Dar organizmhoi serhuchayra huchayraho makhsus gashtaand, yane har yaki onho sokht va vazifai khudro dorand. Davomnokii ha- yoti huchayraho vobasta ba ichroi vazifai khud muayyan megardad. Masalan, huchayrahoi asab va mushak badi ba okhir rasidani dav- rai inkishofi chanin digar taksim nameshavand. Dar davomi ta-
momi hayoti organizm vazifai khudro ijro mekunand. Hujayrahoi digar boshand, chunonchi, hujayrahoi magzi ustukhon va pardai ruda badi ijroi vazifai khud nobud megardand. Binobar in, dar chu- nin boftaho, hujayraho payiham qobiliyati taqsimshavi dorand.
Ba hamin minvol, sikli hayoti hujayra vaqti muayyanro dar bar girifta, az davrai paydo shudani on, ki dar natijai taqsim- shavi rukh medihad, to mahv shudan yo taqsimshavii oyanda idoma meyobad. Dar in muddat hujayra mesabzad, inkishof meyobad va va- zifai khudro dar hayoti boftaho va organizmhoi serhujayra ijro mekunad.
Dar baze boftaho (magzi ustukhon, pardai ruda va gayraho), ki hujayraho doimo taqsim meshavand, yak qismi sikli hayoti onho bo sikli mitoz barobar ast. Majmui ravandhoi paydarham va bo hamdigar aloqamandi davrai omodagii pesh az taqsimshavi va rafti mitozro, sikli mitozi menomand (rasmi 5.18). Az rasm dida meshavad, ki badi ba okhir rasidani mitoz, hujayra ba taq- simshavii nav omodagi mebinad va davrai interfaza meguzarad.
Davri tayyorii pesh az sintezi KDN ba harfi O1 (az anglisi dar – masofai bayni) ishora shudaast. Dar in davr dar hujayra KRN va safedaho paydo shuda, faoliyati fermenthoe, ki dar bio- sintezi KDN ishtirok mekunand, afzun megardad. Badi khotimai fazai O1, hujayra ba sintezi KDN shuru karda, duchand megar- dad (fazai 8). Dar in faza du spirali kuhnai molekulai KDN az ham judo shuda, har yaki onho baroi paydo kardani zanjiri navi KDN chun qolab khidmat mekunand (rasmi 5.19)..
Duchandshavii KDN:
A – molekulai ibtidoii KDN,
B – judo shudani du zanjir,
V – du molekulai dukhtarii KDN.
Dar hardui in molekulahoi dukhtary yake az zanjir (tor)-i polinukleotidii kuhna va digare zanjiri nav ast. Dar jarayoni sintezi KDN baze guruhhoi fermentho ishtirok mekunand, ki yake az asositarini onho KDN polimeraza ast.
Duchandshavii molekulai KDN bo tavri khos amaly shuda, ba sokhti duzanjirii molekula vobasta ast: sokhti molekulai nav purra ba sokhti molekulai kuhna monand ast va mohiyatu mazmuni asosii biologii on mahz dar hamin ast. Agar sokhtori molekulai KDN vayron shavad, dar natija mazmuni ramzi genetiki tagyir yofta, nigohdorii akhbori irsi va ba nasl guzashtani alomathoi baroi organizm khos gayrimumkin megardad, vale dar natijai tasiri omilhoi khimiyavi va fizikavi (nurhoi ultrabunafsh, nurhoi rentgeni, baland shudani harorat va gayra) sokhtori az nav sintezshudai molekulai KDN vayron meshavad.
In holatro fermenthoi makhsus metavonand bartaraf kunand, yane onho joyi vayronshudai molekulai KDN-ro, ki bo qolabi (matritsa) muvofiq nestand «shinokhta», tajziya mekunand va bo nukletidhoi muvofiq purra menamoyand. Davomoti sintezi KDN, yane fazai 8-i sikli mitozi dar hujayraho yak khel nabuda, az chand daqiqa (dar bakteriyaho) to 6-12 soat (dar hujayrahoi shirkhuron)- ro dar bar megirad. Dar natijai duchandshavii KDN dar har khro- mosoma miqdori KDN nisbat ba ogozi fazai 8 du barobar ziyod ast, ammo miqdori khromosomaho tagyir nameyoband.
Dar natijai ba okhir rasidani reduplikatsiyai KDN dastai khromosomahoi hujayra 2p 4s (rasmi 5.18) tashkil mekunad. Ba- di khotimai sintezi KDN, yane fazai 8-i sikli mitozii taqsim- shavii hujayra yakbora shuru nameshavad, zero az vaqti ba okhir rasidani sintezi KDN to ogozi taqsimshavii mitozro davrai 02 tashkil medihad. Mahz dar hamin davra tayyori ba taqsimshavii mitozi ba okhir merasad. Baroi ba taqsimshavii mitozi shuru kardan, gayr az duchandshavi KDN boz duchandshavii sentriolaho, sintezi safedaho, ki az hisobi on torhoi akhromatini sokhta me- shavand, zarur ast.
