4 Vocabulary before we get started: DNA: DeoxyriboNucleic Acid—The genetic material of all of life! DNA is made up of nucleotides, and is the basis of all natural heredity traits of an organism.
5 Vocabulary before we get started: Prokaryotes- ‘Simple’ one-celled organisms that do not have a nucleus.Bacteria and Archeabacteria.Eukaryotes- ‘Higher’ organisms that have a nucleus and a more complete DNA.
6 Vocabulary before we get started: Centriole —Organelles found in animal cells that help with the process of mitosisCentromere —The area where sister chromatids are held together.
7 Vocabulary before we get started: Homologous Chromosome — A pair of similar chromosomes. In most organisms, one of these chromosomes came from the father, and the other chromosome came from the mother.Sister Chromatid —A sister chromatid is two copies of the same DNA sequence, held together by a centromere.
8 Vocabulary before we get started: Chromatin — A thread-like mass of DNA seen in the nucleus during most of the a cell’s lifeChromosome — a rod-like bundle of DNA seen during mitosis.
9 Vocabulary before we get started: Mother Cell — A cell that is about to divide by mitosis.Daughter Cells — The two cells that result from mitosis. Daughter cells will have identical DNA to each other, which is the same DNA that the mother cell had.
10 Mitosis Mitosis is the process of asexual cell division. Mitosis brings about growth & developmentMitosis enables healing when we get cut.Mitosis creates two identical cells from one cell.Each cell will have a full copy of the original DNA.
11 Why are we made up of so many tiny cells? Wouldn’t it be easier to just have fewer and larger cells?Cells are bustling with activity! They need proteins and smaller inorganic compounds to come in to and move out of the cell. They use these resources all throughout the cell, and every organelle needs to have access to these resources.
12 Why are we made up of so many tiny cells? Wouldn’t it be easier to just have fewer and larger cells?If a cell becomes bigger, the ratio of its surface area to its volume decreases. With a poorer ratio, resources can’t move into the cell quick enough to reach all of organelles.
13 Why are we made up of so many tiny cells? Wouldn’t it be easier to just have fewer and larger cells?Also:There is only one area in the cell where there is DNA, yet all of the cell needs the proteins that are made from the DNA. If a cell becomes too large, the demand onthe DNA to copy the necessary genesfor all of the cell to function becomestoo great.
14 Interphase The majority of the cell cycle. Interphase is made up of the G1, S, and G2 phases of the cell cycle.During this phase, chromosomes are copied.Chromosomes appear as threadlike coils (chromatin) during this phase.Cell MembraneNucleusCytoplasm
15 The bigger picture: The Cell Cycle! Interphase is made up of the G1, S, and G2 phases of the cell cycle.
17 Prophase 1st step in Mitosis The nuclear membrane breaks down.The chromatin condenses, and chromosomes become visibleCentrioles appear and begin to move to opposite end of the cell.Spindle fibers form between the centrioles.CentrioleschromosomesNuclear membraneSpindle fibers
19 Metaphase 2nd step in Mitosis Sister chromatids line up at the mid-line of the cell.Centromeres (the area where the sister chromosomes are held together) attach to the spindle fibers.CentriolesSpindle fibers
23 Telophase 4th step in Mitosis Two new nuclear membranes form.Chromosomes begin to appear as chromatin (threads rather than rods).Spindle fibers break down.Mitosis ends.NuclearMembraneNuclearMembraneChromatinforming
25 Cytokinesis after mitosis In animals: cell membrane pinches inward to create two daughter cells – each with its own nucleus with identical chromosomes.In plants: a cell wall forms between the newly divided cells.
29 A short film on mitosis.Mitosis animationCell animations
30 The bigger picture: The Cell Cycle! Mitosis is a very controlled process that only occurs in a small fraction of the cell’s life
31 How do little puppies grow up? Mitosis is the process that allows living things togrow. Without mitosis we wouldn’t ever grow and develop. So if we were to stop the mitosis in this puppy, we would be preventing it from ever getting any bigger.
32 When I get a cut, how do I heal? Mitosis is involved in healing after an injury. If we get a cut or a scrape, our body uses mitosis to heal itself.
33 Summary Thoughts:Every type of organism must grow and develop and then reproduce in order to continue the species.For eukaryotes, mitosis is the process by which organisms grow and develop. A hallmark of higher-order life is having a multi-cellular body, but since reproduction gives only a single fertilized cell, the cell must divide over and over again in order to make an organism. Mitosis is the process across all of the eukaryotic kingdoms by which this growth and development occurs.
34 Closing questions: On a half-sheet of paper, answer these questions: 1. How could you describe the cells that result from Mitosis?1. They contain no organelles.2. They are the same as the cell prior to mitosis.3. They contain half of the amount of DNA of the original cell.4. They must be either plant or animal cells.2. What are the four main stages of Mitosis?22.214.171.124.
35 Closing questions: On a half-sheet of paper, answer these questions: 3. Describe what happens during interphase:4. Describe the role of spindle fibers in mitosis. In what stage do they appear? Where do they connect to? When do they disappear?
36 The bigger picture: The Cell Cycle! The duration of the cell cycle varies in in different organisms, different tissues, and at different points in development, but it is a very controlled process.
37 How is the Cell Cycle Regulated? The cell cycle is regulated by a protein called cyclin.The cell cycle is also regulated with ‘Internal regulators.’The cell cycle is also regulated by ‘external regulators.’
38 What if the regulation fails? If a cell has too many cyclins, if the internal regulators fail, or if there are external regulators that are constantly signaling for mitosis to occur, a cell will continue to divide without stopping.A scenario where a cell is continually dividing when it shouldn’t be is called uncontrolled cell growth.