Txhua lub xov tooj pib nws lub neej thaum nws sib cais los ntawm niam lub cell, thiab xaus nws lub neej, tso cai rau nws cov ntxhais cell tshwm sim. Xwm muab ntau tshaj ib txoj hauv kev los faib lawv cov nucleus, nyob ntawm lawv cov qauv.
Txoj kev faib cell
Nuclear faib nyob ntawm hom cell:
- Binary fission (pom hauv prokaryotes).
- Amitosis (kev faib ncaj qha).
- Mitosis (pom hauv eukaryotes).
- Meiosis (tsim rau kev faib cov kab mob).
Hom kev faib hluav taws xob yog txiav txim siab los ntawm qhov xwm txheej thiab sib haum rau cov qauv ntawm lub xov tooj ntawm tes thiab kev ua haujlwm nws ua haujlwm hauv macroorganism lossis los ntawm nws tus kheej.
Binary fission
Hom no feem ntau tshwm sim hauv cov hlwb prokaryotic. Nws muaj nyob rau hauv ob npaug rau lub voj DNA molecule. Binary fission ntawm lub nucleus yog hu ua li ntawd vim hais tias ob tug zoo tib yam-loj ntxhais cell tshwm sim los ntawm leej niam cell.
Tom qab cov khoom siv caj ces (DNA lossis RNA molecule) tau npaj rau hauv txoj kev tsim nyog, uas yog, ob npaug, los ntawm phab ntsa ntawm tes pibib qho transverse septum yog tsim, uas maj mam nqaim thiab faib cov cytoplasm ntawm lub xov tooj ntawm tes rau hauv ob qho tib si kwv yees li.
Cov txheej txheem fission thib ob yog hu ua budding, lossis tsis sib xws binary fission. Nyob rau hauv cov ntaub ntawv no, ib tug protrusion tshwm nyob rau ntawm qhov chaw ntawm lub cell phab ntsa, uas maj mam loj hlob. Tom qab qhov loj ntawm "lub raum" thiab niam cell sib npaug, lawv yuav sib cais. Thiab ib ntu ntawm phab ntsa ntawm tes tau rov ua dua.
Amitosis
Qhov kev faib hluav taws xob no zoo ib yam li cov lus piav qhia saum toj no, nrog qhov sib txawv uas tsis muaj qhov sib npaug ntawm cov khoom siv caj ces. Txoj kev no tau piav qhia thawj zaug los ntawm biologist Remak. Qhov tshwm sim no tshwm sim hauv cov kab mob pathologically hloov pauv (cov qog degeneration), thiab tseem yog ib qho kev cai ntawm lub cev rau daim siab, pob txha mos thiab pob txha.
Cov txheej txheem ntawm kev faib tawm nuclear hu ua amitosis, vim hais tias lub xovtooj ntawm tes tuav nws txoj haujlwm, thiab tsis poob lawv, zoo li thaum lub sijhawm mitosis. Qhov no piav qhia txog cov yam ntxwv ntawm pathological muaj nyob hauv cov hlwb nrog txoj kev faib tawm no. Tsis tas li ntawd, kev faib hluav taws xob ncaj qha yuav tshwm sim yam tsis muaj fission spindle, yog li cov chromatin nyob rau hauv cov ntxhais cell yog unevenly faib. Tom qab ntawd, cov hlwb no tsis tuaj yeem siv lub voj voog mitotic. Qee zaum, amitosis ua rau tsim cov cell multinucleated.
Mitosis
Nov yog qhov tsis ncaj ncees lawm nuclear fission. Nws yog feem ntau pom nyob rau hauv eukaryotic hlwb. Qhov sib txawv tseem ceeb ntawm cov txheej txheem no yog tias cov cell cell thiab niam cell muaj tib tus lej ntawm chromosomes. Li notus naj npawb ntawm cov hlwb yuav tsum tau khaws cia hauv lub cev, thiab cov txheej txheem ntawm kev tsim dua tshiab thiab kev loj hlob kuj tseem ua tau. Flemming yog thawj tus piav txog mitosis hauv cov tsiaj cell.
Cov txheej txheem ntawm kev faib nuclear hauv qhov no tau muab faib ua interphase thiab ncaj qha mitosis. Interphase yog qhov so ntawm lub cell ntawm kev faib tawm. Nws tuaj yeem muab faib ua ob peb theem:
1. Presynthetic lub sij hawm - lub cell loj hlob, proteins thiab carbohydrates nyob rau hauv nws, ATP (adenosine triphosphate) nquag ua ke.
