QONUNI YAKUMI MENDEL – QONUNI HAMSHAKLII NASLHOI YAKUMI GIBRIDI

QONUNHOI MENDEL: Qonunhoi merosguzorii alomathoi irsiro G.Mendel kashf namuda, onhoro dar maqolai «Tajriba dar rastanihoi gibridi» chop menamoyad va onho bo nomi qonunhoi Mendel malumand. Badi az jonibi genetiki gollandi G.De-Friz, botaniki olmoni K.Korrens va genetiki avstriyagi E.CHermak takroran kashf shudani in qonunho, genetika hamchun fan dar borai irsiyat va tagyirpaziri tashakkul yoft va taraqqi kard. Malum gardid, ki qonunhoi Mendel kharakteri umumi dorand va baroi genhoi alleli, ki dar khromosomahoi gunoguni gomologi joygirand, khos meboshand.

Baroi malum gardidani qonuni hamshaklii naslhoi yakumi gibridi Mendel tajribai khudro dar duragahoi monogibridii rastanii nakhud guzarond. Duraga kardani du organizmro duragakuni (gibridkunoni) menomand. Naslero, ki az du fardi irsiyatashon gunogun paydo shudaast, duraga (gib-rid) menomand. Duragakunii monogibridi gufta, duraga-kuniero menomand, ki agar volidon az hamdigar bo yak juftialomati mukholif (alternativi) farq kunand. CHunin duragakuni imkon medihad dar naslhoi payiham paydoshuda qonuniyati ba meros guzoshtani yak alomat, ki bo yak jufti allelho vobastagi dorad, omukhta shavad. Masalan, alomati rangi zardu sabzi donahoi nakhud, ki ba ham mukholifand.

Digar alomathoi volidoni duragashuda ba etibor girifta nameshavand. Agar rastanii nakhudi donai zard va sabzdorro bo ham duraga kunem, dar natija donahoi naslhoi yakumi gibridi zard meshavand. CHunin natijaro dar duragakunii rastanihoi nakhudi donaashon hamvor va purchin niz didan mumkin ast. Dar nasli yakumi gibridhoi paydoshuda hamai donaho hamvorand. Hamin tavr, dar gibridhoi nasli yakum az jufti alomathoi bo ham mukholif faqat yake az onho zohir shuda, digarash inkishof nameyobad. G.Mendel on alomathoero, ki dar nasli yakum zohir gardidaand, dominant nomid. Alomatero, ki dar nasli yakum zohir shuda, inkishofi alomati digarro pakhsh mekunad, dominant nom dorad (az kalimai lotinii dominantus – bartari doshta, yo golib). Alomate, ki zohir nashud, alomati resessivi menomand (az kalimai lotinii recessiv – poyonnishin yo maglub). Alomati dominanti (golib) bo harfi «A»-i kalon, vale alomati resessivi (maglubshuda) bo harfi «a»-khurd ifoda karda meshavad.

Rastanihoe, ki Mendel baroi tajriba istifoda kardaast, ba khathoi sofi gunogun mansub budand va baroi hamin dar naslhoi pai ham paydoshudai onho alomathoi irsi betagyir memonand. Az in jost, ki allelhoi genii in rastaniho yakkhelaand. Hamin tavr, malum megardad, ki dar genotipi in organizmho (zigota) dutoi genhoi alleli yakkhela mavjud buda, paydarhamii nukleotidhoi genashon niz monandand. CHunin organizmhoro gomozigoti menomand. Organizmhoi gomozigoti dominanti (AA), (VV) va resessivi (aa), (vv) meshavand. Agar allelhoi geni, az jumla, paydar-hamii nukletidho yakkhela naboshand, on goh yak allel dominanti, vale digarash resessivi (Aa, Vv) meshavad, ki onhoro organizmhoi geterozigoti (gunogunshakl) menomand.

Qonuni hamshaklii naslhoi gibridii yakumro qonuni yakumi G.Mendel menomand. On bazan qonuni dominanti niz nomida meshavad. CHunki dar nasli yakum hamai fardho alomati yakzayl zohir mekunand. Hamin tariq, in qonunro chunin tarif dodan mumkin ast: duragakunii du organizmi doroi khathoi sofi gunogun (gomozigoti), ki bo yak juft alomathoi mukholif az hamdigar farq mekunand va dar nasli yakum naslhoi gibridi (G1) monand buda, yake az alomathoi volidon zohir megardad, qonuni hamshaklii naslhoi yakumi gibridi meboshad.

