---
title: "Cancer & Stem Cells"
description: "Explain that cancer occurs when mutations in DNA disable normal cell-cycle controls, causing uncontrolled cell division and tumour formation; describe how stem cells differ from specialised cells and "
canonical: https://lightmysky.com/learn/science/cancer-and-stem-cells-mt_roinupb_7L
source: https://lightmysky.com/learn/science/cancer-and-stem-cells-mt_roinupb_7L.md
retrieved: 2026-10-19
---

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# Cancer & Stem Cells

Explain that cancer occurs when mutations in DNA disable normal cell-cycle controls, causing uncontrolled cell division and tumour formation; describe how stem cells differ from specialised cells and their potential for regenerative medicine; and evaluate the ethical debates around embryonic stem cell research and genetic testing

Subject: Science · Area: The Human Body · Ages 13 to 14
Page: https://lightmysky.com/learn/science/cancer-and-stem-cells-mt_roinupb_7L

## Ready when they can

- Explains cancer as the result of DNA mutations that disable tumour suppressor genes or activate oncogenes, causing unchecked mitosis
- Distinguishes stem cells (unspecialised, can differentiate) from specialised cells (fixed function) and explains why stem cells are medically valuable
- Presents the embryonic stem cell debate with at least two specific scientific arguments in favour and two ethical objections against, without simply asserting one side is correct

## Lesson: Cancer & Stem Cells

You have probably heard someone talk about cancer. DNA carries the instructions for running a cell, and normal cells divide only when the body needs new cells, then stop. Special genes act like brakes and checkpoints, making sure a cell copies its DNA correctly before it splits in two. Most cancers need several such mutations over time, not just one.

*(drawing: A mutation can damage the checkpoint genes. Once the brakes fail, the cell keeps dividing without stopping.)*

**Example.** Ali's skin took years of sun damage without sunscreen. A mutation broke a checkpoint gene in some skin cells. Those cells stopped listening to stop signals and kept dividing, piling up into a lump of extra cells: a tumour. That is what cancer is: cells growing out of control because their division controls are broken.

Not every cell works the same way. A specialised cell, like a skin cell or a nerve cell, already has one fixed job. A stem cell is different: it has not chosen a job yet, so it can still divide and turn into several different cell types. That is why doctors want stem cells, to grow new heart muscle, nerve tissue, or skin to replace what is damaged.

One source of stem cells is a very early embryo. Some scientists argue these cells can become almost any tissue and are easier to study, but many people object because removing them destroys the embryo, which they believe deserves protection. There is no single right answer here, and thoughtful people disagree.

**Recap.** Cancer starts when mutations break a cell's division controls, while stem cells are valuable precisely because they have not yet chosen a job.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [DNA & Genes](https://lightmysky.com/learn/science/dna-and-genes-mt_0sELh0MYWb)
- [Parts of Plant and Animal Cells](https://lightmysky.com/learn/science/parts-of-plant-and-animal-cells-mt_bABr-c2DfV)

## Opens up

- [Differentiation and Stem Cells](https://lightmysky.com/learn/science/differentiation-and-stem-cells-mt_UmLJgmcCjO)