题目内容

Which of the following statement is correct about DNA topoisomerase inE.coli:()

A. to catalyze the ligation of gaps in DNA double strands.
B. to release the supercoiled structure of DNA ahead of replication fork.
C. to break hydrogen bond and base stacking force and improve the extension activity of DNA polymerase.
D. to break phosphodiester bond of DNA and separate two strands of DNA.
E. to hydrolyze ATP and connect two strands of DNA.

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Which of the following statement is correct about the DNA replication in E. coli:()

A. One strand of DNA double helix is synthesized discontinuously.
B. Okazaki fragments are generated in this process.
C. RNA primer is needed.
D. Single-strand binding protein can prevent the unwinding of DNA double helix in the replication process.
E. DNA polymerase I are mainly responsible for DNA replication.

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DNA replication requires: (1) DNA polymerase III, (2) helicase, (3) DNA polymerase I, (4) DNA-directed RNA polymerase, (5) DNA ligase, the correct order of their participation is:()

A. 4,3,1,2,5
B. 2,3,4,1,5
C. 4,2,1,5,3
D. 4,2,1,3,5
E. 2,4,1,3,5

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The enzyme catalyzing the formation of phosphodiester bond between 5’phosphate group and the 3’hydroxyl in DNA is: ()

A. methyltransferase
B. ligase
C. primase
DNA pol I
E. terminal transferase

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The wrong statement about the semi-discontinuous synthesis of DNA is:()

A. Leading strand is synthesized continuously
B. Lagging strand is synthesized discontinuously
C. The discontinuously synthetic fragments are Okazaki fragments
D. Half of the leading strand as well as half of the lagging strand is discontinuously synthesized
E. Synthesis of lagging strand is later than the leading strand

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