Lecture Exam IV

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Lecture Exam IV
2012-04-02 08:38:39
Bio 101

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  1. Simple Cell Cycle
    • Step One: The cell copies its DNA
    • Step 2: The cell splits in half by binary fission. Forms 2 "daughter cells"
    • ONLY applicable to Prokaryotes
  2. Replication
    • DNA replication begins with the unzipping of the double-stranded DNA at a point called the origin of replication
    • a new double helix is formed by adding complementary nucleotides to the exposed DNA strands that have been unzipped
    • the end result of replication is that the cell possess two complete copies of the hereditary information
  3. Elongation
    The growing of a cell after replication has taken place
  4. Daughter Cell
    • eventually the cell constricts in two to form
    • two daughter cells

    each daughter cell is a complete, living cell with its own DNA identical to that of the parent cell
  5. Complex Cell Cycle
    The eukaryotic cell cycle is divided into distinct phases:

    • Interphase (G1,S, and G2
    • phases)

    Mitosis (M phase)

    Cytokinesis (C phase)

    Eukaryotic cells divide by separating copies of their chromasomes into daughter cells
  6. Mitosis (M Phase) (Step 2)
    • A cell division mechanism that occurs in non-reproductive cells
    • These cells are called somatic cells
    • A microtubular
    • apparatus binds to the chromosomes and moves them apart
  7. Meiosis
    • A cell division mechanism that occurs in cells that participate in sexual reproduction
    • •these cells are called germ cells
    • Halves the number of chromosomes found in somatic cells
  8. Interphase (Step One)
    • The first phase of the cycle
    • It is comprised of three phases:

    •G1 phase

    –the primary growth phase of the cell following division

    –most cells spend the majority of their lifespan in this phase

    •S phase

    –DNA replication occurs in preparation for cell division

    •G2 phase

    • –further preparation for cell division, including replication of mitochondria and
    • synthesis of microtubules
  9. Prophase
    • (In M Phase) (Step 1)
    • The chromosomes condense, the nuclear envelope breaks down, and the spindle forms
  10. Metaphase
    • (In M Phase) (Step 2)
    • The chromosomes line up on the central plane of the cell
  11. Anaphase
    • (In M Phase) (Step 3)
    • The centromeres divide, and the chromatids moves toward opposite poles
  12. Telophase
    • (In M Phase) (Step 4)
    • The chromosomes uncoil, and a new nuclear envelope forms. The spindle fibres dissapear.
  13. C Phase (Cytokinesis)
    The cytoplasm divides, creating two daughter cells
  14. The Cell Cycle Diagram
  15. Chromosomes
    • Most eukaryotes have between 10 and 50 chromosomes in their somatic cells
    • Where all eukaryotic cells store their hereditary information
    • Coiling of the DNA allows it to fit in the nucleus
  16. Homologous Chromosomes/ Homologues
    • Carry information about the same traits at the same locations on each chromosome
    • The actual information can vary between homologues
  17. Centromere
    The site where two sister chromatids are linked before cell division
  18. Chromatin
    • Comprises chromosomes
    • A complex of DNA & protein
  19. Histones
    DNA is coiled around protiens called histones
  20. Nucleosome
    • •The DNA coils around a core of eight histone proteins to form a complex called a nucleosome
    • The nucleosomes in turn can be coiled together further to ultimately form a compact chromosome
  21. Checkpoints
    Ensure that the previous phase is fully completed before advancing to the next phase

    • Three principal checkpoints control the cycle in eukaryotes
    • •G1, G2, and M checkpoints
  22. Gametes
    Reproductive cells (Eggs & Sperm)
  23. Zygote
    • Formed by gametes fusing together.
    • Contains two complete copies of each chromosome
    • the fusion of gametes is called fertilization
  24. Diploid
    Have two sets of chromosomes
  25. Haploid
    Have one set of chromosomes
  26. Meiosis I
    • Meiosis I separates the homologues in a homologous pair
    • Includes Prophase I, Metaphase I, Anaphase I, & Telophase I
  27. Meiosis II
    • Separates the replicate sister chromatids
    • Involves Prophase II, Metaphase II, Anaphase II, & Telophase II
    • When Meiosis is complete, the result is that one diploid cell becomes four haploid cells
  28. Meiosis Diagram
  29. Meiosis vs. Mitosis
  30. Law of segregation
    • The two alleles of a trait
    • separate from each other during the formation of gametes, so that half of the
    • gametes will carry one copy and half will carry the other copy
  31. Law of Independant Assortment
    • Genes located on different
    • chromosomes are inherited independently of one another