Q.41 A researcher wants to clone
3 DNA fragments of sizes
1.1 Mb,
0.097 Mb and
0.045 Mb.
The choice of the vectors for cloning each of the fragments are:
Introduction
In molecular biology, the selection of a suitable cloning vector depends mainly on the
size of the DNA fragment. Competitive examinations such as CSIR-NET, GATE,
DBT, and JAM often test this concept by asking candidates to match DNA fragment sizes with
appropriate cloning vectors.
Problem Statement
A researcher wants to clone three DNA fragments of sizes:
- 1.1 Mb
- 0.097 Mb (97 kb)
- 0.045 Mb (45 kb)
Cloning Capacity of Common Vectors
- Plasmids: up to 10 kb
- Bacteriophage λ: 10–20 kb
- Cosmid: 35–45 kb
- Bacteriophage P1: 70–100 kb
- Bacterial Artificial Chromosome (BAC): 100–300 kb
- Yeast Artificial Chromosome (YAC): 200 kb to >1 Mb
Step-by-Step Vector Selection
Fragment 1 (1.1 Mb): This very large DNA fragment can only be cloned using
a Yeast Artificial Chromosome (YAC).
Fragment 2 (0.097 Mb): This fragment (~97 kb) falls within the optimal range
of bacteriophage P1.
Fragment 3 (0.045 Mb): A fragment of ~45 kb is ideally cloned using a
cosmid.
Correct Answer
Option (B): Yeast artificial chromosome, bacteriophage P1, cosmid
Conclusion
Correct selection of cloning vectors is based on the insert size. In this problem,
a combination of YAC, bacteriophage P1, and cosmid provides the most
efficient and biologically accurate solution. Understanding vector capacity is essential
for solving cloning-based questions in competitive exams.
