GEN

GEN(yun. genos – mabdai nasl, paydoish), vohidi odditarini irsiyat. G. yak qismi molekulai kislotai dezoksiribonukleat – KDN (dar baze virusho kislotahoi ribonukleat – KRN) meboshad. Avvalin farziyai nazariyavii ba nasl guzashtani nishonahoi volidonro hanuz donishmandoni YUnoni Qadim Demokrit, Buqrot va dig. bayon karda budand. Ammo mavjudiyati omilhoi odditarini irsiro tabiatshinosi chekh Gregor Mendel s. 1865 isbot kardaast. Vay oid ba omilhoi irsii diskreti farziyae peshnihod namud, ki muvofiqi on har yake az chunin omilho inkishofi irsii muayyanro idora menamoyad va amaliyoti on ba dig. omilhoi irsi itoat namekunad. Mendel G.-horo ba du guruh – G.-hoi dominanti (padidahoyashon ba dig. G.-ho vobastagi nadorand) va G.-hoi retsessivi (onhoro G.-hoi dominanti furu menishonand) judo kard. S. 1909 olimi daniyagi U. Iogansan peshnihod namud, ki manbahoi irsii mazkurro G. nomand. S-hoi 1910 – 13 biologi amerikoi T. Morgan va shogirdoni u isbot kardand, ki G.-ho dar tashkilahoi makhsusi yadroi hujayraho – khromosomaho darozruya joygir meshavand va hamai G.-hoi khromosoma ba nasl guzashta, guruhi yagonai payvastaro tashkil medihand. Hamin tavr, dar har organizm adadi guruhhoi payvasta ba miqdori khromosomahoi hujayraho barobar ast. Inchunin malum gardid, ki khromosomaho metavonand juzhoi darozu kutohi khudro bo yakdigar ivaz kunand.
Bad az on ki s. 1899 olimi rus S. I. Korjinskiy va s. 1900 olimi gollandi de Friz dar sharoiti tabii tagyir yoftani G.-hoi judogona (mutatsiyaho)-ro kashf namudand va s-hoi 1925 – 28 tahti tasiri radiatsiya va moddahoi khimiyavi ba dast ovardani mutatsiyahoi suni muyassar gasht, baroi omukhtani tagyirpazirii G.-hoi judogona imkoniyat paydo shud. Dar barobari in oshkr gardid, ki G.-hoi judogona chun qismi yaklukht tahavvul meyoband. Ba hamin tariq, fikre ba miyon omad, ki G. hamchun vohidi oddii mavodi irsi dar asnoi tahavvul yaklukhtiro nigoh doshta, hangomi tasolub (krossingover) niz yaklukht intiqol meyobad. Ammo dere naguzashta malumote ba dast omadand, ki taqsimpazirii G.-horo dar jarayoni mutatsiya (tajribahoi A. S. Serebrovskiy va shogirdoni u N.P. Dubinin va dig. dar s.-hoi 1929 – 34) va dar vaqti muovizai juzhoi khromosomaho tasdiq namudand.
