Definitions for "Selectable marker"
A mutation that confers a phenotype on a cell such that when grown on a certain medium only those cells with the mutation will grow. For example, the mutation rpsL1 makes cells resistant to the antibiotic streptomycin -- when grown on medium with streptomycin rpsL1 mutants will grow but rpsL+ cells will die.
A gene carried by a vector and conferring a recognizable characteristic on a cell containing the vector or a recombinant DNA molecule derived from it.
a gene inserted into a cell or organism to allow the modified form to be selectively amplified while unmodified organisms are eliminated