2 Cell Cycle - Mitosis CAMPBELL BIOLOGY TENTH EDITION Reece Urry Cain Wasserman Minorsky Jackson Outline I. Overview II. Mitotic Phase I. Prophase II. III. Telophase IV. Cytokinesis III. Binary fission IV. Cell Cycle Control Lecture Presentation by Dr Burns NVC Biol 20 204 Pearson Education, Inc. Overview: The Key Roles of Cell Division Figure 2. The ability of organisms to produce more of their own kind best distinguishes living things from nonliving matter The continuity of life is based on the reproduction of cells, or cell division Overview: The Key Roles of Cell Division In unicellular organisms, division of one cell reproduces the entire organism Multicellular organisms depend on cell division for Development from a fertilized cell Growth Repair Cell division is an integral part of the cell cycle, the life of a cell from formation to its own division Most cell division results in genetically identical daughter cells Most cell division results in daughter cells with identical genetic information, DNA The exception is meiosis, a special type of division that can produce sperm and egg cells (next weeks lab)
Cellular Organization of the Genetic Material Figure 2.3 All the DNA in a cell constitutes the cell s genome A genome can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells) DNA molecules in a cell are packaged into chromosomes 20 m s Eukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell division Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus Somatic cells (nonreproductive cells) have two sets of chromosomes Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells Distribution of s During Eukaryotic Cell Division In preparation for cell division, DNA is replicated and the chromosomes condense Each duplicated chromosome has two sister chromatids (joined copies of the original chromosome), which separate during cell division The centromere is the narrow waist of the duplicated chromosome, where the two chromatids are most closely attached Figure 2.4 Distribution of s During Eukaryotic Cell Division Sister chromatids During cell division, the two sister chromatids of each duplicated chromosome separate and move into two nuclei Centromere 0.5 m Once separate, the chromatids are called chromosomes 2
Figure 2.5- s Centromere Chromosomal DNA molecules Figure 2.5-2 s Centromere Chromosomal DNA molecules arm arm duplication (including DNA ) and condensation 2 Sister chromatids Figure 2.5-3 s Centromere Chromosomal DNA molecules The region where the chromatids are tightly associated is called 2 3 arm duplication (including DNA ) and condensation Sister chromatids Separation of sister chromatids into two chromosomes. Centrosome 2. Chromatin 3. Centromere 4. 25% 25% 25% 25% 2 3 4 Microtubule-organizing centers have two Eukaryotic Cell Division. Centrioles 2. Chromatins 3. Centromeres 4. s 25% 25% 25% 25% Eukaryotic cell division consists of Mitosis, the division of the genetic material in the nucleus Cytokinesis, the division of the cytoplasm 2 3 4 3
The mitotic phase alternates with interphase in the cell cycle In 882, the German anatomist Walther Flemming developed dyes to observe chromosomes during mitosis and cytokinesis When does DNA replicate? Just prior to cell division Cells need to divide for organisms to grow or to replace old cells, or for one celled organisms to reproduce Before a cell divides it needs to replicate its DNA Phases of the Cell Cycle Phases of the Cell Cycle - Interphase The cell cycle consists of Mitotic (M) phase (mitosis and cytokinesis) Interphase (cell growth and copying of chromosomes in preparation for cell division) Interphase (about 90% of the cell cycle) can be divided into subphases G phase ( first gap ) S phase ( synthesis ) G 2 phase ( second gap ) The cell grows during all three phases, but chromosomes are duplicated only during the S phase The eukaryotic cell cycle is regulated by a molecular control system The frequency of cell division varies with the type of cell These differences result from regulation at the molecular level Cancer cells manage to escape the usual controls on the cell cycle The Cell Cycle Control System The sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to a clock The cell cycle control system is regulated by both internal and external controls The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received 4
