Qhov Tseem Ceeb Qhov Sib Txawv - Kev Tsim Nyog vs Facultative Heterochromatin
Chromosomes yog cov qauv condensed tsim los ntawm Deoxyribose nucleic acids (DNA). Nws yog cov qauv tsim tau zoo, thiab lub hauv paus ntawm DNA ntim yog cov nucleosome. Kev ntim khoom ntawm DNA rau hauv chromosome muaj ntau kauj ruam. Thaum cov chromosomes tau pom nyob rau hauv lub tshuab tsom iav tom qab staining, cov cheeb tsam sib txawv tuaj yeem pom xws li cov cheeb tsam tsaus nti thiab cov cheeb tsam me me. Cov cheeb tsam tsaus nti yog hu ua Heterochromatin, thiab lawv yog thaj chaw uas muaj cov DNA ntim ntom ntom. Cov cheeb tsam me me yog hu ua Euchromatin, thiab lawv yog thaj chaw uas tau ntim cov DNA xoob xoob. Heterochromatin tuaj yeem raug cais ntxiv raws li Kev Tsim Kho Heterochromatin thiab facultative heterochromatin. Constitutive heterochromatin hais txog thaj tsam ntawm DNA hauv chromosome pom thoob plaws hauv lub voj voog ntawm tes. Lawv feem ntau pom nyob ze ntawm thaj chaw peri-centromeric thiab thaj chaw telomeric ntawm chromosome. Facultative heterochromatin yog thaj tsam ntawm DNA nyob rau hauv uas cov noob yog silenced los ntawm kev hloov kho. Yog li ntawd, lawv tsuas yog qhib rau hauv qee yam mob thiab tsis pom thoob plaws hauv lub cell. Qhov sib txawv tseem ceeb ntawm kev tsim thiab facultative heterochromatin yog kev ua haujlwm ntawm ob hom. Constitutive heterochromatin muaj nyob rau hauv lub voj voog ntawm tes thiab tsis code rau cov proteins, whereas facultative heterochromatin yog hais txog qhov ntsiag to DNA thaj tsam ntawm chromosome uas tau qhib rau hauv cov xwm txheej tshwj xeeb.
Kev Sib Raug Zoo Heterochromatin yog dab tsi?
Constitutive heterochromatin yog hais txog qhov tsaus ntuj stained condensed cheeb tsam ntawm DNA uas pom thoob plaws hauv chromosome ntawm eukaryotes. Lawv pom nyob rau hauv peri-centromeric thiab telomeric cheeb tsam ntawm chromosome. Cov cheeb tsam heterochromatin yog pom tau siv cov txheej txheem C banding. Nyob rau hauv lub microscope, lub constitutive heterochromatin zoo nkaus li muaj xim tsaus nti.
Cov kev sib xyaw ntawm cov tshuaj heterochromatin feem ntau yog raws li cov ntawv luam siab ntawm cov tandem rov ua dua. Cov tandem rov tuaj yeem yog satellite DNA, minisatellite DNA lossis microsatellite DNA. Cov cheeb tsam no yog qhov rov ua dua thiab polymorphic. Yog li ntawd, tam sim no, lawv tau siv los ua cov cim hauv DNA ntiv tes thiab kuaj tus txiv.
Lub luag haujlwm tseem ceeb ntawm kev sib koom ua ke heterochromatin tau pom thaum lub sijhawm sib faib ntawm tes, qhov uas nws tau kwv yees tias yuav tsum muaj heterochromatin rau kev sib cais ntawm tus muam chromatids. Nws kuj tseem siv tau rau kev ua haujlwm kom zoo thiab tsim cov centromere.
Txawm hais tias ob qho tib si centromeric thiab telomeric DNA yog tsim los ntawm heterochromatin, ob qho tib si centromeric thiab telomeric DNA tsis tau khaws cia thoob plaws hauv genome. Centromeric sequences tsis tau khaws cia nyob rau hauv ntau hom, tab sis telomeric sequences tau xav tias yuav tsum tau khaws cia ntau dua nyob rau hauv ntau hom. Ob thaj chaw tsis muaj cov noob tab sis tseem ceeb vim lawv ua lub luag haujlwm tseem ceeb.
Daim duab 01: Kev Tsim Kho Heterochromatin - C banding
Kev rov ua dua ntawm cov heterochromatin tshwm sim thaum lub sijhawm S lig. Kev hloov kho histone tau ua tiav los tsim cov heterochromatin, qhov kev hloov kho feem ntau suav nrog - histone hypoacetylation, histone H3-Lys9 methylation (H3K9), thiab cytosine methylation. Cov kev hloov kho no yog cov cuab yeej cuab tam yog li ntawd, poob rau hauv cov ncauj lus dav dav ntawm epigenetics. Kev hloov caj ces yuav ua rau muaj qhov tsis xws luag hauv thaj chaw heterochromatin uas ua rau muaj kev sib txawv ntawm caj ces (Robert's Syndrome)
Facultative Heterochromatin yog dab tsi?
