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Unit 2: The Cell The Cell Cycle Review Notes Med Choi Fill
  1. The continuity of life is based upon cell division , the reproduction of cells. Cell division takes place in a sequence of events called the cell cycle .
     
     
  2. Cell division is asexual and results in genetically identical daughter cells; each of which receives an exact copy of the genetic material, DNA , from its "parent".
     
     
  3. Prokaryotes reproduce by a type of cell division called binary fission, where the DNA is replicated , and then the two daughter DNA strands actively move apart.
     
     
  4. Eukaryotic DNA is packaged into chromatin , a complex of DNA and protein that condenses into chromosomes during cell division.
     
     
  5. Somatic cells have 2 sets of chromosomes and reproduce asexually by mitosis , while gametes (sex cells) have 1 set of chromosomes and reproduce by meiosis .
     
     
  6. The cell cycle consists of an interphase and a mitotic phase.
     
     
  7. Interphase can be divided into subphases G1 , S , and G2 .
     
     
  8. The mitotic phase consists of mitosis , the division of the nucleus, and cytokinesis , the division of the cytoplasm.
       
       
    • Mitosis consists of 5 phases, or stages: 1) prophase , 2) prometaphase , 3) metaphase , 4) anaphase , 5) telophase .
       
       
    • In prophase , chromatin condense into visible chromosomes , and the mitotic spindle arises from the centrosomes and is made of microtubules .
       
       
    • In prometaphase , the nuclear envelope breaks down, and spindle microtubules attach to the kinetochores of chromosomes.
       
       
    • In metaphase , the spindle microtubules move the chromosomes to the metaphase , or equatorial, plate.
       
       
    • In anaphase , sister chromatids separate, and move along the kinetochore microtubules toward opposite ends of the cell.
       
       
    • In telophase , genetically identical daughter nuclei form at opposite ends of the cell.
       
       
    • Cytokinesis:
         
         
      • In animal cells, a cleavage furrow forms, and a contractile ring of microfilaments splits the cell.
         
         
      • In plant cells, a cell plate , fused from vesicles , grows at the equator, then new cell walls form between the daughter cells.
     
     
    Review: Mitosis and Cytokinesis Animation
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Unit 3: Genetics Meiosis and Sexual Life Cycles Review Notes Med Choi Fill
  1. All living organisms can reproduce, and transmit traits from one generation to the next, with variation.
     
     
  2. The units of heredity are segments of DNA called genes . Each gene is found at a region on a chromosome called its locus . An organism's total genes is its genome .
     
     
  3. In asexual reproduction, one parent produces genetically identical offspring by mitosis or binary fission.
     
     
  4. In sexual reproduction, two parents produce offspring that have unique combinations of genes inherited from each parent.
     
     
  5. A karyotype is an ordered, visual representation of the chromosomes in a cell.
     
     
  6. In humans, each somatic cell has 46 chromosomes made up of two sets, with one set coming from each parent.
       
       
    • 44 of these are pairs of homologous chromosomes, or autosomes , and have the same genes ; each of the pair comes from each of the parents of the individual.
       
       
    • The other two chromosomes are sex chromosomes, called X and Y, which determine the gender of the individual. Cells having a full complement of chromosomes are diploid .
       
       
    • Each chromosome consists of two identical sister chromatids , attached to the centromere .
     
     
  7. Gametes are the sex cells involved in sexual reproduction, and are haploid , containing only one set of chromosomes.
     
     
  8. Gametes are produced from germ cells in organs called gonads by meiosis.
     
     
  9. Fertilization occurs when a sperm fuses with an ovum, forming a diploid zygote , which grows and develops into an adult organism.
     
     
  10. Since meiosis reduces the number of chromosome sets from diploid to haploid , two cellular divisions are required.
     
     
  11. Meiosis I is the chromosome reduction division, and meiosis II produces four haploid daughter cells.
     
     
  12. Sexual reproduction produces genetic variation by several mechanisms: independent assortment , crossing over , and random fertilization.
     
     
  13. The tremendous genetic variation made possible by meiosis and sexual reproduction provides raw material for evolution by natural selection.