Partial digestion mapping of YAC C161. YAC C161 was partially digested, as specified in the Materials and Methods, and hybridized with a probe recognizing the left (ARS 1 Trp 1) vector arm. Lanes numbered 1 to 8, respectively, are undigested Mlu I cut,BssHII cut, Sfi I cut, Not I cut, Sal I cut, Nru I cut, and Sac II cut. This result indicates a large cluster of rare cutting sites located 130 kb from the left YAC vector arm. Other clusters of rare cutting sites are located 170 kb and 230 kb from this vector arm.