Bo vujudi komyobihoi nazarrasi tadqiqi G., sokhti khimiyavi va nihod (tabiat)-i fizikii on malum nabud. S. 1944 olimi amerikoi T. Eyveri oshkor kard, ki dar bakteriyaho alomathoi irsiro molekulahoi kislotai dezoksiribonukleat – KDN (nig. Kislotahoi nukleat) intiqol medihand. Vale, bo vujudi in, to okh. solhoi 40 olimon chi budani moddai irsiyatro namedonistand. Faqat s. 1953 badi az jonibi biologi amerikoi D. Uotson va fiziki anglis F. Krik kashf shudani sokht va khususiyati KDN isbot gardid, ki G.-ho dar molekulai KDN joy giriftaand. To in vaqt muqarrar shuda bud, ki dar G.-ho oid ba sokhti durusti safedahoi fermentie, ki tamomi taassuroti mavjudoti zindaro idora mekunand, nishonae hast va har G. yak qismati molekulai KDN-ro ishgol karda, tartibi dar zanjirhoi polipeptidii safedahoi fermenti joygir shudani aminokislotahoro ba kod medarorad, yane bo ramz intiqol medihad (nig. Kodi genetiki). Hislathoi ba kod daroranda ba qismathoi tarkibii molekulai KDN – nukleotidho mansuband. Ba har aminokislota se nukleotid, ki dar KDN pasi ham qaror dorand (ba nom triplet yo kodon), muvofiq meoyad. Hamin tavr, har G. az G.-i digar bo joygirii paihami ba hamin G. khosi nukleotidho farq mekunad. Dar natijai isboti tasavvurot roje ba asoshoi molekulavii tagyiroti nishonahoi nasli chun jarayoni taviz va idkholi ilovagii nukleotidhoi judogona (yo guruhi nukleotidho), joyivazkunii juzhoi G. (nig. Mutagenez) imkonpazir gardid. Sobit shud, ki tagyirot dar G. metavonad az tasiri radiatsiyai ionho, neytronho va g., inchunin payvasthoi khimiyavii mukhtalif (mutagenho) ba amal oyad. Dar sharoiti tabii har G. ba hisobi miyona dar yake az 100 haz. yo 1 mln fardi yak avlod tagyir meyobad. Istifodai mutagenhoi khimiyavi va shuoi surati tagyirot (mutatsiya)-ro dahho va sadho marotiba ziyod menamoyad. Baroi on ki nishonahoi irsi dar nasl mahfuz monand, boyad joygirii paihami nukleotidho dar G. tagyir nayobad. Dar aksi hol zeri tasiri G.-i tagyiryofta safedai sokhtu faoliyatash vayron hosil meshavad, yo on umuman ba vujud nameoyad. Dar barobari in, malum shud, ki tagyiri joygardoni yo tavizi hatto nuleotid dar G. boisi bagoyat tagyir yoftani khosiyathoi fermenti ramzshavanda megardad (in sababi rukh namudani bemorihoi irsi khohad shud).
S-hoi 60 a. 20 ba tufayli komyobihoi genetikai molekulavi tarkibi hamai nukleotidhoi segona, ki 20 aminokislotai asosiro ba kod medarorand, muayyan va qonuniyati amaliyoti G. oshkor karda shud. In tadqiqot isbot kard, ki hujayra metavonad molekulahoi KDN-ro chun noqili alomathoi genetiki afzun namoyad. Hosiyati mazkur replikatsiya nom girift.
S. 1961 olimoni fransavi F. YAakob va J. Mono oshkor kardand, ki G.-ho amalan yakkhela nabuda, du guruh meshavand: G.-hoi tarkibi (strukturi), ki hosil gashtani safedahoi khos (asosan fermentho)-ro idora mekunand va G.-hoi munazzim, ki faoliyati G.-hoi tarkibiro nazorat menamoyand.
Tamomi organizmhoi zindaro az rui nishonahoi sokhti yadroi hujayraho ba du guruh judo mekunand: eukariotho va prokariotho. Dar eukariotho, az jumla inson, har khromosoma yak molekulai darozi KDN dorad, ki ehtimol noqili chand hazor G. boshad. Dar prokariotho mushobehi khromosoma yagona molekulai KDN dar hujayra meboshad; vay safedahoi yadroro namekashonad va doroi sadho G. ast, ki ba darozii molekula paydarham joygir shudaand. Muqarrar gardidaast, ki ham dar eukariotho va ham dar prokariotho, gayr az G.-hoi khromasomaho, yak miqdor G.-ho dar molekulahoi kutohtari KDN (dar tashkilayu organellahoi hujayraho – mitokhondriyaho, khloroplastho va g. joy giriftaand) va plazmidaho (omilhoi jinsii bakteriyaho, muqobilat ba antibiotikho va g., ki dar sitoplazmai hujayra joygirand) vujud dorand. Onhoro G.-hoi sitoplazmavi menomand. Majmui G.-hoe, ki ba tarkibi khromosomahoi hujayrai eukariotho (yo khromosomai yagonai prokariotho) dokhil meshavand, sarfi nazar az G.-hoi protoplazmavi, bo taklifi biologi nemis G. Vinkler genomi hujayra nomida shudand. Majmui G.-hoi sitoplazmavi plazmon nom dorad.