Dominanti nopurra

Dar organizmhoi geterozigoti (Aa) geni dominanti hamesha qobiliyati pakhsh kardani geni resessiviro nadorad. Dar bisyor mavridho dar duragahoi nasli yakum (G1) na geni dominanti va na resessivi purra zohir nameshavand. Dar natija duragahoi nasli yakum (G1) kharakteri miyona zohir menamoyand va dar onho hissae az genhoi dominanti va resessivi dida meshavad.

Guftan joiz ast, ki dar duragahoi nasli yakum monandi  ba vujud meoyad. Masalan, az duraga kardani gulhoi rastanii shomusahari gulash surkh (AA) va gulash safed (aa) dar nasli yakum (G1) rangi gulho gulobi (bunafsh) meshavand, yane rangi miyonai (Aa) bayni ranghoi surkh va safed paydo shuda, ranghoi hamai naslhoi G1 yakrang memonand. Baroi hamin, qonuni yakumi Mendel na qonuni dominanti, balki qonuni hamshaklii naslhoi gibridi nom dorad (rasmi 9.1). Dominanti nopurra dar tabiat hodisai vase pahnshuda buda, dar omuzishi sokhti parhoi parrandagon, rangi pashmi gov va gusfandon, alomathoi biokhimiyavi dar inson dida meshavad.

Serallelizm

To hol mo misolhoero dida baromadem, ki har gen az dualleli geni, yake dominant (A) va digare resessivi (a), iborat ast. In du holati gen dar natijai mutatsiya paydo meshavad. Vale mutatsiya (ivaz va nest shudani qismhoi nukleotidhoi molekulai KDN) metavonad dar qismhoi gunoguni gen, dar hujayrahoi jinshoyash gunoguni yak organizm ba amal oyad. Dar natija chand alleli yak gen paydo shuda, onho alomathoi gunogunro nazorat mekunand. Geni (A) dar natijai mutatsiya chunin holatro megirad: a1, a2, a3, a4. Geni (V), ki dar digar joyi (lokus) khromosoma joygir ast, ba holathoi v1, v2, v3……vn va gayra sohib meshavad.

CHunin holati payiham paydo shudani allelhoi yak genrohodisai serallelizm menomand va on dar olami zinda vomekhurad. Masalan, dar magasi drozofil silsilai allelhoi geni rangi chashm, ki az 12 qism iboratand, az rangi surkh to rangi safedro darbar megirad. Dar khargushon ham silsilai serallelizmi rangi muina duchor meoyad: rangi yaklukhti siyoh, khokistarrang (shinshila), himoloi va safed (albinos).

Dar khargushoni himoloi dar zaminai rangi safed, nugi gushho, dum va fuk siyoh ast. Albinosho az sababi sintez nashudani pigment berangand (rasmi 9.2). Azoi in silsilai alleli nisbati yakdigar dar holathoi gunoguni dominantiyu resessivi buda, geni rangi siyoh nisbat ba digar rangho dominanti ast. Alleli geni khargushi rangash himoloi nisbat ba geni khargushi rangash safed dominanti buda, nisbat ba khokistarrang resessivi ast. Inkishofi in se shakli rang ba se alleli gunogun vobastagi dorad va dar yak joy (lokus) voqe gashtaand.

Ba etibor giriftan lozim ast, ki dar genotipi organizmhoi diploidi faqat du geni silsilai alleli joygirand. Boqimondai allelhoi in gen dar shakli juft-juft yakjoyashavi dar genotipi fardhoi digari hamin namud vomekhurand. Hamin tavr, serallelizm gunogunshaklii genofond meboshad. (Genofond majmui hamai shaklhoi har yak gen buda, dar tarkibi genotiphoi guruhhoi fardi yo namudi joy giriftaand).

Hamin tavr, genofond alomati fardi nabuda, balki alomati namudi ast. Dar inson niz hodisai serallelizm baroi bisyor genho malumand. Masalan, ba meros guzashtani guruhi khuni AVO, shaklhoi gunoguni fermentho, antitelaho va bisyor safedaho mavjudand, ki tabiati serallelizm dorand. Mavjud budani allelhoi gunoguni yak gen dar genofond alomati muayyansozanda va nodiri irsiyati har yak fard ast.