EMBL lambda replacement vectors: What insert size range can be accommodated by EMBL3 and EMBL4 lambda vectors?

Introduction / Context:
EMBL3 and EMBL4 are classic lambda replacement vectors designed to accept large DNA inserts by removing a central nonessential “stuffer” fragment. Knowing their insert capacity is important for planning genomic library construction and ensuring efficient packaging.

Given Data / Assumptions:

• Lambda packaging has size limits that define total recombinant genome length.
• Replacement vectors allow larger inserts than insertion vectors.
• EMBL3/EMBL4 are optimized for large genomic fragments.

Concept / Approach:
By replacing a stuffer region, EMBL vectors can accept inserts on the order of tens of kilobases while keeping the total DNA within the λ packaging window. Their advertised capacity commonly falls in the ~40 kb range, enabling robust genomic library coverage.

Step-by-Step Solution:

Verification / Alternative check:
Library construction manuals specify that EMBL replacement vectors handle inserts near 40 kb to obtain high-titer packaged phage.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing total genome length with insert length; forgetting to account for the remaining λ arms when calculating packaging size.

Final Answer:
40–44 kb.