Name _______________________
Per ____
Human Karyotyping
Occasionally chromosomal material is lost or rearranged during the formation of
gametes or during cell division of the early embryo. Such changes, primarily the result
of nondisjunction or translocation, are so severe that the pregnancy ends in miscarriage
– or fertilization does not occur at all. It is estimated that one in 156 live births have
some kind of chromosomal abnormality.
Some of the abnormalities associated with chromosome structure and number can be
detected by a test called a karyotype. A karyotype can show prospective parents
whether they have certain abnormalities that could be passed on to their offspring, or it
may be used to learn the cause of a child’s disability. Karyotypes can also reveal the
gender of a fetus or test for certain defects through examination of cells from uterine
fluid – a procedure called amniocentesis – or through sampling of placental
membranes. Over 400,000 karyotype analyses are performed each year in the U.S. and
Canada.
To create a karyotype, chromosomes from a cell are stained and photographed. The
photograph is enlarged and cut up into individual chromosomes. The homologous pairs
are identified and arranged in order by size (with the exception of the sex
chromosomes; these appear last). These tests are typically done on a sample of blood,
although any body cell could be used. The cell must be undergoing mitosis – preferably
in metaphase – so that the chromosomes are replicated, condensed, and visible under
a microscope.
(adapted from: http://www.slic.wsu.edu/bios/biol107/107Karyotypesp05.pdf)
“Spread” of human chromosomes from
a single cell
A karyotype of human chromosomes
Karyotype Instructions
1. You will completing two karyotypes using the two photographs you are given.
2. Cut out one chromosome from the page. Find its EXACT match elsewhere on the
page. Cut out this chromosome and place it on the karyotype page. DO NOT glue it in
place yet!
3. Continue this procedure until you have matched all chromosomes. Keep the pairs
together!
4. In the event that you have an extra chromosome, DO NOT THROW IT OUT! It is the
chromosome that causes your disorder and you must match it correctly. Find where it
belongs and place it with the other two.
5. Arrange the pairs of chromosomes on the karyotype page in order from largest to
smallest, with the largest pair in box 1 and the smallest pair in box 22. The
chromosomes labeled X and Y should be placed in box 23.
6. Glue all chromosomes in place and fill out the box in the bottom right corner before
starting your second karyotype.
7. Repeat the above procedure for your second karyotype.
8. When all members of your group have finished creating their karyotypes, fill out the
Karyotype Data and Conclusions page and answer the questions.
Karyotype Data and Conclusions
Fill in the following table with information from your group’s karyotypes.
Karyotype ____
Sex _____
# of Chromosomes _____
Karyotype ____
Sex _____
# of Chromosomes _____
Genetic disorder yes or no (circle one)
Genetic disorder yes or no (circle one)
If yes, name of disorder
If yes, name of disorder
______________________________
______________________________
Symptoms associated with disorder:
Symptoms associated with disorder:
Karyotype ____
Sex _____
# of Chromosomes _____
Karyotype ____
Sex _____
# of Chromosomes _____
Genetic disorder yes or no (circle one)
Genetic disorder yes or no (circle one)
If yes, name of disorder
If yes, name of disorder
______________________________
______________________________
Symptoms associated with disorder:
Symptoms associated with disorder:
Karyotype ____
Sex _____
# of Chromosomes _____
Karyotype ____
Sex _____
# of Chromosomes _____
Genetic disorder yes or no (circle one)
Genetic disorder yes or no (circle one)
If yes, name of disorder
If yes, name of disorder
______________________________
______________________________
Symptoms associated with disorder:
Symptoms associated with disorder:
Questions:
1. What are some limitations of the karyotype as a test for genetic abnormalities?
2a. These abnormalities were caused by non-disjunction at some point during meiosis.
Did the non-disjunction occur during anaphase I or anaphase II?
b. Draw the diagrams showing the parent cell undergoing meiosis for one of the
gametes with a abnormality. Draw just the one chromosome of interest, and label which
chromosome it is.
Place a star (*) next to the gamete that was passed onto the offspring with the genetic
disorder.