Insert capacity question: λ gt10 and λ gt11 lambda vectors typically accommodate cloned DNA fragments up to about what size range?
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A6–7 kb
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B1–2 kb
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C40–44 kb
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D20–23 kb
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E≥100 kb
Answer
Correct Answer: 6–7 kb
Explanation
Introduction / Context:Different λ vectors have different insert capacities depending on whether they are insertion or replacement types. λ gt10 and λ gt11 are classic insertion/expression vectors with modest capacities, appropriate for cDNA clones and short genomic fragments rather than very large inserts.
Given Data / Assumptions:
- λ insertion vectors carry additional sequences, limiting insert size.
- Replacement vectors (other λ types) can accept larger inserts by replacing dispensable regions.
- Physical packaging constraints of lambda heads set upper and lower genome size limits for viable phage production.
Concept / Approach:Viable lambda particles require a genome within a defined size window. Insertion vectors like λ gt10/11 allow only several kilobases of foreign DNA (commonly about 6–7 kb, sometimes up to ~8–10 kb depending on the build), whereas replacement vectors can accept larger fragments up to roughly 20 kb or more.
Step-by-Step Solution:
Recall that λ gt10/11 are not high-capacity replacement vectors.Match to typical insertion vector capacity: around 6–7 kb.Eliminate ranges that are either too small or indicative of BAC/cosmid capacities.Verification / Alternative check:Historic manuals and vector maps list capacities for λ gt10/11 in the mid–single-digit kilobase range for reliable cloning and packaging.
Why Other Options Are Wrong:
- B: Too small; standard plasmids handle >1–2 kb easily.
- C/D: Reflect cosmid or λ replacement capacities, not λ gt10/11 insertion vectors.
- E: ≥100 kb indicates BAC/YAC scales, not lambda.
Common Pitfalls:Assuming all λ vectors accept very large inserts; capacity depends on vector architecture.
Final Answer:6–7 kb