Lambda gt10 vs. lambda gt11 — Which statement correctly distinguishes these two λ vectors used in cloning and expression?

Introduction / Context:
Classic λ vectors differ in purpose: some are optimized for insert capacity and library construction, while others enable expression screening. λ gt10 and λ gt11 exemplify this split, and recognizing their roles prevents misapplication during library screening or expression cloning.

Given Data / Assumptions:

• λ gt11 carries lacZ elements to permit expression of inserted sequences as fusion proteins.
• λ gt10 is used primarily for cloning (replacement) rather than expression screening.
• Both are lambda phage derivatives, not plasmids or cosmids.

Concept / Approach:
Expression vectors (like λ gt11) allow antigenic screening of plaques using antibodies against expressed fusion proteins. Replacement vectors (like λ gt10) maximize insert capacity by replacing dispensable lambda regions with foreign DNA, facilitating genomic library construction without necessarily expressing inserts.

Step-by-Step Solution:

Verification / Alternative check:
Historic manuals for expression screening protocols (immunoscreening) reference λ gt11 specifically; mapping guides categorize λ gt10 as a high-capacity cloning vector.

Why Other Options Are Wrong:

• B/D: Invert or deny expression capability of λ gt11.
• C: Neither is a cosmid; both are phage λ derivatives.
• E: Blue–white screening is a plasmid/phagemid trait (e.g., pUC/M13), not the primary feature of λ gt10.

Common Pitfalls:
Assuming any lacZ-related screening equates to blue–white colony selection; plaque immunoscreening in λ gt11 is a different methodology.

Final Answer:
λ gt11 is an expression vector that enables lacZ fusion expression, whereas λ gt10 is a cloning (replacement) vector