CELL DIVISION

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CELL DIVISION
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LETS WARM UP!

• Decide if these statements are true. If not
  true, correct them.
• Cell theory tells us that cells arise from
  chemical reactions.
• Cells passively receive energy and nutrients.
• In a multicellular organism, some cells
  specialize.

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CELL DIVISION OCCURS IN ALL ORGANISMS All
organisms start out as a single cell

• Unicellular
• Reproduction
• Two new organisms
• Genetically Identical
• Process called Binary Fission
• http//www.microbelibrary.org/microbelibrary/files
  /ccImages/Articleimages/MondoMedia/2bhirez.mov

• Multicellular
• Growth
• Development
• Repair
• Reproduction

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Binary Fission

• TEM Image of Bacteria

• SEM Image of Bacteria

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REVIEW OF EUKARYOTIC CELLS

• Eukaryotic cells include the following
• Distinct Nucleus
• Membrane-bounded organelles
• Genetic Material is organized in chromosomes
• Cells are neatly arranged

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DNA

• DNA stands for Deoxyribonucleic Acid
• Blueprint of an organism
• Located in the nucleus of a cell
• Can be found in two forms
• 1. Chromatin
• 2. Chromosome

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JAMES WATSON and FRANCIS CRICK

• Discovered the structure of DNA in 1953
• Figured out the following
• DNA is made up of two strands
• Resembles a twisted ladder or a Double Helix

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THE DOUBLE HELIX

• DNA Structure
• Sugar-Phosphate Backbone (Sides of the Ladder)
• Nitrogen Base Pairs
• (A bonds with T
• G bonds with C)
• Rungs of the Ladder
• DNA - The Double Helix

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CHROMATIN OR CHROMOSOME?

• Chromatin
• Thin, uncoiled strands thread-like
• In this form during most of a cells life cycle
  (Cell is NOT dividing)
• DNA Replicates
• Made of DNA and Protein

• Chromosome
• Coiled strands wrapped around globules of
  proteins called Histones
• Rod-Shaped
• In this form during cell division
• Can be seen under a light microscope
• Made of DNA and Protein

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TRANSITION FROM CHROMATIN TO CHROMOSOME

• Only the Physical Arrangement of the DNA is
  CHANGED
• Chemical Make-Up of the DNA Remains the SAME

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CHROMOSOMES

• Two identical parts, each called a chromatid
• Two chromatids are known as sister chromatids
  (Identical)
• Chromatids are held together at a point called a
  centromere

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CHROMOSOME NUMBERS

• Number of chromosomes in each cell differs among
  species
• Potato, Plum, and Chimpanzee 48
• Fruit Fly 8
• Ameba 50
• Human 46
• Chromosome Number DOES NOT Indicate the
  Complexity of an Organism!

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CELL DIVISION IS NEEDED FOR GROWTH

• By adulthood your body 100 trillion cells
• Limits to cell growth (Surface area to volume
  ratio)
• Cell getting too BIG could possibly trigger cell
  division

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DEVELOPMENT

• Organisms grow through Cell Division
• During Development , cells become specialized
• Shape Function

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REPAIR

• Cell Division is needed to heal cuts and broken
  bones
• Old and Damaged Cells
• Human Body 200 different types of cells
• You lose 40,000 skin cells every minute
• Mature Muscle, Nerve, and Brain Cells DO NOT
  Divide

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THE CELL CYCLE

• A cycle of the events of a cells life
• Includes growth, development, and division
• Interphase G1, S, and G2
• Mature Muscle, Nerve, and Brain Cells DO NOT
  Divide
• ML Content Review
• Cell Cycle An Interactive Animation
• Control of the Cell Cycle