Do not write on this lab.
Human Karyotypes
Background:
Several human genetic disorders are caused by the adding, missing, or damaged chromosomes.
One way of studying genetic disorders is to observe the chromosomes themselves. In order to do
this, cells from a person are grown in a laboratory. After they have reproduced a few times,
the cells are treated with a chemical that stops cell division during metaphase. During
metaphase, the chromosomes are at their best length for identification.
The cells are treated further, stained, and then placed on glass slides. The chromosomes are
observed under the microscope and counted, checked for abnormalities, and photographed. The
photograph is then enlarged and the chromosomes are cut out individually. Finally, the chromosomes
are identified and arranged in homologous pairs (identical or matching). The arrangement of these
homologous pairs is called a karyotype.
In this investigation, you will use a sketch of chromosomes to make a karyotype. Using a key
that shows a normal human, you will determine the gender and the presence or absence of genetic
defects.
Problem:
How can chromosomes from somatic cells be used to determine the health of a newborn?
Materials:
Scissors
Glue
Scatter sheet Answer sheet
Normal karyotype key
Procedure:
Part A: Analyzing a karyotype
1. Observe the karyotype below. How many chromosomes are present?
2. Notice that the two sex chromosomes (pair number 23) do not look alike. Is this a male or
female karyotype?
3. Identify the centromere in each pair. The centromere is the area where each chromosome
narrows.
Part B: Using a Karyotype to Identify a Genetic Disorder
1. Write the number found on your scatter sheet at the top left on the answer sheet.
2. Cut the scatter sheet in half so that you and your partner can cut out each chromosome. Cut a
tight rectangle around each chromosome to save time rather than cutting along the lines.
3. Identify the homologous chromosomes you have cut out by looking for matches using the key
provided. Look at their overall size, the position of the centromere, and the pattern of light and
dark bands. Lay these over their corresponding numbers on the answer sheet ***Note – you
may have a genetic disorder resulting in extra or missing chromosomes.
4. When you are done matching all the chromosomes, glue them to the answer sheet. DO NOT
GLUE DIRECTLY ON YOUR TABLE. Lay a scratch piece of notebook paper underneath the
chromosomes to avoid creating a sticky desk.
5. Determine the sex of your karyotype then determine if the person is normal or not by looking at
the defective karyotype chart on your answer sheet. What disorder did you find, if any?
6. Answer the rest of the questions.
Data/Observations: (this will be your pasted karyotype – only one person will turn this in, stapled to their
lab sheet)
Results:
Observe the following karyotypes to answer the questions on your answer sheet.
Human Karyotype Lab
Name: ______________________________________
Partner: _____________________________________
Per: _______ Date: ____
Scatter Sheet # _______
Observations:
1. What is the gender of your karyotype? ___________________
2. How many autosomes are present? ________
3. How many sex chromosomes are present? ________
4. Is the karyotype normal? ________
Karyotype
XXY
XYY
X0
XXX
#5 defective in short arm
Extra #13
Extra #18
Extra #21
Syndrome
Kleinfelter’s male
“XYY” male
Turner’s female
Super female
“Cri du chat”
Patau’s syndrome
Edward’s syndrome
Down’s syndrome
Characteristics
Unusual body proportions and sterility; subnormal mental ability
Tall, prone to acne, impaired fertility, mentally normal
Short stature, webbing of the neck, may have low mental
ability and sterility
May have low mental ability, fertile, secondary male characteristics
Catlike cry, severe physical and mental abnormalities, non-lethal
Physical abnormalities; lethal soon after birth
Unusual features of the head and fingers, often dies in infancy
Characteristic facial features, low mental ability, stocky build,
sometimes heart defects, irregular hand and footprints, thick tongue
5. If your karyotype is not normal, use the chart above to determine what disorder it has.
_______________________________________________
Results/Analysis:
6. What disorder does the person have in the karyotype corresponding to figure 1 (see instructions)?
_______________________________________________
7. What disorder does the person have in the karyotype corresponding to figure 2 (see instructions)?
_______________________________________________
Conclusion: What happens during meiosis that ultimately results in a defect characterized by the addition or
deletion of chromosomes? Explain both potential scenarios.
Chromosome Scatter Sheet # __________
Names:
Karyotype Sheet
1
6
2
7
3
8
4
9
13
14
15
19
20
21
5
10
16
11
17
22
12
18
X
Y