Microarray Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA. chou@niehs.nih.gov|Microarray Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA. chou@niehs.nih.gov|Microarray Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA. chou@niehs.nih.gov|Microarray Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA. chou@niehs.nih.gov|Microarray Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA. chou@niehs.nih.gov