Pre-AP Biology, Mrs. Krouse Cancer Biology Pre-AP Biology, Mrs. Krouse

What types of cells in the human body normally have high rates of cell division? Why? Skin cells, cells that line the digestive tract, blood cells, etc. divide frequently because they must be replaced frequently due to damage What about in plants?! Cells in the root tips of plants have a high rate of cell division as they continue to grow into the soil to maximize absorption of water, nitrogen, phosphorus, etc.

G0 State Some cells exit the cell cycle and enter a non- dividing state called the G0 state. This can be temporary or permanent. Examples… -Once you reach age 25, your brain is finished growing. At this point, the nerve cells in your brain enter the G0 state and stop dividing permanently. Even if there is damage to the brain, these cells cannot divide again to repair the injury. -Once your liver is finished growing, your liver cells enter the G0 state, but they can return to the normal cell cycle if there is damage to the liver. If this happens, they will divide to repair the injury.

Cell Cycle Checkpoints Points in the cell cycle where progression to the next stage of the cycle can be stopped until conditions in the cell are favorable The three checkpoints are… -G1 checkpoint -G2 checkpoint -M checkpoint

Cell Cycle Checkpoints What does the cell check for at each checkpoint? -G1 checkpoint: checks that the cell is large enough to divide, has enough nutrients, and has undamaged DNA -G2 checkpoint: checks that the cell is large enough to divide and that DNA replication has occurred without errors -M checkpoint: checks that all the chromosomes are correctly attached to spindle fibers before the cell enters anaphase

What is cancer? Cancer occurs when cells ignore normal cell cycle checkpoints and divide too frequently. When this happens, a mass of cells called a tumor can form.

What is apoptosis? In normal tissue, cells that are not functioning correctly are marked for apoptosis. Apoptosis is “programmed cell death,” meaning the cell intentionally destroys itself.

How does apoptosis relate to cancer? If apoptosis does not occur correctly, damaged cells can divide and over-proliferate, resulting in a tumor Oncogenes are genes in human DNA that can become mutated (altered) and prevent normal apoptosis. They can also cause cell division rates to increase. Some things that can cause mutations in oncogenes include… cigarette smoke, UV radiation from sunlight, asbestos, viruses like HPV (human papilloma virus)

Types of Tumors There are two main types of tumors— benign and malignant -Benign tumors do not move from the original tumor location -Malignant tumors can move from the original tumor location when cells break off the tumor and spread through the blood or lymph vessels to set up secondary tumors in new locations. This movement is called metastasis.

Chemotherapy One potential treatment method for cancer Targets quickly-dividing cells (like cancer cells). Unfortunately, it also targets cells that normally divide quickly like hair follicle cells and cells that line your digestive tract. This can result in hair loss and nausea.