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					 Q: What is the difference between a
     diploid and a haploid cell?

A haploid cell has half the number of chromosomes in a diploid cell.

    Today: Beginning Unit on Cell
  Power Point Notes: Chromosomes

    Homework: 8.2 Section Review
               1-6, 8
Fluorescent In-Situ Hybridization (FISH) identification of human chromosomes
Cell Reproduction: Chromosomes
                   - replicated
                  DNA that is
                  coiled and
                  wrapped around
                  histone proteins
                   - replicates and
                  condenses when
                  the cell is about
                  to divide
- Proteins that help
maintain the shape
of the
- Aid in tight
packing of DNA.
Chromosome Structure
          Chromatid - each half of
          the chromosome
          Centromere – point
          where chromatids attach
            – Thin, uncoiled strands of
              DNA and protein
            – This form of DNA is
              found during interphase
              of the cell cycle
        Chromosome Numbers
 - all non-sex chromosomes.
 - Humans have 22 pairs of autosomes
Sex Chromosomes
 - Genetic information that determines gender of an
 - In humans, Females have XX chromosome pair; males
   have an XY pair
 - 1 pair of sex chromosomes
 - Humans have a total of 23 pairs of chromosomes.
                        2n Chromosomes

Honeybee (female) – 32 Adder’s Tongue Fern - 1262   Common Frog - 26

    Human - 46                Cat - 38               Maize - 20

     Does more chromosomes does bigger
    Chromosome number mean anot
     or more complicated organism?
    determine complexity of organism
      Animal                                    Chromosome number (2n)
1.    Ascaris megalocephala (horse roundworm)   2

2.    Drosohila melanogaster (fruit fly)        8

3.    Musca domestica (house fly)               12

4.    Rana hexadactyla (frog)                   26

5.    Apis mellifera (honey bee — female)       32

6.    Hydra vulgaris                            32

7.    Fells domestica (cat)                     38

8.    Pattus rattus (rat)                       42

9.    Homo sapiens (man)                        46

10.   Bos indicus (cow)                         60

11.   Canis familiaris (dog)                    78

12.   Columbia livia (pigeon)                   80
13.   Amoeba proteus                            250

14.   Aleucantha (radiolarian)                  1600

      Plant                                     Chromosome number (2n)
1.    Mucorheimalis (bread mold fungus)         2

2.    Penicillium notatum (fungus)              4

3.    Pisum sativum (pea)                       14

4.    Zea mays (maize)                          20

5.    Oryza sativa (rice)                       24
6.    Lycopersicon (Tomato)                     24

7.    Solanum tuberosum (potato)                48
8.    Saccharum offtinalis (sugarcane)          80

9.    Ophioglossum (Adder’s tongue fern)        1262
  Chromosome Numbers cont.
  – Two chromosomes that are the same size,
    shape and DNA makeup
• DIPLOID – contain both chromosomes of
  a homologous pair. “2N”
• HAPLOID – contain only one of the
  chromosomes of a homologous pair. “1N”
A photomicrograph
of the chromosomes
in a normal dividing
cell found in a
Does this karyotype
appear to be male
or female?
Trisomy 21, a chromosomal abnormality indicative of down syndrome
       Karyotyping Questions:
•   What characteristics did you use to pair up the
•   How many autosomes are there? How many
    sex chromosomes?
•   Is the organism male or female? What sex
    chromosomes do females have? Males?
•   Why are Karyotypes impt for geneticists?
•   What disease would be caused if you had
    three chromosomes on 21?
     Q: What is the difference chromatids,
        centromeres, and chromatin?
Chromatids are the halves of the chromosomes,
centromeres are where the chromatids are joined,
chromatin is the coiled up DNA that makes up the chromatids/chromosomes

         Power Point Notes: Cell Division
           Prokaryotes vs. Eukaryotes

         Homework: draw binary fission p
         154, and cell cycle with bulleted
                  notes p 155.
   Cell Division In Prokaryotes
- Prokaryotes use binary fission, the division
  of a prokaryotic cell into two offspring cells
- Cell membrane divides
- Prokaryotes do no have a nucleus
    Cell Division in Eukaryotes
Mitosis – results in new cells with genetic
 material identical to the original cell
Asexual reproduction – the production of
 offspring from one parent
Meiosis – occurs during the formation of
Gametes – haploid reproductive cells
Q: What are the stages of the cell cycle
(included in interphase and cell division)
                 in order?
     G1, S, G2, Mitosis, and Cytokinsis. Also G0