Barobari khotima yoftani tashakkuli hujayra jam shudani energiya dar shakli ATF lozim ast. Taqsimshavii mitozi az chor fazai payiham, yane az profaza, metafaza, anafaza va telofaza (rasmi 5.20 va 5.21) iborat ast.
Davrahoi mitozi dar reshai piyoz: 1 – interfaza, 2, 3 – profaza,
- – metafaza,
- – tori akhromatini,
- – anafaza,
- – telofaza.
Dar davrai profaza hajmi yadro kalon shuda, galizii shirai on kam va khromosomaho namoyon megardand, zero onho shakli spi- ralro girifta, du sentriola ba qutbho ravona meshavand. Dar na- tijai shakli spiralro paydo kardani khromosomaho imkoniyati nuskhabardorii akhbori genetiki az KDN qat megardad va sintezi KRN ba okhir merasad. Dar bayni qutbho torhoi akhromatini qad kashida, sokhtore tashkil meyobad, ki ba qutbho kashish khurdani khro- mosomahoro tamin menamoyad. Dar okhiri profaza pardai yadro ba qismhoi khurd taqsim shuda, gushaki in hissacha ba ham mechaspand.
Dar natija hubobchahoi khurd ba vujud omada, hamchun vakuo- laho ba turi endoplazmavi yakjoya meshavand. Dar muddati pro- faza pechutobi khromosomaho idoma meyobad va onho kutohu gafs meshavand. Badi hazm shudani pardai yadro khromosomaho dar si- toplazma ozod va betartib joy megirand.
Dar metafaza pechutobi khromosomaho ba nuqtai balandtarin merasad, onho kutoh meshavand, ba markazi hujayra harakat kar- da, dar masofahoi gunoguni qutbi joy meyoband. Qismi sentrome- riyai khromosomaho bo tartibi muayyan dar khatti markazi voqe gashta, dushhoi khromosomahoi khohari ozodona dar sitoplazma joy dorand. Torhoi mitozi komilan tashkil yofta, az nakhhoe ibo- rat megardand, ki qutbro ba markazi khromosoma payvastaand.
Dar metafaza ba nazar merasad, ki khromosoma az du khromatid iborat buda, onho faqat bo sentromera payvasta meboshand.
Dar anafaza sentromerai har khromosoma judo shuda, az hamin lahza khromatidhoi khohari, khromosomahoi mustaqili dukhtariro tashkil mekunand. Tori akhromatini (duk), ki bo sentromera pay- vast ast, khromosomahoro bo qutbhoi hujayra kashida, kitfhoi khromosoma az pasi on ravon meshavand va shakli U-ro megirand.
Hamin tavr, dar anafaza khromatidhoi duchandshudai davrai interfaza khromosomahoi mustaqili khohariro tashkil karda, onho ba qutbhoi ba yakdigar muqobili hujayra kashida mesha- vand. Dar in vaqt dar hujayra du dastai diploidii khromosomaho mavjud ast. Davrai ba okhir rasidani mitozro telofaza dar bar megirad. Dar fazai mazkur khromosomahoi ba qutbho jafsshuda ba shakli rishta meguzarand va nagz namudor meshavand. Az sokh- torhoi membranavii sitoplazma pardai yadro tashakkul meyobad. Dar hujayrai hayvonot sitoplazma ba rohi kashishkhuri ba du qismi sitoplazmavi taqsim meshavad, ki har yaki onho doroi miq- dori dastai diploidii khromosomaho ast. Dar hujayrai rustani boshad, membranai sitoplazmavi az bayni hujayra paydo shuda, ba kanor meravad va hujayraro ba du qismi barobar judo meku- nad. Badi paydo shudani membranai sitoplazmavii ufuqi dar hujayrai rustaniho devorai sellyulozagi tashakkul meyobad. Dar sikli hujayra mitoz davrai nisbatan kutoh buda, az 0,5 to 3 soat idoma meyobad.
Hujayratukhmi bordor (zigota) ba taqsimshavii mitozy shuru menamoyad. Hamai hujayrahoi dukhtarie, ki az vay bo rohi mitoz taqsim shudaand, dastai khromosomaho va genhoi yakkhela dorand. Pas, malum megardad, ki mitoz tarzi taqsimshavii aniqi hujay- ra buda, hangomi on mavoddi genetiki dar bayni hujayrahoi dukh- tary barobar taqsim meshavad.
Ahamiyati biologii mitoz. Sokhtori betagyir va faoliyati durusti har uzvu boftai organizmhoi serhujayra bo yakkhela buda- ni mavoddi genetiki dar naslho vobasta ast.
Mitoz ravandhoi muhimmi faoliyati hayoti, masalan inki- shofi janin, sabzish, barqarorshavii uzvho va boftaho badi oseb didan va gayraro ijro mekunad. Hamchunin, nigoh doshtani umumiyati sokhtori boftaho hangomi mahv shudani hujayrahoi onho (ivaz shudani eritrotsithoi murda, pustpardai rudaho va gayra) ba mitoz vobasta ast.
