Chapter 8: Cell Reproduction by G2iv1V

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									Chapter 8: Cell
Reproduction
                      Review
Organelles
   Centrioles
      Made of microtubules
      Acts as anchors in cell division
   Mitotic Spindle fibers
      Two Main types
         Kinetochore Fibers- Attach from centriole to centromere of
         chromosomes and assists in movement of chromosomes
         Polar Fibers – Extend from pole to pole and keep the shape of
         the cell during cell division
   Nuclear envelope
      Double Phospholipid bilayer surrounding nucleus
      Allows selective passage of RNA and other material
   Nucleolus
      Dense area where DNA is concentrated in the nucleus
                     Section 8.1
Chromosomes
  Chromosome Structure
     Rod-shaped and made of DNA and proteins called histones
     Two full copies of DNA
     Form it takes before cell division
     Has two identical halves called chromatid
  Chromatid
     Half of the chromosome
     One full copy of DNA
     Attached in the center
  Centromere
     Center where chromatids are
     held together
  Chromatin
     Less tightly coiled DNA-protein complex
     Tin = thin *Think spaghetti
     Form taken during transcription
            Section 8.1
Sex Chromosomes
  Determine gender of the organism
  May carry genes for other characteristics
  Either X or Y
  Female = XX Male = XY
  One pair (or two chromosomes)

Autosomes
  Remaining chromosomes
  Contain genes for many traits
  22 pairs (or 44 chromosomes)
                Section 8.1
Homologous Chromosomes
  Two copies of each autosome
  One copy from each parent
  Same size and shape
  Carry genes for the same trait

Karyotype
  Photomicrograph of chromosomes
  Notice there are 22 pairs of
  autosomes and 1 pair of sex
  chromosomes
  What is the gender of this
  organism?
                   Section 8.1
Diploid
   Cells that are diploid contain two autosomes from each
   homologous pair and two sex chromosomes
   Abbreviated as 2n
      Memory key * di = two
   Occurs in all cells except sperm and egg cells

Haploid
   Cells contain only one set of chromosomes
   Therefore, half the number of chromosomes of a diploid
   cell
   Abbreviated as 1n
      Memory key * hap = half
   Sperm cell (1n) and egg cell (1n) create a diploid cell (2n)
Section 8.1
              Notice high number
                of chromosomes
                in fern compared
                to humans!
              Section 8.1
Activity
   Create a karyotype!
     Arrange in pairs according to length, centromere
     position, and banding pattern
     Questions
     1. How many autosomes are there? How many sex
        chromosomes?
     2. Is the organism a male or female?
     3. Why are karyotypes important tools for geneticists?

Homework
   Review questions on p. 153 #1-5
 Section 8.1 Review Answers
1.   Name the proteins that DNA wraps around to form a
     chromosome in eukaryotic cells.
     •   Histones.

2. How do the structure and location of a prokaryotic
   chromosome differ from that of a eukaryotic
   chromosome?
     •   A prokaryotic chromosome consists of a circular DNA
         molecule. Eukaryotic chromosomes are rod-shaped,
         associated with histone and nonhistone proteins, and found
         within the cell’s nucleus.

3. Does chromosome number indicate whether an organism
   is a plant or animal? Explain.
     •   No. For example, chimpanzees have the same number of
         chromosomes as potatoes or plums.
Section 8.1 Review Answers
4. Contrast sex chromosomes with autosomes.
   •   Sex chromosomes determine the gender of an organism.
       Autosomes are all of the other chromosomes in an
       organism.

5. Using Table 8-1, list the haploid and diploid number of
    chromosomes for each organism.
      Section 8.1 Review Answers
Organism              Diploid # Chromosomes   Haploid # Chromosomes

