Cosmid Hot! Jun 2026

| Start | End | Feature Name | Description | | :--- | :--- | :--- | :--- | | 1 | 12 | | Lambda phage cohesive end site ($\cos L$); required for packaging DNA into phage particles. | | 250 | 1,100 | ori | Origin of replication (ColE1); allows the vector to replicate as a plasmid inside the bacterial host. | | 1,500 | 2,361 | AmpR | Beta-lactamase gene conferring resistance to ampicillin; used for selecting transformed bacteria. | | 2,400 | 2,800 | MCS | Multiple Cloning Site; contains unique restriction sites (e.g., BamHI, EcoRI, HindIII) for DNA insertion. | | 3,500 | 3,512 | cos site | Second lambda phage cohesive end site ($\cos R$); pairs with the first site to form the circular packaging signal. |

Using viral infection to deliver DNA is significantly more efficient than chemical transformation or electroporation, especially for large molecules. cosmid

In the field of molecular cloning, the cosmid represents a powerful hybrid vector that bridges the gap between standard plasmids and bacteriophage lambda (λ) systems. Developed in the late 1970s, cosmids were designed to address a key limitation of traditional plasmid vectors: their inability to efficiently clone DNA fragments larger than 10–15 kilobases (kb). | Start | End | Feature Name |