Department of Statistics, Seoul National University, Seoul 151-742, Korea.|Division of Structural and Functional Genomics, Korean National Institute of Health, Osong, Chungchungbuk-Do 363-951, Korea.|Division of Structural and Functional Genomics, Korean National Institute of Health, Osong, Chungchungbuk-Do 363-951, Korea.|Division of Structural and Functional Genomics, Korean National Institute of Health, Osong, Chungchungbuk-Do 363-951, Korea.|Division of Structural and Functional Genomics, Korean National Institute of Health, Osong, Chungchungbuk-Do 363-951, Korea.|Department of Mathematics and Statistics, Sejong University, Seoul 143-747, Korea.|Department of Statistics, Seoul National University, Seoul 151-742, Korea.