Cell Cycle and Cell Communication 3. A Cell Cycle and Cell Communication 3.A.2 – In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle, meiosis and mitosis Recommended Reading: 10.2, 10.3, 10.4

Phases of the Cell Cycle The cell cycle consists of Mitotic (M) phase (mitosis and cytokinesis) Interphase (cell growth and DNA synthesis/copying of chromosomes in preparation for cell division/mitosis) Some texts divide this into three phases: growth, DNA synthesis, and preparation for meiosis.

Interphase (about 90% of the cell cycle) can be divided into subphases G1 phase (“first gap”) S phase (“synthesis”) G2 phase (“second gap”) The cell grows during all three phases, but chromosomes are duplicated only during the S phases.

INTERPHASE S (DNA synthesis) G1 Cytokinesis G2 Mitosis Figure 12.6 INTERPHASE S (DNA synthesis) G1 Cytokinesis G2 Mitosis MITOTIC (M) PHASE Figure 12.6 The cell cycle.

Cell Cycle How does the cell “know” how to do this though? Different “factors” exist that help promote this growth (molecules that trigger a response or reaction with other molecules). Mitosis-promoting factor (MPF) which preps/starts mitosis. Disruption to some of these triggers can contribute to cancerous growth as well disruptions in transcription/translation.

Cell Cycle – Cyclin and Cyclin-Dependent Kinases Cyclin and Cyclin-Dependent Kinases control the cell cycle. What are they? When cells specialize, their cell cycle may stop unless retriggered. Any cells you’ve heard of that don’t divide or we get more of?

Cyclin and cyclin-dependent kinases Cyclin acts as a “promoter” or “halter” of different forms of growth in the cell cycle.

Mitosis/Meiosis Review Do we remember these? Mitosis represents a small percentage of the cell cycle outside of interphase. Peer-peer instruction – study and create a quiz for each other to do on Kahoot or Socrative?

Mitosis is conventionally divided into five phases Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis overlaps the latter stages of mitosis For the Cell Biology Video Myosin and Cytokinesis, go to Animation and Video Files. BioFlix: Mitosis © 2011 Pearson Education, Inc.

Chromosome, consisting of two sister chromatids Figure 12.7 10 m G2 of Interphase Prophase Prometaphase Metaphase Anaphase Telophase and Cytokinesis Centrosomes (with centriole pairs) Chromatin (duplicated) Early mitotic spindle Fragments of nuclear envelope Nonkinetochore microtubules Aster Metaphase plate Cleavage furrow Nucleolus forming Centromere Figure 12.7 Exploring: Mitosis in an Animal Cell Plasma membrane Nucleolus Nuclear envelope Chromosome, consisting of two sister chromatids Kinetochore Kinetochore microtubule Nuclear envelope forming Spindle Centrosome at one spindle pole Daughter chromosomes

Chromosome, consisting of two sister chromatids Figure 12.7a G2 of Interphase Prophase Prometaphase Centrosomes (with centriole pairs) Fragments of nuclear envelope Chromatin (duplicated) Early mitotic spindle Aster Nonkinetochore microtubules Centromere Figure 12.7 Exploring: Mitosis in an Animal Cell Plasma membrane Nucleolus Kinetochore Kinetochore microtubule Chromosome, consisting of two sister chromatids Nuclear envelope

Metaphase Anaphase Telophase and Cytokinesis Metaphase plate Figure 12.7b Metaphase Anaphase Telophase and Cytokinesis Metaphase plate Cleavage furrow Nucleolus forming Figure 12.7 Exploring: Mitosis in an Animal Cell Nuclear envelope forming Spindle Centrosome at one spindle pole Daughter chromosomes

Mitosis Passes a ____________________ from a parent cell to a daughter cell. Occurs after ___________________. Is followed by _____________ which produces two genetically identical daughter cells. Order:

Mitosis Passes a complete genome from a parent cell to a daughter cell. Occurs after DNA replication. Is followed by cytokinesis which produces two genetically identical daughter cells. Order: Replication of DNA, Alignment of chromosomes, separation of cells. OR PMAT!

Meiosis Creates ______________ for fertilization to occur in sexual reproduction. Each gamete receives one ______________ set of chromosomes (___). During meiosis homologous chromosomes are paired (each of which originating from the organism’s maternal and paternal parents). When these homologues separate this ensures that each gamete gets a haploid set of chromosomes. ______________ occurs as well in which homologues “react” with one another exchanging genetic information increasing variation in gametes. Fertilization is when two gametes meet and form a ______________!

Meiosis Creates gametes for fertilization to occur in sexual reproduction. Each gamete receives one haploid set of chromosomes (1n). During meiosis homologous chromosomes are paired (each of which originating from the organism’s maternal and paternal parents). When these homologues separate this ensures that each gamete gets a haploid set of chromosomes. Crossing over occurs as well in which homologues “react” with one another exchanging genetic information increasing variation in gametes. Fertilization is when two gametes meet and form a diploid zygote!