Essential Questions…
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What is a karyotype?
What can it help you determine?
What does a karyotype of a human
look like?
Karyotyping Lab
50 points
- 40 points for correct karyotype
- 10 points questions
Due tomorrow but you could finish in class
Objective
 In this lab, you will create and analyze a
karyotype of cells from a fetus to count
chromosomes & determine the sex of the fetus.
 Get into groups and collect materials
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Karyotyping directions
Karyotyping questions
Karyotyping blank
Karyotyping spread
Scissors
Glue
What is a
Karyotype?
 A karyotype is a diagram that
shows a cell’s chromosomes
arranged in order from largest to
smallest.
 A karyotype is made from a photomicrograph (photo taken through a
microscope) of the chromosomes from a cell in some phase of
meiosis.
 The photographic images of the chromosomes are cut out and
arranged in homologous pairs by their size and shape.
 The karyotype can be analyzed to determine the sex of the individual
and whether there are any chromosomal abnormalities.
 For example, the karyotype of a female shows two X
chromosomes, and the karyotype of a male shows an X
chromosome and a Y chromosome.
Directions
 In groups of two, read through and follow directions.
 Create your karyotype, analyze it, and answer the
associated questions.
 You will turn in:
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Karyotype
Answers to questions
One worksheet per group of two with both partners’
name on it.
 WARNING: THE PIECES GET LOST EASILY AND
YOU HAVE TO HAVE ALL OF THEM TO
COMPLETE THE ASSIGNMENT. TAKE CARE OF
THEM.
Determining Sex of a Child
 Look at the directions page. Outline the
following chromosomes.
AUTOSOMES = contain the genes for
regular traits
SEX CHROMSOMES =
contain the genes that
determine gender.
XX = female, XY = male
Chromosome Abnormalities
A Common Abnormality…
Down Syndrome
 Trisomy is an abnormality in which a cell
has an extra chromosome, or section of a
chromosome. This means that the cell
contains 47 chromosomes instead of 46.
Down syndrome, or trisomy 21, is a
chromosomal abnormality that results from
having an extra number 21 chromosome.
This extra chromosome means too many
genes and developmental problems
generally result.
 A variety of developmental problems
from functional (able to drive, live
alone) to seriously debilitating (mental
retardation that requires 24-hr
monitoring) can result.
 Odds: 1:1000 births
Other Chromosome Anomalies
Trisomy X
 Three ‘x’ chromosomes
 Odds: 1:1000 females
Turner’s Syndrome
 Generally only female with only 1 ‘x’ chromosome.
 Odds: 1:2500 females
More
 Klinefelter syndrome
 XXY (1:500-1000 males)
 XYY Syndrome
 XYY (1:1000 males)
 Cri du chat
 Missing part of #5 (1:50,000)
 Others can occur with the other chromosomes as well.
Chromosomal Abnormalities
How Do They Happen?
 Chromosomal
abnormalities often result
from nondisjunction, the
failure of chromosomes to
separate properly during
meiosis.
 Nondisjunction results in
cells that have too many or
too few chromosomes.
What’s the Problem?
47
Chromosomes
in gamete
Procedure:
1.
2.
3.
4.
5.
6.
7.
Make sure to write the letter of the version of your
chromosome spread on your karyotype spread!
READ the directions page. This is a class set so please do not take
or write on this.
CUT OUT EACH CHROMOSOME from the chromosome spread in
Figure 2. Be sure to leave a slight margin around each
chromosome.
ARRANGE THEM IN HOMOLOGOUS PAIRS. The members of
each pair will be the same length, have similar banding, and will
have the centromere in the same location. Use the banding patterns
and compare them to the key. Arrange the pairs according to their
length, from largest to smallest.
TAPE OR GLUE each homologous pair to a human karyotyping
form positioning the centromeres on the same lines. Place the pairs
in order, with the longest pair at position 1, the shortest pair at
position 22, and the sex chromosomes at position 23.
CLEAN UP your materials before leaving the lab.
ANALYZE the karyotype to determine the sex of the individual and
whether or not the individual will have Down syndrome.
ANSWER THE QUESTIONS in pairs on a separate sheet of paper.
Possible Outcomes
 Normal Male
 XY
Answer all 10 questions on a
 Normal Female
separate sheet of paper.
 XX
10. Use the green “The Living
 Down’s Syndrome
World” book, pg. 187, to draw
 3x #21 (1:1000 births)
non-disjunction.
 Trisomy X
 XXX (1:1000 females)
DUE TOMORROW
 Turner’s syndrome
50pts.
 X (1:2500 females)
 Klinefelter syndrome
 XXY (1:500-1000 males)
 XYY Syndrome
 XYY (1:1000 males)
 Cri du chat
 Missing part of #5 (1:50,000)
Questions
What is your karyotype spread letter? ___________
1. How many chromosomes do you have in your karyotype?
2. What is a HOMOLOGOUS PAIR and how many does your
karyotype have?
3. What are AUTOMSOMES and how many are present?
4. What are SEX CHROMOSOMES and how many does your
karyotype have?
5. What is a chromatid and how many chromatid does your karyotype
have?
6. What is the haploid number for this organism? n = ____
7. What is the diploid number of this organism? 2n = ____
8. Does your karyotype reveal an abnormality? (yes or No). IF YES,
describe it.
9. What sex is the organism?
10. In your biology books, non-disjunction is diagramed. Copy this
diagram to explain how chromosomal abnormalities might occur in
organisms.