho cov kab mob (los ntawm cov kab mob mus txog rau tib neeg)
- Ob txheej txheem hloov pauv cov duab ntawm DNA strand.
- Lawv cuam tshuam rau cov qauv ob-helical ntawm DNA.
- Ntxiv mus, ob lub tswv yim tseem ceeb rau kev yooj yim ntawm ntau lub xov tooj ntawm tes.
- Enzymes tswj qhov zoo thiab tsis zoo supercoiling ntawm DNA.
Dab tsi yog qhov txawv ntawm qhov zoo thiab qhov tsis zoo ntawm DNA supercoiling?
Qhov sib txawv tseem ceeb ntawm qhov zoo thiab qhov tsis zoo supercoiling ntawm DNA yog tias, thaum lub sij hawm zoo supercoiling ntawm DNA, DNA strand yog overwound piv rau lub xeev so thaum lub sij hawm tsis zoo supercoiling ntawm DNA, DNA strand yog nyob rau hauv qhov txhab piv rau lub lub xeev so. Feem ntau cov kab mob DNA yog qhov tsis zoo supercoiled nyob rau hauv ib txwm muaj. Zoo supercoiling tsuas yog tshwm sim thaum lub sijhawm ua haujlwm ntawm tes. Ntxiv mus, qhov zoo supercoiling ntawm DNA tshwm sim ntawm sab xis sab xis, thaum tsis zoo supercoiling ntawm DNA tshwm sim ntawm sab laug-tes.
Cov hauv qab no infographic nthuav tawm qhov sib txawv ntawm qhov zoo thiab qhov tsis zoo supercoiling ntawm DNA hauv daim ntawv tabular rau ib sab ntawm kev sib piv.
Summary – Positive vs Negative Supercoiling of DNA
DNA supercoiling yog ib qho tseem ceeb hauv ntau cov txheej txheem ntawm tes, xws li DNA compacting thiab gene qhia, los ntawm kev tswj kev nkag mus rau cov caj ces. Nws kuj pab txhawb thiab tswj DNA supercoiling los txhim kho DNA replication thiab transcription. Qhov sib txawv tseem ceeb ntawm qhov zoo thiab tsis zoo supercoiling ntawm DNA yog tias thaum lub sij hawm zoo supercoiling ntawm DNA, DNA strand yog overwound piv rau lub xeev so, thaum lub sij hawm tsis zoo supercoiling ntawm DNA, DNA strand yog nyob rau hauv qhov txhab piv rau lub xeev so. Ob qhov txheej txheem supercoiling ntawm ib txoj hlua muab tau piav qhia los ntawm tus lej lej. Cov txheej txheem ob yog muab piv rau lub xeev siv hu ua lub xeev so ntawm DNA lossis so B daim ntawv ntawm DNA.
