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Inkishofi hujayrahoi jinsi (gametogenez)

Dar gadudhoi jinsi inkishofi hujayrahoi jinsi, ki onhoro gameta menomand, ba amal meoyad. Hujayrahoi narina (nutfa) dar nasldon va modina (hujayratukhm) dar tukhmdon inkishof meyoband. Judojinsi az nigohi evolyutsioni bartari dorad. Judojinsi sokht va raftori volidonro makhsus gardonida, hamchun omili navi evolyutsioni, yane intikhobi jinsi tashakkul meyobad va nisbati naslhoi khud gamkhori zohir menamoyad. Dar in holat narinaho asosan roli muhofizat va gizoyobiro bozida, dar muhoriba baroi ba dast ovardani modina ishtirok mekunand. Dar ravandi paydoish hujayrahoi jinsi ham dar spermatogenez va ham dar ovogenez davrahoi gunogunro az sar meguzaronand (rasmi 6.4).

6-4

Davrai avvalro davri afzoish nomida, dar in jo hujayrahoi ibtidoii jinsi bo rohi mitozi taqsim va miqdoran ziyod meshavand. Dar spermatogenez afzoishi hujayrahoi avvalini jinsi khele faol buda, az vaqti ba balogatrasi ogoz meyobad va dar tamomi davrai nasldihi, yane vaqte ki hayvonot dar afzoishi jinsi ishtirok dorad, davom mekunad, sipas, tadrijan dar dami piri qat megardad. Hujayrahoi avvalini jinsii modina dar muhradoroni darajai past dar davomi hayotashon inkishof meyoband. Dar shirkhuron, az jumla dar odam, in guna hujayraho dar batni modar inkishof yofta, nisbatan faoland va dar holati oromi to pukhta rasidani hujayrahoi jinsi mahfuz memonand.

Davrai duyum davrai sabzish ast. Dar gametahoi norasidai narina sabzish chandon ba nazar namerasad va andozai onho niz khurd meboshad. Baraks, hujayratukhmi oyanda, ki oosit nom dorad, hajman sadho, hazorho, bazan millionho marotiba kalon meshavad.

Dar baze hayvonot oosit bo surati nihoyat tez, masalan, dar davomi chand ruz yo hafta inkishof meyobad, dar namudhoi digar boshad, davomoti sabzishi on mohho va solhoro darbar megirad. Sabzishi oositho az hisobi moddahoe, ki hujayrahoi

digari organizmho paydo mekunand, ba amal meoyad. Masalan, dar mohiho, obkhokiho va beshtar dar khazandagonu parrandagon massai asosii tukhmro zardi tashkil mekunad.

Zardi dar jigar dar shakli mahluli makhsus sintez shuda, ba vositai khun ba tukhm meguzarad. Dar on jo vay ba oositi sabzanda dokhil shuda, dar shakli zardii serqabat jam megardad. Fayr az in, dar hujayrai jinsii oyanda safedahoi gunogun, hamchunin miqdori ziyodi KRN (naqliyoti, ribosomi, akhbori) sintez meshavand. Zardi dar shakli moddahoi gizoi (ravganho, safedaho, angishtobho vitaminho va gayra) buda, baroi inkishofi janin lozimand. KRN sintezi safedahoro dar davrai ogozi inkishof tamin mekunad, zero dar in vaqt KRN-a khud hanuz ba faoliyat shuru nakardaast. Davrai digar yo seyum, davrai pukhtarasi yo meyozi ast, ki dar rasmi 6.5 nishon doda shudaast. Hujayrae, ki ba davrai balogat shuru mekunad, dastai khromosomaash diploidi buda, miqdori KDN duchand gardidaast (2p,4s).

Dar ravandi afzoishi jinsi organizmhoi har namud dar naslhoi khud miqdori muayyani khromosomahoi khosro nigoh medorand. In holat dar natijai taqsimshavii meyozi ba amal meoyad, chunki dar rafti pukhta rasidani hujayrahoi jinsi miqdori khromosomaho kam (reduksiya) va az hujayrai dastai diploidi (2n) hujayrai gaploidi (1n) paydo meshavad. Badi bordorshavi, yane omekhtashavii hujayrahoi jinsi, dastai khromosomaho boz miqdori peshinai khudro paydo mekunand (2n).

Qonuniyathoi jarayoni meyoz dar hujayrahoi jinsii narina va modina mohiyatan monandand. Binobar in, avval qonuniyathoi umumii meyoz va sipas, jihathoi farqkunandai spermatogenez va oogenezro dida mebaroem. Mohiyati meyoz az on iborat ast, ki har yak hujayrai jinsi nisfi khromosomahoro megirad, yane dastai khromosomaho gaploidi (toq) ast.

Az tarafi digar, meyoz davrae meboshad, ki omezish (kombinatsiya)-i navi genho dar natijai yakjoyashavii khromosomahoi volidon ba amal meoyad. Ba tavri digar guem, dar meyoz omezishi hissachahoi irsi hamchunin dar natijai ivazshavi (dodu girift)-i khromosomahoi gomologi ba amalmeoyad. Meyoz du davrai taqsimshavii payihamro darbar megirad, ki qarib dar bayni onho fosila nest. Meyoz hamchun mitoz chor marhila – profaza, metafaza, anafoza va telofazaro az sar meguzaronad.

 

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