IRSIYAT

IRSIYAT (Hereditas), qobiliyati nigoh doshtan va ba nasl guzaronidani alomatho, sokhtu faoliyat va khususiyathoi inkishofi fardi, ki ba hamai organizmho khos ast.
Az qadimulayyom diqqati odamonro sirri irsiyat ba khud jalb menamud, dar borai tabiati on takhminhoi gunogunu goho afsonavi izhor meshudand. Vale faqat s.1944 muqarrar gardid, ki omili modii I. kislotai dezoksiribonukleat – KDN meboshad. Dar baze virusho khosiyathoi irsiro kislotai ribonukleat – KRN muayyan mekunad. Muvofiqi tasavvuroti hozira molekulai KDN az du zanjiri ba tavri morpech tobkhurdai nukleotidhoi pay dar pay iborat ast. Gayr az in, paydarpayii nukleotidhoi yak zanjir paydarpayii nukleotidhoi zanjiri digarro muayyan mekunad. CHunin khususiyati sokhti molekulai KDN hamon vaqt boztavlidi aniqi materiali genetikiro tamin khohad kard, ki har du tor nuskhai mutaqobili yakdigar boshandu ba nukleotidi yak zanjir faqat nukleotidi qatiyan muayyani zanjiri digar muqobil istoda tavonad (hodisai komplementi). Dar marhalai muayyani taqsimshavii hujayraho zanjirhoi KDN az yakdigar judo meshavand va dar har yaki onho, chun dar matritsa, tori navi komplementarii KDN gun megardad. Dar natija du molekulai KDN hosil meshavad, ki har kadomi on az yak tori volidayniyu yak tori navi komplementarii volidayni iborat ast. Hangomi taqsimshavii hujayra molekulahoi dukhtarii KDN bayni hujayrahoi dukhtari joy girifta, bo hamin hifozatu payvastagii moddai irsiyat, yane alomathoi khosi naslro tamin mekunand.
Dar hayvonotu rastani miqdori asosii KDN dar tashkilahoi makhsusi yadroi hujayra – khromosomaho, ki shumora va sokhtu shaklashon baroi har navi organizm makhsus ast, mavjud meboshad. Mas., odam 46 khromosoma dorad, ki 44-toi on 22 jufti khromosomahoi gomologi (ba istiloh autosomaho) va du khromosoma yakjuft khromosomahoi jinsiro tashkil medihand. Jufti khromosomahoi jinsii mardho va zanho gunogun meboshand. In juft dar zanho az du H-khromosomai yakkhela (jufti HH) va dar mardon az yak khromosomai H va yak khromosamai Y (jufti XY) iborat ast. Hromosomai alohida guruhi genhoi pay dar pay joygirifta meboshad, ki har kadom dar on joi muayyan (lokus)-ro ishgol mekunad. Ahamiyati gen dar tashakkuli alomat az hamin iborat ast, ki dar on binobar bonavbatii nukleotidho akhbor dar borai paydarpayii aminokislotahoi safedai muayyan ba ramz darovarda meshavad. Safeda mustaqilona yo yakjoya bo safedahoi digar boisi dar organizm paydo shudani alomati khos megardad. Juft budani khromosomaho dar navbati khud juft budani genhoro dar majmui umumii genho – genotip muayyan mekunad. Gen chizi tagyirnayobanda nest, dar on metavonad mutatsiya ruy dihad. Dar jarayoni tahavvulot yak mutatsiya nest shuda, mutatsiyai digar boqi mondaast. Mas., gene, ki mutasaddii rangi chashm ast, du variant dorad: yake rangi qahvagi, digar rangi kabudro muayyan mesozad; gene, ki guruhi khuni odamro muayyan mekunad, se variant dorad va g. Jufti az varianthoi hamon gen hosilshudaro genhoi alleli yo allelho menomand.
