Science: The Cell Cycle and Cancer
How normal cell division is controlled and how cancer can develop
Science: The Cell Cycle and Cancer
How normal cell division is controlled and how cancer can develop
Biology - Grade 9-12
- 1
List the main stages of the eukaryotic cell cycle in order, including interphase and the stage when the cell splits.
Remember that interphase has three parts before mitosis begins.
The main stages of the eukaryotic cell cycle are interphase, mitosis, and cytokinesis. Interphase includes G1, S, and G2, mitosis divides the nucleus, and cytokinesis divides the cytoplasm to form two daughter cells. - 2
Describe what happens during the S phase of interphase.
During the S phase, the cell replicates its DNA. This produces a complete copy of the genetic material so each daughter cell can receive the same set of chromosomes after division. - 3
Explain the purpose of a cell cycle checkpoint.
Think about why a cell should pause before moving to the next stage.
A cell cycle checkpoint helps the cell decide whether it is safe to continue dividing. It checks conditions such as cell size, DNA accuracy, and whether chromosomes are properly prepared so damaged or unready cells do not keep progressing. - 4
What is the difference between a proto-oncogene and an oncogene?
A proto-oncogene is a normal gene that helps regulate cell growth and division. An oncogene is a mutated or overactive version of that gene that can push cells to divide too often and contribute to cancer. - 5
Tumor suppressor genes are often compared to brakes in a car. Explain this comparison.
Focus on how these genes prevent unsafe growth.
Tumor suppressor genes are compared to brakes because they slow down or stop cell division when necessary. If these genes are damaged or lost, the cell may keep dividing without proper control, which can increase the risk of cancer. - 6
A mutation prevents a cell from repairing damaged DNA at a checkpoint. Explain how this can increase the chance of cancer.
If a cell cannot repair damaged DNA at a checkpoint, it may continue dividing with mutations still present. Over time, additional mutations can build up in genes that control growth and division, increasing the chance that the cell becomes cancerous. - 7
Define cancer in terms of cell cycle regulation.
Use the idea of lost control over cell division.
Cancer is a disease in which cells lose normal control of the cell cycle and divide uncontrollably. These abnormal cells can form tumors, invade nearby tissues, and sometimes spread to other parts of the body. - 8
How is metastasis different from the formation of a primary tumor?
A primary tumor forms at the original site where abnormal cells first begin growing. Metastasis occurs when cancer cells break away, travel through the blood or lymph system, and form new tumors in other parts of the body. - 9
Why do rapidly dividing cancer cells often respond to chemotherapy, and why can healthy cells also be harmed?
Think about what chemotherapy targets rather than where the cells are located.
Chemotherapy often targets cells that divide quickly, so it can be effective against many cancer cells. However, some healthy cells also divide rapidly, such as cells in hair follicles, the digestive tract, and bone marrow, so they can be damaged as well. - 10
Compare benign tumors and malignant tumors.
Benign tumors are noncancerous growths that usually remain localized and do not invade nearby tissues. Malignant tumors are cancerous, can invade surrounding tissues, and may spread to distant parts of the body through metastasis. - 11
A scientist finds that a cell has ignored signals to stop dividing and has activated genes that promote constant growth. What does this suggest about the cell, and why?
Connect the behavior of the cell to normal growth controls.
This suggests that the cell may be developing into or already functioning as a cancer cell. Ignoring stop signals and activating constant growth pathways are signs that normal regulation of the cell cycle has been disrupted. - 12
Explain why studying the cell cycle helps scientists develop cancer treatments.
Studying the cell cycle helps scientists identify which molecules and checkpoints control cell division. This knowledge allows researchers to design treatments that target specific failures in cancer cells, such as overactive growth signals or damaged checkpoint systems.