Late G1 Cell Cycle Molecular Pathways

Abstract

Abstract The most critical stage of the cell cycle is the transition point in late G1 where the cell commits to initiating DNA synthesis. Multiple pathways of stimulation and inhibition converge, and it can be difficult for students to comprehend how all these inputs influence the outcome. This presentation demonstrates a principal pathway of stimulation involving chain reactions of cyclins and kinases whose actions are focused around the phosphorylation of a master switch; the tumor suppressor retinoblastoma. Overlaid on this stimulatory pathway are inhibitory inputs that focus on another tumor suppressor, p53, which can act to stop DNA synthesis temporarily until damage is repaired or to shunt the cell into a suicide pathway if replication is inappropriate. Students can selectively view the animations of these various stimulatory and inhibitory pathways and observe how their outcomes affect the overall process of G1 to S-phase transition. The series of pathways is displayed as one large chart for an overview. The visual approach to the material is easy to follow and integrates multiple themes into one diagram. The student next has the option of choosing which specific pathway to examine more closely. The chosen pathway is subsequently displayed, presenting each ordered step as an animation. By using a more interactive approach to an abstract concept, it was found that students are more enthusiastic about learning such complex material. The color-coding of specific elements in the pathways allowed for better recollection and understanding. The pathways involved in the cell cycle contain numerous steps, so only the main steps were included. Combining all of these main steps into one, easy-to-read visual aid allows for a much better understanding of the material and how all the molecules involved interact with each other.

Keywords

• DNA Replication
• Cyclins
• Phosphotransferases
• Tumor Suppressor Proteins
• DNA Synthesis