Jufti allelii genho hangomi bordorshavi tashakkul meyobad. Dar organizmhoi bo rohi jinsi afzoishyobanda du navi taqsimshavii hujayra mushohida meshavad. YAke az onho (mitoz) ba hujayrahoi organizm khos buda, dar mavridi taqsimshavii onho moddai irsiyatro mahfuz medorad. Dar in holat pesh az taqsimshavii hujayra hamai majmui khromosomaho duchand gashta, sipas bayni hujayrahoi dukhtari juft – juft joy megirand. Navi duyumi taqsimshavi (meyoz) faqat dar mavridi hosil shudani hujayrahoi jinsii bolig – gametaho (dar zanho hujayratukhm, dar mardho nutfa) ba mushohida merasad. Hangomi meyoz ba yak davrai duchandshavii khromosoma du bor pasi ham taqsim gashtani hujayra rost meoyad. Dar natija az yak hujayrai avvala 4 hujayrai dukhtari hosil meshavad, ki adadi khromosomahoyash nisbat ba hujayrai avvala du barobar kam buda, az har juft yaktoi khromosoma dorad. Zimni bordorshavi yadroi nutfa va hujayratukhm, inchunin khromosomahoi onho omekhta meshavand va majmui duchandi khromosomaho, ki khosi organizm ast, barqaror megardad. Vale aknun nisfi on az khromosomahoi modar, nisfash az khromosomahoi padar iborat ast. Tajdidi jufti khromosomaho boisi tashakkuli jufti navi allelie megardad, ki bo zuhuroti khud az volidayn tafovut dorad. Az sababi on ki ham taqsimi khromosomahoi gemologi dar bayni gametaho va ham vasli gametaho dar asnoi bordorshavi az rui qonuni tasoduf ruy medihad, dar hujayratukhmi bordor – zigota, ki az on organizmi kudaki oyanda inkishof meyobad, bo ehtimoli barobar har kadom khromosomai gomologi (az in ru ham geni volidayn) ru ba ru gashta, jufti alleliro ba vujud meovarand. Jufti alleli, odatan, az allelhoi yakkhela yo gunogun paydo meshavad. Agar allelho yakkhela boshand (hodisai gomozigoti), onho dar tashakkuli alomat yaktarafa shirkat mevarzand, zero hosil shudani safedahoi monandro har du nazorat menamoyand. Agar allelho gunogun boshand (hodisai geterozigoti), bayni onho robitai dutarafai khos tashkil meyobad: yake zuhuroti digarro purra yo qisman furu menishonad (hodisai bartari) yo hardu zohir megardand, sarfi nazar az on ki sintezi safedahoi gunogunro nazorat menamoyand (hodisai kodominanti). Har yaki in holatho doroi qonuniyathoi khos ast, binobar in chunin namudhoi merosgiri – autosomiyu dominanti va autosomiyu retsessiviro farq mekunand. Meros giriftani nishonahoe, ki geni onho dar khromosomahoi jinsi joygirand, ba qonuniyathoi merosgirii khromosomahoi jinsi tobe meboshand.
Alomathoe, ki allelhoi dominanti nazorat mekunand, ba darajai barobar dar mardho va zanho oshkor megardand va onhoro dar baze naslhoi pay dar pay mushohida kardan mumkin ast. Agar chunin alomat dar kudak oshkor gardad, pas yake az volidayn niz boyad onro hatman doshta boshad. Az tarafi digar, mavjudiyati alomathoi dominanti dar volidayn manoi onro nadorad, ki in alomat, albatta, dar kudak paydo gardad. Agar jufti allelii har du volidayn az genhoi gunogun tarkib yofta boshad (volidayn geterozigoti boshand), on goh dar ravandi bordorshavi ishtirok namudani gametahoi ori az geni dominanti ehtimol dorad. Binobar in mumkin ast dar kudak alomati dominanti ba mushohida narasad. Az alomathoi patologi bo rohi autosomiyu dominanti polidaktiliya (serangushti), brakhidaktiliya (kutohangushti) va g. meros girifta meshavand.
Agar navi merosgirii autosomiyu dominanti nisbatan oson muqarrar gardad, pas dar odam mushohidai merosgirii nishonae, ki onro alleli retsessivi nazorat mekunad, khele dushvor ast. Sabab dar on ast, ki zuhuroti hamin nishona az bayn raftaast va mumkin dar tuli chandin nasl dar holati nuhufta intiqol gardad. Homiloni alomati retsessivi az odami solim zohiran tafovut nadorand va az homilii khud bekhabarand. Baroi zuhur yoftani alomati retsesivvi zarur ast, ki ham padar va ham modar homili chunin alomat boshand va dar bordorkuni gametahoi chi padari va chi modari, ki alleli retsessivi dorand, ishtirok kunand. Qonuniyathoi navi merosgirii autosmiyu retsessivi ba darki on chiz imkon medihand, ki charo dar oilai volidaynashon solim kudakoni giriftori bemorihoi irsi tavallud meshavand. Basomadi homilii nishonai patologi dar holati nuhufta khele kam ast. Ehtimoli izdivoji odamone, ki genashon tagyiroti yakkhela dorad, az on ham kamtar meboshad. Vale agar kheshoni nazdik izdivoj kunand, khavfi afzoishi bemori beshtar megardad, zero genhoi onho paydoishi umumi dorand. Dar bayni alomathoi patologii inson, ki az rui navi autosomiyu retsessivi meros girifta meshavand, chunin bemoriho mavjudand: albinizm (berangii modarzodi pust), galaktozemiya (dar khun paydo shudani galaktoza), karii modarzodi, mikrosefaliya (modarzod khurd budani sar) va g.
