In order to detect physical exchange of DNA segments, the cells resulting from recombination must be phenotypically different from the parents. Detection of Recombination Strains that lack some selectable characteristic that the recombinants will possess. For instance, the recipient may not be able to grow on a particular medium, and genetic recombinants are selected that can. Various kinds of selectable and nonselectable markers (such as drug resistance, nutritional requirements, and so on) may be used.In order to detect physical exchange of DNA segments, the cells resulting from recombination must be phenotypically different from the parents. Detection of Recombination Strains that lack some selectable characteristic that the recombinants will possess. For instance, the recipient may not be able to grow on a particular medium, and genetic recombinants are selected that can. Various kinds of selectable and nonselectable markers (such as drug resistance, nutritional requirements, and so on) may be used