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Chapter 12 Notes

by: Kennedy Neil

Chapter 12 Notes BIO 120 35

Kennedy Neil

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Chapter 12 notes on Mitosis, Everything in bold is important information that should be spent extra time studying.
General Biology I
Dr. Jennifer Winther
Class Notes
Mitosis, General Biology I, general biology, Biology, BIO 120
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This 5 page Class Notes was uploaded by Kennedy Neil on Monday November 2, 2015. The Class Notes belongs to BIO 120 35 at Grand Valley State University taught by Dr. Jennifer Winther in Fall 2015. Since its upload, it has received 46 views. For similar materials see General Biology I in Biology at Grand Valley State University.


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Date Created: 11/02/15
Wednesday, October 28, 2015 BIO 120 - Chapter 12 Mitosis - Occurs in the somatic cells (all body cells except reproductive cells) - Required for growth and development - Required for tissue renewal - Cell division that results in genetically identical daughter cells (resulting cells of mitosis) - Occurs in eukaryotes - Involves duplication and the division of linear chromosomes - Usually followed by cytokinesis - Mitosis and the cell cycle • Only a very small part of the life span of a cell is spent in mitosis • Most of the time a cell is in interphase (not part of mitosis) - The times a cell prepares for mitosis - Three phases o interphase: • G1 - Cell doing its job in the organism • S (synthesis) - Chromosomes are duplicated • G2 - When the cell checks to make sure there were no errors and makes repairs - Division of chromosomes depends on microtubules and associated proteins in the mitotic spindle - Mitotic spindle Centrosomes: the origin of microtubules • 1 Wednesday, October 28, 2015 - Microtubules: Tubulin structures that elongate and shorten - Move and separate chromosomes - Kinetochores - a group of proteins that recognizes - 5 stages (Summarized on pages 236 and 237 of textbook) • Prophase - Centrosomes moving to opposite sides if cells - Chromosomes begin to condense • Prometaphase - Chromosomes completely condensed - No nuclear membrane - Mitotic spindle is attached to kinetochores • Metaphase - M for Middle - All chromosomes line up in the middle of the cell - Sister chromatids are facing opposite centromeres • Anaphase - A stands for Apart - Splitting apart sister chromatids • Telophase - Reform nuclear membrane - Chromosomes begin to unwind - Cytokinesis (Not part of mitosis) • Cytoplasm of a single parent cell is divided into two daughter cells - Start off smaller than the parent cell will grow • Uses a contractile ring made of actin that constricts cell membrane creating a cleavage furrow 2 Wednesday, October 28, 2015 - Cytokinesis in Cells with a Cell Wall (Plant cells) • No cleavage furrow • Requires formation of cell wall and plasma membrane - Mitosis without cytokinesis • Occurs in all types of eukaryotes • Results in large multinucleate cells - Advantages: Better cellular communication Chromosomes - A linear end to end arrangement of genes and other DNA with associated proteins (in eukaryotes; circular in bacteria and prokaryotes) - Structure: • DNA is packaged very efficiently in a chromosome • Chromosomes is the most tightly packed and condensed DNA can be • A way to keep things organized, prevent mistakes DNA + proteins = chromatin (all DNA and protein found in Chromosomes • • Chromatin varies in compactness/coiled-ness - Heterochromatin: Very dense, highly, repetitive, not very gene rich - Euchromatin: Less dense, gene rich • Parts of each chromosome has heterochromatin and others have euchromatin - Centromere: An area of DNA that is the same across all eukaryotes • Where duplicated chromosomes are attached • Required for mitosis • Defines a chromosome - 1. DNA is wrapped around Histones (proteins) to form Nucleosomes - 2. DNA nucleosome chain is further coiled and super-coiled 3 Wednesday, October 28, 2015 • Chromatin staining - Karyotype: Number and appearance of chromosomes - Duplication of chromosomes • Chromatid: identical subunits produced by chromosome replication ( I ) • Sister chromatids: are the two chromatids of a duplicated chromosome attached at centromere ( X ) - You can never have just one chromatid - Each diploid (2n) eukaryotic organism has own number of chromosomes in nucleus from 2n=2 up to 2n=1260 - Chromosomes come in pairs • Homologous chromosomes (code for the same things) - Humans are 2n = 46 chromosomes 22 pairs of homologous chromosomes • • 2 sex chromosomes Cell Cycle Controls - The stages of the cell cycle are controlled by a set of cyclically operating molecules - Before preceding to a new stage there are checkpoints (control points) where molecular signals are checked - Only if conditions are met at the checkpoints does the cell cycle proceed - Checkpoints during G1, end of G2, end of mitosis before cytokinesis - Most cells in an organism are in the stage of cell cycle before the first checkpoint (G0) - In cancer cells the checkpoints are either bypassed or don’t work - Cell culture • Manipulation of cell cycle control to obtain cells for research • Over 50 proteins have been identified that promote cell division (known as growth factors) 4 Wednesday, October 28, 2015 - Growth factors are often cell-type specific - HeLa Cells • Don’t ever stop dividing - Cell division in bacteria • Binary fission (Not Mitosis) 5


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