Mitosis • Definition: nuclear division and cytokinesis • Functions: • tissue growth and repair • asexual reproduction (binary & multiple fission)
Cell division requires coordinated division of chromosomes (mitosis)… …and division of the cytoplasm (cytokinesis).
Because DNA stores genetic information and is faithfully replicated, information is passed largely unaltered from cell-to-cell, generation-to-generation.
Proteins and Their Production The Primary Reason for DNA
duplicated chromosome chromatin DNA is Packaged into Chromosomes Two meters DNA fit into a sphere ~ 0.000005 meters in diameter.
DNA is Condensed into Visible Chromosomes Only For Brief Periods in the Life of a Cell 95% of the time, chromosomes are like this.
A Karyotype is an Arranged Picture of Chromosomes At Their Most Condensed State Note that almost all chromosomes come in homologous pairs. Boy or girl? A normal human karyotype
nuclear membrane disintegrates chromatin thickens spindle apparatus appears Prophase
centromers divide chromatids move toward opposite poles Anaphase
nuclear membrane reforms cytokinesis daughter cells Telophase
In Animal Cells, a Cleavage Furrow Forms and Separates Daughter Cells Cleave furrow in a dividing frog cell.
In plants, a cell plate forms; separating daughter cells during cytokinesis
Stages of Mitosis • Prophase– DNA is condensed and packaged • Metaphase– “middle stage”; Condensed chromosomes line up along the equatorial plane. • Anaphase- Copies of each chromosome move to opposite poles of the cell. • Telophase– “end stage”; Nuclear membranes reform around the chromosomes and cytokinesis occurs resulting in two daughter cells.
Licentious division - prostate cancer cells during division. Cancer is Runaway Mitosis