Vectorette PCR of pAL301. (A) Schematic representation of vectorette PCR showing location of anchor-F primer (UMHis3SK-F, Table 1). Note that the primer ‘bubble-amplify’ only hybridizes to the complement of the top strand of the vectorette bubble, and therefore can only be amplified after DNA synthesis (dotted lines) has been extended from the anchor primer. (B) Schematic representation showing approximate locations of internal primers. Primer sequences are shown in Table 1 designated UMHis3SK-X, where X refers to the primer shown here (F, G or H). Gel showing hemi-nested PCR of the product derived from PCR with the primers ‘anchor F’ and ‘bubble-amplify’. (C) Relevant sequence of vectorette clones. The sequence of the vectorette bubble primers are shown in italics, with the AGCT of the HindIII (H) site used for ligation of the bubble primers underlined.