2. Synthetic Period - Cov khoom siv caj ces yog ob npaug.
3. Tom qab-synthetic lub sij hawm - cellular ntsiab ob, cov proteins tshwm uas ua rau lub division spindle.
Mitosis phases
Kev faib tawm ntawm lub nucleus ntawm eukaryotic cell yog txheej txheem uas yuav tsum tau tsim cov organelle ntxiv - lub centrosome. Nws nyob ib sab ntawm lub nucleus, thiab nws lub luag haujlwm tseem ceeb yog tsim cov organelle tshiab - kev faib spindle. Cov qauv no pab faib cov chromosomes sib npaug ntawm cov menyuam ntxhais.
Muaj plaub theem ntawm mitosis:
1. Prophase: Chromatin nyob rau hauv lub nucleus condenses rau hauv chromatids, uas sib sau nyob ze ntawm lub centromere los tsim chromosomes ua khub. Cov nucleoli disintegrate thiab cov centrioles txav mus rau cov ncej ntawm lub cell. Lub fission spindle yog tsim.
2. Metaphase: Chromosomes kab nyob rau hauv ib txoj kab los ntawm qhov chaw ntawm lub cell, tsim cov metaphase phaj.
3. Anaphase: Chromatids txav los ntawm qhov chaw ntawm lub cell mus rau tus ncej, thiab ces lub centromere faib ua ob. Xws liKev txav mus los yog ua tau vim qhov sib faib spindle, cov xov uas cog lus thiab ncab cov chromosomes nyob rau hauv ntau cov lus qhia.
4. Telophase: Tus ntxhais nuclei raug tsim. Chromatids tig mus rau hauv chromatin dua, lub nucleus yog tsim, thiab nyob rau hauv nws - lub nucleoli. Nws tag nrho xaus nrog kev faib cov cytoplasm thiab tsim cov phab ntsa ntawm tes.
Endomitosis
Qhov nce ntawm cov khoom siv caj ces uas tsis cuam tshuam nrog kev faib tawm nuclear hu ua endomitosis. Nws muaj nyob rau hauv cov nroj tsuag thiab tsiaj hlwb. Hauv qhov no, tsis muaj kev puas tsuaj ntawm cytoplasm thiab lub plhaub ntawm lub nucleus, tab sis cov chromatin hloov mus ua chromosomes, thiab tom qab ntawd despiralizes dua.
txheej txheem no tsim cov nuclei polyploid nrog cov ntsiab lus DNA ntxiv. Zoo sib xws tshwm sim nyob rau hauv colony-forming hlwb ntawm cov pob txha liab. Tsis tas li ntawd, muaj cov xwm txheej thaum DNA molecules ob npaug ntawm qhov loj, thaum tus naj npawb ntawm cov chromosomes tseem zoo ib yam. Lawv hu ua polytene thiab tuaj yeem pom hauv kab kab.
Meaning of mitosis
Mitotic nuclear kev faib yog ib txoj hauv kev los tswj cov chromosomes tas li. Cov menyuam ntxhais muaj tib cov noob caj noob ces raws li niam, thiab txhua tus yam ntxwv muaj nyob hauv nws. Yuav tsum muaj Mitosis rau:
- kev loj hlob thiab kev loj hlob ntawm ntau lub cev muaj sia (los ntawm kev sib xyaw ntawm cov kab mob);
- txav cov hlwb los ntawm cov txheej txheem qis mus rau sab saud, nrog rau hloov cov qe ntshav (erythrocytes, leukocytes, platelets);
- kho cov ntaub so ntswg puas (hauv qee cov tsiaj, muaj peev xwm rov tsim dua tshiab yogib qho xwm txheej tsim nyog rau kev ciaj sia, xws li ntses hnub qub lossis lizards);
- asexual reproduction ntawm cov nroj tsuag thiab ib co tsiaj (invertebrates).
Meiosis
Lub tshuab ntawm kev faib tawm ntawm cov kab mob ntawm cov kab mob sib txawv me ntsis ntawm somatic. Yog li ntawd, cov hlwb tau txais uas muaj ib nrab ntawm cov ntaub ntawv genetic ntau npaum li lawv cov neeg ua ntej. Qhov no yog qhov tsim nyog txhawm rau tswj kom muaj tus lej ntawm chromosomes nyob rau hauv txhua lub cell ntawm lub cev.
Meiosis tshwm sim hauv ob theem:
- txo theem;
- theem equational.
Qhov tseeb ntawm cov txheej txheem no tsuas yog ua tau hauv cov hlwb uas muaj cov chromosomes (diploid, tetraploid, hexaproid, thiab lwm yam). Tau kawg, nws tseem muaj peev xwm dhau mus rau meiosis hauv cov hlwb nrog cov khib nyiab ntawm chromosomes, tab sis tom qab ntawd cov xeeb ntxwv yuav tsis siv tau.
