CELL DIVISION As cells grow they must divide Why?…(write your own answer) DNA and cell division Both daughter cells need a complete set of DNA, nothing missing, nothing extra DNA starts out as Chromatin (spread out DNA molecules) Chromatin turns into Chromosomes by the process of Condensation (tightly folding)

Chromosomes Chromosomes are the structures that contain genetic material we are passing from generation to generation in our cells. Chromatin is the relaxed form of DNA in a cell’s nucleus. Chromosomes are much more organized than chromatin.

Wound up in a big mess=Chromatin! nucleus DNA Very, very long! Wound up in a big mess=Chromatin! A very small piece of a chromosome=a GENE! Very Organized = Chromosomes

How do we get chromosomes from our DNA?

CELL DIVISION A Chromosome 1 chromatid Centromere 2 Identical copies

CELL CYCLE Open book to pg 246 Cell cycle is in 5 phases G1 ; S ; G2 ; M ; C G1 - Most of cell’s growth and activity S - DNA replicates G2 - Final preparations for division M - Nuclear division (mitosis) - Divided into 4 stages C - Cytokinesis - division of the cell

INTERPHASE . In between cell divisions (G1 , S, and G2 phases) Most of the cell’s life is in interphase Chromosomes are in the form of chromatin (diffuse and invisible) Each DNA replicates (makes a copy of itself) Centrioles begin to move to poles of cell

PROPHASE First stage of actual mitosis Chromatin condenses into chromosomes Nuclear membrane disappears Asters form at poles of cell (Not visible in plants) Astral rays connect to centromeres on chromosomes Asters and Astral rays together called the spindle Astral rays Chromosomes Aster

METAPHASE Chromosomes are pulled by astral rays Chromosomes line up along the equator of the cell

ANAPHASE Centromeres break Each chromosome is pulled apart into separate chromatids Spindle pulls chromatids toward poles

TELOPHASE Chromosomes disappear Nuclear membranes reappear Spindle disappears Cytokinesis -Cell membrane divides cell into 2 daughter cells (In plants cell wall forms between daughter cells) Daughter cells go back to interphase

Mitosis: animal cell

Mitosis: plant cell

The Internet is full of great Mitosis study tools…. http://www.youtube.com/watch?v=pOsAbTi9tHw