MITOSIS AND CELL DIVISION Chapter 6 Key Terms

MITOSIS AND CELL DIVISION Chapter 6

Key Terms Mitosis: The process in which the nucleus divides to form two identical nuclei Chromosome: structure in the nucleus that contain DNA Asexual reproduction: new organism is produced from one organism

Other Words to Know Chromatid: one copy of duplicated chromosome usually joined to the other by a centromere Centromere: part of the chromosome that links sister chromatids

Tennessee State Standards Addressed Grade 7 GLE 0707. 1. 4 Illustrate how cell division occurs in sequential stages to maintain the chromosome number of a species. SPI 0707. 1. 4 Sequence a series of diagrams that depict chromosome movement during plant cell division.

Why do cells divide? Why do you think cells divide? � Cells have to divide in order to live � Complex organisms need cells to carry out functions (Cell Theory) � Organisms have cells that break down and become non-working everyday Red Blood cells & bone marrow

How do cells divide? • Life Cycles Every living thing has a life cycle • Formation Cells also have a life cycle Cell Cycle Death Growth & Developme nt

The Cell Cycle has 3 Phases: Interphase Mitosis � Prophase � Metaphase � Anaphase � Telophase Cytokinesis

Interphase Most of the cell cycle is spent in INTERPHASE This is a period of growth & development Cells like our muscle & nerve cells are always in interphase (they do not divide any longer) Our skin cells prepare for Mitosis by going through Interphase � They copy their DNA during this time

Why would a cell copy its DNA? Cells have to copy DNA in order for us to survive DNA contains all of our instructions for life DNA is replicated so that the daughter cells can have a copy of the DNA

Mitosis After interphase, the cell begins the next step in the cell cyle: MITOSIS Mitosis: is the process of dividing the cell’s nucleus into two nuclei There are 4 phases of MITOSIS � Prophase � Metaphase � Anapase � Telophase

s a h p o r P e An ap ha se Me tap ha se e s a h p o el

Prophase can be divided into two parts � Early Prophase & Late Prophase Early Prophase: Chromosomes begin to condense Centrioles moves to opposite ends of cell (ANIMAL CELLS ONLY) Plants DO NOT have

Prophase Late Prophase � Centriole pairs move apart � Nuclear envelope starts to break down/disentegrate

Metaphase 2 nd stage of Mitosis Chromatids line up at center of cell Spindle fibers attach to centromeres

Anaphase Anaphase is the THIRD phase of Mitosis Each pair of chromatids separate, because the spindle fibers begin to shorten The separated chromatids are now called chromosomes

Telophase is the LAST phase of Mitosis TWO NEW NUCLEI form, but the two new cells are still connected Spindle fibers start to disappear

Cytokinesis occurs after the last phase of Mitosis The CYTOPLASM separates and two new cells form

Mitosis in Plant Cells

Plant Cytokinesis Plant cells have walls, so cytokinesis cannot proceed with a cleavage furrow. During telophase a cell plate forms across the cell in the location of the old metaphase plate. Eventually, the growing cell plate fuses with the existing plasma membrane, producing two daughter cells, each with its own plasma membrane. A new cell wall forms between the two membranes of the cell plate.

Plant & Animal Cytokinesis

Results of Mitosis 3 Important Things to Remember: 1. 2. 3. Mitosis is the division of the nucleus Produces 2 nuclei identical to each other & the original nucleus The original cells no longer exists

Other Things to Consider: Not all cells are the same Certain cells only use part of the DNA with info needed to become a specific cell type � Muscle cells, nerve cells � Cells take the DNA and become specific cells with certain jobs Cell division allows growth and replaces worn out or damaged cells

Asexual Reproduction Asexual reproduction: A new organism (sometimes more than one) is produced from one organism The new organism will have DNA identical to the parent DNA Do eukaryotic cells produce sexually, asexually, or both?

Cellular Asexual Reproduction Eukaryotic cells reproduce asexually by mitosis & cell division Sweet potato growing in a jar The potato’s stem, leaves, & roots produced are the same as the parent’s

Bacterial Reproduction: Fission Do bacteria have a nucleus? How do they reproduce? Bacteria reproduce asexually by Binary Fission. During fission, the one-celled organism without a nucleus copies its genetic material and then divides into two identical organisms

Binary Fission: Monera

Binary Fission: Monera DNA replicates

Binary Fission: Monera DNA separates and new cell wall divides Cell in two

Binary Fission: Monera 2 new Identical cells are produced

Budding as Reproduction Budding is another type of asexual reproduction Budding is made possible by cell division and mitosis An adult organism will have a “bud” on it and it eventually gets large enough to live on its own

Regeneration as Reproduction Regeneration: process that uses mitosis & cell division to re-grow body parts Sponges, planaria, sea stars, and some lizards all use regeneration � If the organism breaks into pieces, a whole new organism can grow from each piece � Because sea stars eat oysters, oyster farmers dislike them: What would happen if an oyster farmer cut sea stars into pieces & threw them back into the ocean?

Questions for Understanding What is mitosis? How is it different in plant & animal cells? What are two examples of asexual reproduction in many-celled organisms? What happens to chromosomes before Mitosis? Compare/Contrast the two new cells formed after mitosis & cell division.