Molecular Basis of Inheritance
DNA Polymerase
DNA polymerase wo enzyme hai jo naya DNA strand banata hai, ek-ek nucleotide existing strand ke 3' end par jodta hua.
Jab DNA khud ko copy karta hai, to kisi ko naye building blocks sahi order me jodne padte hain. Wahi DNA polymerase hai. Ye purane strand ko template ki tarah padhta hai aur har base match karta hai, A ke saath T aur G ke saath C, naye nucleotides ko ek badhti chain me jodta hai.
Ye sirf ek direction me bases jod sakta hai, 5' se 3'. Yahi ek rule wajah hai ki ek naya strand smoothly banta hai (leading strand) aur doosra chhote pieces me (lagging strand).
Yahaan students galti karte hain
Gene cloning me students aksar sochte hain ki inserted gene copy karne ke liye DNA polymerase bahar se daalte hain. Aisa nahi. Jab recombinant plasmid bacterium ke andar aa jaata hai, to bacterium ka apna DNA polymerase use copy karta hai, apne baaki DNA ke saath. Living host use karne ka yahi to point hai.
Yaad rakho
Ye bases 5' se 3' jodta hai, hamesha ek 3' end par.
Exam me kaise kaam aata hai: do favourites: 5' se 3' direction aur wo leading versus lagging strands kyun banata hai, aur cloning me host cell ka apna polymerase plasmid ko copy karna.
Ye kahaan jud'ta hai
Ek-direction ka rule ek limitation lagta hai, par yahi wajah hai ki replication ko primers, chhote Okazaki fragments, aur enzymes ki poori team chahiye. Ek single constraint poori machinery ka shape decide karta hai.
Ek quick check
DNA polymerase naye nucleotides kahaan jodta hai?
- A5' end par, 3' se 5' direction me
- B3' end par, 5' se 3' direction me
- CKisi bhi end par freely
- DSirf origin of replication par