This activity analyzes a published scientific figure from a study that investigated the role of p53 in cell cycle regulation.

In this study, scientists genetically engineered cell lines with disrupted alleles of the p53 gene. The scientists exposed the cell lines to DNA-damaging gamma (γ) radiation, then observed the proportion of cells that entered mitosis (cell division). The figure shows the mitotic index (proportion of cells undergoing mitosis at a given time) for each cell line. The shaded squares represent cells with two normal alleles of the p53 gene. The half-shaded squares represent cells with one normal and one disrupted allele of the p53 gene. The unshaded squares represent cells in which both alleles of the p53 gene were disrupted. The “Educator Materials” document includes a captioned figure, background information, graph interpretation, and discussion questions. The “Student Handout” includes a captioned figure and background information.