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Biochemistry

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Purines, Pyrimidines and Nucleic Acid Metabolism

Question
31 out of 59
 

Gaps between segments of DNA produced by restriction enzyme are sealed by. (AIIMS May 2009)



A DNA ligase

B DNA polymerase

C DNA helicase

D DNA topoisomerase

Ans. A DNA ligase

a. Restriction enzymebreaks ssDNA or dsDNA at the restriction site.

b. In molecular biology, DNA ligase is a special type of ligase (EC 6.5.1.1) that can link together two DNA strands that have double-strand break (a break in both complementary strands of DNA).

c. The alternative, a single-strand break, is fixed by a different type of DNA ligase using the complementary strand as a template[citation needed] but still requires DNA ligase to create the final phosphodiester bond to fully repair the DNA.

d. DNA ligase has applications in both DNA repair and DNA replication (see Mammalian ligases).

e. In addition, DNA ligase has extensive use in molecular biology laboratories for Genetic recombination experiments.

Ligase mechanism

a. The mechanism of DNA ligase is to form two covalent phosphodiester bonds between 3' hydroxyl ends of one nucleotide with the 5' phosphate end of another.

b. ATP is required for the ligase reaction.

Purines, Pyrimidines and Nucleic Acid Metabolism Flashcard List

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