Sequence determination of restriction-endonuclease recognition sites.

the enzyme DpnII, produced by another strain of D. pneumoniae, recognizes the same sequence, but is inhibited by this same methylated base. The significance of the occurrence of modified nucleotides in eukaryotic DNA is not as yet understood, although a relationship between modification and gene expression has been proposed by several workers (Waalwijk & Flavell, 1978; Bird et al., 1979). By using appropriate restriction endonucleases a simple method can be used in order to probe and map the location of such modified nucleotides (Bird & Southern, 1978). Several pairs of restriction endonucleases would be useful for this purpose: MboI (GATC) (Gelinas et al., 1977) and Sau3A