Summer Research Program for Science Teachers

 

Steven Oszust

Gateway School for Environmental Research and Technology

Bronx, NY

 

August 2004

 

 

What is the purpose of Karyotyping?

 

 

 

IO:      1.   Students will be able to define the term karyotype.

2.      Students will be able to use karyotypes to make observations and analyze chromosomal errors.

3.      Students will be able to explain how karyotyping is used to diagnose specific genetic disorders.

4.      Students will make ethical decisions on the use of karyotyping.

 

Materials:   Hardcopy:  Karyotyping activity worksheet, and scissors.

                     On-Line:    Courtesy of University of Arizona

http://www.biology.arizona.edu/human_bio/activities/karyotyping/karyotyping.html

 

Method:          This lesson is designed as a hardcopy worksheet activity should computer internet access be unavailable, or as an interactive online activity.

Students will work in groups of 4 using the hardcopy or individually online.

Students will follow the instructions and match-up the chromosomes with their homologous pair.  They will have a normal set for comparison.

The finished work will then be analyzed and diagnosed using the chart provided.  They will then answer the questions on the worksheet.

 

POE:            Students will read the introduction on karyotyping and how the chromosomes are stained.  They will summary the text and define karyotyping.

 

Vocabulary:

                        Amniocentesis              Centomere                   Chromatid

Chromosome                Epithelial Cells             Homologous Pair

G Band                        Giemsa Dye                 Karyotype

                        Polydactyly                  Syndrome                    Trisomy

 

Board Notes:

 

I.                   What is a Karyotype?

 

  1. Karyotyping is a picture of an individualís chromosomes arranged in homologous pairs.  They are stained with Giemsa dye which highlights A-T base pairs creating ďG BandsĒ (areas on the chromosome that are rich in A-T pairs). 

[How would you arrange the chromosomes? On what features would you focus?]

    1. Homologous pairs (sets of chromatids that carry the same genetic material) are identified by their length, centromere placement, and banding pattern.

 

           II.      How can we use a Karyotype?

 

1.    Analysis of karyotypes requires a comparison between a normal set of chromosomes and the subjectís chromosomes.  If there are missing chromosomes (monosomy), or extra chromosomes (trisomy or polydactyl); or if individual chromosomes have extensions or deletions; the subject will then have a chromosomal disorder.

                  a.  Common Chromosomal disorders:

                                                              i.      Klinefelter's Syndrome- one or more extra sex chromosomes (i.e., XXY).

                                                            ii.      Down's Syndrome- Trisomy 21, extra chromosome 21.

                                                          iii.      Trisomy 13 Syndrome- extra chromosome 13.

           

            III.      Karyotyping Activity

           

            Have students write out their group responses to the worksheet questions on the board.  Discuss answers as a class.

           

            IV.      Ethical Issues

 

What would you do If you knew in advance that your unborn baby had a chromosomal disorder?

Allow students to brainstorm options and debate proís and conís.  Notes will be determined by student responses.       

 

 

V.                Summary

 

Have students summarize what they learned from the activity and about karyotyping.

 

VI.             Assessment

 

Assessment will be based on responses to worksheet question and on summary statements.

 

VII.          New York State Science Standards

 

S4a, c, d, e; S5b, c, d, e, f; S6a, b, c, d,; S7a, b, d, e.

 

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