In the new IB guide the IBO have, quite rightly, added some new concepts which have become important recently but were unknown when many of us were studying Biology full time at university. The control of mitosis and the cell cycle is one example.

Research into cancer has made huge advances in recent years and much has been discovered about the control of the cell cycle. This now forms an area of medicine called Oncology. The word "onco" means bulk, mass, while "-logy" means study. You could say it was the study of unwanted cell growth when control of the cell cycle runs out of control. Learning how to prevent this may help us find cures for cancer. That is without a doubt an important new area of biology.

One of the new concepts in the guide is that Cyclins (a type of protein) are involved in the control of the cell cycle. Their level rises and falls due to the activity of genes which produce the cyclin proteins. Proto-oncogenes control the normal levels of the cyclin molecules but when mutagens trigger the wrong sort of change in a proto-oncogene it can mutate and become an oncogene. The cells containing these oncogenes lose control of the cell cycle and they divide continuously making identical copies of themselves, including the oncogene and they grow into a lump of cells. This we call cancer.

Find out more in the Control of cell cycle lesson plan for the new guide.