The High Mobility Group 1 protein (HMG1) is an abundant and highly con
served chromosomal protein. Mouse HMG1 is encoded by the Hmg1 gene, co
ntaining four introns, but the murine genome contains many related seq
uences that are mostly retrotransposed pseudogenes. By using an inters
pecific cross, we have mapped the functional Hmg1 gene on mouse Chromo
some (Chr) 5 and seven Hmg1-related sequences on Chrs 6, 8, 17, 18, an
d X.