An agarose gel showing sizes of DNA extracted from bone marrow and fixed cytogenetic preparations. A. A 0.7% agarose gel showing representative total genomic DNA prepared from bone marrow specimens and chromosome suspensions. BM, bone marrow refrigerated for one day (160 ng); 26 days (235 ng); and 36 days (100 ng); CHR, fixed cytogenetic preparations stored at -80°C for one year (80 ng); and nine years (40 ng). The molecular weight marker (left) is λ/HindIII and the sizes of its bands are indicated on the left in kb.