Single- and dual-parameter cell cycle analysis of BM and MPB CD34⁺ cells. DNA histogram of BM (A) and MPB (B) CD34⁺ cells, respectively, showing the relative absence of replicating progenitor cells in MPB. Simultaneous DNA/RNA staining with Hst and PY, identifying G₀ and G₁ regions in similar samples of BM (C) and MPB (D) CD34⁺ cells.