Gene therapy processes. Diagram showing methods used to obtain samples for gene therapies. From top: brain tissue sampling, blood sampling, and in vitro culturing of embryonic stem cells. These brain tissue samples are from the pre-frontal cortex and the hippocampus. The blood sample (three types of blood cells shown) is being processed in a cell suspension. These embryonic stem cells, from the blastocyst stage of embryo development, have been cultured in a petri dish and used to make nerve cells. The methods right) include: DNA methylation, histone modifications, and genome sequencing. Labelled digram: C027/0574.