Nws yog qhov txheej txheem no uas ua kom tsis muaj menyuam hauv kev sib yuav. Txij li thaum cov hlwb sib deev muaj cov chromosomes sib txawv, qhov no ua rau nws nyuaj rau lawv sib koom ua ke thiab tsim cov xeeb ntxwv zoo los yog xeeb tub.
thawj division of meiosis
Lub npe ntawm cov theem rov ua dua cov hauv mitosis: prophase, metaphase, anaphase, telophase. Tab sis muaj ntau qhov sib txawv tseem ceeb.
1. Prophase: ob chav chromosomes ua ib qho kev hloov pauv, dhau los ntawm tsib theem (leptotene, zygotene, pachytene, diplotene, diakinesis). Tag nrho cov no tshwm sim ua tsaug rau conjugation thiab hla dhau.
Conjugation yog kev sib sau ua ke ntawm homologous chromosomes. Nyob rau hauv leptoten nruab nrab ntawm lawv yog tsimnyias threads, ces nyob rau hauv lub zygoten, cov chromosomes yog kev cob cog rua nyob rau hauv khub thiab yog li ntawd, cov qauv ntawm plaub chromatids yog tau.
Crossingover yog cov txheej txheem ntawm kev sib pauv ntawm ntu ntawm chromatids ntawm tus muam lossis homologous chromosomes. Qhov no tshwm sim nyob rau theem ntawm pachytene. Hla (chiasmata) ntawm chromosomes yog tsim. Ib tug neeg muaj peev xwm muaj los ntawm peb caug-tsib rau rau caum-rau xws li kev sib pauv. Qhov tshwm sim ntawm cov txheej txheem no yog cov caj ces heterogeneity ntawm cov khoom tshwm sim, los yog qhov hloov pauv ntawm cov kab mob.
Thaum lub sijhawm diplotene los txog, cov complexes ntawm plaub chromatids tawg thiab tus muam chromosomes ntxeev siab rau ib leeg. Diakinesis ua tiav qhov kev hloov pauv ntawm prophase mus rau metaphase.
2. Metaphase: Chromosomes kab nyob ze ntawm lub xov tooj ntawm txoj kab nruab nrab.
3. Anaphase: Cov chromosomes, tseem muaj ob chromatids, txav sib nrug ntawm cov ncej ntawm tes.
4. Telophase: Lub spindle tawg, ua rau ob lub hlwb haploid nrog ob npaug ntawm DNA.
thib ob division of meiosis
txheej txheem no tseem hu ua "mitosis of meiosis". Thaum lub sijhawm ntawm ob theem, DNA duplication tsis tshwm sim, thiab lub cell nkag mus rau qhov thib ob prophase nrog tib txheej chromosomes uas nws tau tso tseg tom qab telophase 1.
1. Prophase: chromosomes condense, lub cell chaw sib cais (nws cov seem diverge mus rau tus ncej ntawm tes), lub hnab ntawv nuclear raug rhuav tshem thiab ib qho kev faib spindle yog tsim, nyob rau perpendicular mus rau spindle los ntawm thawj faib.
2. Metaphase: chromosomes nyob rau ntawm txoj kab nruab nrab, tsimmetaphase phaj.
3. Anaphase: Chromosomes faib ua chromatids, uas txav sib nrug.
4. Telophase: lub nucleus yog tsim nyob rau hauv cov ntxhais cell, chromatids despiralize rau hauv chromatin.
Thaum kawg ntawm theem ob, los ntawm ib lub xov tooj ntawm niam txiv, peb muaj plaub tus ntxhais nrog ib nrab ntawm cov chromosomes. Yog tias meiosis tshwm sim ua ke nrog gametogenesis (uas yog, tsim cov kab mob hlwb), ces qhov kev faib tawm sai sai, tsis sib xws, thiab ib lub xov tooj ntawm tes tau tsim nrog cov chromosomes haploid thiab peb lub cev txo qis uas tsis nqa cov ntaub ntawv tsim nyog ntawm caj ces. Lawv tsim nyog kom tsuas yog ib nrab ntawm cov khoom siv caj ces ntawm niam txiv cell yog khaws cia hauv qe thiab phev. Tsis tas li ntawd, daim ntawv no ntawm nuclear kev faib ua kom muaj kev tshwm sim ntawm kev sib txuas tshiab ntawm cov noob, nrog rau cov qub txeeg qub teg ntawm cov ntshiab alleles.
Nyob rau hauv protozoa, muaj qhov sib txawv ntawm meiosis, thaum tsuas yog ib qho kev faib tawm hauv thawj theem, thiab thib ob muaj kev hla. Cov kws tshawb fawb qhia tias daim ntawv no yog ib qho evolutionary precursor rau ib txwm meiosis nyob rau hauv multicellular kab mob. Tej zaum yuav muaj lwm txoj hauv kev ntawm nuclear fission uas cov kws tshawb fawb tseem tsis tau paub txog.