       Today: Cell Cycle, Mitosis

   Homework: Draw and label stages of Mitosis
     and Cytokinesis, with 3-4 notes for each.
    Print: Graphic organizer for Thurs, Meiosis
                  flipbook for Fri.
Cell Cycle
       - the time between
       - the cell spends
          most of its time in
       Cell Division
       - mitosis and
How long does
mitosis take?
It depends on cell
type and culture
          Cell Cycle Interphase
• G1 stage of interphase
  – Cell grows to normal size
  – Cell carries out regular functions (protein synthesis,
• S stage
  – DNA is synthesized
• G2 stage
  – Organelles are replicated, preparing for cell division
• G0 stage
  – Cells stop dividing, sometimes permanently (ex:
    nerve cells)

      G1 → S → G2              OR            G 1→ G 0
Division of the cell nucleus in which
chromosomes of the parent cell divide into
two identical daughter cells

  1. Nucleolus and nuclear
     membrane disappear
  2. Chromatin condenses to
     form chromosomes
  3. Centrioles and spindle
     fibers appear
    - Centrioles are not in plants.
1. Kinetochore fibers
   move the
   chromosomes to the
   center of the cell
2. Chromosomes line
   up along the center
   of the cell
3. kinetochore fibers
   hold chromosomes
   in place
  1. Chromatids separate at
     the centromere
  2. Chromatids move,
     centromere first, toward
     opposite poles
  3. Chromatids are
     considered to be
     chromosomes after
One chromosome (unduplicated)

                                one chromatid
                                                two sister
                                one chromatid
One chromosome (duplicated)
        Telophase and Cytokinesis
1.   Centrioles and spindle
     fibers disappear
2.   chromosomes unwind into
     chromatin “spaghetti”
3.   nuclear membrane forms
     around set of chromatin
     and the nucleolus appears
4.   Cytoplasm divides
     (cytokinesis), forming two
     new cells
5.   Organelles are separated
     into two new cells
Control of Cell Division
         • signals from the cell can
           trigger the next phase of
           the cell cycle
         • 3 checkpoints:
           – Cell growth (G1) checkpoint
              • decide whether cell should
                divide or not.
                  – Yes - cell begins G2 phase
                  – No - cell goes into G0 phase
           – DNA synthesis (G2)
              • signal the cell to enter mitosis
           – Mitosis checkpoint
              • signal the cell to exit mitosis
1. Growth

2. Self Healing

3. Cancer
 - uncontrolled growth of cells
 - error at G1 checkpoint
Which stage?
• http://www.biologycorner.com/flash/mitosis
Mitosis vs. Meiosis
  – Takes place in two sets of divisions, meiosis I
    and meiosis II
  – Occurs in Germ cells found in the ovaries and
• Meiosis I
  – Reduces the number of chromosomes from
    diploid to haploid
• Meiosis II
  – Produces four haploid daughter cells
                  Prophase I
• Like Mitosis:
  –DNA is coiled into
  –Spindle fibers appear
  –Nucleolus and nuclear
   membrane disassemble
• Different than Mitosis
    • Synapsis - homologous
    chromosomes pair up
    • Crossing over - exchange
    genetic information, or
    genetic recombination
Meiosis I continued
          Metaphase I:
          tetrads line up at the
             tetrad – a pair of
             homologous chromosomes
          Anaphase I:
             Independent assortment
             - tetrads move to opposite
             sides of the cell (random)
          Telophase I and
             chromosomes reach
             opposite sides of the cell
             and the cell divides
                           Meiosis II
-   Begins with the two cells           Meiosis I
    formed in Meiosis I
-   DNA is NOT copied
    before Meiosis II

Prophase II, Metaphase II,
and Anaphase II – similar to
  Meiosis I, but each half
  receives only half of the
  genetic information

Telophase II and
   Cytokinesis II - Like
   Meiosis I                              Meiosis II

-   Ends with four cells
    instead of two
-   Cells are haploid instead
    of diploid
• In animals, gametes
  are the only cells
  that use meiosis.
• Spermatogenesis –
  produces 4 sperm
• Oogenesis –
  produces 1 egg cell,
  or ovum, and three
  polar bodies, which
      What is crossing over?
Crossing over occurs when pieces of
 chromatids break off and attach to the
 homologous chromosome by it.
What are some key differences and
 similarities between mitosis and
• Mitosis is used by regular cells, meiosis is
  used by reproductive cells
• There is one division in Mitosis, and two
  divisions in Meiosis
• Mitosis ends with two diploid cells, Meiosis
  ends up with four haploid cells
• In both Mitosis and Meiosis DNA is
  doubled just once.

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