Hemoglobin gene expression changes over the course of human development, which of the following is con Hemoglobin genes are turned off after embryonic development by adding an acetyl groups to the HBB Hemoglobin genes are turned on after fetal development by specific micro-RNA molecules Hemoglobin genes are continually expressed, as they are in the centromere of chromosome 4 O O The hemoglobin genes are expressed when activated by specific chemical modifications at the level of O