Unit 6 - The Cell Cycle The white sections summarize key information and vocabulary terms are underlined.

Dreams I look to the sky and what do I see? A castle, a rainbow, and dreams for me, An end to this battle that I must fight, To rid my feelings of depression and fright, An end to cancer is not far away, It will be here someday... someday.cancer ~ Anonymous

Observations

What is the cell cycle? Much as your body goes through different stages in your life, the cells and viruses do too. The life cycle of the cell is known as the cell cycle. In this unit we will discuss the of the cell cycle (the process of making of new cells). mcewen/Media/fig_1_cell_mitosis.jpg

5 Reasons Cells Divide 1.Growth- an organism will increase in size as the number of cells making up that organism increase 2.Differentiation- cells develop specialized cells to carry out specific tasks ex: the heart cell versus the muscle cell 3.Repair- to repair lost or damaged cells ex: mending of skin, blood vessels and bone 4.Regeneration- ability to replace a lost limb or body part by rapid cell division ex: starfish, lizard

5 Reasons Cont. And finally… 5.Reproduction – the making of a new organism E981849F2E31603F7154F

Cell Division The splitting of a single cell into two new daughter cells is called cell division. This will occur when a cell reaches it’s maximum size and the nucleus initiates cell division; proteins called cyclins and enzymes begin this process. ei.ac.jp/PDB/Ima ges/Sarcodina/H eliozoa/Actinosph aerium/cell_divisi on_1.jpg

Two Types of Cell Division Mitosis- the division of body cells (AKA somatic cells) due to the splitting of the nucleus to create two new cells. Meiosis – the creation of gametes (AKA sex cells) by cutting the # of chromosomes in half to create sex cells. smeiosis;jsessionid=B368026AB01E981849F2E3 1603F7154F

Chromosomes Review: We have already learned that genetic information is held within the nucleus (of eukaryotes) in the form of DNA. Therefore, it is very important that cells must copy their genetic information before dividing. Cells tightly coil their DNA into chromosomes during the process of mitosis. museum.org/exhibitdna/images/ dna/intro02.gif

Chromosomes Cont.

Chromosomes Cont. During mitosis, identical chromosomes pair up and are now called sister chromatids (1), held together by a centromere (2). Sketch it! n/5/54/Chromosome.png

Stage #1 Interphase 1.Interphase = The period of growth for the cell before cell division (the longest stage) which is broken up into the following phases: G 1 – growth and development organelles copied –After G 1 cells typically enter a resting phase, G 0 S – synthesis phase; copies of the DNA G 2 – more growth tosis-26hzktr.jpg

Knowledge Check During the course of the life of a cell, there is a complicated series of checkpoints to ensure that everything is going according to plan. When something happens to the genes for these “checkpoints”, cancer can develop.

Stage #2 Prophase 2.Prophase = The beginning of M phase [mitosis] DNA condenses and forms chromosomes Identical chromosomes (Xsomes) join Nucleus disappears Centrioles (the organelles which form the spindles) move to opposite poles Spindle fibers (long strings that help the cell divide) begin to grow tosis-26hzktr.jpg

Stage #3 Metaphase 3.Metaphase = Xsome pairs line up along the middle of the cell on the metaphase plate Centrioles have moved to the poles; spindle fibers attach to Xsomes. 26hzktr.jpg

Metaphase Cont. Arep/images/metaphase1_pc.jpg

Stage #4 Anaphase 4.Anaphase = The centromeres divide and spindle fibers pull the chromosomes apart from their partners The chromatids move to opposite poles of the cell

Stage #5 Telophase 5.Telophase = The nuclei reform at each end of the cell Chromosomes uncoil into chromatin (or loose genetic material) Spindles release Xsomes and shorten. The cell begins to pinch as the cytoplasm begins to divide 26hzktr.jpg

Stage # 6 Cytokinesis 6.Cytokinesis = The final stage in M phase that divides the cell cytoplasm –In animals, the cell membrane is drawn inward (cleavage furrow). –In plants, a cell plate is built to create new cells walls and membranes. Each half has one nucleus and gets own set of centrioles (+ organelles) The cell is now two and enters Interphase (G1). Animation s/i77_dwa_1_mitosis.gif

“During mitosis, after all the genetic material is sorted out, the cell splits all of its cytoplasmic goodies in two and sends them to opposite ends. It then constricts in the middle and eventually ‘pinches’ in half, producing two daughter cells. The location at which the pinching in occurs is known as the cleavage furrow.” Imagemitosiscytoplasmic goodiesImage Cytokinesis Cont.

Visualizing Mitosis Prophase InterphaseMetaphase Anaphase Telophase

Ex Mnemonics Example: I = “I P = please M = make A = another T = two C = cells!”

Student Created Example: I = “Intelligent P = people M = make A = all T = the C = cash!”

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