Effect of DMSO, MgCl2, and primer concentrations on the yield of the N-avium/C-avium amplicon. A) One hundred picograms of B. avium chromosomal DNA was amplified in the presence of the DMSO, MgCl2, and primer concentrations indicated. B) One hundred twenty picograms of B. avium chromosomal DNA was amplified in the presence of 5% DMSO, 0.5 μM primers, and the MgCl2 concentration indicated. Other conditions were as described in the text.