Ntxaiv - nws yog ... hauj lwm, qauv thiab muaj nuj nqi

Ntxaiv division - ib ntus qauv tsim thaum lub sij hawm tus txheej txheem ntawm mitosis thiab meiosis, thiab muab chromosome segregation thiab cell division. Nws bipolar: microtubule system tsim nyob rau hauv qhov chaw ntawm lub tug, qhov zoo ntawm ib tug ntxaiv. Lub centromere cheeb tsam ntawm chromosome kinetochores uas txuas mus rau lub ntxaiv microtubules. Raws li nws cov chromosomes mus lawm tug.

qauv

Ntxaiv muaj peb tej yam ntxwv hais: microtubules, chromosomes thiab division ntawm tug. Ncej faib cov tsiaj yog ib lub koom haum ntawm lub centrosome, uas muaj centrioles. Nyob rau hauv cov ntaub ntawv ntawm qhov chaw tsis muaj centrosomes (nyob rau hauv cov nroj tsuag, thiab nyob rau hauv oocytes ntawm ib co hom) ntxaiv muaj ib tug dav ncej thiab hu ua atsentrosomalnym. Nyob rau hauv lub tsim ntawm lub ntxaiv muab kev koom tes yog lwm cov qauv - lub cev muaj zog proteins. Lawv mus rau lub dynein thiab kinesin.

Ntxaiv division - ib tug bipolar qauv. Ob tug nyob centrosomes - organelles uas yog cov chaw zov me nyuam ntawm microtubule lub koom haum. Tus qauv ntawm lub centrosome paub qhov txawv ob centrioles, uas yog surrounded los ntawm ib tug tibneeg ntau ntau cov sib txawv proteins. Condensed chromosomes muaj rau hauv daim ntawv ntawm ob chromatids nyob ua ke ntawm centromere site, nyob nruab nrab ntawm lub tug. Nyob rau hauv lub centromeres yog kinetochores, uas yuav siv sij hawm muab cov Symptoms ntawm microtubules.

tsim

Txij li thaum division ntxaiv - yog ib tug qauv uas yog lub luag hauj lwm rau cell division, pib nws los ua ke tshwm sim nyob rau hauv prophase. Nyob rau hauv cov nroj tsuag thiab nyob rau hauv oocytes nyob rau hauv lub qhaj ntawv ntawm centrosomes, microtubule organizing chaw ua hauj lwm pab raws li ib tug plhaub ntawm lub nucleus. Microtubules yog nyob ze rau qhov nuclear lub hnab ntawv thiab xaus rau hauv lig prophase lawv orientation, thiab daim ntawv "prophase ntxaiv" - rau yav tom ntej ntxaiv axis.

Vim lub fact tias nyob rau hauv cov tsiaj hlwb yog lub centrosome plays lub luag hauj lwm ntawm lub koom haum ntawm lub chaw, thaum pib ntawm lub tsim ntawm mitotic ntxaiv yog ib tug tsis sib xws ntawm ob centrosomes thaum lub sij hawm prophase. Qhov no yog tau vim tias ib lub cev muaj zog cov nqaijrog dynein lawv txuas mus rau cov txheej nto ntawm cov tub ntxhais thiab sab hauv sab ntawm lub cell daim nyias nyias. dynein pab pawg neeg txuas mus rau cov daim nyias nyias, kev cob cog rua nrog astral microtubules thiab lawv pib tsiv mus nyob rau lub zoo kawg, vim uas muaj dilution ntawm centrosomes ntawm opposite qhov chaw ntawm lub cell daim nyias nyias.

Qhov kawg ntawm lub rooj sib txoos

Qhov kawg tsim ntawm ntxaiv tshwm sim nyob rau prometaphase theem, tom qab lub disappearance ntawm daim nyias nyias nws ua ib tug tag nrho cov tub ntxhais, vim hais tias nws yog ces centrosomes thiab microtubules yuav nce mus lub Cheebtsam ntawm lub ntxaiv.
Txawm li cas los, muaj ib tug kos: lub budding poov mitotic ntxaiv tsim tshwm sim nyob rau hauv lub nucleus.

