Chromosome evolution: The junction of mammalian chromosomes in the formation of mouse chromosome 10

During evolution, chromosomes are rearranged and become Bred into new patte rns in new species. The relatively conservative nature of this process supp orts predictions of the arrangement of ancestral mammalian chromosomes, but the basis for these rearrangements is unknown. Physical mapping of mouse c hromosome 10 (MMU 10) previously identified a 380-kb region containing the junction of material represented in human on chromosomes 21 (HSA 21) and 22 (HSA 22) that occurred in the evolutionary lineage of the mouse. Here, acq uisition of 275 kb of mouse genomic sequence from this region and comparati ve sequence analysis with HSA 21 and HSA 22 narrowed the junction from 380 kb to 18 kb. The minimal junction region on MMU 10 contains a variety of re peats, including an L32-like ribosomal element and low-copy sequences found on several mouse chromosomes and represented in the mouse EST database. Se quence level analysis of an interchromosomal rearrangement during evolution has not been reported previously.