Molecular Basis of Inheritance
DNA Replication
Cell divide hone se pehle apna saara DNA copy karta hai taaki har nayi cell ko poora set mile. Do strands khul jaate hain, aur har ek template ban kar naya matching strand banata hai.
DNA ek double helix hai: do strands jo base pairs se jude hote hain (A ke saath T, G ke saath C). Copy karne ke liye strands alag hote hain. Enzyme DNA polymerase har purana strand padhta hai aur matching bases jod kar naya partner strand banata hai.
Result: do double helix, har ek me ek purana strand aur ek naya strand. Isko semiconservative replication kehte hain, kyunki har naye molecule ka aadha hissa original se conserve hota hai.
Yahaan students galti karte hain
Replication semiconservative hai, conservative nahi. Har naya DNA ek original strand aur ek fresh strand rakhta hai. Students aksar sochte hain purana DNA poora bacha rehta hai aur bilkul naya copy scratch se banta hai. Galat: purane strands alag ho jaate hain, ek-ek har daughter molecule me.
Yaad rakho
Do strands andar, do hybrids baahar. Har ek me ek purana strand.
Exam me kaise kaam aata hai: Meselson-Stahl experiment ne semiconservative replication prove kiya, aur enzymes (helicase, polymerase, ligase) repeat questions hain.
Ye kahaan jud'ta hai
Copying me A ke saamne T aur G ke saamne C rehta hai, wahi base-pairing rule jisse cell ek gene ko RNA me padhta hai. Pairing ek baar seekho aur copying + transcription dono nikal aate hain.
Wahi rule gene kaise padhta hai →Ek quick check
DNA replication ko semiconservative isliye kehte hain kyunki har naye molecule me hota hai:
- ADo bilkul naye strands
- BEk purana strand aur ek naya strand
- CDo purane strands
- DSirf purane strand ke tukde