Bellwork

1. Bellwork What is the end result after a cell goes through the entire cell cycle?

2. Ch. 5 Cell Division Ch. 5.2 Control of the Cell Cycle

3. Target #7- I can explain how cells regulate the cell cycle • Eukaryotic cells have evolved a complex system for regulation of the cell cycle • Controlled by both internal and external signals • Internal Signals • Ensures that the stages follow one another in the normal sequence • Ensures that each stage is properly completed before the next stage begins • External Signals • Tell the cell whether or not to divide

4. Target #8- I can identify the role of apoptosis • Apoptosis • Programmed cell death • Role • Decreases number of cells • Occurs during development to remove unwanted tissue • Plays a role in preventing cancer

5. Target #9- I can state the events involved with apoptosis Target #10- I can describe Caspases • Caspases • Enzymes that bring about apoptosis • Regulated via inhibitors, but are triggered by the external and internal factors • 1st set of caspases, known as initiators, initiate the process • 2nd set of caspases, known as executioners activate the enzymes to dismantle the cell • The cell will progress through a series of events • The cell stops communicating with other cells • The nucleus fragments • The plasma membrane develops blisters • The cell is then engulfed by white blood cells

6. Target #11- I can explain the importance of checkpoints in the cell cycle • The steps of the cell cycle must occur in the correct order • There is a checkpoint after each phase of the cycle • Critical for the prevention of cancer • Progression through the cell cycle is caused by a group of proteins known as cyclins • Plays a role in progressing to the synthesis phase and the mitotic phase

7. Target #12- I can describe the G0 phase • Gap 0 (G0) • If a cell is not prepared to go through the cell cycle, or does not receive the “go ahead” after Gap 1, the cell goes into a hibernation state known as G0 phase

8. Target #13- I can explain what occurs at the G1 checkpoint Target #14- I can describe the p53 protein • Gap 1 Check point • Allows the cell to determine whether conditions are favorable to progress to the synthesis phase • Cell needs to make sure there are enough materials present for DNA replication to begin • Time for checking the structure of the DNA, it can not be damaged • In mammals, a protein known as p53 is responsible for stopping the cycle at the G1 checkpoint • P53 first tries to fix the damaged DNA • If that is not possible, the cell undergoes apoptosis

9. Target #15- I can explain what occurs at the G2 checkpoint • The cell cycle stops at the G2 checkpoint if DNA has not finished replicating • Prevents the initiation of the M stage before completion of the S stage • If DNA is damaged, stopping the cell cycle at this checkpoint allows time for the damage to be repaired • If repair is not possible, apoptosis occurs

10. Target #16- I can describe the M stage checkpoint • M stage checkpoint • Occurs during the mitotic stage • The cycle stops if the chromosomes are not going to be distributed accurately to the daughter cells

11. Target #17- I can identify the external factor of cell division in animal cells Mammalian cells enter the cell cycle only when stimulated by an external factor Growth factor hormones are received at the plasma membrane

12. Target #18- I can describe carcinogenesis • Carcinogenesis • The development of cancer • A multi-stage process involving disruption of normal cell division and behavior • Genetic changes in the cell occur during several of the stages of cancer development • Mutations occur in the DNA • Could be inherited from a parent, a result in error in replication, or induced by an environmental agent • Replication of the cell propagates the mutation • Occurs in two categories of genes: proto-oncogenes and tumor suppressor genes

13. Target #19- I can differentiate between proto-oncogenes & tumor-supressor genes • Proto-oncogenes • Encode proteins that promote the cell cycle and prevent apoptosis • When mutated, they become cancer-causing genes called oncogenes • Can result in the unending division of mutated cells • Tumor-suppressor genes • Encode proteins that stop the cell cycle and promote apoptosis • When mutated, they no longer inhibit the cell cycle • Example p53 • Almost 50% of all human cancers are because of mutation