Explanation
The vector that can clone only a small fragment of DNA is a plasmid (Option C).
Plasmids are small, circular DNA molecules that can replicate independently from the chromosomal DNA in bacteria. They can be used as vectors for cloning and expressing genes of interest. Plasmids are versatile and can be easily manipulated in the laboratory, making them an excellent tool for genetic engineering. However, they have a limited carrying capacity and can only clone small fragments of DNA, usually up to a few thousand base pairs.
Option A (Bacterial Artificial Chromosome or BAC) and Option B (Yeast Artificial Chromosome or YAC) are both vectors that can clone much larger fragments of DNA, up to several hundred thousand base pairs or even more. BACs and YACs are commonly used in genomic research and large-scale DNA sequencing projects.
Option D (Cosmid) is a type of hybrid vector that combines the features of a plasmid and a phage. Cosmids can clone larger fragments of DNA than plasmids but not as large as BACs or YACs.
Therefore, the correct answer is Option C (Plasmid).
