Question

In biotechnology application, a selectable marker is incorporated in a plasmid
A. To increase its copy number
B. To increase the transformation efficiency
C. To eliminate the non transformants
D. To increase the expression of the gene of interest

Answer 1

Selectable markers is a gene which is required for the maintenance of the plasmid in the cell and apart from this, there is artificial selection where plasmid with appropriate marker can survive.

Complete answer:
First of all you should know what a selectable marker is. Selectable marker is a gene which is introduced in the cell to enable the selection of the transformed cells and these markers are also resistant to antibiotics.
For the artificial selection of transformants, a selectable marker is incorporated in a plasmid in biotechnology application where the transformants are selected with the help of this and non transformants get eliminated.
Since the selectable marker is resistance to antibiotics, non transformants will not grow in that media which contains antibiotics as they do not have antibiotic-resistance genes. But the transformants will be able to grow in the media containing antibiotics as they have antibiotic-resistance genes along with the desired gene. This way, non-transformants get eliminated.
If we look at options now:

Option A is To increase its copy number. Selectable marker is not incorporated to increase its copy number but it is incorporated to eliminate the non transformants. Therefore, this option is incorrect.
Option B is To increase the transformation efficiency. This is also incorrect as selectable markers are not incorporated to increase the transformation efficiency but it is incorporated to eliminate the non transformants.
Option C is To eliminate the non transformants. This option is correct as artificial selection is done where transformants are selected and non transformants are eliminated.
Option D is To increase the expression of the gene of interest. This is also incorrect as selectable marker is not incorporated to increase the expression of the gene of interest but it is incorporated to eliminate the non transformants.

Thus, the correct answer is option C i.e., To eliminate the non transformants.

Note:
Selectable marker is used in biotechnology application which is incorporated in a plasmid in order to select the transformants and eliminate the non transformants and these non transformants are unable to grow in the media containing antibiotics and therefore these are eliminated.