Tamomi alomathoi irsie, ki ba organizmi mazkur khosand, az jumla G.-i khromosomaho va sitoplazma bo taklifi U. Iogansen (1909) genotipi hujayra nom giriftand. Genotip naqshai irsii inkishofi tamomi nishonahoi jinsi va fardii organizmro darbar megirad. Majmui nishonaho (ham zohiri va ham dokhili)-i organizmro fenotip menomand. Hujayrahoi jismi organizmhoi olitashakkul va inson az majmui duchandai khromosomaho (onho diploidi meboshand) iborat ast va az hamin sabab du genom dorand. Baze hujayrahoi jismi inson niz az majmui sechandai khromosomaho iboratand. Dar hujayrai uzvhoi tanosul (gametaho)-i organizmhoi diploidi yak genom mavjud ast, chunki dar jarayoni rushdi onho khromosomahoi juft ba hujayrahoi gunogun parokanda meshavand. Hangomi bordori genomi hujayrahoi jinsii padari va modari muttahid megardad. Odatan, genomi gametahoi padari va modari ba ham muvofiqand, vale dar organizmhoi duraga in muvofiqat vujud nadorad.
Muovizai (mubodilai) genho dar bayni organizmho dar natijai jarayoni gunoguni biologi ba amal meoyad. On qabl az hama dar vaqti tashakkuli hujayrahoi jinsi, hangomi ba amal omadani tasolub surat megirad. Dar hujayrahoi har organizm yak juft khromosoma vujud dorad, ki yake az padar, digare az modar girifta shudaast. Onho khromosomahoi yakkhela nom giriftaand. Dar in khromosomaho aksari mutlaqi G.-ho yaksonand (faqat G.-hoi mutatsiyador farq mekunand). Dar arafai rasishi hujayrahoi jinsi dar hamai organizmho taqsimoti makhsusi hujayraho (mayoz) ba amal meoyad. Dar yake az marhalahoi taqsimshavi khromosomahoi yakkhela ba hamdigar sakht aloqamand meshavand (in imkonpazir ast, chunki dastai G.-ho va muttasilii onho dar in khromosomaho asosan yakkhelaand) va bazan bayni hamdigar juzhoi daroz yo kutohi khudro ivaz mekunand. Dar hujayrahoi muqarrarii badan tasolub khele kam mushohida meshavad. Mikroorganizmho doroi tarzhoi digari muovizai alomathoi genetiki (ittiloi irsiyat) niz meboshand. Olimon sayu kushish dorand, ki onhoro dar organizmhoi olitashakkul niz tatbiq namoyand. Bo in roh inson metavonad G.-hoi dilkhohro ba jismi organizmhoi darkori jori va yo baraks, az majmui G.-hoi organizmi mazkur G.-hoi nodarkor yo zararnok, mas., bemoriovarro raf namuda, onhoro amalan kor farmoyad. Muovizai G.-ho ahamiyati muhimi tahavvuli dorad, chunki on baroi ba vujud omadani payvasthoi nav ba navi G.-hoi mutadil va tagyiryofta imkon medihad. Payvasthoi navin qobiliyati balandi hayoti doshta, baroi intikhobi tabii sozgor meboshand. Dar natija navhoi behtarini rastani, organizmho va mikroorganizmho intikhob meshavand. Ba hamin tariq, muovizai G.-ho tarzi muhimi ba dast ovardani navhoi tagyiryofta buda, dar tahavvulot mavqei asosi dorad.
Omuzishi muovizai G.-ho baroi darki sababi bisyor bemoriho nihoyat muhim ast. Dar jarayoni muovizai G.-ho mumkin alomathoi genetikii avvala tagyir yofta, ru ba bemori ovarand. In guftaho ba inson ham purra dakhl dorand. CHunonchi, oshkor shudaast, ki har odam mabdai irsii nishonahoi tagyiryoftaro haml mekunad. In mabda (G.-hoi tagyiryofta) metavonad dar khromosomahoi gunogun qaror girad, vale dar natijai dar bayni khromosomaho juft-juft ivaz shudani G.-ho chunin tarkibe ba amal khohad omad, ki hangomi on dar yak khromosoma yakbora chand G.-hoi illati paydo meshavand va in holat nuqsonhoi irsiro vaznintar megardonad. Az tarafi digar, dar natijai dar haddi G.-hoi muayyan kanda shudani khromosomaho sarehii akhbori genetikii dar G.-hoi mazkur ramzshuda tahrif meyobad va in boisi ba miyon omadani bemorii irsi niz megardad. Asosan chor tariqi muovizaho malum ast: krossingover (tasolub), konyugatsiya (mujomaat), transduksiya (intiqoli akhbori genetiki az hujayra ba hujayra) va transformatsiya (tahavvul yo tagyiri shakl).
