In regards to this dotpoint.. you should talk about:
How DNA Repair Genes help to maintain a healthy cell cycle - ie normal DNA replication etc etc.
How Proto Oncogenes and Tumor suppressor genes help to regulate the DNA replication process, so there is no uncontrolled cell divison which may lead to cancerous growths (and thus compromised health).
Also, you should note that genes code for proteins. For example, when there is a cut to the skin, the genes for production of proteins are switched on to assist in the repair of the wound.
When you have an infection, the genes for the production of T-Cells and B-Cells are switched on, increasing the number of T-Cells and B-cells in the blood and lymph so that your body is able to fight the infection. etc.
hope that helps