Cloningsvektorer

Cloningsvektorer are crucial tools in molecular biology, serving as vehicles to carry foreign DNA into a host cell for replication. These vectors are typically small, circular DNA molecules, often derived from plasmids or viruses, which possess specific features that enable their use in cloning procedures. A key characteristic of a cloning vector is its origin of replication, a DNA sequence that allows it to be copied independently by the host cell's machinery. Without an origin of replication, the foreign DNA would not be amplified.

Another essential component of a cloning vector is a selectable marker. This is usually a gene that confers resistance to a specific antibiotic. When the host cells are grown in a medium containing this antibiotic, only those cells that have successfully taken up the vector (and thus the selectable marker gene) will survive and proliferate. This allows researchers to easily identify and isolate the transformed cells from those that were not transformed.

Cloning vectors also contain unique restriction enzyme sites within a polylinker or multiple cloning site (MCS). The polylinker is a short DNA sequence with multiple recognition sites for different restriction enzymes. By cutting both the vector and the foreign DNA with the same restriction enzymes, complementary sticky or blunt ends are generated, facilitating the insertion of the foreign DNA into the vector through ligation. The choice of vector depends on the size of the DNA fragment to be cloned and the host organism used for replication, with plasmids being common for bacterial cloning and bacteriophages or cosmids for larger inserts.