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Vector properties

Vector is the carrier molecule which is used in genetic engineering in order to transfer our gene of interest into the host cell where it will be expressed. There are a lot of reasons for this action ranging from the study of gene expression to the production of needed proteins. Once the vector has accepted our DNA of interest, it becomes a recombinant molecule.

There are several characteristics which are important for the vector molecule in order for it to be efficient and worthy of using in genetic engineering.

Size matters

It is very important that vectors are small molecules (relatively speaking), because this way it will be a lot easier to insert them into the host cell, making the whole process of transformation (insertion of vector molecule into the competent host cell) a lot more efficient.

Reproducibility

It has to have an origin of replication. This is the region on the DNA that will be recognized by the protein complex responsible for the initiation of transcription. Without the origin of replication, our gene of interest will not be expressed in the host cell.

Selectable marker

The process of transformation in not very efficient (depending on the approach), so if we are working with the certain amount of bacterial cells that we want to transform, not all of them will accept our vector (and gene of interest). In fact, probably most of them won’t. How can we know which cells have our vector inside? It is simple - by using vectors with selectable markers which will help us distinguish the cells that have successfully transformed from the ones that haven’t. For example, we can use a certain vector molecule which has the gene for ampicillin resistance in it. Then we can grow the cells in the cell culturing medium which contains the ampicillin. Only the cells that are transformed successfully will be able to grow in the medium, because we will eliminate all of the other ones in a simple and effective way.

Target sites

How can we insert our gene of interest into the vector molecule? We can accomplish this by using restriction enzymes which cut the DNA at specific places. These places are called target sites and they are usually short, palindromic sequences compatible only with specific restriction enzymes. Once they cut the DNA, our gene of interest can be inserted and sealed in the vector molecule using the enzyme ligase, for example.