[A new method for constructing linkage maps of molecular markers: three-point selfcross method]

The method for constructing linkage maps has almost been so far the three-point testcross in higher organisms. This method is, however, considerably limited to a requirement of a parent or line with three recessive genes that can be obtained by only cross breeding. In this paper, the three-point selfcross method for mapping was proposed. This method can also provide us with informations of mapping as the same as the three-point testcross method. However, the three-point selfcross method does not have any limitation of requiring a parent with three recessive genes. It was theoretically proved that this method could be used to map molecular marker loci in small sample of F2 population. Exactly to test both the methods for mapping, Fisher information content was applied to prove that the three-point selfcross method is powerful for mapping. Further to test this method, data of the first 6 loci were chosen from 12 RFLP loci detected in 333 F2 individuals in SAMPLE. RAW file in MAPMAKER/EXP version 3.0 that Lander et al. (1987) provided. The result showed that, like MAPMAKER program, the three-point selfcross method is powerful to detect linkage relationship among loci, to order them on linkage groups and to calculate distances between nearest neighbor loci. Besides, this method could provide us with the other information of map such as the positive or negative interference and couple or repulsion configuration.