Krossingover amali mamulest, ki muovizai G.-horo dar organizmhoi mutashakkil tamin menamoyad. Tarjumai tahtullafzii in istiloh tasolub (chalipo, salib) ast. Dar haqiqat hangomi tashakkuli hujayrahoi jinsi, vaqte ki khromosomahoi yakkhelai duchand juft-juft vasl meshavand va sokhti yagonaro, ki az chor rishta (lift)-i khromosoma iborat ast, tashkil medihand, bazan rishtaho az tasolub gusasta nugi onho bo tartibi nav payvast megardand. Dar natija az nav taqsim shudani G.-i khromosomaho ba amal meoyad. Juzhoi az yak yo chand G. iboratbudai khromosomaho bo qismhoi dig. khromosoma ivaz meshavand. Zimni mushohidai payvasthoi nav ba navi G.-ho dar nasli organizmhoi tasolubyofta T. Morgan qonunero kashf kard, ki baroi tahiyai kharitahoi genetiki asos gardid. u isbot namud, ki agar G.-ho dar khromosoma chi qadar az yakdigar dur istoda boshand, gusastan va minbad bo tartibi nav payvastani onho hamon qadar osontar megardad.
Dar asosi omuzishi ajdodi oilahoi judogona baroi bisyor G.-hoe niz, ki sababi bemorihoi irsii inson meshavand, tahiyai kharitahoi genetiki imkonpazir gardid. In malumot ahamiyati kaloni nazari va amali doshta, baroi darki imkoniyat va tedodi ehtimolii dar ajdodi volidayne, ki homilini yagon khel G. meboshand, yakbora paydo shudani du yo az in ziyodtar bemorii irsi imkon medihad. Badi isboti on ki dar asosi har yak khromosoma rishtai molekulai KDN meistad va on bo safedahoi khosai yadro payvast meshavad, ravshan gardid, ki omuzishi tabiati molekulavii tasolub pesh az hama boyad dar zaminai tagyiroti molekulahoi KDN surat girad. Malum gasht, ki ogozi tasolubro gusastani rishtahoi alohidai KDN tashkil medihand va dar natijai on qismati rishtahoi mazkur dar khromosomahoi gunogun raho yofta, bad bo tartibi nav bo yakdigar vasl meshavand.
Konyugatsiya khosi bakteriyahost. Dar onho muovizai G.-ho dar natijai konyugatsiya ba amal meoyad. Hangomi konyugatsiya du hujayrai bakteriyaho (narina va modina) bo yakdigar ba vositai kuprukcha (kuprukchai sitoplazmavi) vasl meshavand. Tavassuti in kuprukcha az hujayrai narina ba hujayrai modina yak qismati molekulai KDN intiqol meyobad; sipas ba molekulai KDN-i hujayrai modina vorid meshavad. Mavodi genetikii voridgashta khosiyati irsii bakteriyahoro tagyir medihad, ki in baroi tahavvuli onho ahamiyati kalon dorad.
Tariqi digari muovizai G.-ho dar mikroorganizmho bo yorii virusho (bakteriofagho) transduksiya (intiqol) kardani onho meboshad. S. 1952 olimon D. Lederberg va N. Zinder muayyan kardand, ki baze bakteriofagho metavonand qismathoi KDN-i hujayrahoi bakteriyahoro, ki dar on afzudaand, ishgol namuda, bad ba digar hujayraho kashonand. Qismati KDN, ki onro virus zabt karda, intiqol dodaast, chand G.-ro kashonda metavonad.