Figure 2.5 G checkpoint The Cell Cycle Control System For many cells, the G checkpoint seems to be the most important G M Control system G 2 S If a cell receives a go-ahead signal at the G checkpoint, it will usually complete the S, G 2, and M phases and divide M checkpoint G 2 checkpoint If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G 0 phase Figure 2.6 Figure 2.6 INTERPHASE G checkpoint G 0 G S (DNA synthesis) G 2 G G (a) Cell receives a go-ahead signal. (b) Cell does not receive a go-ahead signal. Mitotic Phase Mitosis is divided into four phases Prophase Anaphase Telophase Cytokinesis overlaps the latter stages of mitosis BioFlix: Mitosis 5
0 m 0 m 0 m Figure 2.7 Figure 2.7a G 2 of Interphase Prophase Prometaphase Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Fragments Aster of nuclear Centromere Nonkinetochore microtubules G 2 of Interphase Prophase Prometaphase Anaphase Telophase and Cytokinesis Centrosomes (with centriole pairs) Chromatin Fragments (duplicated) Early mitotic Aster of nuclear spindle Centromere Nonkinetochore microtubules plate Cleavage furrow Nucleolus Plasma Nucleolus Nuclear membrane, consisting of two sister chromatids microtubule Spindle Centrosome at one spindle pole Daughter chromosomes Nuclear Nucleolus Nuclear Plasma membrane, consisting of two sister chromatids microtubule Figure 2.7b Figure 2.7c Anaphase Telophase and Cytokinesis plate Cleavage furrow Nucleolus G 2 of Interphase Prophase Prometaphase Spindle Centrosome at one spindle pole Daughter chromosomes Nuclear Figure 2.7d G2 of Interphase Anaphase Telophase and Cytokinesis G 2 of Interphase Prophase Prometaphase Centrosomes (with centriole pairs) Nucleolus Nuclear Chromatin (duplicated) Plasma membrane Nuclear present Centrosomes are duplicated s are in the duplicated state (DNA occurred during S phase of interphase) 6
Prophase Prophase Early mitotic Aster spindle Centromere, consisting of two sister chromatids Prometaphase s condense Nucleolus disappear Mitotic spindle appears Centrosomes move to opposite poles of the cell Nuclear fragments Microtubles attach to the kinetochore Spindle plate Centrosome at one spindle pole Centrosomes are at opposite ends of cell Telophase and Cytokinesis s line up at the metaphase plate Anaphase Anaphase Daughter chromosomes Cohesion proteins are cleaved, sister chromatids separate, now each are a chromosome microtubules shorten, moving the daughter chromosomes to opposite poles of the cell Cell elongates due to nonkinetochore microtubules lengthening Telophase Telophase and Cytokinesis Cleavage furrow Nuclear Nucleolus Two identical daughter nuclei form, nuclear s form Nucleolus reappears s uncondense Spindle microtubles depolymerize Cytokinesis Telophase and Cytokinesis Cleavage furrow Nuclear Nucleolus Cytoplasm divides In animal cells, cleavage furrow pinches the cell in two The Mitotic Spindle: A Closer Look The mitotic spindle is a structure made of microtubules that controls chromosome movement during mitosis In animal cells, assembly of spindle microtubules begins in the centrosome, the microtubule organizing center The centrosome replicates during interphase, two centrosomes that migrate to opposite ends of the cell during prophase 7
The Mitotic Spindle: A Closer Look An aster (a radial array of short microtubules) extends from each centrosome The spindle includes the centrosomes, the spindle microtubules, and the asters The Mitotic Spindle: A Closer Look During prophase, some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes s are protein complexes associated with centromeres At metaphase, the chromosomes are all lined up at the metaphase plate, an imaginary structure at the midway point between the spindle s two poles Figure 2.8 Sister chromatids Aster Overlapping nonkinetochore microtubules microtubules Centrosome plate (imaginary) s Microtubules s Centrosome m The place where microtubules attach is called the. Centriole 2. Chromatin 3. Centromere 4. 25% 25% 25% 25% 0.5 m 2 3 4 Where does DNA take place? During this stage the nuclear membrane breaks down. Cytosol 2. Nucleus 50% 50%. 2. Anaphase 3. Prophase 4. Telophase 25% 25% 25% 25% 2 2 3 4 8
