Chapter 8 The Cellular Basis of Reproduction and Inheritance PowerPoint Lectures for! Biology: Concepts and Connections, Fifth Edition! Campbell, Reece, Taylor, and Simon Lectures by Chris Romero
Objective: a. Recognize the chromosomes of daughter cells, formed through the processes of asexual reproduction and mitosis, the formation of somatic (body) cells in multicellular organisms, are identical to the chromosomes of the parent
! Reproduction is one phase of an organism's life cycle! Sexual reproduction! Fertilization of sperm and egg produces offspring
Asexual reproduction! Offspring are produced by a single parent, without the participation of sperm and egg! Cell division is at the heart of organismal reproduction
CONNECTIONS BETWEEN CELL DIVISION AND REPRODUCTION Like begets like, more or less! Asexual reproduction! Chromosomes are duplicated and cell divides! Each daughter cell is genetically identical to the parent and the other daughter! Sexual reproduction! Each offspring inherits a unique combination of genes from both parents! Offspring can show great variation
Cells arise only from preexisting cells! 1858 Rudolf Virchow: "Every cell from a cell"! This is at the heart of the perpetuation of life! Can reproduce an entire unicellular organism! Is the basis of sperm and egg formation! Allows for development from a single fertilized egg to an adult organism! Functions in an organism's renewal and repair
Prokaryotes reproduce by binary fission! Prokaryotic cells reproduce asexually by a type of cell division called binary fission! Genes are on one circular DNA molecule! The cell replicates its single chromosome! The chromosome copies move apart! The cell elongates! The plasma membrane grows inward (cleaves), dividing the parent into two daughter cells
LE 8-3a Prokaryotic! chromosome Plasma! membrane Cell wall Duplication of chromosome! and separation of copies Continued elongation of the! cell and movement of copies Division into! two daughter cells
LE 8-3b Prokaryotic chromosomes Colorized TEM 32,500
THE EUKARYOTIC CELL CYCLE AND MITOSIS The large, complex chromosomes of eukaryotes duplicate with each cell division! Eukaryotic genes! Many more than in prokaryotes! Grouped into multiple chromosomes in the nucleus
Eukaryotic chromosomes! Contain a very long DNA molecule associated with proteins! Most of the time occur in the form of thin, loosely packed chromatin fibers! Condense into visible chromosomes just before cell division
Eukaryotic cell division! 1. Chromosomes replicate! Sister chromatids joined together at the centromere! 2. Sister chromatids separate! Now called chromosomes! 3. Cell divides into two daughter cells! Each with a complete and identical set of chromosomes
LE 8-4b Sister chromatids Centromere TEM 36,600
LE 8-4c Chromosome! duplication Centromere Sister! chromatids Chromosome! distribution! to! daughter! cells
The cell cycle multiplies cells! The cell cycle: an ordered series of events extending from the time a cell is formed until it divides into two! 3 Major processes:! I. Interphase! II. III. Mitosis! Cytokinesis
Most of the time of cell cycle is in interphase! 3 Stages:! G1: cell grows in size! S: DNA synthesis (replication) occurs! G2: Cell continues to grow and prepare for division!
The cell actually divides in mitotic (M) phase! Mitosis: nuclear division! Cytokinesis: cytoplasmic division! Duplicated chromosomes evenly distributed into two daughter nuclei
LE 8-5 INTERPHASE G 1 S! (DNA synthesis) MITOTIC! PHASE (M) Cytokinesis Mitosis G 2
Cell division is a continuum of dynamic changes! Interphase: Duplication of the genetic material ends when chromosomes begin to become visible! Prophase (the first stage of mitosis): The mitotic spindle is forming. Centrosomes migrate to opposite ends of the cell Chromatins completely coil into chromosomes; nucleoli and nuclear membrane disperse
Metaphase: The spindle is fully formed; chromosomes are aligned single file with centromeres on the metaphase plate! Anaphase: Chromosomes separate from the centromere, dividing to arrive at poles! Telophase: Cell elongation continues, a nuclear envelope forms around chromosomes, chromosomes uncoil, and nucleoli reappear! Cytokinesis: The cytoplasm divides
LE 8-6a LM 250 Centrosomes! (with centriole pairs) INTERPHASE PROPHASE PROPHASE Chromatin Early mitotic! spindle Centrosome Fragments! of nuclear! envelope Kinetochore Nucleolus Nuclear! envelope! Plasma! membrane! Chromosome, consisting! of two sister chromatids! Centromere! Spindle! microtubules!