Boyad qayd kard, ki az volidayni zohiran solim ba dunyo omadani kudaki inkishofash nomutadil alomati irsi budani in nuqs nest. Mikrosefaliya dar kudak, mas., mumkin ast oqibati shuozanii rentgeni dar davrai inkishofi u dar batn boshad; bazan sababi kariyu gungii modarzod surkhakon – bemorii virusie meboshad, ki modar dar davrai homilagi az sar guzaronidaast. Hatto agar dar oila chand kudaki giriftori hamon yak bemori tavallud shavad ham, dar borai paydoishi irsii on yaktarafa sukhan rondan mumkin nest. Ba in metavonad tasiri zarari kasbi ba volidayn, sharoiti zindagi, tagziyai oila va dig. omilho sabab shuda boshad. CHunin alomathoi ba irsi monandro fenokopiya menomand. Tabiati irsi doshtani bemori yo fenokopiya budani onro (muqarrar kardani in baroi durust peshgui namudani inkishofi bemori dar kudakoni oyanda zarur ast) dukhturi genetik muayyan mekunad.
Merosgirii alomathoi jinsiro qonuniyathoi merosgirii khromosomahoi jinsi muayyan mesozad. Agar hama hujayrahoi jinsii boligi zan (hujayratukhm) faqat H-khromosoma doshta boshand, pas nisfi nutfai mard H- khromosoma va nisfi digarash Y- khromosoma dorad. YAne jinsi kudaki oyanda ba on vobasta ast, ki hujayratukhmro kadom nutfa (H – yo Y- khromosoma) bordor mekunad. Misoli merosgirii marbut bo H- khromosoma gemofiliya ast, ki binobar sintezi globulini ziddigemofilii noqis khun shakh nameshavad. Gene, ki sintezi globulini mazkurro nazorat mekunad, dar H- khromosoma joygir ast. Agar geni khromosomai duyumi zan globulinro mutadil sintez kunad, on goh bemori padid nameoyad. Dar zane, ki homili gemofiliya ast, hangomi hosil shudani hujayrahoi jinsi jufti khromosomahoi jinsi ba gametahoi gunogun meravand. Binobar in nisfi hujayratukhm H- khromosomai tagyiryofta dorad. Agar chunin hujayratukhmro nutfai doroi H- khromosoma bordor kunad, on goh dukhtarchai solim, vale misli modarash homili gemofiliya ba dunyo meoyad. Agar dar bordorkuni nutfai doroi Y-khromosoma shirkat varzad, on goh pisarchai giriftori gemofiliya tavallud meyobad, zero Y- khromosoma geni alleli nadorad. Hamin tavr, gemofiliya faqat dar jinsi mard zohir megardad, vale homili in bemori zanho meboshand. Azbaski nutfai doroi H- khromosoma bo ehtimoli barobar metavonad ham hujayratukhmi H- khromosomahoyash mutadil va ham H- khromosomahoyash tagyiryoftaro bordor kunad, on goh bo ehtimoli barobar mumkin ast pisarchai komilan solim yo giriftori gemofiliya tavallud yobad. Hamin tavr, bo ehtimoli barobar mumkin ast dukhtarchai komilan solim yo homili gemofilliya ba dunyo oyad. Dar navbati khud alomathoe, ki geni onho dar Y-khromosoma joygirand, faqat ba pisaron meguzarand, zero dukhtaron hej goh az padar Y-khromosomaro meros namegirand. Vale faqat dar mardho zohir gashtani yagon alomat manoi onro nadorad, ki geni mazkur dar Y-khromosoma joygir ast. Mas., chunin alomatho chun ovozi bariton, ovozi tenor, ovozi gafs faqat dar mardho vomekhurad. Genhoe, ki inkishofi in alomathoro nazorat mekunand, dar autosomho joygirand va ba darajai barobar chi az tarafi mardho va chi az tarafi zanho meros girifta meshavand, vale zuhuroti onho ba jins vobasta ast. Dar baze sharoit chunin alomatho metavonand dar jinsi muqobil qisman yo purra padid oyand. Bazan jins khususiyati zuhuroti allelro muayyan mekunad. CHunonchi, geni dar autosomaho mavjuda, ki boisi rekhtani mui sar megardad, dar mardho bartari doshta, dar zanho nuhufta ast.
