The estimation of the amount of sequence variation in samples of homologous DNA segments is considered. The data are assumed to have been obtained by restriction endonuclease digestion of the segments, from which the numbers and frequencies of the cleavage sites in the sample are determined. An estimator, p, of the proportion of sites that are polymorphic in the sample is derived without assumi...

REF Select, expert system software, has been developed to assist in the selection of optimal restriction endonucleases for restriction endonuclease fingerprinting (REF), a method for rapid and sensitive mutation screening of long DNA segments (1-2 kb). The REF method typically involves six separate digestions with up to two restriction endnonucleases used in each digestion. If done manually, pe...

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 us...

Although all Type II restriction endonucleases catalyze phosphodiester bond hydrolysis within or close to their DNA target sites, they form different oligomeric assemblies ranging from monomers, dimers, tetramers to higher order oligomers to generate a double strand break in DNA. Type IIP restriction endonuclease AgeI recognizes a palindromic sequence 5΄-A/CCGGT-3΄ and cuts it ('/' denotes the ...

We have performed restriction mapping of DNA molecules using restriction endonucleases in nanochannels with diameters of 100-200 nm. The location of the restriction reaction within the device is controlled by electrophoresis and diffusion of Mg2+ and EDTA. We have successfully used the restriction enzymes SmaI, SacI, and PacI, and have been able to measure the positions of restriction sites wit...

Type II restriction endonucleases usually recognize 4-6-base pair (bp) sites on DNA and cleave each site in a separate reaction. A few type II endonucleases have 8-bp recognition sites, but these seem unsuited for restriction, since their sites are rare on most DNA. Moreover, only one endonuclease that recognizes a target containing 8 bp has been examined to date, and this enzyme, SfiI, needs t...

Two new site-specific endonucleases, N1a III and N1a IV, have been isolated from Neisseria lactamica. N1a III recognizes the sequence, CATG, and cleaves 3' of the sequence to produce a four base 3' extension. N1a IV recognizes the sequence, GGNNCC, and cleaves between the two N's to produce blunt ended fragments.

Restriction and modification are two opposing activities that are used to protect bacteria from cellular invasion by DNA (e.g. bacteriophage infection). Restriction activity involves cleavage of the DNA; while modification activity is the mechanism used to "mark" host DNA and involves DNA methylation. The study of Type I restriction enzymes has often been seen as an esoteric exercise and this ...

The clastogenic ability of the restriction endonucleases (MspI, HpaII and HaeIII) in germinating seeds of reconstructed barley karyotype was assessed. An effective induction of chromosomal aberrations after restrictase treatment was observed. The frequency, types and cell-cycle dependence of the observed abnormalities are discussed in relation to the distinct characteristics of the enzymes and ...

In the past seven to eight years we have witnessed the development of a new DNA technology that has fundamentally altered our approach to modern genetics. The basic ingredients of this new technology are the cleavage-site-specific restriction enzymes: a special class of bacterial endonucleases that can recognize specific nucleotide sequences in duplex DNA and produce double-stranded cleavages. ...