The Strength of Selection on Ultraconserved Elements in the Human Genome

Ultraconserved elements are stretches of consecutive nucleotides that are perfectly conserved in multiple mammalian genomes. Although these sequences are identical in the reference human, mouse, and rat genomes, we identified numerous polymorphisms within these regions in the human population. To determine whether polymorphisms in ultraconserved elements affect fitness, we genotyped unrelated human DNA samples at loci within these sequences. For...