Cell division

Lub division tsis yog tsuas yog ib tug tseem ceeb mus rau restore lub sam xeeb ntawm ntaub so ntswg, tab sis lub tu tub tu kiv ntawm cov kab mob no. Nyob rau hauv nws tus kheej, cell division yuav tsim ntawm ob los yog ntau tshaj tus ntxhais lub hlwb los ntawm ib tug niam txiv. Chromosomes nyob ib qho tseem ceeb heev qhov chaw nyob rau hauv tus txheej txheem ntawm cell division. Nws yog lawv uas yog lub luag hauj lwm rau cov kis ntawm cov ntaub ntawv ntawm lub tiam.

Cell division. Mitosis thiab meiosis

Muaj ob lub ntsiab ntawm ntau yam division - mitosis thiab meiosis. Tus thawj yuav tsim ntawm ib tug tib niam txiv cell ob tus me nyuam. Cov nab npawb ntawm cov chromosomes nyob rau hauv lub hlwb ntawm ob tshua tib yam li nyob rau hauv lub niam txiv ntawm tes, xws li hlwb yog cov tib. Ua lub xov tooj ntawm chromosomes tshwm sim ua ntej division. Yog li, lub cell yog hloov los ntawm diploid rau tetraploid. Qhov kawg ntawm ob diploid hlwb yog tsim.

Meiosis yog hu ua tus tsim ntawm lub plaub hlwb. Nyob rau hauv cov ntaub ntawv no, txhua tus ntawm cov chromosomes nyob rau hauv ib nrab tsawg tshaj li hais tias ntawm lub niam txiv. Meiosis feem ntau tshwm sim sai li sai tau tom qab thawj zaug faib. Raws li ib tug tshwm sim ntawm ib tug tib diploid tau plaub haploid.

Ntawm cell division yuav tsum loj hlob thiab kev loj hlob, kev npaj rau lub tshiab division. Thaum lub sij hawm lub sij hawm no, nws accumulates ib tug ntau ntawm cov nqaijrog thiab kuj ob npaug qhov tseem ceeb organelles, thiab nrog lawv, thiab chromosomes.

Yuav kom paub qhov txawv cov plaub theem ntawm mitosis, uas ua raws li txhua lwm yam thiab ntev li ob teev. Mitotic cell division yuav cov nram qab no cov kauj ruam.

Nyob rau hauv thawj theem mus cuag centrioles ncej ntawm lub cell. Tom qab ntawd, ntxaiv tsim. Chromosomes ua ntau pom. Nyob rau tib lub sij hawm yaj lub nuclear membrane, lub nucleolus thiab ces disappears.

Qhov thib ob theem ntawm kev faib yog hais tias lub chromosomes muaj nyob nrog qhov ncaj ntawm lub cell thiab xa mus rau lub ntxaiv division.

Nyob rau hauv lub thib peb kauj ruam ntxhais chromosomes los yog chromatids pib cov txheej txheem ntawm divergence vim lub ncej ntawm lub hlwb koob.

Nyob rau hauv lub kauj ruam tom ntej ploj ntxaiv, nyob ib ncig ntawm lub twb dispersed chromosomes pib tsim lub nuclear lub hnab ntawv. Tom qab uas faib lub cytoplasm thiab tus ntxhais lub hlwb yog tsim. Txij li thaum cell division tshwm sim.

meiosis

Meiosis yog feem ntau txuam nrog kev sib deev tu tub tu kiv ntawm hlwb thiab lub tsim ntawm txiv neej pw hlwb nyob rau hauv fungi, cov nroj tsuag thiab cov tsiaj. Cell division yog muaj li ntawm ob successive kev ntawm division, txawm li cas los chromosome doubling tshwm sim ua ntej lub thawj faib. Uas yog vim li cas lub resulting hlwb muaj ib nrab ntawm cov xov tooj ntawm chromosomes. Tus txheej txheem ntawm meiosis muaj ob lub ntsiab theem - ua ntej faib thiab faib mus, txhua tus uas yog muab faib mus rau hauv nyias muaj nyias ib theem.

Nyob rau hauv thawj kauj ruam ua ntej faib chromosomes yog haum zoo pom. Yog li homologous chromosome khub pib tsim, nruj nreem adhering rau txhua lwm yam, thiab ces sib ntswg raws nws tag nrho ntev. Tom qab ntawd, homologous cov cheeb tsam ntawm lub chromosomes pauv feem ntawm txhua tus lwm yam thiab yog sib cais. Ntxiv homologous chromosomes yuav tsum kab raws qhov ncaj. Thaum lub theem tom ntej lub chromosomes, uas muaj xws li ob chromatids pib diverge ntawm tug. Lub sib xws ntawm txhua khub yog ywj siab ntawm lwm officers ntawm chromosomes divergence. Yog li tsim tus ntxhais lub hlwb nrog ib nrab ntawm cov xov tooj ntawm chromosomes.

Qhov thib ob cell division. Thawj kauj ruam yuav kev puas tsuaj ntawm cov nuclear lub hnab ntawv thiab lub disappearance ntawm nucleoli. Tom qab ntawd tshwm sim ntxaiv. Tom qab ntawd, cov chromosomes yuav tsum kab nyob rau ntawm qhov ncaj los ntawm attaching lub ntxaiv. Nyob rau hauv lub thib peb theem ob chromatids ntxhais hlwb maj diverge rau tug. Tom qab hais tias muaj hlwb nrog ib tug hluas txheej chromosomes. Ntxiv kab hlwb yog tsim. lub xov tooj ntawm chromosomes nyob rau hauv lub tshiab cell yog rov qab los tom qab lub merger ntawm gametes.