Discuss with group Look at notes from yesterday Review cell cycle Discuss with group Look at notes from yesterday

Control of the Cell Cycle Why is this important?

Not all of our cells behave in the same way Not all of our cells behave in the same way. Most of our cells have very specialized functions that allow them to carry out their tasks. This is good, as long as everything works the way that it should all of our cells behave in the same way. Most of our cells have very specialized functions that allow them to carry out their tasks. This is good, as long as everything works the way that it should

Purpose Cells divide for different reasons Repair Example = cut in your skin or a broken bone Growth Reproduction Allow the baby to become strong and healthy

Speed of Growth Some cells grow and divide constantly Example = skin, stomach, mouth Some cells never divide Example = Brain and nerve

Controls on the Cycle Proteins called cyclins regulate the timing of cell cycle processes Cyclins ‘tell’ the ell when to start and stop dividing Allows normal cell cycle to be precisely controlled

OH NO!!! SOMETHING WENT WRONG Consequences of uncontrolled cell growth are very severe

CANCER A ‘disease of the cell cycle’ Occurs because of a DNA mutation Normal checkpoints regulating mitosis are ignored or overridden by the cancer cell Causes abnormal cell growth Tumors Benign = non-spreading Malignant = spreading Usually grows uncontrollably Cancerous cells divide repeatedly out of control even though they are not needed; they crowd out other normal cells and function abnormally. They can also change functioning of major organs CANCER

Causes Errors during replication Aging Carcinogens (toxins) Examples = Mutagens Genetics

Cell Differentiation Generic , less specialized cell, becomes a more specialized cell type Occurs during development as we change from a zygote (fertilized egg cell) to a complex system of cells and tissues Stem Cells develop into these specialized cells

How do cells differentiate? Remember – all cells contain DNA not all of the DNA is expressed in a cell This is called GENE EXPRESSION Specific pieces of our DNA are ‘turned on’ depending on the function of a cell

Regeneration Often serves as a defensive mechanism to escape predators Animals lose a limb and can then regrow the lost appendage Cells that mimic stem cells are found at the site where the arm, tail, or other body part may be lost These cells then differentiate to form the correct piece of the animal As the cells are replicating during MITOSIS they are reading certain pieces of the DNA This GENE EXPRESSION is crucial to healthy and correct regrowth!

Axolotl https://www.youtube.com/watch?v=EsCSwVx3GvA