<p> PreAP/GT Cell Cycle Notes 2015</p><p>Why Do Cells Divide Instead of Just Growing Bigger and Bigger?  The cell's _____ would no longer be able to serve the increasing needs of the growing cell.</p><p> The cell has more trouble moving enough ______and ______across the cell membrane. </p><p> o Larger cells have a smaller ratio of surface area to volume. </p><p>Prokaryotic vs. Eukaryotic Prokaryotic Cell Division: Binary Fission</p><p></p><p>Eukaryotic Cell Division: ______</p><p>Eukaryotic vs. Prokaryotic DNA  Prokaryotic DNA – located in the ______o Lack nucleus and many eukaryotic organelles o Have a single circular DNA molecule (usually referred to as the cell's chromosome)  Eukaryotic DNA- located in the ______in form of various chromosomes</p><p>Deoxyribonucleic Acid (DNA)  Definition:</p><p> Responsible for determining all organism’s traits (sequence of bases): </p><p> o Ex’s ______</p><p>The Components of DNA  DNA is a long molecule made up of repeating individual units </p><p> called ______</p><p> Nucleotides are made up of three parts: 1.1.1. 1.1.2. 1.1.3. **Nucleotides Put Together = DNA </p><p>DNA contains four nitrogenous bases: 1. 2. 3. 4.</p><p>______discovered that there were always equal amounts of A & T. And equal amounts of C & G in cells. The base pairs are held together by ______bonds. (No matter what organism it is!!!!)</p><p>Purines and Pyrimidines</p><p> Purines have ______rings in their structures. ( ______& ______belong to this group)  Pyrimidines have ______ring in their structure.(______&______belong to this group)</p><p>Structure of DNA  ______&______- Form the backbone or sides of the ladder.</p><p> ______- Form the “rungs” of the ladder or middle of the molecule.</p><p>Shape of DNA: DNA looks like a “twisted ladder” called a ______.</p><p>Discovering DNA</p><p>1. ______- Used X-ray diffraction; Showed the X-shaped pattern of DNA (helix shape)</p><p>2. ______and ______– Two scientists that discovered the double helix shape in 1953</p><p>You Try It!</p><p> What is the complimentary DNA strand if the original DNA strand is AGTCTA? ______</p><p>Chromosomes ______- Very long, continuous single piece of DNA, contains many genes ______- Sequence of DNA that codes for a protein and thus determines a trait</p><p> In eukaryotic cells, the genetic information that is passed on from one generation of cells to the next is carried by chromosomes. </p><p> The cells of every organism have ______</p><p> o The cells of fruit flies have 8 chromosomes.</p><p> o Human cells have ______chromosomes.</p><p> o Carrot cells have 18 chromosomes.</p><p> Chromosomes are not visible in most cells except during ______. </p><p> Well before cell division, each chromosome is ______(During the S Phase of Interphase). </p><p> DNA molecules are surprisingly long: 4, 639, 221 base pairs in E. coli</p><p> At the beginning of cell division, however, the chromosomes condense into compact, visible structures; they are folded and tightly packed to fit within the cell.</p><p> Each chromosome consists of two identical “sister” ______. </p><p> o When the cell divides, the “sister” chromatids separate from each other. </p><p> o One chromatid goes to each of the two new cells.</p><p> Each pair of chromatids is attached at an area called the ______.  If a meerkat’s parent skin cell contained 34 chromosomes; after cell division how many chromosomes would each of the meerkat’s daughter skin cells contain? ______</p><p>S-Phase: DNA Replication</p><p> Before a cell divides, it duplicates its DNA via a process called ______</p><p> Occurs during ______of cell division</p><p> Ensures that each resulting cell will have a complete ______set of DNA molecules</p><p>Result: Two identical DNA molecules (each DNA molecule has one original strand and one new strand)</p><p>How DNA Replication Occurs  Step 1: </p><p> o Helicase, an enzyme, ______</p><p> o Hydrogen bonds between ______are broken</p><p> o Result = 2 separated strands of DNA</p><p> Step 2: A replication fork is formed.</p><p> Step 3: Free floating nucleotides pair up with complimentary bases </p><p> o Each strand of DNA serves as a template, or model, for the new strand </p><p> o DNA Polymerase –</p><p>Eukaryotic Cell Cycle  Cell Cycle - Series of events that cells go through as they grow and replicate.</p><p> o Interphase - Period of the cell cycle between cell divisions (consists of ______phases)</p><p> o M Phase – </p><p>. (division of the cell nucleus) </p><p>. (division of the cytoplasm) </p><p> o There are 3 “______” that allow the cells to continue moving through the cell cycle.</p><p>Regulating the Cell Cycle  Not all cells move through the cell cycle at the same rate.  Cell growth and cell division are controlled.</p><p> ______are proteins that regulate the timing of the cell cycle in ______. </p><p> If cells are placed in a petri dish containing nutrient broth (provides food for the cells): </p><p> o Cells will grow until they form a thin layer covering the bottom of the dish. </p><p> o Then, the cells stop growing, when they come into ______with other cells. </p><p> If cells are removed from the center of the dish: </p><p> o The cells bordering the open space will begin dividing until they have filled the empty space.</p><p> This occurs in an injury as well:</p><p> o If a cut in the skin or a break in a bone occurs, cells at the edges of the injury are stimulated to divide rapidly.</p><p> o When the healing process nears completion, the rate of cell division slows down.</p><p>Cancer  Cancer –</p><p> o Cancer cell divide ______and form masses of cells (tumors) </p><p> o Cancer cells may spread throughout the body: </p><p> o Disrupts normal activities and causes serious medical problems or even death</p><p> o There are many reasons that cells can divide and grow out of control:</p><p>. Exposure to environmental causes:</p><p>. Nutritional deficiencies; genetic causes; some infections</p><p>Cell Cycle (2 phase)- Interphase</p><p> G1 Phase –</p><p> o G1 Checkpoint </p><p> S Phase – </p><p> G2 Phase – </p><p> o G2 Checkpoint</p><p>Cell Cycle – M Phase (cell division)</p><p> Cell Division –  M Phase –Mitosis (division of the cell nucleus)  Cytokinesis (division of the cytoplasm) o Before cell division occurs, the cell replicates, or copies, all of its DNA. o Each daughter cell gets one complete set of genetic information. </p><p>Asexual Reproduction  Reproduction by Mitosis is classified as asexual, since the cells produced by mitosis are: </p><p> Asexual Reproduction - Reproduction without the fusion of gametes; not necessary to have ______parents </p><p> o Examples include: </p><p>.</p><p>.</p><p>Four Phases of Mitosis 1. ______(chromosomes visible/centrioles; nuclear envelope disappears)</p><p>2. ______(microtubles line the chromosomes up in middle of cell ) </p><p>3. ______(sister chromatids separate to opposite ends of cell)</p><p>4. ______(chromosomes condense back to chromatin and nuclear envelope reappears)</p><p>(Four phases are followed by ______)</p><p>Cytokinesis - Usually occurs at the same time as ______. </p><p>It is the division of the ______</p><p> Animal Cells: ______</p><p> Plant Cells: ______</p>