In order to take advantage of non-radioactive methods, we have develop
ed two plasmids (p lambda LE and p lambda RE) for mapping restriction
sites of long inserts cloned in phage lambda vectors. These plasmids a
re constructed by cloning the left 402-bp and right 560-bp phage lambd
a genome ends, respectively. To map restriction sites, the cloned sequ
ences in p lambda LE and p lambda RE are labeled with digoxygenin and
hybridized to partially digested lambda DNA. The ladder of bands detec
ted with these probes can be used to construct restriction maps in the
same way as those obtained using radioactively labeled cos complement
ary oligodeoxyribonucleotides [Rackwitz et al., Gene 30 (1984) 195-200
].