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Introduction to the Cell Cycle Here’s what we’ll be discussing in MUCH more detail…. Limits to cell growth Why do cells divide? Why don’t they just grow larger and larger? Problem #1. Our DNA has it’s limits. All of the information that a cell needs to function is stored in it’s DNA. • DNA is packaged into chromosomes. A chromosome consists of one very long linear DNA molecule with 1000's of genes. Our DNA has it’s limits! • Each gene is the instructions for making a particular protein that the cell needs. • As the cell grows too large, there is an “information crisis”. The DNA cannot keep up with the demands of running a larger cell. Problem #2. A Growing Cell Needs More Food • A cell must constantly take in food and get rid of waste. • As the cell grows, the volume of the cell increases much more rapidly than the surface area of the cell membrane. • When the cell gets too large, the membrane surface area is not adequate enough to transport the large quantities of food, water, and waste. Cell Division • Cell division is the process by which a cell divides it’s contents into two daughter cells. 1 mother cell 2 daughter cells • The 2 daughter cells will be IDENTICAL to the mother cell. Chromosomes • A cell must first copy it’s chromosomes before division can occur. Chromosomes • Chromosomes condense before cell division occurs. • After condensing and replicating, the chromosomes consist of two sister chromatids. • These chromatids are connected in the middle by a centromere. The Cell Cycle • The cell cycle is a series of events that cells go through as they grow and divide. • During the cell cycle: -A cell grows -A cell prepares for division -A cell divides into two daughter cells The Cell Cycle The cell cycle consists of five major stages: • • • • • G1 (Gap 1) S (Synthesis) G2 (Gap 2) Mitosis Cytokinesis Before a cell can begin mitosis, it must first do two things… 1) Duplicate it’s DNA (chromosomes) 2) Duplicate a supply of organelles This was a CRASH COURSE in what we will cover in this unit. We will discuss all of these things in detail.