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