The Cellular Basis of Reproduction and Inheritance

Transcription

1 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

2 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

3 ! Reproduction is one phase of an organism's life cycle! Sexual reproduction! Fertilization of sperm and egg produces offspring

4 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

5 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

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7 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

8 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

9 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

10 LE 8-3b Prokaryotic chromosomes Colorized TEM 32,500

11 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

12 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

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14 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

15 LE 8-4b Sister chromatids Centromere TEM 36,600

16 LE 8-4c Chromosome! duplication Centromere Sister! chromatids Chromosome! distribution! to! daughter! cells

17 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

18 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!

19 The cell actually divides in mitotic (M) phase! Mitosis: nuclear division! Cytokinesis: cytoplasmic division! Duplicated chromosomes evenly distributed into two daughter nuclei

20 LE 8-5 INTERPHASE G 1 S! (DNA synthesis) MITOTIC! PHASE (M) Cytokinesis Mitosis G 2

21 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

22 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

23 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!

24 LE 8-6b METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Metaphase! plate Cleavage! furrow Nucleolus! forming Spindle Daughter! chromosomes Nuclear! envelope! forming

25 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

26 LE 8-7a Cleavage! furrow SEM 140 Cleavage furrow Contracting ring of! microfilaments Daughter cells

27 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

28 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

29 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

30 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).

31 LE 8-8b After forming a! single layer,! cells have! stopped dividing. Providing an! additional supply of! growth factors! stimulates! further cell division.

32 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

33 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

34 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

35 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

36 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

37 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

38 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

39 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

40 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

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