LE 8-6b METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Metaphase! plate Cleavage! furrow Nucleolus! forming Spindle Daughter! chromosomes Nuclear! envelope! forming
Cytokinesis differs for plant and animal cells! Animals! Ring of microfilaments contracts into cleavage furrow! Cleavage occurs! Plants! Vesicles fuse into a membranous cell plate! Cell plate develops into a new wall between two daughter cells Animation: Cytokinesis
LE 8-7a Cleavage! furrow SEM 140 Cleavage furrow Contracting ring of! microfilaments Daughter cells
TEM 7,500 LE 8-7b Cell plate! forming Wall of! parent cell Daughter! nucleus Cell wall New cell wall Vesicles containing! cell wall material Cell plate Daughter cells
8.8 Anchorage, cell density, and chemical growth factors affect cell division! An organism must be able to control the timing of cell division! Anchorage dependence!! Most animal cells must be in contact with a solid surface to divide
Density-dependent inhibition! Cells form a single layer! Cells stop dividing when they touch one another! Inadequate supply of growth factor causes division to stop
LE 8-8a Cells anchor to! dish surface! and divide. When cells have! formed a complete! single layer, they! stop dividing! (density-dependent! Inhibition). If some cells are! scraped away, the! remaining cells! divide to fill the dish! with a single layer! and then stop! (density-dependent! inhibition).
LE 8-8b After forming a! single layer,! cells have! stopped dividing. Providing an! additional supply of! growth factors! stimulates! further cell division.
8.9 Growth factors signal the cell cycle control system! The cell cycle control system regulates the events of the cell cycle! If a growth factor is not released at three major checkpoints, the cell cycle will stop! G 1 of interphase! G 2 of interphase! M phase
LE 8-9a G 0 G 1 checkpoint G 1 Control! system S PowerPoint Lectures for! Biology: Concepts and Connections, Fifth Edition! Campbell, Reece, Taylor, and Simon M G 2 M checkpoint Lectures by Chris Romero G 2 checkpoint
How a growth factor might affect the cell cycle control system! Cell has receptor protein in plasma membrane! Binding of growth factor to receptor triggers a signal transduction pathway! Molecules induce changes in other molecules! Signal finally overrides brakes on the cell cycle control system
LE 8-9b Growth factor Plasma membrane Receptor! protein Relay! proteins G 1 checkpoint Signal! transduction! pathway PowerPoint Lectures for! Biology: Concepts and Connections, Fifth Edition! Campbell, Reece, Taylor, and Simon G 1 M Control! system G 2 S Lectures by Chris Romero
CONNECTION 8.10 Growing out of control, cancer cells produce malignant tumors! Cancer cells do not respond normally to the cell cycle control system! Divide excessively! Can invade other tissues! May kill the organism
If an abnormal cell avoids destruction by the immune system, it may form a tumor! Benign: abnormal cells remain at original site! Malignant: abnormal cells can spread to other tissues and parts of the body! Metastasis: spread of cancer cells through the circulatory system
LE 8-10 Lymph! vessels! Tumor Blood vessel! Glandular! tissue! A tumor grows from a! Cancer cells invade! Neighboring tissue.! PowerPoint single cancer Lectures cell.! for! Biology: Concepts and Connections, Fifth Edition! Campbell, Reece, Taylor, and Simon Cancer cells spread through! lymph and blood vessels to! other parts of the body.! Lectures by Chris Romero
Cancers are named according to location of origin! Carcinoma: external or internal body coverings! Sarcoma: tissues that support the body! Leukemia and lymphoma: blood-forming tissues! Radiation and chemotherapy are effective as cancer treatments because they interfere with cell division
8.11 Review of the functions of mitosis: growth, cell replacement, and asexual reproduction! When the cell cycle operates normally, mitotic cell division functions in! Growth! Replacement of damaged or lost cells! Asexual reproduction Video: Hydra Budding