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Apart from resistance to infectious disease, there are few examples of adaptive molecular evolution in humans. A new study indicates that olfactory receptors are exceptions, with natural selection maintaining considerable allelic diversity in this multigene family.
Pair-wise genome comparisons offer new sources of information about the patterns and processes that influence genomic designs. Replication-dependent rearrangements, as indicated by the symmetric gene organization pattern in the genomes of Chlamydia pneumoniae and Chlamydia trachomatis, may provide a missing link in the reconstruction of historical events from modern genomes.