
ON THE COVER: Back in 1968, several traits had already been linked to the X chromosome, but not a single phenotype had been linked to any of the 22 autosomes. This changed when Roger Donahue and colleagues in Victor McKusick's lab reported that the Duffy blood group locus resided on 1q (PNAS 61:950–955). Donahue examined his own chromosomes and those of his relatives and noted that the “uncoiled” region of chromosome 1 segregated with the Duffy blood group in his family. The cover shows a metaphase spread illustrating this extended heterochromatic region near the centromere of chromosome 1. Now considered a clinically insignificant variant, this heterochromatic region was originally referred to as the “uncoiled” element and is indicated here by an arrow. Special thanks to Azra Ligon, Brigham and Women's Hospital, Department of Pathology, Clinical Cytogenetics Laboratory, Boston, for the metaphase image.