What are selectable markers? How are antibiotic resistance genes used as selectable markers?
Let’s begin with selectable
marker
What is a Selectable
marker in a vector?
Selectable marker is a
region or gene sequence (here for Antibiotic resistance) of the vector that
helps in selection of recombinant colonies that contain our gene of interest.
You can also watch our video on Selectable markers at the end of this post for easy understanding.
Let’s take an example
to understand this concept
An example is the use of pBR322, which has genes
that encodes polypeptides which confer resistance to ampicillin and
tetracycline antibiotics. That means a bacterium with this vector can grow both
tetracycline and ampicillin containing medium.
In the given example (figure above), we have
inserted our gene of interest in the tetracycline gene coding region. So that,
tetracycline resistance gene is no more functional. This process is called
insertional inactivation.
What is Insertional inactivation?
Inactivation of a gene upon insertion of another
gene within its gene sequence.
The inserted gene disrupts continuity of the gene
sequence, thereby making it inactive or non-functional.
recombinant colonies. Recombinant colonies with desired gene inserted at
tetracycline coding region can grow only in ampicillin containing medium,
whereas transformed colonies with unchanged vector can grow in both tetracycline
and ampicillin medium. We can select the
recombinant colonies by comparing the position of the colonies after replica
plating with the master plate. (Understand More on replica plating)
Watch
this 5-minute video for better understanding.
Thank you so much:)
