Insert capacity of P1 cloning vectors Approximately what length of foreign DNA can be accommodated by a P1 cloning vector system?

Introduction / Context:
P1-based cloning systems were developed to handle larger genomic fragments than λ vectors, facilitating genomic library construction and physical mapping prior to BAC/PAC era dominance. Knowing approximate capacities guides vector choice for large-insert projects.

Given Data / Assumptions:

• P1 vectors package DNA using bacteriophage P1 functions.
• They accept substantially larger inserts than λ vectors.
• Different P1 derivatives (e.g., PACs) achieve even higher capacities, but the basic system accommodates around ~100 kbp.

Concept / Approach:
While λ replacement vectors peak around ~20–25 kb, P1 vectors support much larger inserts on the order of ~70–100 kb. PAC (P1-derived artificial chromosomes) can exceed this, but the question targets the canonical P1 range near 100 kbp.

Step-by-Step Solution:

Verification / Alternative check:
Standard references list P1 vectors in the ~70–100 kbp class; options provided include 100 kbp, which is consistent as an approximate capacity.

Why Other Options Are Wrong:

• 50 kbp is too low for the classic upper range of P1 systems.
• 20 or 10 kbp align more with plasmids/λ insertion vectors.
• 5 kbp is a small-insert plasmid domain.

Common Pitfalls:
Confusing P1 with λ or with much larger BACs (which can exceed 150 kbp); ensure the vector class matches the intended insert size.

Final Answer:
100 kbp