10 – 2 Cell Division Mitosis

Chromosomes DNA is passed on in chromosomes DNA is passed on in chromosomes Every organism has a specific # of chromosomes: Every organism has a specific # of chromosomes: fruit flies 8 humans 46 Before division called sister “chromatids” Before division called sister “chromatids” Chromatids are attached with a centromere and become … Chromosomes are only visible during cell division Chromosomes are only visible during cell division

The Cell Cycle During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which then begins the cell cycle again. During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which then begins the cell cycle again. 1. Interphase = growth 1. Interphase = growth 2. Mitosis = division 2. Mitosis = division

Events of the Cell Cycle Interphase Interphase Period of growth Period of growth Hereditary material is in the form of chromatin Hereditary material is in the form of chromatin 3 stages: 3 stages: G 1 - “growth” G 1 - “growth” Increase in cell size in # of organelles, and in # of proteins Increase in cell size in # of organelles, and in # of proteins S – “synthesis” S – “synthesis” DNA replication (chromatin is doubled) DNA replication (chromatin is doubled) G 2 – “growth” G 2 – “growth” Continued cell growth Continued cell growth nucleolus chromatin centrioles

Mitosis Begins Mitosis is when a cell divides into two new cells. Mitosis is when a cell divides into two new cells. Mitosis is one of the shortest parts of a cells life. Mitosis is one of the shortest parts of a cells life. However, it has the most stages. However, it has the most stages.

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Mitosis (1. prophase) Mitosis – period of cell division Mitosis – period of cell division 4 stages: 4 stages: Prophase – “prepare” Prophase – “prepare” Longest phase of mitosis Longest phase of mitosis Chromatin coils up and forms chromosomes Chromatin coils up and forms chromosomes Duplicated chromosmes are made up of 2 identical sister chromatids connected at the centromeres Duplicated chromosmes are made up of 2 identical sister chromatids connected at the centromeres Sister chromatid centromere Identical Sister chromatid

Mitsosis (1. prophase) Prophase (continued) Prophase (continued) Nucleolus and nuclear membrane fade away, causing the nucleus to disappear. Nucleolus and nuclear membrane fade away, causing the nucleus to disappear. Centrioles move to opposite ends of the cell Centrioles move to opposite ends of the cell Centrioles – cylindrical structures made of microtubles Centrioles – cylindrical structures made of microtubles Spindle fibers form between the centrioles Spindle fibers form between the centrioles Spindle – Pulls the sister chromatides apart. Spindle – Pulls the sister chromatides apart. *the spindle attaches to the chromosome at the centromere* spindle centriole

Mitosis (2. Metaphase) Metaphase “middle” Metaphase “middle” Chromosomes attach to the spindle fibers at their centromere Chromosomes attach to the spindle fibers at their centromere Chromosomes line up along the middle of the cell (equator) Chromosomes line up along the middle of the cell (equator)

Mitosis (3. Anaphase) Anaphase – “apart” Anaphase – “apart” Sister chromatids are pulled apart by centrioles. Sister chromatids are pulled apart by centrioles.

Mitosis (4. Telophase) Telophase – “tear into two” Telophase – “tear into two” Chromatids reach the opposite sides (pole) of the cell Chromatids reach the opposite sides (pole) of the cell Chromosomes uncoil or unwind (chromatin) Chromosomes uncoil or unwind (chromatin) Spindle fibers begin to break down Spindle fibers begin to break down Nucleolus reappears Nucleolus reappears New nuclear membrane forms around each new set of chromosomes New nuclear membrane forms around each new set of chromosomes Plasma membrane begins to separate into 2 new nuclei Plasma membrane begins to separate into 2 new nuclei

Cytokinesis Division of cytoplasm Division of cytoplasm In animals: “cleavage furrow” pinches the plasma membrane to divide the cytoplasm In animals: “cleavage furrow” pinches the plasma membrane to divide the cytoplasm In plants: “cell plate” forms to divide the cytoplasm In plants: “cell plate” forms to divide the cytoplasm

Cell division-again! Fmg Fmg Fmg Fmg