BiotechKhaga · Class 6-8
DNA, gene aur chromosome: jeevan ki kitaab, aur kismon ka pustakalaya
Meera ke gaon mein is saal baadh aayi. Chacha ke khet ki ek kism ka chawal do hafte dooba rehkar bhi bach gaya, par padosi ki doosri kism teen din mein sad gayi — jabki dono 'chawal' hain. Meera ne dadi se poocha, 'Farak kahan likha hai?'
Socho pehle… phir dekho jawab
Meera ko laga farak mitti mein hoga. Uski science teacher Sunita ma'am ne bataya, 'Dono ki cells ke andar — DNA mein. DNA nirdeshon ki kitaab hai, gene uske adhyay, aur chromosome woh bandle jinme kitaab mudi rehti hai. Baadh jhelne wali kism ke ek gene mein woh nirdesh hai jo doosri mein nahi.'
Ma'am ne Meera ki copy pe ek ghumaavdaar seedhi banayi. 'DNA (deoxyribonucleic acid) har cell ke nucleus mein ek bahut lamba, dohri seedhi (double helix) jaisa ghuma hua anu hai. Uspar chaar akshar (A, T, G, C) ek kram mein lage hain; is kram mein hi nirdesh likhe hain.' Phir dhaan ke patte ki taraf ishaara kiya, 'Gene = DNA ka ek tukda jo ek kaam ka nirdesh deta hai, jaise patte ka hara rang banane wala protein. Chromosome = DNA ka mud kar bana bandle; insaan ki har cell mein 46 (23 jode), paudhon mein kism ke hisaab se alag.' Har cell ka DNA seedha karo toh lagbhag do metre — phir bhi woh nucleus mein kas kar muda rehta hai.
'Par yeh kitaab paudhe se beej tak kaise jaati hai?' Meera ne poocha. 'Jab cell banti hai, DNA apni poori nakal banata hai, isliye har nayi cell ke paas poori kitaab hoti hai. Beej mein nar (paraag) aur maada (beejand) ka DNA milta hai — aadha-aadha — isliye santaan maa-baap dono jaisi par bilkul ek jaisi nahi. Yahi variation hai.' Meera ko yaad aaya ki dadi har saal sabse acche paudhe ka beej alag rakhti hain. 'Haan,' ma'am boli, 'yahi kisaan ke chunne ka aadhaar hai: jo paudha is baarish mein behtar nikla, uska beej agle saal.'
Meera boli, 'Toh sab log sabse acchi nayi kism bo lein!' Ma'am ne samjhaya, 'Har desi kism (landrace) peedhiyon ke chunaav se bani ek alag kitaab hai — baadh, sookha, namak wali mitti, kisi rog ke liye. Jab sab kisaan ek hi nayi kism bote hain, purani kitaabein bone wale nahi bachte, aur unke gene hamesha ke liye kho sakte hain. Isliye do tareeke: kisaan khet mein bote rahein (in-situ) aur beej-bank thande kamron mein rakhe (ex-situ).' Meera ne apni dadi ki purani dhaan ki potli ko school ke 'beej-mela' mein rakha — 'is kitaab ko padhne wala koi toh ho.'
Ghar lautte hue dadi ne bargad ke neeche ek purani kahani sunayi. Chandogya Upanishad (6.12) mein Uddalaka apne bete Shvetaketu se bargad ka beej todne ko kehte hain — 'kya dikhta hai?' 'Kuch nahi.' — 'jo sookshm tumhe nahi dikhta, usi se yeh vishaal bargad khada hai.' Hazaaron saal pehle ki yeh baat aaj DNA ke baare mein bhi utni hi sach lagti hai: ek vyakhya yahi hai.
Tum Meera hoti toh gaon ki purani kismon ki kitaabein kaise bachaati?
Humne kya kiya :- Baadh jhelne wale aur na jhelne wale chawal ka farak DNA, gene aur chromosome tak dhoondha.
Isse kya hua :- Samjhe ki har kism ek alag kitaab hai, variation kisaan ke chunaav ka aadhaar hai, aur beej bachaane ke do raaste hain — khet aur bank.
Ghar pe try karo
Ek lambi kaagaz ki patti par A, T, G, C ko kisi bhi kram mein 30 baar likho — yeh tumhara 'gene' hai. Dost se kaho woh ek akshar badal de. Ab milao: kitne akshar alag? Yahi variation hai. Phir rasoi ke 5 alag beej ki potliyaan banao, har par naam-taareekh — tumhara ex-situ beej-bank.
Wow!
Tumhari har cell ka DNA seedha karo toh lagbhag do metre — aur woh nucleus ke andar itna kas kar muda hai ki 46 chromosome ek bindu jitni jagah mein aa jaate hain!
3 sawaal
- Gene kya hai?
Jawab dekho
DNA ka ek tukda jo ek kaam ka nirdesh deta hai. Gene DNA ka woh hissa hai jo ek protein ya ek gun ka nirdesh rakhta hai.
- Santaan maa-baap jaisi par bilkul ek jaisi kyun nahi hoti?
Jawab dekho
Nar aur maada ka aadha-aadha DNA milta hai, isliye naya mel banta hai. Beej ya bachche mein dono ka DNA aadha-aadha milta hai — yahi variation ka srot hai.
- In-situ sanrakshan ka matlab?
Jawab dekho
Kism ko uske apne khet/ilaake mein bote rehna. In-situ = apni jagah par; ex-situ = beej-bank jaise bahar ki jagah par.
NCERT se jodo: NCERT Class 8 Science — cell: nucleus aur chromosome; Class 8 Science — reproduction in animals; Class 10 ka heredity wala vichar (idea in words)