Multiple Choice
Which of the following enzyme-function matches is incorrect?
14. DNA Synthesis
Steps of DNA Replication
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The removal of the RNA primer and addition of DNA nucleotides to the 3' end of Okazaki fragments in its place is carried out by __________.
A
nuclease
B
primase
C
DNA polymerase III
D
ligase
E
DNA polymerase I
Verified step by step guidance1
Understand the role of RNA primers in DNA replication: RNA primers are short sequences that provide a starting point for DNA synthesis. They are necessary because DNA polymerases can only add nucleotides to an existing strand of DNA.
Identify the function of DNA polymerase I: DNA polymerase I is responsible for removing RNA primers from the lagging strand and replacing them with DNA nucleotides. This enzyme has both exonuclease activity, which removes the RNA primer, and polymerase activity, which adds DNA nucleotides.
Recognize the role of Okazaki fragments: During DNA replication, the lagging strand is synthesized in short segments called Okazaki fragments. Each fragment begins with an RNA primer that must be removed and replaced with DNA.
Differentiate between DNA polymerase I and DNA polymerase III: DNA polymerase III is primarily responsible for the synthesis of the leading strand and the elongation of Okazaki fragments. However, it does not remove RNA primers; this task is performed by DNA polymerase I.
Conclude that DNA polymerase I is the enzyme that removes RNA primers and adds DNA nucleotides to the 3' end of Okazaki fragments, completing the synthesis of the lagging strand.
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