Cell Division http://www.cellsalive.com/cells/3dcell.htm

A. Introduction Multicellular & Unicellular organisms must divide to produce new cells for: *Reproduction *Growth (by increasing in cell #; multicellular organisms only) *Replace cells that have died from disease, injury, old age

2. Types of Cells **Eukaryotic (multicellular) organisms have 2 types of cells= Somatic Cells: Regular body cells that divide using Mitosis (used by unicellular organisms to reproduce) b. Germ Cells: Cells that produce gametes (reproductive cells known as the egg or sperm) and divide using Meiosis

3. Cell Division & DNA a. The nucleus of a cell contains a material known as chromatin which is actually DNA in a thin, spaghetti-like form. It tightly coils up to form chromosomes, but only during cell division. centromere Chromatid Chromosome Sister

Cell Division & DNA b. During cell division, the chromatin condenses and coils into structures known as chromosomes. c. Every organism of a specific species has the same number of chromosomes in each somatic cell. EXAMPLES:. *human = 46 *chimpanzee = 48 *chicken = 78 *fruit fly = 8

*Matching chromosomes form Homologous Pairs. Cell Division and DNA Chromosomes can be matched into pairs (one from mom and one from dad) by size and appearance. *Matching chromosomes form Homologous Pairs.

Terms that refer to Chromosome Number: e. Diploid: a cell that has a complete set of chromosomes. Both chromosomes in each homologous pair are present in the cell. Example = a SOMATIC cell.

Terms that refer to Chromosome Number: Haploid: a cell that has half of the complete set of chromosomes. Only one chromosome of each homologous pair is present in the cell. Example = GAMETES = Egg or Sperm

B. Cell Cycle G1 S G2

B. Cell Cycle *G1 = Growth 1: Cell is growing Interphase: Cell is producing proteins and carrying out normal cell function. NOT a phase of Mitosis or Meiosis! *G1 = Growth 1: Cell is growing *Synthesis: Cell is replicating DNA *Growth 2: Cell is preparing to divide 2. Cell Division: Cell divides its genetic material in the nucleus by way of mitosis or meiosis.

Cell Cycle Cytokinesis = the division of the cytoplasm following cell division; NOT a part of mitosis or meiosis.

MITOSIS Definition = the division of the nucleus and the chromosomes of a diploid somatic cell that results in the formation of 2 identical, diploid somatic cells.

C. MITOSIS Stages: 1. Prophase Nuclear membrane & nucleolus disappear Centrioles move to opposite sides of the cells Chromatin becomes chromosomes Spindle fibers appear; will help to move chromosomes

PROPHASE CENTRIOLES SPINDLES CHROMOSOME DISAPPEARING NUCLEAR ENVELOPE

PROPHASE PROPHASE CELL

METAPHASE

METAPHASE METAPHASE CELL

MITOSIS Chromosomes line up individually in the center of cell 2. Metaphase Chromosomes line up individually in the center of cell Spindles fibers connect to each chromosome at the centromere.

ANAPHASE

ANAPHASE ANAPHASE CELL

MITOSIS 3. Anaphase Chromatids of each chromosomes are separated by the spindle fibers Separated chromatids move to centrioles at opposite sides of the cell

TELOPHASE

TELOPHASE

MITOSIS 4. Telophase Chromosomes uncoil into chromatin Nuclear membranes form around each area of chromatin Spindle fibers disappear Nucleoli reappear in each nuclear area Two nuclei form, each with a complete set of chromosomes. Mitosis ends (cells not separated yet) A cleavage furrow begins to form

D. AFTER MITOSIS Cytokinesis The division of the cytoplasm following mitosis or meiosis In animal cells, a cleavage furrow divides the cytoplasm to form two new cells. In plants, a cell plate divides the cytoplasm Cells are genetically identical Called Daughter Cells Each is diploid Each is in interphase

CYTOKINESIS

Mitosis and Cytokinesis Animation Cell division animation New Animation of mitosis Actual mitosis