Why does a restriction enzyme not cut DNA randomly?Restriction enzyme DNA को random तरीके से क्यों नहीं काटता?
Answer and explanationउत्तर और व्याख्या
Correct answer:सही उत्तर: Because it recognizes a specific DNA recognition sequenceक्योंकि यह specific DNA recognition sequence को पहचानता है
The governing concept is sequence specificity of restriction enzymes. Each restriction enzyme has a particular three-dimensional active site that binds a defined recognition sequence, often a short palindromic DNA sequence. Only when the correct bases and local structure are present can the enzyme position the phosphodiester backbone properly and cleave at a characteristic site or distance. Consequently, DNA molecules are cut at predictable locations rather than at random positions. Being a protein does not prevent an enzyme from catalysing cleavage; in fact, the protein structure provides the catalytic activity. DNA does carry electrical charge, and water is a normal component of the reaction, so neither distractor explains the specificity.इसका मुख्य सिद्धांत restriction enzymes की sequence specificity है। प्रत्येक restriction enzyme की three-dimensional active site एक निश्चित recognition sequence से bind करती है। कई recognition sequences छोटी और palindromic होती हैं। जब सही bases और स्थानीय DNA structure उपस्थित होते हैं, तभी enzyme phosphodiester backbone को सही स्थिति में रखकर निश्चित site या निश्चित दूरी पर cleavage कर पाता है। इसी कारण DNA predictable locations पर कटता है, random स्थानों पर नहीं। Enzyme का protein होना cutting में बाधा नहीं है; protein की संरचना ही catalytic activity प्रदान करती है। DNA पर electrical charge होता है और reaction में पानी सामान्यतः उपस्थित रहता है, इसलिए ये दोनों विकल्प specificity का कारण नहीं हैं।
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