CAG TRIPLET ANALYSIS IN FAMILIES WITH ANDROGEN INSENSITIVITY SYNDROMEBY CAPILLARY ELECTROPHORESIS IN POLYMER NETWORKS

The potential use of capillary zone electrophoresis in polymer network s (linear polymers above the entanglement threshold, added to the back ground electrolyte for sieving purposes) for analysis of DNA fragments amplified by a polymerase chain reaction, is shown. In typical runs, the capillary is filled with Tris-borate-EDTA buffer, at pH 8.3, conta ining 6% linear polyacrylamide as a dynamic sieving matrix. Such formu lations allow replenishing the capillary with fresh sieving solution w hen resolution decays after prolonged use (typically >30 injections pe r capillary are obtained). The DNA fragments are detected by their int rinsic absorbance at 254 nm. This system has been applied to the analy sis of CAG triplet polymorphism in families carrying the androgen inse nsitivity syndrome. While easy separation is obtained for fragments 13 9 base pairs (bp) and 160 bp (in families carrying a difference of 7 C AG repeats) even more difficult cases (such as those of families exhib iting fragments of 136 and 139 bp, thus differing by only one CAG repe at) are resolved with precision and diagnostic value.