Hangomi transduksiyai nomakhsus andaruni pardai safedanoki zarrachahoi virusi asosan KDN-i bakteriyavi vorid meshavad va in guna zarrachaho KDN-i kheshro namebarand. Vale azbaski qobiliyati ba hujayrahoi bakteriyavi vaslgashtanro safedahoi pardai virus muqarrar menamoyand, zarrachaho khosiyati az sathi hujayrahoi bakteriyaho jabbida shudanro nigoh medorand va badi ba hujayraho ilhoq gardidan, andaruni bakteriyaho porachahoi molekulahoi KDN-i qablan zabtshudaro vorid menamoyand. Azbaski KDN-i khudi hamin virus baroi afzoishi zarrachahoi virusii nav kofi nest, siroyati virusi minbad inkishof nameyobad; dar hujayrahoi bakteriyavi boshad, qitahoi KDN-i az digar hujayrahoi bakteriyavi ilhoqgashta vujud dorand. Onho metavonand andaruni KDN vorid shuda, bo in roh muovizai G.-horo dar bayni bakteriyahoi gunogun tamin namoyand. Dar mavridi transduksiyai gayrimuqarrari virusho az har kadom qismati KDN-i bakteriyaho qitaero ishgol karda, bo in roh muovizai har G.-i bakteriyahoro tamin mesozand.
Hangomi transduksiyai makhsus KDN-i virus ba qitahoi baralo mahdudi KDN-i bakteriyaho ilhoq meshavad. Dar vaqti az tarkibi KDN-i bakteriyavi khorij shudani KDN-i virusi KDN-i okhiri G.-hoi bakteriyavii mujovirro hamrohi khud girifta, ba digar hujayrahoi bakteriyavi intiqol medihad.
S. 1961 ba olimoni amerikoi S. Merril, M. Geyer va J. Petrichchiani muyassar shud, ki in G.-horo bo yorii bakteriofagho ba dast ovarda, onhoro na ba hujayrahoi bakteriyavi, balki ba hujayrahoe, ki az jismi marizi irsii mubodilai angishtobho dar natijai ikhtiloli hazmi laktoza paydo shudaand, intiqol dihand. S. 1973 aynan hamin guna sanjishro olimoni avstraliyagi S. Doy va P. Gresshof bo hujayrai rastanihoe, ki dar muhiti doroi laktoza namesabzidand, ba roh mondand. Vale in rastaniho bad az tamos bo bakteriofaghoe, ki bo khud G.-hoi zaruriro hamrohi hujayrahoi bakteriyavi ovardaand, qobiliyati sabzish paydo kardand.
Tajribahoi har du guruhi muhaqqiqon nafaqat az on jihat shavqovarand, ki amalan mumkin budani transduksiyaro dar hujayrahoi organizmhoi darajai oli, inson va rastani nishon dodand, balki az on khusus ham maroqovarand, ki umumiyati biokhimiyavi doshtani reaksiyahoi hujayrahoi bakteriyaho, hayvonot va nabotot, inchunin bo yorii alomathoi genetikii begonai az hujayrahoi gunogunzod judokarda mumkin budani muolijai bemorihoi irsiro isbot namudand.
Tavizi G.-horo bo usuli odditar ham metavon ba jo ovard: KDN-ro az yagon hujayrai bakteriyaho judo va ba dig. hujayrai az jihati nishonahoi genetiki farqdoshta ilova mekunand. In hodisaro transformatsiya nomidaand. Avvalho hodisai transformatsiya dar pnevmokokkho, qalamchamikrobi khasbedagi va bakteriyai toifai gemofilis mushohida shuda bud, badho in ruykhat vase gardid. Transformatsiya dar namunai (modeli) hujayrahoi organizmhoi darajai oli niz tasvir yoftaast. Nakhustin bor ozmoishhoi zayl s. 1962 bo hujayrahoi odam va avv. s-hoi 70-umi a. 20 bo hujayrahoi rastani anjom yofta budand. Omuzishi jarayoni muovizai akhbori genetiki dar markazi diqqati genetikho va biokhimikho qaror dorad. Pajuhishhoi eshon bakhshi muhimi raviyai navi genetikai tajribi gardid, ki maqsadi on daryofti rohhoi muayyani tagyir dodani irsiyat, asosan bartaraf namudani bemorihoi irsii mukhtalif ast.
