What will happen if a vector ori does not work in a host?

Correct answer: Plasmid will not replicate stably

The direct answer is A: the plasmid will not replicate stably. An ori, or origin of replication, is the DNA region from which a vector is copied inside a host. The ori must be recognised by the host’s replication machinery. Step by step: first, the vector enters the host; second, the host must recognise its ori; third, replication begins and copies are maintained. If the ori does not function in that host, new vector copies are not made properly. As the host divides, the vector may be lost, so stable maintenance and expression cannot be expected. Option A is correct because it directly describes this loss of replication and maintenance. Option B is wrong because an ori defect does not make a protein digest immediately; protein degradation is a different process. Option C is biologically meaningless: a host does not become a leaf because of vector replication. Option D is wrong because antibiotic production is not an automatic result of an inactive ori; an antibiotic-resistance marker may help selection only if the vector is maintained. Memory cue: ori means “origin of replication”; without a working origin, the vector cannot reliably stay and multiply.