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Cell Division and Mitosis Test Cellular differentiation • Cell tissues organs organ systems • As cells grow and divide, many of them may form tissues inside the body – Muscle Tissue • If many tissues group together, they form organs – Ex: Bicep • Organ systems are the same as body systems it is when multiple organs work together to achieve a common goal – Ex: Muscular system Differentiation • When sperm and egg come together, one cell is created • That fertilized egg gives rise to an increased number of cells through cell division, which must divide creating identical cells • As cell division proceeds, cells also undergo differentiation becoming specialized in structure and function • This is done by a process called induction the use of chemical signals and proteins to alter a cells DNA to specify or determine its developmental fate • Once a cell differentiates-becomes specific cell- it cannot be reversed Stem cells • Stem cells unspecialized cells that continually reproduce themselves and have, under appropriate conditions, the ability to differentiate into one or more types of specialized cells • Two types: – Embryonic-embryos at a very early stage – Adult- various places in body can be stem cells • Under appropriate laboratory conditions, stem cells can differentiate into specialized cells Drawing Why do cells divide instead of just get larger? • The larger a cell gets, the more demand it puts on DNA to control the cell (DNA is the same regardless of size) • Large cells are not very efficient • Transport is very difficult • Cell division makes it easier to dispose of bad cells • If you had fewer larger cells, you would lose large portions of information when a cell dies Cell division and Mitosis If you want to make two batches of cookies instead of just one, what do you have to do to the recipe? Double it For a cell to be able to split in two, what does it need to do? Double the “ingredients” Organelles, DNA, etc. Vocabulary Chromosome one long continuous thread of DNA that contains many genes Looks like an “X” Chromatin loose combination of DNA, like a shoe string with knots in it Chromatid one half of a duplicated chromosome Half of the X Centromere junction between two halves Centrioles organelle responsible for cell division What’s the relationship between a chromosome and DNA A chromosome is made up of DNA DNA twists and folds itself to make a condensed chromosome The cell cycle Four main stages Interphase G1 (First Gap) cell goes through normal functions (growth) Checkpoint-cell must be big enough, mature enough, and have undamaged DNA Preparation stage for cell division Synthesis (S) cell makes a copy of DNA; nucleus now contains two sets of DNA G2 (second gap) additional growth-normal functions Checkpoint • Mitosis and cytokinesis Cell splits into two cells Mitosis and cytokinesis In the end, there will be two genetically identical “daughter” cells Interphase G1, S, G2 Mitosis Prophase Metaphase Anaphase Telophase Interphase • Preparing the cell to divide • Growth phase • DNA duplication • Cell has two identical sets of DNA, or chromatids and is large enough to divide Prophase Chromatin condenses into tightly coiled chromosomes Nuclear membrane breaks down The nucleolus disappears Centrioles begin to migrate to opposite poles Spindle fibers-made up of microtubules begin to grow from centrioles form what is called an Mitotic spindle Metaphase • Spindle fibers attach to centromere of each chromosome • Chromosomes line up on the “middle” Anaphase Chromosomes split, resulting in two half sized chromosomes X splits in half Spindle fibers begin to shorten which pulls the chromosomes away from each other Telophase • A complete set of identical chromosomes is positioned at each pole • Nuclear membrane begins to reform in each cell • Chromosomes begin to uncoil back into chromatin • Spindle fibers fall apart Cytokinesis In most eukaryotes • Divides the rest of the cell into two pieces • Actual splitting process • A cleavage furrow is formed from actin microfilaments • The filaments start contracting much like a drawstring Cytokinesis in Plant cells • The difference is in plants, the cell wall must also divide after telophase • Cannot form a clevage furrow, instead they must form a cell plate that enables the cell wall to divide The cell cycle control system • The cell cycle control system allows the cell to monitor and regulate cell division in order to prevent mistakes from happening • Checkpoints critical control point where stop and goahead signals can regulate the cycle – G1 checkpoint – G2 checkpoint – M checkpoint • External factors – Cell to cell contact if cells are “bumping” against one another, cell division will stop until some die to make room for new cells – Growth factors protein signals from neighboring cells that stimulate cell division • Internal factors – Apoptosis programmed cell death Application-Uncontrolled cell division • Cancers use the process of cell division to make bad cells multiply without any control • Transformation when a normal cell changes into a cancer cell and all regulation stops – The immune system usually recognizes this and destroys the cell • Cancers form disorganized groups of cells called tumors Two types of tumors • Two types: – Benign non-cancer cells that do not invade other cells. This usually means that the tumor is harmless and can be removed • This person is usually said to not have cancer – Malignant some of the cancer cells can break away, or metastasize from the tumor. These cells can be carried in the bloodstream or in lymph nodes and can form new cancerous tumors in other places • This person is said to have cancer Carcinogens • Carcinogen substances known to promote or produce the development of cancer cells • Smoking, drinking, drugs, too much of a lot of things can lead to cancer and apoptosis • Sometimes your body can detect when there is a problem • Ex: skin cells Treatment for cancer • Radiation therapy the use of radiation to kill cancer cells and shrink tumors. – It works by damaging the DNA of cells so they cannot divide – Radiation is localized-its use is targeted to a specific region-because it can hurt regular cells • Chemotherapy the use of drugs/poisons to kill actively dividing cells On your final sheet to turn in • Write a good test question on something we covered today. • Write down something that you are still struggling with and need some more explanation on. • What was the main idea of the lesson today? (your answer must be a sentence, not just mitosis)