Practice question

DNase I hydrolyzes phosphodiester bonds in extracellular DNA, fragmenting it to oligonucleotides unable to transform cells. Transformation dependence on intact naked DNA makes it uniquely sensitive to DNase treatment, while conjugation requires pilus contact and protected single-strand transfer through secretion channel, and transduction packages DNA inside phage capsid shielding it from nuclease. Lederberg and Tatum used DNase resistance to distinguish conjugation from transformation. Experimentally, loss of recombinant formation after DNase addition confirms transformation mechanism versus other horizontal transfer modes in microbial genetics.