Understanding DNA Replication: The Importance of Proofreading
What does "proofreading" refer to with regard to DNA replication?
a. Proofreading allows DNA to fix errors that may occur during DNA replication.
b. Proofreading is the initial step of DNA replication.
c. Proofreading involves the synthesis of new DNA strands.
d. Proofreading prevents mutations in RNA transcription.
Answer:
Proofreading in DNA replication is a process where DNA polymerase corrects mistakes by ensuring the newly added base pairs correctly with the template strand, and removing any incorrect bases.
Explanation: Proofreading refers to a critical mechanism during DNA replication, where most of the mistakes introduced are promptly corrected. This function is performed by DNA polymerases that read the newly added base, ensuring that it pairs correctly with the template strand before adding the next one. Should an erroneous base have been added, the enzyme exhibits 3' exonuclease activity, cutting at the phosphodiester bond to remove the incorrect nucleotide, thus allowing the correct base to be inserted. This is essential for maintaining genetic fidelity.