Donistani navi merosgiri baroi muqarrar namudani paydoishi alomathoi mavridi omuzish dar nasl hatmist. Dar sharoiti tajriba navi merosgiriro dar hayvonot va rastani, odatan, tavassuti juftikunonii gunogun muayyan mekunand. Azbaski baroi odam chunin usul nomaqbul ast, navi merosgirii alomatho faqat bo rohi omuzishi nasab muqarrar karda meshavad. Qonuniyathoi zikryofta dar alomathoi monogenie, ki yak gen nazorat mekunad, ravshan mushohida meshavand. Vale dar organizmhoi olitashakkul va odam adadi chunin alomatho kam ast. Alomathoi onho beshtar zeri nazorati chand gen tashakkul meyoband, yane onho poligeni meboshand. Hususiyati merosigirii nishonahoi poligeni, az qabili qad, vazn, tobovari yo mayl ba bemorihoi gunogun, darajai fishori sharayoni va g. zeri tasiri mutaqobilai genhoi ziyode, ki dar tashakkuli onho shirkat mevarzand, muayyan karda meshavad. CHunonchi, ovozi khushu foram ba khususiyathoi sokhti qafasi sina, javfi bini, zabon, lab, quvvai mushakhoi nafas, hajmi shush vobasta ast. Dar ayni hol rushdi alomathoi poligeni ba tasiri muhiti zist niz vobastagi dorad. Vazni odami moil ba kharobi dar mavridi tagziyai barziyod mumkin ast az vazni odami moil ba farbehi ziyod shavad.
Bar khilofi I.-i khromosomi (ba istiloh mendeli), genhoe, ki dar sitoplazma (plazmogenho) dar KDN-i tashkilahoi sitoplazmavii hujayra (mitokhondriyaho dar eukariotho, mitokhondriyahoyu khloroplastho dar rastaniho va obsabzho, plazmidaho dar mikroorganizmho) voqe gashtaand, tajziya nameshavand va bayni hujayraho tasodufan taqsim megardand. Azbaski hujayratukhmi odam sitoplazma dorad va hajmi on az sitoplazmai nutfa qarib 85 hazor marotiba kalon ast, amalan hamai akhbori genetikii dar sitoplazma joygirshuda bo rohi modari intiqol meyobad.
Gunogunshaklii hayvonotu rastani dar rui Zamin ba tufayli I. mahfuz doshta meshavad. Vale odam hej goh noziri beparvoi zuhuroti I. dar fardhoi gunogun nest. Marhalai avvali faoliyati u oid ba tagyiri khususiyathoi irsi dar organizmho bo intikhob (seleksiya)-i hayvonotu rastanihoi mufid nigaronida shuda bud. Dertar baroi ruyondani organizmhoi dilkhoh usulhoi juftikunonii gunogun istifoda gashtand. Dar natija zothoi sermahsul va serhosili hayvonotu rastani ba vujud ovarda shudand. Olimon ba tagyir dodani moddai irsi (mutatsiya) qobiliyat doshtani baze omilhoro muqarrar namuda, ba ruyondani organizmhoi doroi khususiyathoi zaruri vusat bakhshidand. Vale peshrafti muhim dar in samt bo rushdi injeneriyai genetiki vobastagi dorad. On imkon medihad, ki organizmhoi doroi khususiyathoi muayyanro muvofiqi maqsad ba vujud ovarand, mas., mikroorganizmhoe, ki mahsuloti bahri khudashon nolozim, vale baroi odam zarur (gormoni rushdi odam, insulin va g.) hosil mekunand. Komyobihoi injeneriyai genetiki baroi peshgiri namudani bemorihoi irsi dar odam zaminai musoid faroham ovardand.