Molecular cloning factoid — In classic vaccine research, the gene coding for the VP1 capsid protein (a major antigenic protein in picornaviruses such as FMDV or poliovirus) was commonly cloned in which standard plasmid vector for expression/analysis?

Introduction / Context:
VP1 is a key capsid protein in several picornaviruses and an important antigenic target. Early molecular cloning studies frequently used widely available plasmids. Recognizing these classical vectors helps students interpret historic protocols and exam-style questions.

Given Data / Assumptions:

• pBR322 is a pioneering, medium-copy-number plasmid vector with ampicillin and tetracycline resistance markers.
• pUC series (pUC18/19) are later high-copy derivatives.
• pMB9 is an early plasmid with limited use compared with pBR322 for teaching examples.

Concept / Approach:
Many textbook problems and early studies reference pBR322 as the “standard” cloning vector used to insert viral genes like VP1 for subcloning, mapping, and expression in E. coli. While other vectors are certainly possible, pBR322 is the canonical answer in such classic MCQs about VP1 gene cloning from picornaviruses.

Step-by-Step Solution:

Verification / Alternative check:
Older literature and academic exercises often feature pBR322 for inserting viral capsid genes due to its availability and well-characterized restriction map.

Why Other Options Are Wrong:

• pMB9: historically important but less commonly cited in teaching for VP1 cloning.
• pUC18/pUC19: widely used later; the question’s classic framing usually expects pBR322.
• pBluescript: versatile but from a later generation and not the stereotypical “first-choice” historical vector.

Common Pitfalls:
Assuming the newest vector must be correct; exam questions often seek the historically famous pBR322 answer.

Final Answer:
pBR322.