The Process of Cell Division

Section 10.2The Process of Cell Division What happens when you are done growing?Does cell division STOP?

Chromosomes Chromosome = Genetic information bundled into packages of DNACells must package large molecules very carefully. They are able to do this because of chromosomes

Even small cells like E-Coli have A LOT of DNATotal amount of DNA = 1.6mm1,000 times longer than the cell!

Chromosomes have an important role in cell divisionThey must make a complete copy of their genetic information before cell division begins

3Prokaryotic Chromosomes No nucleusTheir DNA is found in the cytoplasm

Most prokaryotes contain a single, circular DNA chromosome that contains all of the cells genetic information

Eukaryotic Chromosomes Eukaryotic cells generally have a lot more DNA than prokaryotes and will contain multiple chromosomes.

The number of chromosomes depends on the organism.Fruit flies = 8 chromosomes per cellHuman cells = 46 chromosomes per cellCarrot cells = 18 chromosomes per cellDog cells = 78 chromosomes per cell

Chromosomes form a close association with histonesHistones = type of protein

Chromatin = DNA tightly coiled around histones

DNA tightly coils around the histones and together they form a beadlike structure called nucleosomes

The Cell CycleCells go through a series of events known as the cell cycleDuring the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells

Prokaryotic Cell CycleAsexual reproduction also known as binary fissionResults in the production of 2 genetically identical daughter cells

Eukaryotic Cell CycleConsists of 4 phasesG1SG2 M

Interphase period in the cell cycle between cell divisionG1 S G2

G1phase = cell growthS phase = DNA replicationG2 = preparing for cell division

M phase = cell division2 main stages: 1. mitosis2. cytokinesis

MitosisMitosis the division of the cell nucleus Four phasesProphaseMetaphaseAnaphaseTelophaseDepending on the cell mitosis can last a few minutes to several days

Prophase The first phase of mitosis Usually the longest phase

What happens during prophase?Chromatin condense into chromosomesThe centrioles move to opposite ends of the pole and begin to make spindle fibersThe nuclear membrane and nuclear envelope break down

Metaphase Second phase in mitosisGenerally the shortest phase

What happens during metaphase?Chromosomes line up in the middle of the cellChromosomes are connected to spindle fibers at the centromere

Anaphase 3rd phase of mitosis

What happens during anaphase?Chromosomes separate and pulled to opposite ends of the cell by the spindle fibers

Telophase The fourth phase of mitosis

What happens during telophase? Spindle fibers begin to break apartThe nuclear envelope begins to form around each set of chromosomes

Cytokinesis Cytokinesis = division of the cytoplasm

The cytoplasm pinches in halfEach daughter cell has an identical set of chromosomes