Facultative heterochromatin cheeb tsam yog thaj tsam DNA uas tsis pom thoob plaws hauv chromosome, thiab yog li, lawv tsis sib xws ntawm ntau hom. Qhov no DNA code rau cov noob uas qhia tsis zoo.
Cov facultative heterochromatins yog silenced genes uas tau qhia nyob rau hauv tej yam kev mob. Cov xwm txheej no suav nrog;
- Temporal (piv txwv li, kev loj hlob hauv xeev lossis theem ntawm lub voj voog tshwj xeeb)
- Spatial (piv txwv li, nuclear localization hloov pauv los ntawm qhov chaw mus rau qhov chaw ib puag ncig lossis rov ua dua vim yog cov xwm txheej exogenous / teeb liab)
- Parental/heritable (xws li, monoallelic gene expression)
Cov noob yog ntsiag to los ntawm cov txheej txheem chromatin. Cov piv txwv classic ntawm facultative heterochromatin hloov kho yog X chromosome inactivation nyob rau hauv cov poj niam, qhov twg ib txheej ntawm X chromosome yog inactivated thiaj li hais tias cov caj ces muaj pes tsawg leeg ntawm X chromosome nyob rau hauv cov txiv neej thiab poj niam yog sib npaug.
Daim duab 02: Heterochromatin
Facultative heterochromatin muaj peev xwm hloov mus rau hauv thaj tsam euchromatin; Yog li, thaum lub sij hawm C banding staining txheej txheem, facultative heterochromatin tsis stained tsaus nyob rau hauv kev sib piv rau constitutive heterochromatin.
Dab tsi yog qhov zoo sib xws ntawm Kev Tsim Kho thiab Kev Tshawb Fawb Heterochromatin?
- Ob qho tib si Constitutive thiab Facultative Heterochromatin hom yog tsim los ntawm DNA cheeb tsam.
- Ob qho tib si Constitutive thiab Facultative Heterochromatin hom yog cov condensed cheeb tsam ntawm DNA.
- Ob qho tib si Kev Tsim Nyog thiab Facultative Heterochromatin hom tuaj yeem paub qhov txawv ntawm C banding staining.
- Ob qho tib si Kev Tsim Nyog thiab Facultative Heterochromatin hom yog tswj hwm los ntawm cov yam ntxwv ntawm epigenetic.
Qhov txawv ntawm Kev Tsim Kho thiab Kev Tshawb Fawb Heterochromatin yog dab tsi?
Constitutive vs Facultative Heterochromatin |
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| Constitutive heterochromatin hais txog thaj tsam ntawm DNA hauv chromosome pom thoob plaws hauv lub voj voog ntawm tes. | Facultative heterochromatin yog thaj tsam ntawm DNA uas cov noob tau nyob ntsiag to los ntawm kev hloov kho. Yog li ntawd, lawv tsuas yog qhib rau hauv qee yam mob thiab tsis pom thoob plaws hauv lub cell. |
| hom Sequence | |
| Satellite, minisatellite thiab microsatellite sequences yog hom kev tsim heterochromatin. | Ntev interspersed nuclear ntsiab yog ib hom facultative heterochromatin. |
| Muaj peev xwm nthuav tawm | |
| Cov tshuaj heterochromatin tsis tuaj yeem qhia cov noob. | Facultative heterochromatin tuaj yeem hais tau. |
| C Banding Staining | |
| Kev sib xyaw heterochromatin bands stain hauv cov xim tsaus. | Facultative heterochromatin bands tsis stain / stain nrog lub teeb xim. |
| polymorphisms | |
| Tam sim no ntawm cov khoom siv heterochromatin. | Tsis muaj nyob hauv facultative heterochromatin. |
Summary – Constitutive vs Facultative Heterochromatin
Heterochromatin thiab Euchromatin yog ob lub ntsiab banding qauv pom nyob rau hauv C band staining. Heterochromatin zoo li tsaus nti vim lawv muaj condensed heev. Constitutive thiab Facultative heterochromatin cheeb tsam yog cov kev faib loj ntawm heterochromatin. Cov cheeb tsam zoo sib xws uas pom thoob plaws hauv lub voj voog ntawm tes, uas yog qhov tseem ceeb, raug xa mus rau raws li kev tsim heterochromatin. Cov cheeb tsam DNA uas ntsiag to uas thaum kawg tau hloov mus rau thaj tsam euchromatin raug xa mus rau facultative heterochromatin. Lawv raug qhia tsuas yog nyob rau hauv tej yam kev mob. Qhov no yog qhov sib txawv ntawm kev tsim kho thiab kev paub txog heterochromatin.