Savolho baroi sanjish:
- Sikli hayotii hujayra chist?
- Sikli mitozii hujayraro sharh dihed.
- Sintezi KDN chi guna ba amal meoyad?
- Mitozro sharh dihed.
- Mafhumi mitozro muayyan karda, ahamiyati biologii onro fahmo- ned.
- Mohiyat va mazmuni mitoz dar chist?
Istilohot:
- Interfaza – davrai tayyorii hujayra ba taqsimshavi, ki asosi onro duchandshavii KDN tashkil medihad.
- Sikli hayotii hujayra – majmui ravandhoe, ki dar hujayra megu- zarand.
- Sikli mitozii hujayra – majmui ravandhoe, ki dar hujayra megu- zarand, az jumla dar vaqti omodagi ba taqsimshavi va mitoz.
- Tafriqashavi – ravandi makhsusgardii hujayra baroi ijroi vazi- fai muayyan, ki dar sintezi safedahoi alohida ishtirok mekunad.
- Boftai ustuvor – boftae, ki baroi aksariyati hujayrahoi sikli hayotash ba mitozi barobar ast.
- Boftahoi ehyoshuda – yak qismi hujayrahoi tafriqashuda, lekin vaqti lozim metavonand az sari nav dar sikli mitozi tafriqa shavand.
- Boftahoi sabzanda – hujayrahoe, ki differensiatsiyai (tafriq- shavii) bargasht dar janin va avvali davrai badi janini nadoshta, dar tamomi hayoti hujayrahoi organizmho vazifaro ijro mekunand.
- Mitoz – shakli afzoishi hujayra, ki dar on qismho anik, va baro- bar dar hujayrahoi dukhtary taqsim meshavand.
Testho
- Kadom hujayraho badi ba okhir rasidani davrai inkishof digar taqsim nameshavand?
a) asab va mushak; b) epiteli; v) payvastkunanda.
- Kadom huchayraho doimo qobiliyati taqsimshavi dorand?
a) pardai ruda; b) asab; v) magzi ustukhon.
- Sikli mitozi az kadom davraho iborat ast?
a) 61, 02, 8, M; b) 02, M, O1, 8, v) 8, O1, M, N.
- Duchandashavii KDN dar kadom davra ba amal meoyad?
a) O1; b) 8; v) O2.
- Dar duchandashavii KDN kadom ferment naqshi asosi mebozad?
a) replikaza; b) polimeraza, v) preymaza.
- Taqsimshavii mitozi badi kadom davra ogoz meshavad?
a) badi O1; b) badi 8, v) badi O2.
- Taqsimshavii mitozi az chand faza iborat ast?
a) du; b) se, v) chor.
- Dar okhiri davrai profaza kadom digarguni mushohida meshavad?
a) pardai yadro hazm meshavad; b) khromatin nest meshavad; v) rishtahoi duk paydo meshavad.
- Dar kadom davrai mitozi khromosomaho dar khatti ekvator choygir meshavand?
a) profaza; b) metofaza; v) anafaza.
- Dar metofaza khromosoma az chand khromotid iborat ast?
a) du; b) se; v) chor.
- Dar kadom faza khromotidhoi khohari ba qutbho kashida mesha- vand?
a) profaza; b) metafaza; v) anafaza.
- Dar kadom faza sentromera taqsim meshavad?
a) metafaza; b) anafaza; v) telofaza.
- Baroi chi dar taqsimshavii mitoz miqdori khromosomaho dar huchayrai khohari kam nameshavand?
a) khromosomaho butun ba qutbho kashida meshavand. b) khromotidhoi khohari ba qutbhoi bo ham muqobil kashida meshavand; v) sentromera taqsim nameshavad.
- Dar kado faza khromosomaho dar qutbho choygirand?
a) anafaza; b) metafaza v) telofaza.
- Badi telofaza taqsimshavii huchayrai hayvonot az kucho ogoz me- shavad?
a) az du kanori sitoplazma; b) az mobayni sitoplazma; v) az yak tara- fi sitoplazma.
- Dar rustaniho membranai sitoplazmatiki az kujo ogoz meyobad?
a) az markazi sitoplazmai hujayra sar shuda, ba kanori on ravona meshavad; b) az tarafi rosti sitoplazmai hujayra; v) az tarafi chapi sitoplazmai hujayra.
- Davrai sikli hujayrai mitozi chi qadar vaqtro dar bar megirad? a) 0,5 to 3 soat; b) 5-6 soat; v) 7-8 soat;
- Ahamiyati biologii mitoz dar chist?
a) tamin namudani yakkhelagii mavoddi genetiki dar hamai boftaho; b) nigoh doshtani yakkhelagii shakli hujayra; v) tamin namudani hujay- raho bo moddai gizoi;
- Interfazaro chi khel mefahmed?
a) davrai pesh az mitozi; b) davrai bayni du taqsimshavi; v) davrai hayotii yadro;
- Sikli mitotiki az kadom davraho iborat ast?
a) interfaza bo mitoz; b) O1 va mitoz; v) 8 va 61;