Human muscle cells compared to blood cells all contain the same number of chromosomes with the same complement of genes. Yet, the hemoglobin protein which helps to temporarily bond to oxygen is found in blood cells and not muscle cells. Which of the following best explains this difference? A. Some cells have the ability to remove unnecessary DNA sequences.
B. Different cell types use different methods of cell division.
C. There was a mutation of the genes within each cell type.
D. The expression of genes is regulated in different cell types.