Qhov Tseem Ceeb Qhov txawv - Chromatin vs Nucleosome
DNA nyob hauv lub nucleus ntawm cov kab mob eukaryotic thiab muaj cov ntaub ntawv keeb kwm uas tau dhau mus rau tiam tom ntej. Vim nws qhov tseem ceeb, DNA yog nruj nreem qhwv ib ncig ntawm histone proteins thiab condensed mus rau hauv ib tug ruaj khov qauv nyob rau hauv lub chromosomes ntawm eukaryotic hlwb los tiv thaiv nws los ntawm kev puas tsuaj. Qhov no condensed heev, complex qauv ntawm DNA nrog histone proteins yog hu ua chromatin. Chromatin yog tsim los ntawm cov qauv txheej txheem hu ua nucleosomes. Nucleosome tuaj yeem txhais tau tias yog qhov ntev me me ntawm DNA qhwv ib ncig ntawm yim histone proteins. Qhov sib txawv tseem ceeb ntawm chromatin thiab nucleosome yog tias chromatin yog tag nrho cov qauv ntawm cov DNA complex thiab cov proteins thaum nucleosome yog ib chav tsev ntawm chromatin.
Chromatin yog dab tsi?
DNA hauv lub nucleus tsis muaj nyob hauv daim ntawv dawb linear strand. Nws yog txuam nrog cov proteins hu ua histones thiab condensed rau hauv cov qauv hu ua chromatin. Yog li, chromatin tuaj yeem txhais tau tias yog daim ntawv muaj txiaj ntsig zoo ntawm DNA nrog histone proteins. Nyob rau hauv lub microscope, chromatin zoo nkaus li ib txoj hlua ua los ntawm cov hlaws dai raws li qhia hauv daim duab 01. Ib lub hlaws yog hu ua nucleosome, thiab nws yog cov qauv tsim ntawm chromatin. Chromatin tsim cov chromosomes ntawm eukaryotic kab mob thiab tau ntim rau hauv lub nucleus. Cov qauv ntawm chromatin tsuas yog pom thaum lub sijhawm sib faib ntawm tes nyob rau hauv lub microscope.
Muaj ob hom chromatin uas yog euchromatin thiab heterochromatin. Euchromatin yog daim ntawv tsawg dua ntawm chromatin uas tuaj yeem hloov mus rau RNA thaum qhia. Heterochromatin yog daim ntawv condensed heev ntawm chromatin uas tsis nquag hloov mus rau RNA. Highly condensed supercoiled DNA nyob rau hauv daim ntawv ntawm chromatin yog qhov zoo tshaj plaws haum rau ntim rau hauv lub nucleus uas muaj ib tug me me ntim.
Lub luag haujlwm tseem ceeb ntawm chromatin yog txhawm rau ntim DNA zoo hauv lub nucleus uas muaj qhov ntim me me. Chromatins kuj tseem ua haujlwm ntxiv xws li tiv thaiv DNA qauv thiab ntu, tso cai rau mitosis thiab meiosis, tiv thaiv chromosomal breakages, tswj cov noob qhia, thiab DNA replication.
Daim duab 01: Chromatin
Nucleosome yog dab tsi?
Nucleosome yog ib feem me me ntawm chromatin uas yog qhwv ib ncig ntawm cov tub ntxhais histone protein. Nws zoo li cov hlaws dai hauv ib txoj hlua. Core histone protein yog octamer uas muaj yim histone proteins. Ob daim ntawv luam ntawm txhua histone protein nyob rau hauv lub octamer core. Lub histone protein muaj pes tsawg leeg hauv cov tub ntxhais octamer yog H2A, H2B, H3 thiab H4. Core DNA nruj nreem qhwv ib ncig ntawm lub globular core histone octamer thiab ua rau ib tug nucleosome. Nucleosomes tau muab tso rau hauv cov saw zoo li cov qauv thiab qhwv ib ncig ntawm cov proteins histone ntxiv kom nruj kom cov chromatin hauv chromosomes.
Qhov ntev ntawm cov tub ntxhais DNA strand uas qhwv ib ncig ntawm histone octamer hauv nucleosome yog kwv yees li 146 lub hauv paus khub. Qhov kwv yees txoj kab uas hla ntawm nucleosome yog 11 nm, thiab cov kauv ntawm nucleosomes hauv chromatin (solenoid) muaj txoj kab uas hla ntawm 30 nm. Nucleosomes tau txais kev txhawb nqa los ntawm cov proteins histone ntxiv kom ntim rau hauv cov qauv nruj nruj hauv cov nucleolus.
Daim duab 02: A Nucleosome
Qhov txawv ntawm Chromatin thiab Nucleosome yog dab tsi?
Chromatin vs Nucleosome |
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| Chromatin yog daim ntawv muaj txiaj ntsig zoo ntawm DNA nrog histone proteins. | Nucleosome yog ib chav tsev tseem ceeb ntawm chromatin hauv nucleous. |
| Chromatin yog tsim los ntawm DNA thiab histone proteins. | Nucleosome yog tsim los ntawm 147 lub hauv paus khub ntev DNA thiab yim histone proteins. |
| Chromatin zoo li cov qauv fiber ntau supercoiled. | Nucleosome zoo li cov hlaws hauv txoj hlua |
Summary – Chromatin vs Nucleosome
Chromatin yog ib qho nyuaj ntawm DNA thiab histone proteins. Nws muaj xws li ib tug saw ntawm nucleosomes qhwv nrog histone proteins. Nucleosome yog lub hauv paus ntawm chromatin uas yog tsim los ntawm 147 lub hauv paus khub ntev DNA thiab yim histone proteins. Cov saw hlau ntawm nucleosomes qhwv nrog cov proteins histone thiab condenses rau hauv cov qauv chromatin uas yog daim ntawv ruaj khov tshaj plaws ntawm DNA kom ntim rau hauv lub nucleus. Qhov no yog qhov txawv ntawm chromatin thiab nucleosome.
