Cell Cycle

10. Cell Cycle 

  • Functions: reproduction, growth/development, tissue renewal 
  • Genetic material    * Genome: all DNA in cell (gene instructions)     * Prokaryotes: circular      * Eukaryotes: many linear   * Chromatin: loose DNA and proteins   * Chromosomes: DNA/proteins packaged tight      * Eukaryotes have chromatin; condenses during cell division (DNA wound around histone proteins which organize DNA and nucleosomes) 
  • Chromosome number    * Ploidy: number of sets of chromosomes (2 sets of 23 in humans)   * Haploid: 1 set of chromosomes (n)     * Gametes: sex cells    * Diploid: 2 sets of chromosomes (2n)     * Somatic: body cells 
  • Chromosome structure   * Genes are instructions for protein   * Centromere: pinched in part    * Before mitosis DNA is doubled (sister chromatids form, ploidy has no change, same genetic information with 2x mass)
  • Cell cycle    * Goal: identical copies; starting ploidy = ending ploidy      * Prokaryotes: binary fission (double in size, split)      * Eukaryotes: interphase (growth, DNA replication (most of time) and mitotic (M) phase with mitosis/cytokinesis)   * G1 phase     * 90% of life, no DNA synthesis, cell functions/communication/protein manufacture   * S phase     * Chromosomes duplicate, identical sister chromatids, held together @ centromere with cohesion proteins, kinetochores (protein handles) grow from centromere   * G2 phase     * Centrosomes duplicate, 2 centrioles each centrosome, function: move chromosomes   * Prophase     * Chromosomes condense, mitotic spindle forms, centrosomes -> opposite poles, nuclear envelope breaks down, spindles attach to kinetochore handles; chromatids can be observed    * Metaphase     * Longest stage, chromosomes line up @ metaphase plate; chromatids can be observed   * Anaphase     * Shortest, cohesion proteins cleaved by enzyme (disjunction), chromosomes move to opposite poles, 2 complete sets of chromosomes (2n each side)   * Telophase     * 2 new daughter cells that are =, envelope reforms   * Cytokinesis (not part of M)     * Cytoplasm divides (some cells don’t go through this)     * Animals: cleavage furrow     * Plants: cell plate   * Return to interphase

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