Hello,  I have a set of coordinates for mm7 that I have been using try to extract the genomic sequences.  However it doesn't recognize the chromosome name column.  The are currently listed as chr1, chr2, ....chrX.  This is the error I get each time I try to extract sequences:

Chromosome by name 'chr1' was not found for build 'mm7'. Skipped 1181 invalid lines, 1st is #1, "chr1 4558068 4561910 region_0 0 +"

However if I change the build to mm10 it works fine -  but the coordinates are not the same between builds.  Also, mm7 can't be lifted over to mm9 or mm10.  

Does anyone know the proper format for chromosome name in mm7:

Thanks,

Jill