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In view of the importance of DNA polymorphisms, how to detect a large number of polymorphisms quickly from genomic DNA has become a topic of discussion in considering the accuracy of forensic research. "Genome Scanning" is defined as a high-speed scan to simultaneously detect signals from many loci throughout a genome by one process. The restriction landmark genome scanning (RLGS) method has been developed as one type of genome scanning. RLGS has been carried out on rats and mice and its efficacy in genetic analysis has been proven. However, the extent to which it can be used for human genetic analysis has not yet been determined. In this report we have tried to identify DNA polymorphisms within species by means of the RLGS method and to calculate the polymorphic rates in mice, hamsters, rats and humans.

To calculate the intraspecies polymorphic rates two strains of mice, five strains of rats, two strains of hamsters, and human subjects were selected. To calculate the intersubspecies polymorphic rates five strains of mice were selected. All DNA was extracted from the liver and the following RLGS steps were carried out: 1) blocking, 2) landmark cleavage by a restriction enzyme which occurs in more than 100kb of the DNA fragments, 3) labeling, 4) fragmentation of the labeled DNA with restriction enzyme which occurs in more than 10kb of the DNA fragments, 5) first fractionation by agarose gel electrophoresis, 6) fragmentation of the labeled DNA with a restriction enzyme which occurs in less than 10kb of the DNA fragments, 7) second fractionation by polyacrylamide gel, and 8) autoradiography. The resultant intraspecies polymorphic rates were as follows: 11.8-13.4% in mice, 9.5-14% in rats, 7.8-9.4% in hamsters and 3.5% in humans. The RLGS polymorphic ratio in humans was lowest at 3.5%. RLGS detected many fewer polymorphisms in humans than in the other mammals.

The intersubspecies polymorphism rate was 11.8-56.0%; the rates for laboratory-to-wild mice has higher than that for the laboratory-to-laboratory mice. The results show that the intersubspecies polymorphic rates determined by RLGS seem to correlate with hereditary distance.