The correct option is A Transformed cells
Selectable marker
Selectable marker is a gene in a vector that helps in the selection of transformants (host cells which have successfully taken up the foreign DNA) and non-transformants (cells which have not taken up the vector DNA).
For example, antibiotic resistance genes in the vector.
Antibiotic resistance gene as selectable marker
An antibiotic resistance gene in a vector helps in the selection of transformants in the following way:
● The vector containing antibiotic resistance gene as selectable markers enters the competent host cell where multiple copies of the vectors can be made.
● If the host cell gains resistance to a particular antibiotic then it indicates that transformation of the host cell with the vector is successful.
● Thus the presence of the selectable marker helps in identifying and eliminating non-transformants or non recombinant cells and selectively permitting the growth of transformants on a media containing the antibiotic.
Competent cells
Competent cells are the cells that can easily uptake the recombinant plasmid since their permeability is increased by various methods such as heat shock method.
Non-transformants
Non-transformants or non-recombinant cells are the cells that do not contain the recombinant DNA and the desired characteristics from the foreign gene cannot be represented by it on multiplication.
Final answer
(A) Transformed cells