Gene sequencers attained several landmarks in recent weeks. Following the sequencing of the billionth base of the human genome (it was a guanine) by the Human Genome Project, scientists from the Sanger Center (Cambridge, UK), University of Oklahoma (Norman, OK), and Keio University School of Medicine in Tokyo reported on December 2 the first “almost continuous” sequence of the coding region of a human chromosome—that of chromosome 22 (Nature 402, 489– 495, 1999). Although 545 genes were putatively identified (150 of which have homologs in other organisms), 11 sections of the q region of the chromosome remain unsequenced because they were either impossible to clone or resistant to current sequencing techniques. At least 27 disorders have been linked to chromosome 22. In November, scientists at the Institute for Genomic Research (Rockville, MD) also reported the full genome sequence of Deinococcus radiodurans, the most radiation-resistant bacteria currently known (Science 286, 1571–1577, 1999). Publication of the 180 million bp genome of Drosophila melanogaster genome, sequenced by Celera Genomics (Rockville, MD), is expected at the beginning of this year.