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Biochemistry

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Purines, Pyrimidines and Nucleic Acid Metabolism

Question
53 out of 59
 

Okazaki fragments are formed in (AIPG 2011)



A Transcription

B dsDNA replication

C Single stranded DNA replication

D Translation

Ans. B dsDNA replication

a. Okazaki fragments are short fragments of newly synthesized DNA strands produced during double –stranded DNA replication .

b. All the known DNA polymerases can only synthesis DNA in one direction, the 5 ’to 3 ’direction.

c. As the strands separate, replication forks will be moving along one parental strand in the 3 ’to 5 ’direction and 5 ’to 3 ’on the other parental strand.

d. On the former, the leading strand DNA can be synthesized continuously in the 5 ’to 3 ’direction.

e. On the later, the lagging strand DNA synthesis can only occur when a stretch of single stranded DNA has been exposed and proceeds in the direction opposite to the movement of the replication fork (still 5 ’to 3).It is thus discontinuous and the series of fragments are then covalently linked by ligases to give a continuous strand. Such fragments were first observed by Okazaki using pulse labeling with radioactive thymidine.

f. In eukaryotes, Okazaki fragments are typically a few hundred nucleotides long, whereas in prokaryotes they may contain several thousands of nucleotides.

Purines, Pyrimidines and Nucleic Acid Metabolism Flashcard List

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