S. 1969 yak guruh olimon az KDN-i qalamchamikrobi ruda qismi tarkibii yake az G.-horo judo karda, andozai onro sanjidand va zeri mikroskopi elektroni aksbardori namudand. Pajuhishho nishon dodand, ki judo kardani G.-hoi fardi (onhoro dar oyanda metavon baroi bartaraf namudani bemorihoi irsi istifoda namud) amalan mumkin ast. Bahri in kor tahiyai usulhoi bo rohi suni hosil namudani G. ham khele muhim meboshad.
Dar bobati bo rohi suni ziyod kardani molekulahoi judogonai KDN, ki yakbora chand G.-ro intiqol medihand, tadqiqot idoma dorad. Ba olimon muyassar gardid, ki dar surati mavjud nabudani hujayraho molekulai kholisi KDN-i yake az bakteriofaghoro parvarida, qobiliyati zindagi doshtani in nuskhahoi sunii molekulahoi KDN-ro isbot namoyand. Bo yorii hamin guna molekulaho zarrahoi virusii siroyatovar daryoft karda shudand. Sonitar fermente oshkor shud, ki on KDN-ro dar molekulahoi KDN hosil mekunad. S. 1972 yakbora ba se laboratoriya muyassar gasht, ki bo yorii fermenti nomburda dar vujudi behujayra qismhoi tarkibii G.-horo, ki safedahoi gemoglobinii hayvonot va insonro ba ramz medarorand, hosil kunand. Muvofiqi aqidai genetikho har G.-i judogona nishonai fardii muayyanro idora menamoyad; zuhuroti G. ba tasiri beruni va dar kadom joi khromosoma qaror giriftani on vobasta nest. Baroi I. Mendel masalai «mujovirho»-i in yo on G. dar khromosoma fahmo nabud, chunki u dar borai joygiri va khosiyati G. malumot nadosht. S. 1913 dar borai tasiri harjoniba (pleyotropiya)-i G., yane dar borai on ki yak G. metavonad yakbora ba chand nishonaho tasir guzorad, tasavvurot ba miyon omad. Pajuhishhoi minbada onro isbot kardand. Muqarrar gardid, ki ba sababi tagyir yoftani faoliyati yagon ferment va yo vujud nadoshtani on, ravandi hosil gashtani payvasthoi khimiyavie, ki dar chand reaksiyahoi paydarham ishtirok mekunand, khalal meyobad. Sababgori nojurihoi sershumor dar mavridi bemorihoi irsii inson, ki dar natijai nuqsoni yagon G. ba miyon meoyand, mahz pleyotropiya meboshad. Hamzamon isbot shuda bud, ki bisyor nishonaho bo ishtiroki mahsuli chand G. surat megirad va amaliyoti yakjoyayu bonizomi onho inkishofi G.-horo tamin menamoyad (ba nom G.-hoi polimeri; nishonahoero, ki tahti nazorati onho surat megirand, nishonahoi miqdori menomand).
Ba hamin tariq, genetikai muosir dar tamomi organizmho mavjud budani G.-horo isbot namud va muqarrar kard, ki tamomi nishonahoi morfologi, taassuri fiziologi va biokhimiyavi dar onho zeri nazorati G.-ho jarayon megirand. Tarzi nihonii kori G.-ho mufassal omukhta shudaand. Bad az oshkor gardidani prinsiphoi bo ramz navishtani alomathoi irsi va purra manidod kardani ramzho, baroi judo va ba tavri suni hosil kardani G.-hoi fardi imkon paydo shud. Inchunin omukhtani tarzhoi gunoguni muovizai G.-ho dar bayni hujayrai organizm va organizmhoi mukhtalif muyassar gasht. CHi guna amali gardidani programmai genetiki hangomi rushdi hayvonot mufassal omukhta, murakkab budani asli in jarayon isbot shud. Muqarrar gasht, ki ba in jarayon omilhoi gunogun, az jumla omili muhit va doruhoi bisyor (antibiotikho, gormonho, sulfanilamidho va g.), ki G.-horo nuqsdor mekunand va yo ba kori onho khalal merasonand, tasir meguzorand. Hamin tavr, aniq namudani tarzi molekulavii amaliyoti G.-ho va tasiri doruhoi gunogun ba on baroi tahiyai usulhoi samarabakhshi tabobati bisyor bemoriho zaminai musoid faroham ovarda, omili muhimi roh nadodan ba khudmuolija meshavad.