CA 2006 Chapter 6

CA 2006 Why do cells divide?

CA 2006 Cell Reproduction/Cell Cycle A process that your body uses to make new cells in order to grow and repair itself

CA 2006 CELL CYCLE Interphase –A cell spends 90% of it ’ s life in interphase.

CA 2006 Stop! Look at your notes! What are characteristics that you can see in each the Interphase cells? What is happening in Interphase? Sketch a “general” interphase cell in your notes?

CA 2006 Examples of Cells in Interphase

CA Phases of Interphase G1- First growth phase S phase- synthesis G2- Second growth phase

CA 2006 G1 Growth Phase Cell grows rapidly Carries out routine cell functions This phase occupies the major portion of interphase

CA 2006 Synthesis (S) Phase centromere chromatid DNA is copied Each chromosome is composed of two chromatids (sister chromatids) attached together by a centromere.

CA 2006 G2 Second Growth Phase Cell continues to grow and prepares to divide

CA 2006 Cells in Mitosis

CA We will be looking at 5 drawings of cells in mitosis. 2. Try to put them in order. 3. Think through what is a logical sequence. Hint: Which one LOOKS like it must happen 1st? Why? Which one LOOKS like it must happen last? Why?

CA

2

3

4

5

Correct Order 1 st = Slide 4 2 nd = Slide 2 3 rd = Slide 1 4 th = Slide 3 5 th = Slide 5

CA 2006 Mitosis (M) Phase A process by which the material in a cell’s nucleus is divided during cell reproduction

CA 2006 What Cell Parts Are Involved? Cell Membrane Nuclear Membrane Nucleus Chromosomes Cytoplasm Centrioles

CA 2006 Prophase Nuclear Membrane Chromosomes Centriole Spindle Fibers

CA 2006 Prophase Chromosomes become visible by thickening Nuclear membrane begins to disappear Spindle fibers form between centrioles

CA 2006 Metaphase Chromosomes Centriole Spindle Fibers

CA 2006 Metaphase Chromatids line up across equatorial plate (middle) Spindle fibers are attached to each set of chromatids

CA 2006 Anaphase Chromosomes Centriole Spindle Fibers

CA 2006 Anaphase Centromeres divide Chromatids are pulled toward opposite ends of the cell

CA 2006 Telophase Nuclear Membrane Chromosomes Centriole

CA 2006 Telophase Nuclear membrane begins to form at each pole. Chromosomes uncoil (becoming less visible) Spindle dissolves

CA 2006 Cytokinesis Cytoplasm divides and two daughter cells are produced

CA 2006 End of Mitosis Each cell now has original number of chromosomes Each new cell grows until it is ready to divide

CA 2006 Mitosis All body cells (somatic cells) in humans are made through mitosis Sex cells (egg & sperm) are NOT made through mitosis

CA 2006 Put It All Together!!! Animal Cell Mitosis

CA 2006 What Are The Benefits of Mitosis? Helps us grow by producing new cells Replaces cells that were lost due to cell death and injury

CA 2006 Think… In which body organs do cells carry out mitosis the most often? Stomach, Intestine, Skin In which body organs do cells carry out mitosis the least often? Brain and Muscle

CA 2006 All Cells are Different!! All cells live for different lengths of time Cells carry out mitosis at different rates in different organs to replace cells that are worn out Brain cells yrs Red Blood Cells 120 days Platelets 10 days Stomach Lining 2 days Cells Liver Cells 200 days Intestine Lining 3 days Cells Skin cells 20 days

CA 2006 Is the process the same in plants? What is missing? –Centrioles –Furrowing At the end of cell division a cell wall forms

CA 2006 Flaws in Mitosis When cells are dividing out of control, tumors are produced Cancer is one type of tumor that can result from out of control mitosis

CA 2006 Mutations Mutations = random mistakes in mitosis when DNA is duplicating Can result from radiation and pollution in the environment

CA 2006 Stop! Look at your notes! Write a summary that explains the cell cycle in your own words.