Family With Sequence Similarity 222, Member B (FAM222B)

Chromosome 17 is unusual among the human chromosomes in many respects. It is the largest human autosome with orthology to only a single mouse chromosome1, mapping entirely to the distal half of mouse chromosome 11. Chromosome 17 is rich in protein-coding genes, having the second highest gene density in the genome2, 3. It is also enriched in segmental duplications, ranking third in density among the autosomes4. Comparison of the orthologous regions reveals striking differences. In contrast to the typical pattern seen in mammalian evolution5, 6, the human sequence has undergone extensive intrachromosomal rearrangement, whereas the mouse sequence has been remarkably stable. Moreover, although the human sequence has a high density of segmental duplication, the mouse sequence has a very low density.