Date ________
Karyotype Lab
Name ____________________
Introduction
Several human genetic disorders are caused by extra, missing, or damaged chromosomes. In order to
study these disorders, cells from a person are grown with a chemical that stops cell division at the
metaphase stage. During metaphase, a chromosome exists as two chromatids attached at the
centromere.
The cells are stained to reveal banding patterns and placed on glass slides. The chromosomes are
observed under the microscope, where they are counted, checked for abnormalities, and photographed.
The photograph is then enlarged, and the images of the chromosomes are individually cut out. The
chromosomes are identified and arranged in homologous pairs. The arrangement of homologous pairs
is called a karyotype. In this investigation, you will use a sketch of chromosomes to make a karyotype.
You will also examine the karyotype to determine the presence of any chromosomal abnormalities.
Procedures
1. Observe the normal human
karyotype in Figure 1. Notice that
the two sex chromosomes, pair
number 23, do not look alike. They
are different because this karyotype
is of a male, and a male has an X
and a Y chromosome.
2. Identify the centromere in each pair
of chromosomes. The centromere is
the area where each chromosome
narrows.
3. Study the human chromosomes that
are scattered on the page you were
assigned. Notice that some of the
chromosomes have numbers 1
through 22 to give you some
reference points.
4. To match the homologous
chromosomes, look carefully at the
unnumbered chromosomes. Note
their overall size, the position of the
centromere, and the pattern of the light and dark bands.
5. Use scissors to cut out all the chromosomes from your assigned karyotype. Tape or glue them in
their appropriate places on the answer sheet. Make sure that the short arms of the chromosome are
oriented upwards and the centromere is on the line. (You could place the chromosomes above the
line but placing the centromere makes this process easier).
6. Do not lose any of the chromosomes. You will not get any extras. You will lose points for every
chromosome that is lost, mismatched or out of order, so be careful. We can make envelopes to
hold the chromosomes before you leave, please remind me if I do not say anything.
Date ________
Karyotype Lab
Karyotype Results for: _______________________
Name ____________________
Date ________
Analysis Questions:
Karyotype Lab
Name ____________________
1. What clues to the presence of certain genetic disorders can be seen in a karyotype?
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2. Why would it be much more difficult to construct a karyotype of unstained chromosomes?
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3. Which pair of chromosomes can contain two very different chromosomes and still be considered
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normal? Explain your answer.
4. What do the homologous chromosomes for each pair (except for the 23rd pair) have in common?
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5. In the karyotype that you made, what is the sex of the individual? How can you tell?
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6. Does the karyotype that you made show any abnormalities? If so, explain.
7. You are a genetic counselor, and a young pregnant couple, with their first child on the way, is coming to
you for an analysis of their unborn baby’s karyotype. Research the chromosomal abnormality that is
shown in your karyotype. Find out information about the disorder, such as the the name of the disorder,
symptoms of the disorder, how common the disorder is in the human population or anything else that
parents may want to known about their unborn child’s disorder.
As the genetic counselor write a letter to the parents explaining the results of the karyotype. Try to
break the news of the child’s disorder gently, but inform the parents about the disorder so they know
what to expect.
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Date ________
Karyotype Lab
Name ____________________
Date ________
Karyotype Lab
Name ____________________
Date ________
Karyotype Lab
Name ____________________
Date ________
Karyotype Lab
Name ____________________
Date ________
Karyotype Lab
Name ____________________