Biochemistry : DNA Replication

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #21 : Nucleic Acid Synthesis

Why is topoisomerase I necessary during DNA replication?

Possible Answers:

It unwinds the DNA into two separate strands

It extends the existing chain of nucleotides one base at a time

It relieves the tension in the DNA caused by coiling and supercoiling

It creates an RNA primer to begin synthesis of the new strand of DNA

It joins together the Okazaki fragments formed in the lagging strand

Correct answer:

It relieves the tension in the DNA caused by coiling and supercoiling

Explanation:

Topoisomerase I functions as a stress reliever during DNA replication. DNA coils and supercoils, and without topoisomerase, the tension caused by this winding would not be able to dissipate.  

Example Question #22 : Nucleic Acid Synthesis

Which of the following is a correct match between prokaryotic DNA polymerase type and function?

Possible Answers:

DNA polymerase I - DNA repair

DNA polymerase II - DNA repair

DNA polymerase I - primary enzyme for DNA synthesis

DNA polymerase III - fills gaps in lagging strand

DNA polymerase II - primary enzyme for DNA synthesis

Correct answer:

DNA polymerase II - DNA repair

Explanation:

The correct matches between prokaryotic DNA polymerase type and function are:

DNA polymerase I - fills in gaps in lagging strand

DNA polymerase II - DNA repair

DNA polymerase III - primary enzyme for DNA synthesis

Note: The functions of certain DNA polymerases in eukaryotes and prokaryotes are not the same.

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