Researchers investigated the role of p53 in cell cycle regulation by genetically engineering a cell line with deleted copies of the p53 gene. They exposed the cell lines to DNA-damaging radiation and observed how this exposure impacted mitosis.
Copies of the p53 gene were selectively deleted in a line of human cells and then monitored after exposure to DNA-damaging gamma (γ) radiation to determine what proportion of the cells entered mitosis (cell division). The closed squares represent cells with two copies of the p53 gene (the normal state). The half-closed squares represent cells with one copy of the p53 gene. The open squares represent cells in which both copies of the p53 gene were deleted. The Mitotic Index is the proportion of cells undergoing mitosis at a given time.
Project or distribute the image to engage students. The downloadable Educator Materials PDF, which includes background information, graph interpretation and discussion questions, and the Student Handout, which includes the image and background information, have been remediated to comply with Section 508 of the National Rehabilitation Act for accessibility and can be used with screen readers.
Figure 2C from:
F. Bunz et al. (1998) Requirement for p53 and p21 to Sustain G2 Arrest After DNA Damage. Science 282 (5393), 1497–1501.