The retention frequency of the regions which carry the selection marker, thymidine kinase gene 1 ( TK1 ). Panel A: The retention of 2,377 RH vectors in CHI19 of CHIR_1.0, from raw genotyping data before any quality control. Panel B: The retention frequency for 604 markers and the position of these markers on the robust RH map of chromosome CHI19. The retention is roughly constant along the chromosome at 39.0%. The missing region in the robust RH map from 40.9 Mb to 62.1 Mb showed extremely high retention. This region carries TK1 gene at position 52.7 Mb, where the anticipated highest retention near 100% are shown.