CELL DIVISION

Key Concepts What events take place during the three stages of the cell cycle?

Key Terms cell cycle – interphase – replication – The regular sequence of growth and division that cells undergo. The stage of the cell cycle that takes place before cell division occurs. The process by which a cell makes a copy of the DNA in its nucleus.

Key Terms mitosis – chromosome – cytokinesis – The stage of the cell cycle during which the cell’s nucleus divides into two new nuclei and one copy of the DNA is distributed into each daughter cell. A double rod of condensed chromatin; contains DNA that carries genetic information. The final stage of the cell cycle, in which the cell’s cytoplasm divides, distributing the organelles into each of the new cells.

Introduction A multicellular organism grows in size because it’s cells are increasing in number.

Three Stages of Cell Division Stage 1: Interphase Stage 2: Mitosis Stage 3: Cytokinesis The period before cell division. One nucleus divides to create two. Completes the process of cell division.

The period before cell division. Stage 1: Interphase The period before cell division.

The Resting Stage? Growing Copying DNA Preparing for Division The cell grows to full size. The cell makes new structures it needs or duplicates others. Copying DNA A replication (exact copy) for the new cell is made. Preparing for Division Centrioles (structures used for cell division) are made.

One nucleus divides to create two. Stage 2: Mitosis One nucleus divides to create two.

It’s All About the . . . CHROMOSOMES!

The Many “Faces” of A Chromosome Chromatin (threadlike) A mass of genetic material composed of DNA and proteins that condense to form chromosomes. Chromosome (letter X) A condensed, double-rod, form of chromatin. Chromatid Two identical strands of DNA that form a chromosome. Centromere A structure that holds the chromatids together. CHROMATIN CHROMOSOME

Phase 1: Prophase Chromosomes and spindle fibers form. Nuclear envelope (membrane) breaks down.

Phase 2: Metaphase Chromosomes line up across the center and attach to a spindle fiber.

Phase 3: Anaphase Centromeres split. Chromatids separate and move to opposite ends.

Phase 4: Telophase Chromosomes stretch out. New nuclear envelope (membrane) forms around chromosomes.

Completes the process of cell division. Stage 3: Cytokinesis Completes the process of cell division.

Like Mother Like Daughter Cell pinches in two. Each daughter cell has the same number of identical chromosomes.

Animal Cells vs. Plant Cells The cell membrane squeezes together around the middle of the cell. The cytoplasm pinches into two cells. A cell plate forms between the two new nuclei. The cell plate gradually develops into new cell membranes. New cell walls then form around the cell membranes.

Animations Control of the Cell Cycle How the Cell Cycle Works http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html How the Cell Cycle Works http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html Mitosis & Cytokinesis http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html Animal Cell Mitosis http://iknow.net/player_window.html?url=media/prophase_video_auto.swf&width=360&height=285 Plant Cell Mitosis http://iknow.net/player_window.html?url=media/plant_mitosis_auto.swf&width=360&height=285

What is the Purpose of Cell Division? When the cell volume/surface increases, then a cell must divide or split into two, because if it doesn't then it would literally just be one huge blob. Cell division is necessary for all life, without it then you would barely exist. Cells need to divide because if you lose older cells, how else would you replace them? Your body consists of millions or billions of cells, and without them you wouldn't be you!