Why is ori compatibility important?

Correct answer: For plasmid replication

The direct answer is A: ori compatibility is needed for plasmid replication. Ori means origin of replication, the DNA region from which copying of a plasmid begins. Replication requires recognition by the host cell’s replication machinery. If the host cannot recognize or use that ori, the plasmid may not replicate, may be lost during cell division, or may be present at a very low and unstable copy number. Thus compatibility helps the plasmid make copies inside the selected host. Option A directly states this purpose. Option B, protein digestion, is not the function of an ori. Option C, water freezing, is unrelated to DNA replication. Option D, host pigment, does not determine whether the plasmid can copy itself. An exam cue is: ori answers the question “where and with which host machinery does plasmid copying begin?”