Adder’s tongue fern   1262                    631
Carrot                18                      9
Cat                   32                      16
Chimpanzee            48                      24
Dog                   78                      39
Earthworm             36                      18
Fruit fly             8                       4
Garden pea            20                      10
Gorilla               48                      24
Horse                 64                      32
Human                 46                      23
Lettuce               18                      9
Orangutan             48                      24
Sand dollar           52                      26
                     Section 8.2
Cell Cycle
   Repeating set of events in the life of
   a cell
     Interphase
         Time between cell divisions
         Three phases
             G1 – Cell growth
             S – DNA is copied
             G2 – Growth and prep for cell division
     Cell division
         Two phases
             Mitosis – Nucleus of the cell divides
             Cytokinesis – Division of the cell’s cytoplasm
                Section 8.2
Cell Division
   Prokaryotes
      Remember: Has cell wall, no nuclei, no membrane-bound
      organelles
      Binary fission
        Division of prokaryotic cell into two offspring cells
                Section 8.2
Cell Division (cont’d)
   Eukaryotes
      Mitosis
         Division of the nucleus
         Four stages (Prophase, Metaphase,
         Anaphase, Telophase)
      Cytokinesis
         In animal cells, pinching of cell
         membrane occurs
            Cleavage furrow
         In plants, cell plate formation
             Section 8.2
Control of Cell Division
   Checkpoints = traffic signal
   Three main checkpoints
     G1 checkpoint
     G2 checkpoint
     Mitosis checkpoint
                Section 8.2
Activity
   Venn diagram: Cell division in Prokaryotes vs Eukaryotes




   Karyotype Part 2

Homework
   Create the cell cycle
Section 8.2 (cont’d)
   Mitosis
     Prophase
        Tight coiling of DNA into chromosomes
        Nucleolus and nuclear membrane break down
        Centrosomes appear and move to opposite ends
        of the cell
        Kinetochore fibers extend from kinetochore
        from each chromatid to centrosome
     Metaphase = Middle
        Kinetochore fibers move chromosomes to center
        of cell
        All chromosomes line up in a single file line
Section 8.2
 Anaphase
   Chromosomes separate at the centromere and
   chromatids move to opposite poles
   Chromatids are now considered individual
   chromosomes
 Telophase
   Spindle fibers disassemble
   Chromosomes return to less tightly coiled
   chromatin state
   Nuclear envelope forms around each set of
   chromosomes
   Nucleolus forms in each of the newly forming cells
 Animation
    Mitosis vs Meiosis
Where do they occur?
   Mitosis – in the body cells
   Meiosis – in the germ cells

Why does it occur?
   Mitosis
      Asexual reproduction
      Growth and development
      To replace old cells
   Meiosis
      Formation of gametes (egg and sperm cells) that will be
      used in sexual reproduction
    Mitosis vs Meiosis
End result?

                                46
           46



                          23              23
      46        46

                     23    23        23        23


      MITOSIS             MEIOSIS
                   Meiosis
Also known as reduction division
Occurs in germ cells found in the ovaries and testes
Produces sex cells which are haploid
Occurs in two phases
   Meiosis I
      Reduces the number of chromosomes from diploid to
      haploid
   Meiosis II
      Produces four haploid daughter cells
Meiosis I
                 Meiosis I
Prophase I
  DNA coils tightly into chromosomes
  Spindle fibers appear
  Nucleolus and nuclear envelope
  disassemble
  Synapsis =Pairing of homologous
  chromosomes
  Tetrad =Pair of homologous
  chromosomes twisted around each
  other
  Crossing over may occur
  Genetic recombination
                  Meiosis I
Metaphase I
  Spindle fibers attach to centromere of tetrads
  Tetrads line up along midline
Anaphase I
  Homologous chromosome pairs are separated and
  move to opposite poles
  Independent assortment occurs
Telophase I
  Chromosomes reach opposite ends of cell
  Spindle Fibers disappear
  Cytokinesis begins
Meiosis II
                 Meiosis II
Prophase II
   Spindle fibers form and attach to the centromeres of the
   double stranded chromosomes

Metaphase II
   Chromosomes are moved to the midline of the dividing cell

Anaphase II
   Chromatids separate and move toward opposite poles

Telophase II
   Nuclear membrane forms in each of the four new cells

Cytokinesis II occurs resulting in four new cells, each with half
the original cell’s number of chromosomes
               Section 8.3
Results of mitosis vs. meiosis
                 Section 8.3
Development of
Gametes
  Spermatogenesis
  Oogenesis
  Polar bodies
  Sexual
  reproduction

								
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