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NAZARIYAI IRSIYATI HROMOSOMI

MEROSGUZORII HAMPAYVASTAGII GENHO:  Mendel dar tajriba merosguzorii tanho haft juft alomati nakhudro dida baromad. Badan bisyor tadqiqotchiyon merosguzorii jufti alomathoi gunoguni organizmhoi digarro omukhta, qonunhoi Mendelro tatbiq namudand. In qonunho baroi hamai organizmhoi bo rohi jinsi afzoishkunanda khosand. Badtar malum gardid, ki dar nakhudi khushbuy du alomat, yane shakli gard va rangi gulho bevosita ba meros naguzashta, naslho faqat ba volidon monandand.

khromosoma

Tadrijan adadi chunin misolho, ki bo qonuni seyumi Mendel itoat namekunand, ziyod shud. Hamin tavr, malum gardid, ki qoidahoi taqsimshavii bevosita dar naslho, yo kombinatsiyai ozod ba hamai genho khos nest. Dar haqiqat baroi har organizm alomathoi bisyore khosand, vale miqdori khromosomaho mahdud (kam) ast. Az in malum meshavad, ki dar har khromosoma nafaqat yak, balki yakchand gen joygirand. 

CHunin holat boisi digar shudani qonuniyathoi merosguzorii genho gashta, in masalaro olimi barjastai Amriko, genetik T.Morgan isbot namudaast. Farz kardem, ki du geni A va V dar yak khromosoma joygirand va organizme, ki baroi duragakuni intikhob shudaast, bo in genho geterozigot ast.

Dar anafazai yakumi taqsimshavii meyozi khromosomahoigomologi dar vaqti kashish khurdan ba qutbhoi bo ham muqobil dar hujayrahoi gunogun joygir shuda, ba joi chor nav du navi gameta paydo meshavad, ki in mukholifi duragakunii digibridi va qonuni seyumi Mendel meboshad. Agar organizmi gomozigoti bo genhoi resessivi doshta (aa va vv) duraga karda shavand, pas ba joi 1:1:1:1, ki baroi duragakunii tahlili khos ast, tajziyai 1:1 paydo meshavad:

CHunin nomuvofiqi az qonuni taqsimshavii bevositai alomatho daleli on ast, ki genhoi in alomatho dar yak khromosoma joygirand va hamroh ba meros meguzarand. Inro dar misoli mushakhkhas dida mebaroem. Agar magasi drozofilai khokistarrangi bolash mutadilro bo magasi siyohi bebol duraga kunem, on goh dar nasli yakum hamai magashoi duraga boli mutadili khokistarrang dorand. In organizmho digeterozigotiand, yane bo du jufti allelhoi genii khud farq mekunand va geni dorandai boli mutadil nisbat ba boli nopurra va geni khokistarrang nisbat ba siyoh dominant ast. Dar duragakunii tahlili nasli yakumro bo drozofilai gomozigotii resessivi (siyohi bebol) duraga kunem, dar nasl-hoi G2 beshtari naslho fenotipi volidonro sohib meshavand (rasmi 9.5).

Rasmi 9.5. Alomathoi gunoguni irsi dar drozofilaho:

A – khokistarrang, boli mutadil,

B – siyoh, boli nopurra (munkariz),

V – khokistarrang, boli nopurra,

G – siyoh, boli mutadil.

Du shakli okhir dar natijai yakjoya shudani alomathoi volidon dar shakli chilliki paydo shudaand.

Narina Modina

Hodisai hamroh ba meros guzashtani genhoe, ki dar yak khromosoma joygirand, merosguzorii chaspida nom giriftaast. Genhoi dar yak khromosoma joydoshtaro hampayvasti (chaspaki)-i genho menomand.

Ba meros guzashtani genhoi hampayvast (hamroh ba meros guzashtani onho)-ro, ki dar yak khromosoma joygirand, qonuni Morgan menomand. Hamin tariq, qonuni seyumi Mendel faqat baroi merosguzorii jufti allelho (genho), ki dar khromosomai gayrigomologi joygirand, khos ast.

Genhoi dar yak khromosoma joygirifta, ki hamroh ba meros meguzarand, guruhi hampayvastro tashkil mekunand. Az sababi on, ki dar khromosomahoi gomologi genhoi allelidar nuqtahoi yakkhela (lokus) joy giriftaand, guruhi hampayvastro du khromosomai gomologi tashkil mekunand. Guruhi hampayvast barobari miqdori khromosomahoi gaploidii har yak namud ast. Dar inson 46 khromosoma, guruhi ham payvast-23, magasi drozofil-8 khromosoma, guruhi hampayvast 4, nakhud-14 khromosoma, guruhi hampayvast-7 va gayra.

Lekin dar natijai tahlili merosguzorii hamchaspii genho malum gardid, ki dar baze mavridho qoidai hamchaspii genho tagyir meyobad.

Meyozro ba khotir ored. Dar profazai yakumi taqsimshavii meyozi khromosomai gomologi ba ham chaspida (konyugatsiya), dar bayni onho dodu girifti qismho (ivazshavi) ba amal meoyad, ki inro chillikishavi menomand (rasmi 6.7).

Dar natija kombinatsiya (yakjoyashavi)-i navi genho dar khromosomaho ba amal meoyad. Dar natijai chillikishavi, dar baze hujayraho qismhoi ba ham monandi khromosomahoi gomologii genhoi A va V ivaz shuda, gametahoi Av va aV paydo meshavand. Dar naslhoi onho chor shakli fenotipi dida shuda, ba kombinatsiyai bevositai genho monand ast. Ammo miqdori tanosubi fenotipho ba tanosubi 1:1:1:1, ki khosi duragakunii tahlilii gibridi meboshad, muvofiq nest. Baroi isboti in dalel ba misoli dar bolo ovardai magasi drozofila, ki bo alomati khud farq mekunand, menigarem. Dar baze mavridho dar nasli G1 shaklhoi fardhoi nav paydoshuda, nisbat ba fardhoe, ki ba volidon monandand, kamtarand, az jumla, magasi khokistarrangi bebol (rasmi 9.5.) va siyohi bolash mutadil. Paydo shudani in miqdori kami fardho (8,5% az har yak shakl) natijai khalal yoftani hampayvastii genhost.

Hamin tariq, chaspakii genho purra va nopurra buda, sababi vayron shudani chaspakii genho chillikshavi, yane dodu girifti qismhoi khromosomai gomologi dar taqsimshavii profazai meyozi ast.

T.Morgan isbot namud, ki chi qadare genho dar khromosoma az hamdigar dur joygir shuda boshand, ehtimoliyati chillikishavi hamon qadar ziyod va foizi fardho bo omezishi gametahoi nav bisyor buda, az volidon farq mekunand. Dar genetika masofai bayni genhoi dar yak khromosomai gomologi joy doshtaro bo foizi gametahoi chillikshuda nisbat ba miqdori umumii gametaho, ki dar natijai omezish (rekombinatsiya)-i genhoi khromosomai gomologi paydo meshavand, muayyan mekunand. CHenaki masofai bayni genhoi dar yak khromosoma joygirifta ba yak foiz chillikishavi barobar ast. CHunin chenak ba sharafi T.Morgan, morganoid nom giriftaast.

Savolho baroi sanjish:

  1. Hampayvastii (chaspakii) genho chist?
  2. Guruhi hampayvasti az chi iborat ast? Kadom khromosomaho yak guruhi hampayvastiro muayyan mekunand?
  3. Kadom hodisa hampayvastii genhoro vayron mekunad?

 

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