The Process of Cell Division Section 10.2

What happens when you are done growing? Does cell division STOP?

Chromosomes Chromosome = Genetic information bundled into packages of DNA Cells 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 DNA Total amount of DNA = 1.6mm 1,000 times longer than the cell! Chromosomes have an important role in cell division They must make a complete copy of their genetic information before cell division begins

Prokaryotic Chromosomes No nucleus Their DNA is found in the cytoplasm Most prokaryotes contain a single, circular DNA chromosome that contains all of the cell’s 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 cell Human cells = 46 chromosomes per cell Carrot cells = 18 chromosomes per cell Dog cells = 78 chromosomes per cell

Chromosomes form a close association with histones Histones = 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 Cycle Prokaryotic Cell Cycle Cells go through a series of events known as the cell cycle During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells Prokaryotic Cell Cycle Asexual reproduction also known as binary fission Results in the production of 2 genetically identical daughter cells

Eukaryotic Cell Cycle Consists of 4 phases G1 S G2 M Interphase – period in the cell cycle between cell division G1 S G2 G1phase = cell growth S phase = DNA replication G2 = preparing for cell division M phase = cell division 2 main stages: 1. mitosis 2. cytokinesis

Mitosis Mitosis – the division of the cell nucleus Four phases Prophase Metaphase Anaphase Telophase Depending 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 chromosomes The centrioles move to opposite ends of the pole and begin to make spindle fibers The nuclear membrane and nuclear envelope break down

Metaphase Second phase in mitosis Generally the shortest phase What happens during metaphase? Chromosomes line up in the middle of the cell Chromosomes 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 apart The nuclear envelope begins to form around each set of chromosomes

Cytokinesis Cytokinesis = division of the cytoplasm The cytoplasm pinches in half Each daughter cell has an identical set of chromosomes