Why it is selectable marker prefer as antibiotic resistance gene?
Answers
Selectable marker genes are a vital part of most transformation protocols. They are delivered alongside the gene of interest, either on the same plasmid or on a separate plasmid. A wide range of selectable marker regimes is available and is particularly important in species where transformation efficiencies are low. Selectable marker genes can be categorized into those based on resistance genes that confer the ability to grow in the presence of toxic compounds such as antibiotics or herbicides which kill or otherwise compromise untransformed tissue (negative selection). Alternatively, a range of positive selection systems are available which provide transformed tissues with an enhanced ability to utilize, for example, an unusual carbohydrate or amino acid supply and thus enrich the culture for transformed tissue expressing the marker gene. Concerns about the environmental spread of selectable markers, particularly antibiotic resistance genes, from field-planted GM plants prompted the development of approaches to eliminate selectable markers. One concept is to co-transform with a gene of interest and a marker gene at nonlinked loci, thus the primary transformant contains both genes, but genetic segregation in the progeny plants allows identification of individuals lacking the marker but possessing the gene of interest. This concept can be augmented to include co-integrated marker and trait genes by incorporating a transposition system in the vector design. Thus, the marker gene can be separated from the gene of interest by transposition in later generations and then removed by segregation. Yet other approaches, such as cre/lox or flp/frt, use excision/recombination to physically remove selected sequences after transformation.