Question

which statements about error - correction by dna polymerase are correct? select all that apply.
\exonuclease\ is a logical term because the enzyme excises or \pulls out\ a nucleotide - specifically,
a nucleotide that isnt complementary to the base on the existing strand.
\proofreading\ is a logical term because the process is similar to what writers do when they check
their work and catch and correct their own misspellings or grammatical errors.
proofreading occurs after replication of the leading strand and lagging strand are complete - not
when the replisome is moving down the chromosome and the synthesis process is actively
underway.
the increase in accuracy brings the
aw\ rate of 1 mistake in every 10^5 bases added to 1 mistake
in every 10^7 bases added.

Explanation:

• For the first statement:
• DNA polymerase has an exonuclease activity. When a non - complementary nucleotide is added during DNA synthesis, the exonuclease activity of DNA polymerase can excise (remove) that incorrect nucleotide. So, the term “exonuclease” is a logical description of this function.
• For the second statement:
• Proofreading by DNA polymerase is similar to a writer checking their work. DNA polymerase checks the newly added nucleotides. If there is a mismatch (like a misspelling or grammatical error in writing), it corrects the error. So, the analogy for proofreading is logical.
• For the third statement:
• Proofreading occurs during DNA synthesis (when the replisome is moving along the chromosome and synthesis is in progress), not after the replication of the leading and lagging strands is complete. So, this statement is incorrect.
• For the fourth statement:
• The “raw” error rate of DNA polymerase (without proofreading) is about 1 mistake in \(10^{5}\) bases added. With proofreading (and other repair mechanisms), the error rate is reduced to about 1 mistake in \(10^{7}\) bases added.

Answer:

• A. “Exonuclease” is a logical term because the enzyme excises or “pulls out” a nucleotide—specifically, a nucleotide that isn't complementary to the base on the existing strand.
• B. “Proofreading” is a logical term because the process is similar to what writers do when they check their work and catch and correct their own misspellings or grammatical errors.
• D. The increase in accuracy brings the “raw” rate of 1 mistake in every \(10^{5}\) bases added to 1 mistake in every \(10^{7}\) bases added.