During this stage chromosomes line up at the equator During this stage the chromosomes begin to uncondense. 2. Anaphase 3. Prophase 4. Telophase 25% 25% 25% 25%. 2. Anaphase 3. Prophase 4. Telophase 25% 25% 25% 25% 2 3 4 2 3 4 At the end of Mitosis the chromosomes are in the duplicated state. Yes 2. No 50% 50% 2 Animation: Cytokinesis Right-click slide / select Play Animation: Animal Mitosis Right-click slide / select Play Animation: Sea Urchin (Time Lapse) Right-click slide / select Play 9
Videos Cytokinesis: A Closer Look Youtube Mitosis in embryo Mitosis in newt lung cell Mitosis In animal cells, cytokinesis occurs by a process known as cleavage, a cleavage furrow In plant cells, a cell plate made of cell wall material forms during cytokinesis In bacteria, the new cell wall grows out from the existing cell wall Figure 2.0 Binary Fission in Bacteria (a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM) Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission Cleavage furrow 00 m Vesicles cell plate Wall of parent cell Cell plate m New cell wall In binary fission, the chromosome replicates, and the two daughter chromosomes actively move apart Contractile ring of microfilaments Daughter cells Daughter cells The plasma membrane pinches inward, dividing the cell into two. New cell wall grows out from old cell wall. Figure 2.2- Origin of Cell wall Plasma membrane Figure 2.2-2 Origin of Cell wall Plasma membrane begins. Two copies of origin E. coli cell Bacterial chromosome begins. Two copies of origin E. coli cell Bacterial chromosome 2 Replication continues. Origin Origin 0
Figure 2.2-3 Origin of Cell wall Plasma membrane Figure 2.2-4 Origin of Cell wall Plasma membrane begins. Two copies of origin E. coli cell Bacterial chromosome begins. Two copies of origin E. coli cell Bacterial chromosome 2 Replication continues. Origin Origin 2 Replication continues. Origin Origin 3 Replication finishes. 3 Replication finishes. 4 Two daughter cells result. The Evolution of Mitosis Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis Figure 2.3 (a) Bacteria (b) Dinoflagellates (c) Diatoms and some yeasts Bacterial chromosome s Microtubules Intact nuclear microtubule Intact nuclear (d) Most eukaryotes microtubule Fragments of nuclear At the end of mitosis are the chromosomes in the duplicated state? At the end of mitosis in plants the cell wall forms by. Yes 2. No 50% 50%. Proteins constrict and pinch off the new cell 2. Vesicles line up between the cells and join together 3. The new cell wall grows out from old cell wall 33% 33% 33% 2 2 3
Figure 2.UN05 Important concepts for lecture exams Know all the vocabulary presented in the lecture Know the form (condensed vs uncondensed) that DNA is in during cell division vs interphase Know the roles of microtubules, and their structure Know the role of microtubule-organizing centers Know the two stages of cell cycle (interphase and mitotic phase Important concepts for lecture exam Know what happens during the stages of interphase: G phase, S phase, G 2 phase. Know what happens during each checkpoint Know the role of microfilaments in cell division of animal cells, the structure of microfilaments Understand how cytokinesis takes place in animal, plant, and bacterial cells Important Concepts for Lab Exam For Mitosis: Know each stage, the order of the stages, and what happens in each stage. Know what the end result is of mitosis Know what state the cell and the chromosomes are in at the beginning and end of mitosis. For example: Are the cells haploid or diploid? Are the chromosomes duplicated, or not duplicated? How many chromosomes are there in the cell? Are they in pairs? Be able to identify the stages using models and slides 2