1. Chapter 9.5 When Control Is Lost AP Biology Fall 2010

2. Objectives List some of the problems in cell division when cell cycle control mechanisms do not work and control is lost Explain how cancer cells are different from normal cells in the body

3. Cell Cycle Revisited Cell cycle has built in checkpoints where proteins can advance, delay, or block forward progress of the cycle For example, kinases can signal the end of DNA replication Growth factors signal start of mitosis

4. Cell Cycle Revisited

5. Checkpoint Failure and Tumors When checkpoint mechanisms fail, a cell loses control over its replication cycle A checkpoint gene inhibits mitosis and is called a tumor-suppressor gene – In some cases mitosis repeats over and over again – In others, cells do not die as they are supposed to

6. Checkpoint Failure and Tumors Proto-oncogenes code for proteins that stimulate mitosis – Neoplasms are abnormal masses of cells that have lost control over their growth and cell division Can be benign or malignant – Benign growth pose no threat to the body and typically remain in their home tissue

7. Characteristics of Cancer Cancers are abnormally growing and dividing cells of malignant neoplasm All cancer cells display 4 characteristics – Grow and divide abnormally – Cell membrane is leaky, and cytoskeleton is disorganized – Cells have a weakened capacity for adhesion and break away to move to other sites in the body (metastasis) – Cancer cells have lethal effects