Lab: Karyotypes and Genetic Disorders

Lab: Karyotypes and Genetic Disorders
Purpose:
1. To be able to assemble a karyotype of an organism properly for analysis
2. To relate the significance of karyotypes to chromosomal disorders and genetics found in
populations.
Prelab Questions:
1. What is a karyotype
2. Describe how a karyotype is laid out for analysis by geneticists.
3. What are the two types of chromosomes found in a karyotype
Procedures:
Part I: Normal Karyotypes
1. Analyze the karyotypes and identify the sex of each individual in your lab book. Write
down differences you observe between karyotype I and karyotype II.
Normal Karyotype I: Sex: ______ Normal Karyotype II: Sex: ______
Part II: Abnormal Karyotypes
1. Obtain a chromosome spread from teacher. Record patient number on the karyotype sheet
provided.
2. Carefully cut out each chromosome from the chromosome spread and arrange chromosomes in
homologous pairs.
a. The members of each pair will be the same length and will have the centromere in the
same location. Use the ruler to help measure the length of the chromosome and the
position of the centromere.
b. The banding patterns may also help you pair up the homologous chromosomes.
3. Arrange each homologous pair according to their length, from largest to smallest. Keep an eye
out for the sex chromosomes (XX or XY). The Y chromosome will be small and the X
chromosome will be different from the others! Do not glue them down until you have figured
out what the X and Y chromosomes look like!

4. Glue each homologous pair to the sheet of paper titled “Human Karyotyping Form.”
c. Place the pairs in order, with the longest pair first, labeled as position 1 and the shortest
pair at the end, labeled as position 22.
d. The sex chromosomes should be labeled as position 23 and be at the end of your
karyotype. See image in Part I for the layout of a karyotype of a normal individual.
5. Analyze the karyotype.
e. Determine the gender of the individual, how many chromosomes are in the karyotype.
Identify on the karyotype form.
f. Determine whether or not the karyotype shows an abnormality. Identify and record on
the karyotype. If abnormal, identify the abnormality according to the genetic disorders
listed below.
6. On a separate sheet of paper, create a brochure of the disorder for the parents of a child that
may have this disorder. You may use a computer if you choose.
g. Must include description of disorder, support information, and references.
Genetic Disorders Reference Chart
Down’s Syndrome Trisomy 21
Patau Syndrome Trisomy 13
Edward’s Syndrome Trisomy 18
Klinefelter’s Syndrome XXY sex chromosomes
Turner’s Syndrome
Cri Du Chat Syndrome
X sex chromosome only
One chromosome 5 will have a shortened
chromatid
Postlab Analysis:
1. The X chromosome closely resembles many of the other chromosomes. How were you able to
identify it from the other chromosomes
2. If your karyotype indicated a genetic abnormality, what are the characteristics associated with
that abnormality Is it fatal
3. What are the diploid (2n) and haploid (n) number of chromosomes for this organism
4. During what division process (mitosis or meiosis) are cells photographed for karyotypes
5. During which phase of that cycle are cells photographed for karyotype
6. Why are karyotypes important tools for geneticists
7. Do organisms with chromosomal disorders survive in a population Why do you think this