How Cells Divide-Mitosis Chapter 7a Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cell Division in Prokaryotes Prokaryotic cell division occurs as binary fission in which the cell divides into two halves. Genetic information exists as a single, circular double-stranded DNA molecule. Copying begins at replication origin. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Discovery of Chromosomes All eukaryotic cells store genetic information in chromosomes. Most eukaryotes have between 10 and 50 chromosomes in their body cells. Human cells have 46 (23 pairs). Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Structure of Chromosomes Chromosomes are composed of chromatin, a complex of DNA and protein. Heterochromatin and Euchromatin. DNA exists as a single, long double-stranded fiber extending chromosome’s entire length. Forms nucleosome every 200 nucleotides. DNA coiled around histone proteins. Karyotype - An individual’s particular array of chromosomes. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Structure of Chromosomes Diploid - A cell possessing two copies of each chromosome (Human body cells). Homologous chromosomes made up of sister chromatids joined at the centromere. Haploid - A cell possessing a single copy of each chromosome (Human sex cells). Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Phases of the Cell Cycle Five phases of cell division: G1 - Primary Growth Phase S - Genome Replicated G2 - Secondary Growth Phase Collectively called Interphase M - Mitosis C - Cytokinesis Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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G1 - Cells undergo majority of growth. Interphase G1 - Cells undergo majority of growth. S - Each chromosome replicates to produce sister chromatids. Attached at centromere. Contains attachment site (kinetochore). G2 - Chromosomes condense. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

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Nuclear Envelope Breaks. Mitosis Prophase Spindle apparatus assembled. Microtubules connect kinetochores on each pair of sister chromatids to the spindle poles. Nuclear Envelope Breaks. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Chromosomes align in cell’s center. Metaphase plate. Mitosis Metaphase Chromosomes align in cell’s center. Metaphase plate. Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Sister chromatids pulled towards poles. Poles move apart. Mitosis Anaphase Sister chromatids pulled towards poles. Poles move apart. Centromeres move toward poles. Microtubules shorten. Telophase Spindle disassembles. Nuclear envelope forms around each set of sister chromatids. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cleavage of cell into two halves. Animal Cells Cytokinesis Cleavage of cell into two halves. Animal Cells Constriction belt of actin filaments. Plant Cells Cell plate Fungi and Protists Mitosis occurs within the nucleus. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cell Control Cycle Eukaryotic cells employ centralized controller to regulate cell division. (Go/no-go switches) G1 - Cell Growth G2 - DNA Replication M - Mitosis Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Raven - Johnson - Biology: 6th Ed Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Molecular Mechanisms of Cell Control Each growing cell binds minute amounts of positive regulatory signals (growth factors) that stimulate cell division. If neighboring cells use up too much growth factor, there is not enough left to trigger cell division. Growth factors trigger intercellular signaling systems. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cell Proliferation-Signaling Pathway Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cancer and Cell Proliferation Cancer is essentially a failure of cell division control. Gene p53 plays a role in G1 checkpoint. Halts cell division if detects damaged DNA and stimulates activity of repair enzymes. Appears to be absent in many cancerous cells. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Cancer and Cell Proliferation Growth factors influence cell cycle. Proto-oncogenes - Positive approach that stimulates cell growth. Tumor-suppressor genes - Negative approach that inhibits cell division. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Practice identifying phases: Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies