Practice question

TE buffer, composed of Tris and EDTA, is standard for DNA storage. Tris (tris-hydroxymethyl-aminomethane) is a buffering agent with pKa 8.1, effective around pH 7.5-8.5. Its primary function is to maintain stable alkaline pH, typically 8.0, which minimizes acid-catalyzed depurination and keeps DNA deprotonated and soluble. Alkaline pH also inhibits acid-dependent nucleases and preserves phosphodiester backbone integrity. EDTA chelates divalent ions, while Tris does not precipitate DNA or chelate. Thus Tris provides pH homeostasis essential for long-term DNA integrity and enzymatic compatibility.