Written Response #9? Cell Cycle - Handout

Mitosis Foldable

Understanding Mitosis Prophase (1st phase of mitosis) Chromatin condenses to form visible chromosomes 1 chromosome = 2 sister chromatids (packaged copies of DNA from S-phase of interphase) Nuclear envelope disappears Important structures for completion of the cell cycle appear: Centrioles: send out spindle fibers Spindle Fibers: attach to sister chromatids to pull apart Centromeres: hold 2 sister chromatids together

Understanding Mitosis Metaphase (“M” is for Middle) Chromosomes move to the middle of the cell Still paired as sister chromatids Attached in center with a centromere (also to spindles)

Understanding Mitosis Anaphase (“A” is for Apart) Centromeres break and sister chromatids pull apart Spindle fibers shorten and pull chromatids (now each is an individual chromosome) toward opposite sides of cell

Understanding Mitosis Telophase Begins when chromosomes reach opposite poles of cell Chromosomes de-condense to less visible chromatin and nuclear envelope and organelles re-appear Cell begins to pull apart and prepares for division

Understanding Mitosis Cytokinesis Animal Cells – cleavage furrow forms Cell membrane pinches in to divide cells Plant Cells – cell plate Forms a new portion of the cell wall

How Do I Remember All of This? https://www.youtube.com/watch?v=HYKesI9jL8c 1. Prophase – Hands together with fingers locked. 2. Prometaphase – Fingers wiggle. 3. Metaphase – Fingers overlapping facing each other. 4. Anaphase – Tips of fingers touching. 5. Telophase – Fist touching each other. 6. Cytokinesis – Separate fist.

Understanding Mitosis Cell Cycle Regulation Uncontrolled cell division results in tumors / cancer Chemicals monitor each phase of the cycle Reasons why cells may divide uncontrollably: Radiation, carcinogens, mutated genes