Abstract: A process for isolating polynucleotides from aqueous mixtures containing both polynucleotides and polysaccharides is described. The process uses polymer gels containing --B(OH).sub.2 groups, and is useful in purifying deoxyribonucleic acid extracted from plants.

Abstract: Polynucleotides (particularly DNA) formed from a lysate of cellular material in a holding tube are separated from proteins in a two-phase solvent system formed by a mild oxidising perchlorate and an organic solvent such as chloroform. A powder of polymerised silica gel particles containing free aldehyde (CHO) or ketone (CO) groups which react with the proteins is added to the uppermost layer which is the layer containing the polynucleotides of interest and is allowed to descend through that layer thereby cleansing it of protein contaminants. The protein reacted silica gel particles lodge at the interface between the upper polynucleotide containing layer and the lower organic solvent layer which contains the bulk of the proteins and forms a solid disc adherent to the walls of the holding tube. The uppermost layer can thereafter be decanted for precipitation of the polynucleotides therein without contamination from the protein containing solvent layer.