ABSTRACT
Genetic approaches towards understanding biological processes involve the use of genes, which upon expression cause immediate or conditional suppression of growth or eventual lethality. Such genes can be used as negative selection markers for eliminating a particular class of cells within an individual organism or a population. Negative selection markers are drawn from a pool of genes that can adversely affect the cells by interfering with normal growth and development. The first group of marker genes used in negative selection experiments were derived from the Agrobacterium T-DNA. In some cases a second gene which can neutralize or counteract the deleterious one, and restore the cells to normal is available. Before a negative selection gene is chosen for a particular application, several factors must be considered including the potency, level and target of action, the temporal or spatial controllability, transient expression before chromosomal integration, the conditional nature, the availability of restorer genes, and the cell-autonomous property of a given gene.
