Final answer:
The mismatch repair system distinguishes the new strand from the parental strand by recognizing the methylation pattern: the parental strand is methylated, while the new strand is initially unmethylated, allowing for the removal of incorrect nucleotides from the new strand only. The correct answer is a. It must be able to distinguish the newly-made strand from the parental strand.
Step-by-step explanation:
In order to correct errors during DNA replication, the mismatch repair system must be able to distinguish the newly synthesized DNA strand from the parental DNA strand. This is necessary because the system needs to remove the incorrect nucleotide from the new strand and replace it with the correct one. The mismatch repair mechanism depends on recognizing differences in methylation between the old and new strands. Specifically, in bacteria like E. coli, immediately after DNA replication, the parental strand is methylated, while the newly synthesized strand is not yet methylated. This difference allows repair enzymes to identify and excise the incorrect bases only on the new, unmethylated strand.
Therefore, the correct answer to the question is: a. It must be able to distinguish the newly-made strand from the parental strand. This distinction is typically based on the methylation status of DNA strands, with the parental strand being methylated and the new strand being initially unmethylated. Over time, methylation enzymes will methylate the new strand as well, but the mismatch repair system acts during the window when this distinction is apparent.