Chromosome Karyotyping

Gray, JoAnne S. George Henry Corliss High School

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.
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