xov ntxaiv tsim thiab lawv orientation yog tsis yooj yim sua yam uas tsis tau ob tug dab: lub koom haum ntawm microtubules ib ncig ntawm lub chromosomes thiab lawv kev twb kev txuas mus rau txhua lwm yam nyob rau opposite ncej ntawm lub division. Muaj ntau lub ntsiab uas tsim nyog rau zaum kawg tsim ntawm ntxaiv, xws li chromosomes thiab lub cev muaj zog cov nqaijrog nyob hauv lub cell nucleus, thiab microtubules thiab, yog hais tias tus tsiaj cell centrosomes muaj nyob rau hauv lub cytoplasm, i.e., lub Cheebtsam yog cais los ntawm txhua lwm yam. Uas yog vim li cas lub tsim ntawm lub ntxaiv xaus tsuas yog tom qab lub disappearance ntawm lub nuclear lub hnab ntawv.

koom chromosomes

Nyob rau hauv lub tsim ntawm mitotic ntxaiv protein yog muab kev koom tes, raws li zoo raws li ntau lwm yam, thiab tus txheej txheem no tau zoo kawm nyob rau hauv cov tsiaj hlwb. Thaum lub sij hawm prophase, microtubules tsim nyob ib ncig ntawm lub centrosome stellate qauv uas diverges nyob rau hauv radial kev taw qhia. Tom qab lub nuclear membrane so down, dynamic khov ntawm microtubules pib los mus tshawb cov cheeb tsam no thiab kinetochores ntawm chromosomes yuav tsau rau lawv. Ib txhia ib feem ntawm lub chromosome tam sim ntawd puv ntawm opposite tug, thiab tshuav thawj khi rau microtubules ib tug ntawm cov tug, thiab xwb ces pib txav ntawm txoj cai ncej. Thaum cov txheej txheem tiav, cov chromosomes, twb txuam nrog tej ncej pib kinetochores xa mus rau microtubules los ntawm opposite tug, yog li ntawd thaum lub sij hawm metaphase txheej txheem rau kinetochores yog kev cob cog rua ntawm kaum thiab plaub caug hlab. Qhov no tsim yog hu ua tus kinetochore beam. Maj mam txhua chromosome yog txuam nrog rau cov opposite ncej, thiab lawv yog tsim nyob rau hauv lub hauv paus feem ntawm ntxaiv metaphase phaj.

Qhov thib ob xaiv

Yog lwm scenario nyob rau hauv uas lub ntxaiv tej zaum yuav tsim nyob rau division. Nws tseem yog tau rau lub hlwb muaj lub centrosome, thiab rau hlwb nyob rau hauv uas lawv yog tsis tuaj kawm ntawv. Cov txheej txheem yuav lub gamma tubulin nplhaib complex, vim uas muaj ib tug luv luv nucleation ntawm microtubules ib ncig ntawm lub chromosomes. Hlab txuas mus rau lub kinetochore-plus-end, tom qab uas lub polymerization ntawm microtubules pib, uas yog, tswj txoj kev loj hlob. Tsis zoo xaus ntawm lub "Merge" thiab nyob twj ywm nyob rau hauv lub division vim lub cev muaj zog cov nqaijrog tug. Yog hais tias lub tsim ntawm ntxaiv muab kev koom tes ib tug khub ntawm centrosomes, nws tswj kev twb kev txuas ntawm microtubules, tab sis cov txheej txheem yog tau tsis tau lawv.

Attendance

Ib tug meej kev sib cais nruab nrab ntawm ob chromosomes ntawm hlwb generated thaum lub sij hawm fission, tsuas tshwm sim yog hais tias tus khub chromatids lawv kinetochores koom rau ntau tug. Bipolar sib xws chromatids yog hu ua amfitepicheskogo, tab sis muaj lwm yam kev xaiv uas tshwm sim thaum lub sij hawm uas yuav mus rau ob qho tag nrho kev faib ntxaiv. Qhov no monotepicheskoe (ib kinetochores txuas mus rau ib tug ncej) thiab sintepicheskoe (ob kinetochore chromosomes yog kev cob cog rua nrog ib tug ncej). Thaum merotepicheskom ib kinetochore cuab los ntawm ob tug. Yog ruaj khov tsuas pa, bipolar daim ntawv cog lus uas tshwm sim vim qhov nro quab yuam los ntawm cov tug, lwm tsevneeg txoj kev yog tsis ruaj tsis khov thiab reversible, tab sis tej zaum yuav yog vim muaj cov qhov chaw ntawm lub kinetochore.