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Overview

Picture 1. A new born baby has around a billion cells. Her weight will double in about two months because she will have twice as many cells.

There are over 10,000,000,000,000 cells in your body. Although these cells can do different jobs, each one has a nucleus with the same set of 46 chromosomes.

Yet all of this came from a single cell with one set of 46 chromosomes. Within about 6 minutes of fertilisation, this cell copied itself to make two cells. This was your first experience of mitosis. Soon after, these two cells copied themselves to make four and so on. You have been subject to mitosis ever since (billions of times).

By copying the original 46 chromosomes, your body has created more than a hundred billion kilometres of DNA - that's enough to stretch around the Earth 2,500,000 times. Mitosis has copied a total of about 100 ZB of data.

As a rough estimate, this is equivalent to making a million copies of all the hard drives in the world. [1 ZB is a zeta byte of data. This is 1 with twenty four zeros after it].

However, although this is an amazing feat, it does sometimes go wrong. This can result in a cancerous growth.

Picture 2. Stained stem cells in an embryo. These non-specialised cells will copy and develop into every type of cell in the body.

Cells and cancer
	Cancer is a disease that originates in our own cells. A change in the DNA causes a special gene called an oncogene to be switched on. This leads to uncontrollable cell reproduction by mitosis. And this is a cancer. In this resource, you can find out what we mean by the terms in bold and see how an understanding of this area of biology can help us deal with cancer.

Contents
	There are 7 units and a quiz in this electronic resource (e-source): Cells, the body and growth Cell division: mitosis and meiosis Chromosomes and genes When cell division goes wrong What causes cancer? Treatments for cancer Radiation: cause and cure Quiz

Using this e-source

There are a number of interactive features in this e-source:

A glossary of terms: any word with a glossary entry is highlighted. Clicking on the word will open a new window with a definition of that word.

Roll over diagrams: many of the diagrams have highlights or sequences. You can see these by rolling your cursor over part of the picture or part of the text. The text has a roll over highlight.

Quick questions: at the end of e-source, there is a set of quick questions to test your understanding of the scientific ideas.

Quiz: there is a quiz at the end of the resource. It has 10 multiple choice questions and will give feedback on your answers.

Last updated January 2005.