Chromosome Karyotyping

Gray, JoAnne S.                        George Henry Corliss High School
                                       821-2515
                      

Objectives:
1.  Students will be able to demonstrate a microtechnique for reliable 
    chromosomal analysis of leucocytes obtained from peripheral blood.
2.  Students will be able to prepare a karyotype from the chromosomes 
    of a normal human male or female. 
3.  Students will be able to use the karyotyping techniques for 
    diagnosing a chromosomal disorder. 
Apparatus and Materials:
   1.  Centrifuge and Tubes               14.  Overhead Projector
   2.  Construction Paper                 15.  Ruler
   3.  Coplin Jar                         16.  Scissors
   4.  Deionized and Distilled Water      17.  String or Yarn
   5.  Fixative Solution                  18.  Tape or Glue
   6.  Flat- ended forceps                19.  Tape Player and Music
   7.  Human Chromosome Kit (order)       20.  Transparencies 
   8.  Human Chromosome Photographs            a.  Cell Mitotic Stages
   9.  Human Karyotype Forms                   b.  Birth Certificate 
  10.  Incubator or Hotwater Bath              c.  Chromosomes:
  11.  Methanol                                     Normal and abnormal
  12.  Microscope Slides and Cover Slips       d.  Human Karyotype
  13.  Oil Immersion Microscope and Oil   21.  Xylene
Recommended Strategy:
  Order chromosome kit at least three weeks prior to use
  Set up microtechnique one week prior to use
I.  Background:
    A.  Discuss myths, superstitions and misconceptions associated 
        with biological inheritance and human development.
        1.  State an example of a heredity superstition.
        2.  Enlist additional examples from the students.
    B.  State a brief history of Genetics, include Genetic Principles 
        and how teaching has helped in eliminating misconceptions.
II. Motivation:
      Before class place two large circles on the floor one inside the
      other using the string or yarn (represents membranes of cell).  
      Use 2 different colors of construction paper to make hats, label
      one side chromatin and the other side chromosome.  Make 2 
      centromeres cut in half and label. 
   A.  Discuss the normal chromosome complement of human males and females. 
   B.  Explain the history of the establishment of the correct 
       chromosome number in humans.
   C.  Review cell division - explaining how sex cells receive too much 
       or not enough genetic material.        
   D.  Choose a short and a tall student to dance the "Chromosome Jig."
   E.  Note the two circles on the floor and discuss purpose, sizes, 
       arrangement, where "chromatin" should stand, and cell stage 
       represented.
   F.  Place construction paper hats on dancers heads (chromatin sides 
       showing, each hat is a different color).   
   G.  Dancers will now perform within the nucleus, the remaining 
       students will assist in providing clues: 
       Note Steps may be shown on overhead during performance or for 
           review after the dance.  Soft music may be played. 
       1.  New cell stage - Interphase 
           (a)  Chromosomes indistinct (chromatin)...dancers kneeling 
           (b)  Chromosomes unravel (chromosome sides of hats showing) 
           (c)  Chromosomes duplicate and gradually coil
              (1)  2 more dancers, same size as originals, come in 
                   wearing chromosome hats. 
              (2)  Place centromere on locking hands of each two dancers.
       2.  Prophase
           (a)  Chromosomes contracted enough to become distinct
           (b)  Chromosomes twist around while constantly contracting
       3.  Metaphase
           (a)  Chromosomes are fully contracted                
           (b)  Chromosomes separate
           (c)  Teacher quickly, without students being aware of 
                purpose, sprinkles confetti (chemical) on dancers to stop 
                metaphase, before the spindle fibers appear.  Puzzled 
                dancers will stop dancing and separate. 
           (d)  Teacher states, "now nuclear membrane disappears," and 
                asks a sitting student to remove it 
III.   Development: 
          When possible list responses on chalkboard             
    A.  Discuss the purpose and name of the chemical (confetti).
    B.  Describe the position of the dancers, thank dancers as they sit. 
    C.  What process is seen when chromosomes stop in this case?  
        (Ans.  Arrested metaphase)
    D.  Ask why arrest metaphase for chromosome studies?
    E.  Ask how does one obtain his/her own chromosomes?
    F.  Ask why would one need to see his/her chromosome?
    G.  Show on overhead:  
        (1)  Birth certificate showing an error in stating sex
             (a)  Ask class to study certificate and note any errors
             (b)  Use this to lead into karyotyping
        (2)  Examples of the following karyotypes:
             (a)  Normal male and female - try your own
             (b)  Chromosome set used to make karyotypes  
 IV.  Activities:
    A.  Laboratory Exercise - Human Chromosome Study/Karyotyping
              Allow time for students to complete the following:
              (a)  Prepare a normal human karyotype
              (b)  Prepare an abnormal human karyotype
              (c)  Teacher designed analysis and discussion section 
    B.  Chromosome Syndromes
        List disorders and determine name and sex affected by the disorder.
  V.  Evaluation Prepare an evaluation exercise
 VI.  Extension (Homework Exercise)
    A.  List a hypothetical anomaly, its causes, symptoms and 
        probabilities of occurrence, rank the likelihood of aborting the 
        fetus on a scale of 1-5.  1 representing never, and 5 always. 
    B.  Write a paragraph supporting your decision. If you are opposed 
        to abortion in all cases, then write a paragraph that supports 
        your values.