In most cases, genetic diagnosis is performed in experimental laboratories. Because hemoglobin interferes with DNA purification, white cells or white cell nuclei are isolated from whole blood as a preparatory step prior to DNA extraction (1, 2). The purpose is to remove the red blood cells that contain hemoglobin, which can interfere with polymerase chain reaction (PCR) analysis of the DNA. The process of isolating nuclei from white blood cells is called nuclear enrichment. This step is required for accurate quantitation of gene sequences by PCR and other molecular techniques. Nuclear enrichment requires intact nuclei because the DNA must be released from the nucleus for analysis. Therefore, the starting material for nuclear enrichment is usually either whole white blood cells or purified nuclei from these cells. Enrichment of nuclei from white blood cells is necessary for genetic tests that analyze small amounts of DNA, such as prenatal diagnostics. Enrichment of nuclei from other body tissues is needed for tests on small samples of those tissues. Whole blood contains both red and white blood cells, but it is only the white blood cells that contain DNA. Genetic tests on children require collecting large numbers of white blood cells in order to obtain enough for testing. In this case, it is necessary to separate the red blood cells from the white blood cells before extracting their DNA.