Sequencing long DNA fragments cloned in bacteriophage M13 by using internal primers. The sequence analysis of a yeast DNA fragment containing a replication origin

In the ;shotgun' procedure for sequencing DNA, DNA fragments are cloned into a phage M13 vector and sequenced by using a flanking primer. In a variation of this procedure a longer DNA sequence is cloned into M13, the two single-stranded recombinants identified and sequenced by using a set of internal primers prepared by exonuclease III digestion of restriction fragments.